1
An easy-to-understand introduction to slurry pumps and systems
This is the shell or volute of a very, very, very, very large slurry pump.
These are people.
Reader’s Guide
For Our Customers
Editor & Designer Mary A. Sicard Project Editor Thomas Mueller
Meet Digsby. He appears whenever we want to give you a mountain of information but only have room for a mole hill. He tells you where to dig deeper in other sources and in the textbook, “Slurry Transport Using Centrifugal Pumps,” written by Drs. Kenneth C. Wilson, Anders Sellgren Roland Clift and GIW’s VP of Engineering Graeme Addie. The textbook is available from Kluwer Publishing (www.wkap.nl).
Production Controller Pam Welty Tech Team Bob Courtwright, Tom Wujcik, Richard Inglett, Reab Berry and Kevin Kuehne
Copyright © 2005 GIW Industries Inc.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanic, photocopy, recording or otherwise, without the prior written permission of the copyright owner.
giwindustries.com Does your slurry have an attitude? Is it caustic? Corrosive? Abrasive? Erosive? (Or some combination thereof?) If so, talk to us. We can make the biggest, baddest, meanest, nastiest slurry behave. We are the expert in slurry transport, so challenge us to solve your production delays or to improve your slurry pumping systems.
Get in touch and stay in touch 5000 Wrightsboro Rd. • Grovetown, Ga. 30813 Phone: 706.863.1011 • Fax: 706.863.5637
A KSB Company
[email protected]
4
Slurry Pump Fundamentals
Contents Chapter 1: What Is Slurry? .......................................................... 9 Slurry Pumps vs. Water Pumps ....................................................................... 9 Flow Limitations ....................................................................................... 10 Solids Limitations ...................................................................................... 11
5
Selection of Wear Materials ......................................................................... 23 HARD METAL CONSTRUCTION ............................................................................................. 24 WHITE IRONS ................................................................................................................. 24 STEELS ......................................................................................................................
Elastomer Construction .............................................................................. 25 Ceramic Wear Parts ................................................................................... 25 Corrosion Resistance and Wear Resistance ....................................................... 25 Wear Resistance Range ............................................................................... 26 pH Ranges ............................................................................................... 26
Chapter 5: Hydraulics .............................................................. 29 Pumps and Curves ..................................................................................... 29
Chapter 2: Slurry Pumps Defined ............................................... 13 Markets & Applications for Slurry Pumps ......................................................... 14 Installations ............................................................................................. 14 DRY ............................................................................................................................. 15 SEMI DRY ....................................................................................................................... 15 WET ............................................................................................................................ 15
Wear Conditions ....................................................................................... 15 CLASSIFICATIONS AND EXAMPLES ......................................................................................... 16
Chapter 3: Slurry Pump Design & Components ............................... 17 Basic Designs ............................................................................................ 17 Basic Components ..................................................................................... 17 Impeller .................................................................................................. 18 CLOSED IMPELLERS .......................................................................................................... 18 OPEN IMPELLERS ............................................................................................................. 18
Vane Designs ............................................................................................ 19 Shell ...................................................................................................... 19 SHELL TYPES .................................................................................................................. 19 SPLIT AND SOLID SHELLS ............................................................................................. 20
Suction Liner ........................................................................................... 20 Shaft Seals .............................................................................................. 20 STUFFING BOX ................................................................................................................ 20 MECHANICAL SEAL ........................................................................................................... 20 EXPELLER ..................................................................................................................... 20
Shaft and Bearings ..................................................................................... 21 SHAFT .......................................................................................................................... 21 BEARINGS ...................................................................................................................... 21
Drives for Slurry Pumps .............................................................................. 21 BELT DRIVES .................................................................................................................. 21 GEARBOX DRIVES ............................................................................................................ 21 DIRECT DRIVES ............................................................................................................... 21
PERFORMANCE CURVE ...................................................................................................... 29 SYSTEM CURVE ............................................................................................................... 31 THE INTERSECTION .......................................................................................................... 32
Head ...................................................................................................... 32 NET POSITIVE SUCTION HEAD (NPSH) .................................................................................... 32
Vapor Pressure and Cavitation ...................................................................... 33 CAVITATION ................................................................................................................... 33 NPSHR .......................................................................................................................... 33 NPSHA .......................................................................................................................... 34 CAUSES OF CAVITATION ..................................................................................................... 34 HOW TO FIND THE CAUSE .................................................................................................. 34
Pumping Froth.......................................................................................... 35
Chapter 6: Slurry Pump Systems ................................................ 37 Overview ................................................................................................ 37 Pipe Systems ............................................................................................ 37 Friction Losses ......................................................................................... 39 STRAIGHT PIPES .............................................................................................................. 39 FITTINGS ....................................................................................................................... 40 SLURRY EFFECTS ON FRICTION LOSSES ................................................................................. 40 FRICTION LOSSES IN SETTLING SLURRIES ............................................................................... 40 FRICTION LOSSES IN NON-SETTLING SLURRIES ......................................................................... 41
Viscosity ................................................................................................. 41 NEWTONIAN AND NON-NEWTONIAN LIQUIDS ........................................................................... 41 OTHER NON-NEWTONIAN FLUIDS ......................................................................................... 43
Sump Arrangements ................................................................................... 43 Multiple Pump Installations .......................................................................... 44 PUMPS IN A SERIES ........................................................................................................... 44 PUMPS IN PARALLEL ......................................................................................................... 44
Slysel ..................................................................................................... 44
Chapter 7: Best Efficiency Point ................................................. 45 Chapter 4: Wear Protection ...................................................... 23 Wear ...................................................................................................... 23 Corbrasion™ ............................................................................................. 23
Optimal Efficiency ..................................................................................... 45 Radial Load .............................................................................................. 45 Axial Load ............................................................................................... 46
6
Slurry Pump Fundamentals
Shaft Deflection ........................................................................................ 47 Water Hammer ......................................................................................... 47
Chapter 8: Technical Descriptions .............................................. 51 Metal Pumps ............................................................................................ 51 LCC HARD METAL SERIES (LCC-M) ......................................................................................... 51 FEATURES ............................................................................................................... 52 APPLICATION ........................................................................................................... 52 SIZE RANGE ............................................................................................................. 52 LSA-S SERIES .................................................................................................................. 52 FEATURES ............................................................................................................... 52 APPLICATION ........................................................................................................... 53 SIZE RANGE ............................................................................................................. 53
7
Duties Related to Slurry Type ....................................................................... 63 FRAGILE SLURRIES ........................................................................................................... 63 HYDROCARBON SLURRIES (OIL AND REAGENTS CONTAMINATED) ................................................... 64 HIGH TEMPERATURES ABOVE 212˚F (100˚C) SLURRIES .............................................................. 64 HAZARDOUS SLURRIES ...................................................................................................... 64 CORROSIVE SLURRIES (LOW PH) .......................................................................................... 64 HIGH VISCOSITY FLUIDS (NEWTONIAN) .................................................................................. 64 HIGH VISCOSITY FLUIDS (NON-NEWTONIAN) ............................................................................ 64
Selection by Industrial Application ................................................................. 65 HARD ROCK MINING ......................................................................................................... 65 OIL SANDS ..................................................................................................................... 66 PHOSPHATE ................................................................................................................... 66 FGD ............................................................................................................................. 66 INDUSTRIAL PROCESS ....................................................................................................... 66
Rubber Pumps .......................................................................................... 53 LCC RUBBER-LINED SERIES (LCC-R) ....................................................................................... 53 FEATURES ............................................................................................................... 54 APPLICATION ........................................................................................................... 54 SIZE RANGE ............................................................................................................. 54 LSR ............................................................................................................................. 54 FEATURES ............................................................................................................... 54 APPLICATION ........................................................................................................... 55 SIZE RANGE ............................................................................................................. 55
Vertical Pumps ......................................................................................... 55 VERTICAL ...................................................................................................................... 55 FEATURES ............................................................................................................... 55 APPLICATIONS .......................................................................................................... 56 SIZE RANGE ............................................................................................................. 56
High-Pressure, Multi-Stage Slurry pumps ......................................................... 56 WBC ............................................................................................................................ 56 FEATURES ............................................................................................................... 56 APPLICATIONS .......................................................................................................... 56 SIZE RANGE ............................................................................................................. 56 TBC ............................................................................................................................. 57 FEATURES ............................................................................................................... 57 APPLICATIONS .......................................................................................................... 57 SIZE RANGE ............................................................................................................. 58
Chapter 10: Computerized Pump Selection ................................... 67 Slysel ..................................................................................................... 67 SOFTWARE AND HARDWARE REQUIREMENTS ........................................................................... 68 ORDER INFORMATION ....................................................................................................... 68
Chapter 11: General Maintenance .............................................. 69 Maintenance ............................................................................................ 69 RECOMMENDED MAINTENANCE SCHEDULE .............................................................................. 69 DAILY ........................................................................................................................... 70 WEEKLY ........................................................................................................................ 70 QUARTERLY ................................................................................................................... 70 SEMI-ANNUALLY .............................................................................................................. 70
Impeller Removal ...................................................................................... 71 IMPELLER BALANCING ....................................................................................................... 71
Fastener Torque ........................................................................................ 72 TORQUE ACCURACY ......................................................................................................... 72 TORQUE CHARTS ....................................................................................................... 72
Mechanical Seals ....................................................................................... 72 Bearing Temperatures ................................................................................ 73 LUBRICATION – OIL OR GREASE? .......................................................................................... 74 CAUSES OF BEARING FAILURES ............................................................................................ 75
Chapter 9: Application Guide .................................................... 61
Vents and Breathers ................................................................................... 76
Selection by Duty ...................................................................................... 61 COARSE PARTICLES .......................................................................................................... 61 FINE PARTICLES .............................................................................................................. 61 SHARP (ABRASIVE) PARTICLES ............................................................................................. 62 HIGH PERCENT SOLIDS ...................................................................................................... 62 LOW PERCENT SOLIDS ...................................................................................................... 62 FIBROUS PARTICLES ......................................................................................................... 62
Duties Related to Head and Volume ............................................................... 62 HIGH HEAD .................................................................................................................... 62 VARYING HEAD AT CONSTANT FLOW ..................................................................................... 62 VARYING FLOW AT CONSTANT HEAD ..................................................................................... 62 HIGH SUCTION LIFT .......................................................................................................... 63 HIGH FLOW ................................................................................................................... 63 LOW FLOW .................................................................................................................... 63 FLUCTUATING FLOW ........................................................................................................ 63
Chapter 12: Total Cost of Ownership ........................................... 79 Importance of making Smart Pump Purchases ................................................... 79 How GIW Can Help ..................................................................................... 80 Predicting Wear ........................................................................................ 80 Calculating Energy Costs ............................................................................. 81
Chapter 13: Troubleshooting ..................................................... 83 Why Isn’t My Pump Pumping? ....................................................................... 83 Warnings ................................................................................................. 83
8
Slurry Pump Fundamentals
Chapter 1: What Is Slurry?
Chapter 1: EXCESSIVE PUMP DISCHARGE PRESSURE .......................................................................... 83 EXCESSIVE LEAKAGE AT SHAFT SEAL .............................................................................. 83 PUMP DELIVERS INSUFFICIENT FLOW RATE ....................................................................... 83 INCREASE IN BEARING TEMPERATURE .............................................................................. 84 BEARING CONTAMINATION ........................................................................................... 84 HIGH TEMPERATURE OR LEAKAGE AT THE STUFFING BOX ..................................................... 84 OVERHEATING OF PUMP CASING .................................................................................... 85 PUMP CASING LEAKS .................................................................................................. 85 PUMP FLANGE LEAKS ................................................................................................. 85 MOTOR OVERLOAD .................................................................................................... 85 VIBRATIONS OR ABNORMAL NOISES ................................................................................ 86
Help Is Here ............................................................................................. 86
Chapter 14: Appendix ............................................................. 89 Temperature Conversion Chart ..................................................................... 89 Mass Conversion Chart ................................................................................ 89 Velocity Conversion Chart ........................................................................... 89 Flow Conversion Chart ............................................................................... 90 Volume Conversion Chart ............................................................................ 90 Length and Distance Conversion Chart ............................................................ 91
Chapter 15: Glossary ............................................................... 93 Chapter 16: References ........................................................... 99 Chapter 17: Where It All Comes Together ................................... 101 Capabilities ........................................................................................... 101 TESTING AND DEVELOPMENT ............................................................................................ DESIGN ENGINEERING ..................................................................................................... MANUFACTURING .......................................................................................................... PRODUCTS ...................................................................................................................
101 101 102 102
History ................................................................................................. 103 Ownership ............................................................................................. 103 How To Contact GIW ................................................................................. 103 GIW INDUSTRIES ............................................................................................................ SERVICE CENTERS .......................................................................................................... GIW REGEN SERVICE CENTER ...................................................................................... ARROYO PROCESS EQUIPMENT INC. .............................................................................. FT. MCMURRAY SERVICE CENTER .................................................................................
104 104 104 104 104
What Is Slurry? • Slurry is a mixture of something solid and a liquid. • The solids in a slurry can be anything from gold to gravel, copper to coal, sand to cement. They can also be crystalline, sharp, flaky, fibrous or frothy. • Almost any solid can be transported hydraulically via a slurry pipeline using a slurry pump. • Clear water is the primary liquid for slurry transport, but other liquids such as acids, alcohol and light petroleum may be used. In the mining industry, slurry pumps are used to transport slurries. The production of fertilizer, for example, involves massive slurry transport operations. To make the fertilizer, phosphate matrix is recovered by draglines in open-pit mining operations. (Draglines are huge electrically powered excavating machines with buckets that hold as much as 150 tons.) The matrix is then slurried (mixed with water) and pumped to the wash plant through pipelines with a typical length of about six miles.
See Chapter 1.1 Applications of Slurry Transport in “Slurry Transport Using Centrifugal Pumps.”
Slurry Pumps vs. Water Pumps Slurry pumps can be massive and often have replaceable wear parts. They are usually much heavier and larger than clear water pumps sized for the same head and flow. Some of the reasons for their larger size are:
9
10
Slurry Pump Fundamentals
• Slurry pumps are constructed of special materials because of the abrasive nature of most slurries. These materials often require special bolting and assembly arrangements. • Slurry pump components are normally thicker than components for water pumps. • Slurry pump shafts and bearings are often larger than those on water pumps, because slurry Slurry pumps, like the one shown above, pumps handle various are usually much larger than water pumps. sizes and concentrations of solids. • Slurry pumps usually run slower than water pumps to help reduce parts wear. Water pumps account for the largest percentage of pumps installed in the process industry. For every five slurry pumps, 95 water pumps are in operation. The purchase and operating costs of a slurry pump are often many times that of a standard water pump. (Some industry experts put the operating costs of slurry pumps compared to those of water pumps at 80:20.) This is why the correct selection and application of your slurry pump is essential to your operation’s efficiency.
Flow Limitations The flow limitations for a slurry pump installation are from 35 - 132,000 gpm (8 - 30000 m3/hour).
Chapter 1: What Is Slurry?
These limits are determined by the pump’s ability to withstand the forces associated with operating the pump, such as pressure, vibration, axial thrust and the stability of the pump at various flows.
See Chapter 2.2 Basic Relations for Flow of Simple Fluids in “Slurry Transport Using Centrifugal Pumps.”
Solids Limitations Theoretically, there are no limits on what can be hydrotransported. In practice, however, the size and shape of the solids limit what can be pumped because of the risk of the solids blocking passage through the pump. The maximum particle size of material that can be transported in a slurry pump is approximately 12 in. (300 mm). However, sphere passage in large dredge pumps can be up to 18 in. (450 mm).
The solids transported in this dredging operation were as large as a hard hat.
See Chapter 2.4 Basic Relations for Slurry Flow in “Slurry Transport Using Centrifugal Pumps.”
11
12
Slurry Pump Fundamentals
Chapter 2: Slurry Pumps Defined
Chapter 2:
Slurry Pumps Defined A slurry pump is a type of centrifugal pump designed for transporting solids. It isn’t designed for pumping clear liquids. The less liquid that’s used in slurry pumping, the better. It doesn’t make sense to add additional fluids that will need to be removed later in the process. A centrifugal pump uses centrifugal force to impart velocity (speed) to a fluid or slurry. Centrifugal force pushes something outward when it’s spinning rapidly around a center. Consider a swing ride at the fair. As the rotational speed increases, the people in seats slide away from the center pole toward the swings’s outer edge. Another example? Centrifugal force causes water to be thrown from an automobile tire while it’s rotating. A centrifugal pump acts on the same principle, except the tire becomes an impeller and the vanes help move the water. However, the pump impeller doesn’t do all the work. It’s only part of the pump design. The medium being pumped must be controlled.
Centrifugal force pushes something outward when it’s spinning rapidly around a center.
13
14
Slurry Pump Fundamentals
The volute (pump shell) helps control the flow and transforms the velocity of the liquid into static pressure and controls the product being pumped.
Chapter 2: Slurry Pumps Defined
“Chapter 3: Slurry Pump Design & Components” covers the parts of a slurry pump in greater detail.
See Chapter 8: Centrifugal Pumps in “Slurry Transport Using Centrifugal Pumps.”
DRY Most horizontal slurry pumps are installed dry, where the drive and bearings are kept out of the slurry and the wet end is closed. The pumps are free standing and clear from any surrounding liquid.
Volute (Shell)
Vanes
Impeller
The volute or pump shell helps control the flow.
Markets & Applications for Slurry Pumps Market
Application
Mill Discharge
SAG Mill, Rod Mill, Ball Mill
Cyclone Feed
Primary, Secondary, Finishing Scalping
Dewatering Feed
Screen , Fine Screen, Magnetic Separator, Hydro Separator, Vibrating Screen or Shaker, Filter Feed
Tailings Pump
First Stage Pump, Booster Pump, Tailings Feed Pump, Flume Pump
Thickener
Underflow, Overflow, Thickener Feed
Dirty Water
Process, Process Return, Booster Transfer Pump
Dredge
Hydrotransport, Jetting, Booster Pump, Ladder Pump, Cyclone Feed, Wash Water Handling
Installations There are three types of installations: dry, semi dry and wet.
SEMI DRY A special arrangement can be used for dredging applications, where horizontal pumps are used with the pump wet end and bearings flooded and a dry drive. This requires special sealing arrangements for the pump bearings.
Wet End Part of the pump that gets wet from the pumping fluid. It includes the: • • • •
Shell Impeller Hub/Suction Liner Shaft Sleeve/ Stuffing Box
The sump pump has a flooded wet end installed at the end of a cantilever shaft (no submerged bearings) and a dry drive. WET A fully submersible pump and drive are necessary for certain slurry pump applications.
Wear Conditions The following slurry classifications are used in pump design selection to ensure good wear performance under a variety of working conditions and applications. These classifications are based on GIW’s proprietary selection program Slysel. This program is discussed in detail in “Chapter 10: Computerized Pump Selection.”
15
16
Slurry Pump Fundamentals
Chapter 3: Designs & Components
Chapter 3: CLASSIFICATIONS AND EXAMPLES
Classification
Example
Class 1: Mildly Abrasive
Thickener Overflow
Class 2: Slightly Abrasive
Screen Feed
Class 3: Significantly More Abrasive
Sand Plant Operation
Class 4: Highly Abrasive
Mill Discharge, Tar Sand Hydrotransport and Tailings
Slurry Pump Design & Components
Basic Designs The three basic slurry pump designs are horizontal, vertical and submersible.
Horizontal
Vertical
Basic Components The basic components of a slurry pump are the: • Impeller • Shell • Drive
• Suction plate/liner • Sealing arrangement • Bearing assembly
Submersible
17
18
Slurry Pump Fundamentals
Chapter 3: Designs & Components
The impeller, shell and suction liner are the key wet end wear components on all slurry pumps. The pump performance is determined by the design of these three parts. All other mechanical parts serve to seal, support and protect them.
Vane Designs The impeller vanes are the guts of the impeller. Vane design is critical to wear and hydraulic performance of the pump.
Bearing Assembly
Shell The shell derives its name from a spiral-shaped volute casing surrounding the pump impeller. One function of the shell is to pick up the flow coming from around the impeller, convert it into a desirable flow pattern and direct it to the pump discharge.
Impeller
Another function is to reduce the flow velocity and convert its kinetic energy to pressure energy.
The mathematical logarithm found in a seashell is used in all pump design.
Shell
Suction Plate/Liner
Impeller The impeller attaches to the pump shaft and imparts energy to the fluid being pumped. There are three types of impellers: closed, open and semi open. CLOSED IMPELLERS Closed impellers are preferred in slurry pump applications where high efficiencies are required.
Closed Impeller
SHELL TYPES Volute, semi circular and circular are shell types or casings. No matter which type shell is selected, there’s a trade off between wear and efficiency. The more volute the shell, the greater the efficiency and the wear. The more circular the shell, the less the wear and the efficiency.
Solid Shell
Split Shell
A volute casing is like a seashell. It’s a curved funnel. It reduces the speed of the liquid and increases the pressure. This is the most popular design today.
OPEN IMPELLERS Open impellers are slightly less efficient but are more effective for applications with a slurry that’s a mixture of a fluid, solid and gas such as froth pumping.
In the circular casing design, the impeller has a constant clearance between its outside diameter and casing.
Open Impeller
19
20
Slurry Pump Fundamentals
Chapter 3: Designs & Components
Split and Solid Shells
The shell of most hard metal pumps is one solid piece. A one-piece shell simplifies routine maintenance and is cost effective because of simpler sealing requirements. The shell must be split for rubber-lined pumps so that the lining and parts can be replaced as needed.
Shaft and Bearings SHAFT The shaft transmits torque from the drive to the impellers. BEARINGS Rolling element bearings are used to support the shaft and absorb axial thrust. Lubrication can be oil or grease. Oil lubrication allows for higher speeds.
Suction Liner Drives for Slurry Pumps
The suction liner is the part that has the highest wear, especially in the nose/face area.
There are three basic drive designs for slurry pumps: belt, gearbox and direct. Suction Liner
Shaft Seals
There are three shaft seal designs: stuffing box, mechanical seal and expeller. The basic function of a shaft seal is to separate rotating and non-rotating parts. STUFFING BOX This standard seal design uses a lantern ring and packing. MECHANICAL SEAL A mechanical seal is used when gland water isn’t available or can’t be added to the process or when external leakage and process dilution are undesirable.
BELT DRIVES Belt drives are used for both horizontal and vertical pumps, and include the motor, v–belt and sheaves. Belt drives allow for cost-effective speed changes by varying the diameter of the sheaves.
V-Belt Side-Mounted Drive
Expeller
Mechanical Seal Stuffing Box
EXPELLER The expeller is a secondary impeller positioned behind the main impeller. An expeller is used in applications where mechanical seals don’t work. Expellers are a more cost-effective option than mechanical seals.
GEARBOX DRIVES Gearbox drives are used for horizontal pumps. They are typically used on larger motors and pumps. A gear reducer can change the output speed from the motor to the pump. It’s most often used for 300 hp and larger motors. DIRECT DRIVES Direct drives are used for both horizontal and vertical pumps. This drive directly connects the motor to the pump shaft. Direct drives are the optimal selection when speed change isn’t necessary.
V-Belt Overhead Drive
Gearbox Drive
Direct Drive
21
22
Slurry Pump Fundamentals
Chapter 4: Wear Protection
Chapter 4:
Wear Protection
Wear Wear life is the most critical factor in the design of a slurry pump. Wear resistance is a key consideration for both hydraulic design and material selection.
See Chapter 10.2: Wear-Resistant Materials in “Slurry Transport Using Centrifugal Pumps.”
Corbrasion™ Corbrasion is GIW’s trademarked term for the combination of abrasion and corrosion that creates unique wear conditions in slurry pumps. Abrasion is wear produced by hard particles that are moving and forced against a solid surface. The particles producing the abrasion are harder than the surface they are hitting. The particles usually have sharp, angular edges. Corrosion is the loss of material caused by the interaction between the pump material and chemical products within the slurry.
Selection of Wear Materials The proper material selection helps combat the effects of Corbrasion. Material selection is based on: • Solid size • Slurry temperature • Impeller speed
• Solid shape • Slurry pH
• Solid hardness • Slurry chemical content
23
Slurry Pump Fundamentals
Chapter 4: Wear Protection
HARD METAL CONSTRUCTION Hard irons and steels, such as white cast irons and martensitic steels, are used most often in the construction of slurry pumps. White cast irons offer considerably higher wear resistance than steel.
steels would be destroyed by corrosive action. They are recommended for high boiling point liquids at elevated temperatures.
White Irons
Elastomers are available as urethane or natural rubber liners and impellers. Elastomer linings are usually specified when:
White iron is a cast iron that is free of graphite. Most of its carbon content is present in the form of hard carbides. GIW’s Gasite® white irons are: Grade
Gasite¨
Description
NiHard IV
4G, 6G
ASTM A532, Class I, Type D
Cr-Mo
18G, 20G
ASTM A532, Class II
High-Cr
27G, 28G
ASTM A532, Class III
Special
29G
Ultra-high strength/toughness
Special
T32G, 38G
Eutectic/hypereutectic grade
Special
OS34G
High wear with improved corrosion resistance (for some applications such as Oil Sands)
Special
30G
Regular corrosive-erosion grade
Special
40 G
Premium corrosive-erosion grade
Special
T90G
Super corrosive-erosion grade
Elastomer Construction
• • • • • • •
The solids are fine. The particles do not have sharp edges. The presence of tramp material is minimal. Oils, solvents or hydrocarbons aren’t present. The pH is less than 6.0. The head is below 131 feet (40 m). The temperature is below 150° F (65° C).
Ceramic Wear Parts Ceramic wear parts are used for highly abrasive slurries where parts are experiencing extreme wear. They are not suitable for high-impact and highpressure applications.
Corrosion Resistance and Wear Resistance T32G
White iron is usually preferred when: • • • • • •
The solids are greater than .25 inches (6 mm). The pH is greater than 4.5. Temperatures are to 250° F (120° C). The slurries are hydrocarbon based. The particles are coarse or sharp. Tramp material or debris may be present.
18G
38G OS34G
28G
Wear Resistance
24
4G/6G 29G
40G T90G High-Alloy Martensitic Steels
CD4MCU
81D
Steels
GIW’s steels are martensitic and heat-resistant grades (18CS, HH and HK). Steels are distinguished by their ability to serve where carbon and low-alloy
80D/35C
Ni-Resist 82D/83D
65D
SS316
Corrosion Resistance
This chart shows the relative corrosion and wear resistance of various alloys, which may vary because of the application and other factors.
25
Slurry Pump Fundamentals
Chapter 4: Wear Protection
Wear Resistance Range This chart shows the regular and possible wear resistance range for various alloys. Regular Wear Resistance Range Possible Wear Resistance Range
82D/83D 65D CD4MCu Marten. Steel Alloys
26
40G 29G 6G OS34G 18G T32G 0
20
40
60
80
100
120
140
160
Wear Resistance Index
pH Ranges This chart shows the relative pH range for various alloys. 4G 18G T32G 28G OS34G 40G T90G
0
1
2
3
4
5
6
7
8
pH
9
10 11 12 13 14 15
180
200
27
28
Slurry Pump Fundamentals
Chapter 5: Hydraulics
Chapter 5:
Hydraulics
Pumps and Curves Pump efficiency is determined principally by two parameters (head and flow) in addition to other factors such as properties of the fluid, impeller design and motor speed. An improperly applied pump with a high efficiency can be worn to total failure within just a few hours. A thorough knowledge of the duty is necessary to reduce wear on the pump. In fact, most pump problems arise because the pump’s performance characteristics don’t match the application requirements. This results in higher power consumption, and shorter bearing and wear life. The system parameters and pump performance must be matched carefully to ensure efficient, trouble-free operation. The easiest way to visualize this requirement is to consider two separate curves: a pump performance curve and a system curve. A pump performance curve is a graphical representation of the head (hydraulic pressure) produced by the pump for various flow rates at a given speed. The curve is always downward sloping, which means head decreases as flow rate increases. A system curve is a graphical representation of the head required for a given system at various flow rates. In slurries, the system curve is more complex and often resembles a “U” formation. PERFORMANCE CURVE A complete performance curve array includes: • A number of operating speeds with a constant impeller diameter
29
Slurry Pump Fundamentals
280
60%
70%
1100 rpm
Pump performance prediction is difficult. GIW has developed sophisticated computer models through years of experience and can predict performance before the pump is ever built. However, pump curves can be certified only by full-size performance testing in accordance with the Hydraulic Institute Standards in an approved laboratory.
75% 80%
82%
240
83% 83%
1000 rpm
82% 80% 78%
200 900 rpm
30 0
160
75%
hp 25
See Chapter 8: Centrifugal Pumps in “Slurry Transport Using Centrifugal
0 hp
800 rpm
0
20 hp
Pumps.”
0
16
120
hp
700 rpm
0
13 hp
50
500 rpm
25
40 400 rpm
0 1000
hp rpm 000 R at 1 NPSH
hp
500 NPSHR at
rpm
2000
3000
4000
5000
6000
7000
SYSTEM CURVE System curves represent graphically the energy (head) required to move slurry through a piping system (including process equipment) at various flow rates.
Gallons Per Minute
The curve data is based on A pump performance curve is a graphical representation of the head produced by the clear water, so curves must be pump at various flow rates. adjusted when pumping slurries. Your GIW representative or Slysel, GIW’s proprietary selection program, can assist you with these calculations and modifications.
Required energy is plotted on the vertical axis and given in terms of head. Capacity is plotted on the horizontal axis and is given in cubic meters per hour or gallons per minute.
At a given speed, slurry pumps can be operated at a variety of flow rates. However, only one specific flow rate achieves the maximum efficiency. This is called the Best Efficiency Point (BEP).
System curves for liquids are always upward sloping, whereas slurry system curves may be “U” shaped and difficult to predict. In most cases, slurry system curves can be determined only experimentally in a laboratory environment. Your GIW representative can assist you in getting an accurate system performance curve test in the GIW Hydraulic Laboratory.
The power to operate a pump can be calculated from the information presented on the performance curve using one of the following formulas: Metric P = H x Q x SG 367 x Eff H = Head in Meters Q = Capacity in Cubic Meters per Hour Eff = Efficiency in Percent SG = Specific Gravity of the Slurry P= Power in Kilowatts
U.S. BHP = H x Q x SG 3960 x Eff BHP = Brake Horsepower H = Head in Feet Q = Capacity in Gallons per Minute Eff = Efficiency in Percent SG = Specific Gravity of the Slurry
280
240
Total Dynamic Head
0
hp
hp
75
600 rpm
0
80
10
• Data about the head produced by the pump over a range of capacities • Power required to deliver a given flow and head • Efficiency ratio of energy transferred to energy required (power) for various flow rates • Net Positive Suction Head (NPSH) required. (See NPSH section in this chapter.)
Chapter 5: Hydraulics
Total Dynamic Head
30
200
160
120
80
40
0 0
1000
2000
3000
4000
5000
6000
7000
Gallons Per Minute
A system curve is a graphical representation of the head required for a given system at various flow rates.
31
Slurry Pump Fundamentals
280
60%
70%
1100 rpm
75% 80%
82%
240
83% 83%
1000 rpm
Vapor Pressure and Cavitation
82% 80% 78%
200 900 rpm
30 0
160
75%
hp 0
25 hp
800 rpm
If vapor pressure is reached, vapor bubbles form and follow the liquid into the impeller to areas with higher pressure. The vapor bubble then collapses or implodes in these areas. This creates extremely loud noises. These small implosions are called cavitation.
0
20 hp
0
16
120
hp
700 rpm
0 hp
40 400 rpm
50 25
hp
hp
hp
75
600 rpm
0
10
80
500 rpm
Head
If the suction pressure is too low, the pressure in the suction area decreases to the lowest possible pressure (the vapor pressure) of the pumped liquid.
13
THE INTERSECTION Pumps always operate at the point where the system curve intersects the pump performance curve. This point is called the duty point. It represents the capacity where the energy required to move the liquid through the piping system equals the energy transferred to the liquid by the pump.
Chapter 5: Hydraulics
Total Dynamic Head
32
hp R NPSH
m 00 rp at 10
500 rpm NPSHR at
0 7000 0 1000 2000 3000 4000 5000 6000 The Total Dynamic Head Gallons Per Minute (TDH) is the sum of kinetic and potential energy per unit of Pumps always operate at the point where the fluid transferred from the system curve intersects the pump curve. impeller vanes to the fluid. In pumping terminology, “head” is often used when referring to TDH. Head is usually expressed in meters or feet.
NET POSITIVE SUCTION HEAD (NPSH) Net Positive Suction Head (NPSH) is an important concept for judging the suction behavior of a centrifugal pump. A drop in the static pressure, particularly in the suction (inlet) area, occurs as the material flows across the pump impeller. The magnitude of this pressure decrease depends upon the: rotational speed, operating point, design of the impeller inlet, velocity and static pressure of the approaching flow and its density, and viscosity. The static pressure of the liquid must be above the vapor pressure inside the pump to avoid cavitation. This is achieved by having sufficient pressure on the suction side of the pump and a well-designed pump inlet.
CAVITATION Cavitation is more than air bubbles in the liquid. In most cases, cavitation is the liquid boiling at ambient temperatures because of the reduction in pressure. Cavitation should be suspected when:
Don’t operate a pump if cavitation is suspected. The problem must be corrected!
• Pump capacity is reduced. • The head produced by the pump is reduced. • Noise can be heard when the pump is running. • Pitting or other damage can be seen on the pump impeller and shell. Cavitation can be an issue when the operations are at a high altitude or when pumping liquids at a high temperature. These variables may not have been considered during pump selection. NPSHR All pumps require a value for NPSH. This value is called Net Positive Suction Head Required (NPSHR). NPSHR is not a calculated value. It is a property of the pump. All pump curves show the NPSHR for assorted flows and speeds. However, the criteria for NPSHR must be defined for your application. The criteria can be based on a head requirement for a given flow rate and speed. As NPSH is reduced, head remains constant for a time and then begins to drop off.
33
34
Slurry Pump Fundamentals
For slurry pumping systems, a head reduction up to five percent is usually acceptable. Therefore, the pump can be operated safely within these parameters, which must be predetermined. A similar process holds true for efficiency, but isn’t used as regularly as head. As NPSH is reduced, efficiency remains stable until the pressure reduction causes efficiency to drop. Too low of an NPSH can cause cavitation. NPSHA The complete pump system must provide the Net Positive Suction Head Available (NPSHA) to function properly without cavitation. NPSHA is a system characteristic and must be calculated. The value of NPSHA must always be greater than the NPSHR. The safety margin against cavitation is defined as NPSHA minus NPSHR. To calculate NPSHA, add all the pressure heads and then subtract all losses in the piping system on the suction side. NPSHA = Atmospheric pressure (converted to head) + static head + pressure head – the product’s vapor pressure – the friction loses in the suction piping, valves and fittings
Chapter 5: Hydraulics
See Chapter 8.3: Cavitation and Net Positive Suction Head or page 191, Net Positive Suction Head in “Slurry Transport Using Centrifugal Pumps.”
Pumping Froth The transfer of froths with a slurry pump is a special-purpose application. The large proportion of air in froth adversely affects the pump performance. The usual relationships for predicting the pump performance don’t hold true. The selection process also requires special considerations. Follow these steps when selecting a froth pump: 1. Oversize the pump. Oversizing the pump helps in handling froth by increasing the pump’s impeller eye diameter. This allows the pump to run at a lower speed. 2. Avoid pump throttling. The suction or inlet pipe must be at least the same size as the outlet pipe 3. Increase the sump height. Proper discharge orientation can assist in evacuating air from the pump.
CAUSES OF CAVITATION What causes cavitation? • • • •
The flow rate is too high for the given suction and speed. Atmospheric pressure is too low. The application is at a high altitude. The pump speed is too high for given suction and flow.
HOW TO FIND THE CAUSE To find the cause of cavitation: • • • •
Use gauges. Check pump speed. Check pump suction (inlet) for blockage. Refer to the pump performance curve.
35
36
Slurry Pump Fundamentals
Chapter 6: Slurry Pump Systems
Chapter 6:
Slurry Pump Systems
Overview Once the operating conditions have been selected, pump selection amounts to determining the specific performance of each available pump for the head and flow required and selecting the best pump suited for the duty. Pumps must be selected by matching their head/flow performance to the requirements of the piping systems as explained in Chapter 5. The largest energy savings are made through the design and control of the pump system. Unfortunately, pumps are too frequently oversized because of uncertainty over future plant expansion and system characteristics. Never overestimate the system resistance. Doing so results in a greater flow and a higher power consumption. You also risk overloading the motor and experiencing cavitation, high wear or gland problems. Always use the best estimate of system head. Add safety margins to the calculated power only.
Pipe Systems The pump provides flow and develops hydraulic pressure (head) to overcome the differential in head between two points in pumping systems. This total head differential consists of pressure head, static head, velocity head and total friction head produced by friction between the slurry and the pipe, bends and fittings. Use head instead of pressure to measure a centrifugal pump’s energy because the pressure from a pump changes if the specific gravity (weight) of the liquid changes, but the head won’t.
37
38
Slurry Pump Fundamentals
Chapter 6: Slurry Pump Systems
Head is measured in feet or meters and can be converted to common units for pressure as psi or bar.
The head of a pump in metric units can be expressed as: h = (p2 - p1) / ( g) + v22 / (2 g)
Types of Pump Head Total Dynamic Head
Total head when the pump is running.
Total Static Head
Total head when the pump isn't running.
Static Suction Head Static Suction Lift
Head on the suction side with pump off if the head is higher than the pump impeller. Head on the suction side with pump off if the head is lower than the pump impeller.
Static Discharge Head
Head on discharge side of pump with the pump off.
Dynamic Suction Head/Lift
Head on suction side of pump with pump on.
Dynamic Discharge Head
Head on discharge side of pump with pump on.
Pumps will pump all fluids to the same height if the shaft is turning at the same rpm. The only difference between the fluids is the amount of power it takes to get the shaft to the proper rpm. The higher the specific gravity of the fluid, the more power is required. The total friction head is the most difficult to determine because of the complex, nonlinear nature of the friction loss curve. This curve can be affected by many factors. A pump’s vertical discharge pressure head is the vertical lift in height. It’s usually measured in feet or meters of water at which a pump can no longer exert enough pressure to move water. If the discharge of a centrifugal pump is pointed straight up into the air, the fluid pumps to a certain height or head. This is called the shut off head. In the flow curve chart for a pump, the shut-off head is the point on the graph where the flow rate is zero. This maximum head is mainly determined by the outside diameter of the pump’s impeller and the speed of the rotating shaft. The head changes as the capacity of the pump is altered.
h = total head developed (m)(metric units) p2 = pressure at outlet (N/m2) p1 = pressure at inlet (N/m2) p = density (kg/m3) g = acceleration of gravity (9,81) m/s2) v2 = velocity at outlet (m/s) Pump flange conditions are unknown, so select one point on each side of the pump where you know the conditions and then allow for pipe work losses between these points and the flanges to determine the total head at the flanges.
Friction Losses The resistance to flow as a liquid moves through a pipe results in a loss of head and is called friction. STRAIGHT PIPES The friction loss in a straight pipe varies with: • • • •
Pipe diameter Pipe length Material (roughness) Flow rate (velocity)
Never oversize your pump by adding a safety factor to the head. Oversizing can result in unnecessary capital expense and untold start-up costs. Instead, apply the factor to the power required by the pump.
To determine friction loss: • Look it up in a table. • Extract it from a Moody diagram. • Calculate from a semi-empirical formula such as the William and Hazen Formula. • Use Slysel, GIW’s pump selection program. (See the end of this chapter for more information.)
39
40
Slurry Pump Fundamentals
Chapter 6: Slurry Pump Systems
FITTINGS When a system includes valves and fittings, an allowance for additional friction is necessary, because the fittings can add a significant amount to the total dynamic head that must be produced by the pump.
FRICTION LOSSES IN NON-SETTLING SLURRIES We highly recommend that you calculate the friction loss of non-settling slurries with the aid of computer software such as Slysel. Manual assessments can be difficult with all the associated variables.
Total Equivalent Length (TEL) is the most common method for calculating an allowance for additional friction. It can be used for liquids other than water. The fitting is treated as a length of straight pipe giving equivalent resistance to flow.
It is very important that all of the losses in a slurry system be calculated in the best way possible. This provides the correct head and capacity. It also enables the pump to balance the total system resistance and to operate at the correct duty point.
TEL = Straight pipe length + equivalent length of all pipe fittings SLURRY EFFECTS ON FRICTION LOSSES Friction losses are also impacted by slurries because they behave differently than clear water. Slurries must be classified as either settling or non-settling (viscous). As a rule of thumb, slurries with particle size < 50 micron are treated as non-settling. FRICTION LOSSES IN SETTLING SLURRIES The calculation of friction losses for settling slurries is very involved and best accomplished using computer software such as Slysel. For short runs of pipe at higher velocities, head loss can be taken as equal to the water loss. When calculating the pipe friction losses for slurry, allow for a certain increase when compared with the losses for clear water. Assume the suspension will behave like water for concentrations of around 15 percent by volume. At low velocities, head loss is difficult to predict and there is a real risk of solids settling out and blocking the pipe. The minimum velocity nomogram provides a safe minimum velocity. (A nomogram is a chart representing numerical relationships.)
See Chapter 5: Heterogeneous Slurry Flow in Horizontal Pipes in “Slurry Transport Using Centrifugal Pumps.”
Viscosity Pull the trigger on a water pistol and the water squirts out. Pull the trigger harder and the water squirts out faster. Fluids resist flow. This phenomenon is known as viscosity. Viscosity is a measure of the thickness of the liquid. Think of it as a slurry’s ability to flow. Molasses and motor oil are thick or high viscosity liquids. Gasoline and water are thin or low viscosity liquids. Viscosity discussions generally includes two types of liquid: Newtonian and non-Newtonian. NEWTONIAN AND NON-NEWTONIAN LIQUIDS Newton devised a simple model for fluid flow to demonstrate how hard you have to pull the trigger to how fast the liquid will squirt out of the pistol. Frederick A. Senese, an associate professor in the Department of Chemistry at Frostburg State University in Maryland, explains it this way on General Chemistry Online: Picture a flowing liquid as a series of layers of liquid sliding past each other. The resistance to flow arises because of the friction between these layers. If you want one layer to slide over another twice as fast as before, you’ll have to overcome a resisting force that’s twice as great, Newton said. The slower one layer slides over another, the less resistance there is, so if
41
42
Slurry Pump Fundamentals
there wasn’t a difference between the speeds the layers were moving, there would be no resistance. Fluids, like water and gasoline, behave according to Newton’s model and are called Newtonian fluids. But ketchup, blood, yogurt, gravy, pie fillings, mud and cornstarch paste don’t follow the model. They’re non-Newtonian fluids, because doubling the speed that the layers slide past each other doesn’t double the resisting force. It may less than double (like ketchup) or it may more than double (as in the case of gravy). That’s why gravy thickens as it’s stirred and why struggling in quicksand makes it harder to escape. For some fluids such as mud or snow, you can push and get no flow at all—until you push hard enough and the substance begins to flow like a normal liquid. This is what causes mud slides and avalanches. Two or more pumps can be operated in a Most high-concentration, fine series when required head can’t be reached particle slurries are nonwith a single pump. Newtonian and have plastic behavior. Plastic means that energy must be put into the slurry to start it to flow.
To establish friction losses or effects on pump performance for plastic slurries, the true plastic dynamic viscosity and the energy level (yield stress) for the float point must be verified. GIW can provide test work to verify these parameters.
Chapter 6: Slurry Pump Systems
OTHER NON-NEWTONIAN FLUIDS There are other fluids in which the shear stress is not linear with shear rate. Dilatant fluids, such as paper pulp, increase in viscosity with energy input. Pseudo-plastic fluids, such as mayonnaise or paint, decrease in viscosity with energy input.
Sump Arrangements Poor sump design is often the largest contributing factor to inadequate pump performance. Most pump malfunctioning can be attributed to the suction side of any pump installation. For best results include the following in the design: • Sump feed should be below the liquid surface to avoid air entrainment. This is especially important with frothy slurries. • Sump connection to the slurry pump should be as short as possible. A basic rule is five times the pump diameter in length and the same size as the pump inlet. • Suction pipe should never be smaller than the suction flange of the pumps and should be one size larger to accommodate settling velocity. • Drain connection should be included on the inlet pipe. Use a floor channel under the drain to recover the slurry. • A reinforced, flexible inlet connection is recommended for a possible vacuum condition. • Include a full bore shut off valve. Two or more pumps can be operated in parallel when required flow can’t be achieved with a single pump.
43
44
Slurry Pump Fundamentals
Chapter 7: Best Efficiency Point
Chapter 7: • Separate sumps are preferred for standby pump installations. This avoids settling in the standby pump sump when not in use.
Best Efficiency Point
Multiple Pump Installations Two reasons for using multiple installations of slurry pumps are: 1. When the head is too high for a single pump. 2. When the flow is too great for a single pump.
Optimal Efficiency PUMPS IN A SERIES When required head can’t be reached with a single pump, two or more pumps can be operated in a series. This application is used often to meet the high head required in long-distance tailings or to reduce the head of a singlestage pump in a demanding mill circuit application. Series operation allows a lower operating speed, which results in reduced wear.
The efficiency of the pump and its components is one of the factors that affects a pumping system’s performance, and optimizing a pumping system’s efficiency can result in up to a 60 percent reduction in energy and maintenance costs. But, in the real world, pumps are seldom operated at their Best Efficiency Point (BEP).
The discharge from the first-stage pump is connected directly to the second pump. This doubles the head produced. Two identical pumps in a series provide the same system efficiency as the individual pumps.
BEP, in technical terms, is the point where the brake horsepower going into the pump is the closest to the water horsepower coming out of the pump. It’s at this point where the pump has the least amount of shaft vibration and deflection.
PUMPS IN PARALLEL When required flow can’t be achieved with a single pump, two or more pumps can be operated in parallel. The discharge from both pumps is connected to the same line. Parallel pumps must be identical. Parallel pumping for slurry is uncommon.
Slysel Slysel, GIW’s proprietary pump selection program, is easy to use and aids in all aspects of pump selection. It’s free for GIW customers. Slysel: • • • • •
Calculates performance curves. Evaluates slurry and horizontal friction. Calculates overall pipeline system resistance. Selects or evaluates pumps. Evaluate operational factors.
Pump efficiency can decrease significantly when the pump operates away from the its BEP. Over-specifying the duty when selecting a pump increases energy costs. In this chapter, we look at reasons pumps don’t operate at BEP.
See Chapter 13, Practical Experience with Slurry Systems in “Slurry Transport Using Centrifugal Pumps.”
Radial Load The radial direction is 90 degrees or at a right angles to the centerline of the shaft.
45
46
Slurry Pump Fundamentals
The radial bearing supports the shaft from defection caused by impeller or drive loads. There are multiple causes of a radial deflection of the shaft, including: • • • •
A non-concentric shaft sleeve Pipe loads at the pump flange, either physical or thermal Operating off the BEP causes the shaft to deflect in a radial direction. Dynamic unbalance of the rotating assembly changes as the impeller wears. • The pump and driver are misaligned. The coupling may not compensate for this. • Vibration causes radial deflection. Vibration includes cavitation and water hammer. See Chapter 5 for information on cavitation. Water hammer is discussed at the end of this chapter.
Axial Load Axial movement is movement along the length of the shaft. The thrust bearing resists movement axially and transfers this force from the shaft to the housing. The pressures generated inside a centrifugal pump work on both the stationary and rotating components. On single-inlet impellers, an axial force exists because of differences in pressure on the front and back of the impeller and the difference in the areas subject to the pressure. Axial thrust is the sum of these unbalanced forces acting in an axial direction. Several ways to compensate for axial thrust are: • Install a double-row thrust bearing in the end of the casing next to the coupling. • Install a wear ring on the back of the impeller with holes drilled through the impeller to equalize some of the forces.
Chapter 7: Best Efficiency Point
• Use pump out vanes or radial ribs on the back of the impeller to reduce the pressure behind the impeller. • Use a hydraulic balancing device mounted in a chamber connected to the suction side of the pump or a low point in the system as some multi-stage pumps do.
Shaft Deflection A number of forces act on the shaft to cause it to deflect including: • • • •
Forces causing rotation (torque) of the shaft The weight of the parts Radial and axial hydraulic forces Vibration
The deflection can be along the length of the shaft (axial) or 90 degrees to the length of the shaft (radial). Here are suggestions to help reduce the deflection caused by operating off the BEP: • Go to a larger diameter shaft replacing the mechanical end with a larger unit. • A variable speed motor makes sense if the pump’s primary head is friction head. • Tell the operator to operate the pump at its BEP. (Good luck with that one!)
Water Hammer Water hammer is a destructive pressure surge that takes place in piping systems when the rate of flow changes suddenly. This is of greater significance in low head pumping systems than in high head systems. There are multiple causes for this change in rate of flow including:
47
48
Slurry Pump Fundamentals
• The power to the pump is lost for some reason and the pump slows down faster than the fluid flowing in the lines and liquid separation takes place. • Small pipe sizes can cause rapid velocity changes. • A valve closes rapidly in the suction line. • Surge tanks and air chambers can protect some piping systems from the affects of water hammer.
See Chapter 13, Section 13.6 Water Hammer in “Slurry Transport Using Centrifugal Pumps.”
Chapter 7: Best Efficiency Point
49
50
Slurry Pump Fundamentals
Chapter 8: Technical Descriptions
Chapter 8:
Technical Descriptions
A number of factors affect GIW’s slurry pump design including: • Certified performance by hydraulic testing in GIW’s Hydraulic Testing Laboratory, the largest lab of its kind in the world • Computer-generated, cutting-edge hydraulic designs for high efficiency and maximum wear life • Innovative wear materials, such as GIW Gasite® white iron, for longer parts wear life • Linatex® rubber liners, a superior wear product compared to any other natural rubber in today’s market • Special design features, such as a split stuffing box, to reduce maintenance down time • Designs with optional mechanical seal or expeller
Metal Pumps LCC HARD METAL SERIES (LCC-M) The LCC hard metal slurry pump is a horizontal, end suction, centrifugal slurry pump. The hydraulic wet end consists of three components: a shell or casing, an impeller and a suction plate/liner to permit easy removal for maintenance and inspections. The LCC-M slurry pump does not require a separate outer housing.
LCC Hard Metal Series pumps are suitable for high discharge head, mildly corrosive slurries and a wide range of particle sizes.
51
52
Slurry Pump Fundamentals
Chapter 8: Technical Descriptions
Features
• A horizontal shaft • A single-wall shell • A three-vane impeller and a suction plate/liner of high-chrome white iron for long, predictable wear life
• The standard fused carbide-coated shaft sleeve provides a smooth, extremely hard surface for long packing life. Optional sleeve materials are available. Application
The pumps are suitable for high discharge head, mildly corrosive slurries and a wide range of particle sizes. Custom materials are available for highly corrosive slurries.
LSA-S slurry pumps are widely used in ore transport, mill discharge, cyclone feed, tailings and plant process. The LSA can also be found in environmental cleanup, dewatering (low head type), pulp and paper (liquor transfer), food processing (sugar and sugar beets), coke and resin pumping and ash handling.
Size Range
Size Range
Application
• • • • •
Discharge diameters: 2 - 12 in. (50 - 300 mm) Flows to 17,000 gpm (3865 m3/h) Total head to 300 ft. (90 m) Capabilities to 700 hp (520 kW) Shaft sizes from 1.5 - 5 in. (35 - 125 mm)
LSA-S SERIES Pumps in the highly efficient LSAS Series are primarily for heavyduty service in a wide variety of slurry applications. The pump’s rugged design and wet end parts are made from proprietary GIW Gasite® material, which is recognized worldwide for superior abrasion resistance and excellent performance. Optional impeller designs can fine tune pump performance to meet your specific system needs.
• Discharge diameters: 2 - 26 in. (50 - 600 mm) • Flows: 100 - 60,000 gpm (22 - 13600 m3/h) (Contact GIW for higher flow needs.) • Total head to 300 ft./stage (91 m) • Capabilities to 2,500 hp (1862kW) • Special high-pressure design up to 900 psi (62 bar) test available
Rubber Pumps LCC RUBBER-LINED SERIES (LCC-R) The LCC pump design incorporates state-of-the-art hydraulic design and wear materials for heavy-duty applications. LCC pumps provide a low total cost of ownership.
LSA-S slurry pumps are widely used in ore transport, mill discharge, cyclone feed, tailings and plant process.
Features
• The heavy-duty, split-cartridge bearing assembly with spherical roller radial bearings and steep angle, self-aligning thrust bearing ensures maximum efficiency and minimum shaft deflection.
The series offer two pedestal sizes, which cover the entire range of seven wet end sizes to maximize system flexibility and reduce inventory. Interchangeable rubber and metal designs enable you to make the best material choice for any application. Easy wet end change can adapt existing pumps to new applications. LCC’s are available with either oil or grease lubrication.
LCC-R slurry pumps are suitable for moderate discharge head, fine particles and highly corrosive slurries.
53
54
Slurry Pump Fundamentals
Chapter 8: Technical Descriptions
Features
• The LCC Rubber-Lined Series features a split casing design with molded, replaceable rubber liners. • The LCC rubber pump is fitted with a Linatex® rubber liner. Linatex is a superior wear product compared to any other natural rubber in today’s market. • Liners may be specified in a variety of natural and synthetic rubbers to meet specific slurry applications • The liners are vulcanized to metal backing plates and captured at the split casing, suction discharge flanges and stuffing box area to maintain hydraulic and hydrostatic integrity. Application
LCC-R slurry pumps are suitable for moderate discharge head, fine particles and highly corrosive slurries.
• LSR pumps are lined with Linatex® rubber, a superior wear product compared to any other natural rubber in today’s market. • The LSR holds its original operating efficiency rating longer than any of its competitors. Application
Designed for heavy-duty mill circuit and fine grind slurries. Size Range
• • • •
Discharge diameters: 6 - 26 in. (150 - 650 mm) Flows to 40,000 gpm (9000 m3/h) Total head to 200 ft. (60 m) Shaft sizes: 5 - 6 in. (125 - 175 mm)
Vertical Pumps
Size Range
• • • • •
Discharge diameters: 2 - 12 in. (50 - 300 mm) Flows to 17,000 gpm (3865 m3/h) Total head to 300 ft. (90 m) Capabilities to 700 hp (520 kW) Shaft sizes: 1.5 - 5 in. (35 - 125 mm)
LSR With the addition of the LSR, GIW now offers a solution for all of your slurry pumping needs. The LSR is built to operate at the lowest total cost of ownership with its superior hydraulic design.
Features
• Wear components are available in a wide range of proprietary hard iron alloys along with rubber and urethane casing The LCV Series is ideal for liners to meet any application. industrial process pumping, tailings disposal in mining • The v-belt drive system accepts high and pit use for dredge and horsepower motors and the structural other operations. parts can be ordered in corrosion resistant alloys. • Performance and efficiency, plus easy maintenance, provide the best value with a GIW vertical slurry pump.
Features
• Double-wall construction with an outer ductile iron casing and inner molded rubber liners • Three-vane impellers cast of hard metal or polyurethane
VERTICAL GIW heavy-duty vertical pumps are the answer for the most aggressive corrosive and abrasive slurry applications. These rugged pumps combine long wear life with high sustainable hydraulic efficiency for the lowest total cost of ownership.
The LSR is designed for heavy-duty mill circuit and fine grind slurries.
55
56
Slurry Pump Fundamentals
Applications
The LCV Series is ideal for industrial process pumping, tailings disposal in mining and pit use for dredge and other operations. Size Range
• • • • •
Discharge sizes: 2 - 12 in. (50 - 300 mm) Flows to 6000 gpm (1360 m3/h) Total head up to 125 ft. (38 m) Shaft sizes: 3.5 - 8 in. (90 - 200 mm) Cantilevers: 35 - 71 in. (900 - 1800 mm)
Chapter 8: Technical Descriptions
• Total head to 260 ft. (80 m) • Capabilities up to 4,000 hp (2980 kW) • Hydrostatic tested up to 600 psi TBC These pumps are constructed as horizontal, end suction centrifugal pumps to give maximum resistance to wear while simplifying maintenance. The conventional single-wall design transfers stress loads to non-wearing side plates in high-pressure applications. Features
High-Pressure, Multi-Stage Slurry pumps WBC The patented design of the WBC slurry pump incorporates state-of-the art hydraulic wear technologies for severe-duty, high-pressure applications. The pump shell is designed to reduce bending movements and associated stresses that can cause a structural failure during a pressure surge. Features
• • • •
The shell, impeller and suction liner are made of GIW Gasite® alloys, which are recognized for superior abrasion resistance. Three-vane impellers offer maximum particle size passage. The pump is equipped with GIW’s proven heavy-duty mechanical end with spherical roller radial bearings and separate steep-angle thrust bearing. The standard fused carbide-coated shaft provides a smooth, extremely hard surface for long packing life. Optional sleeve materials are available.
Applications
Primary services are in ore and tailings transport lines subject to sudden pressure spikes. Size Range
• Discharge diameter: 18 - 26 in. (460 - 660 mm) • Impeller diameters: 46 - 54 in. (1168 - 1372 mm) • Flows to 60,000 gpm (13600 m3/h )
• Impeller and casing hydraulics are designed with proprietary GIW computer programs for high efficiency, maximum suction performance and large solids passage. • Standard bearing assemblies feature an integrated Bearing Isolator System. Designed by GIW, it consists of a labyrinth seal machined into the end cover and covered with an elastomer v-ring and metal flinger. This double seal excludes contaminants. • Forward flush stuffing box comes standard on TBCs. • Oil lubrication is standard. GIW’s Blue 150 synthetic oil is included for the initial fill. • Optional oil recirculation and powered coolers are available options for large units. Applications
TBC pumps feature high head and high flow rates for dredging, pipeline booster stations and other severe duties. TBC pumps feature high head and high flow rates for dredging, pipeline booster stations and other severe duties.
57
58
Slurry Pump Fundamentals
Size Range
• • • •
Discharge diameters: 12 - 44 in. (305 - 1118 mm) Flows: 5,000 - 140,000 gpm (1136 - 31900 m3/h) Total head to 300 ft.+/stage (91 m) Capabilities beyond 12,000 hp (8940 kW)
Visit www.giwindustries.com or call your local GIW representative.
Chapter 8: Technical Descriptions
59
60
Slurry Pump Fundamentals
Chapter 9: Application Guides
Chapter 9:
Application Guide
Selection by Duty Slurry pumps are often selected based on the duty or the type of slurry being pumped. A thorough knowledge of the application is needed to select the right pump for the application and to reduce wear on the pump. When selecting by duty, consider the: • Size, shape and density of the solids being pumped • Head requirements • Type of liquid Use the following guidelines when selecting your pump by duty:
COARSE PARTICLES • Any solid larger than 12 in. (300 mm) • Metal pumps (Never use rubber.) • Upper limit solid size is 2 in. (50 mm). • The impact on the impeller is the limitation. Recommendation: LSA, WBC, TBC
FINE PARTICLES • Use rubber for sharp particles. • If particles are not sharp, rubber or metal is fine. Recommendation: All series
61
62
Slurry Pump Fundamentals
SHARP (ABRASIVE) PARTICLES • Use rubber for sizes below .20 in. (5 mm). • Use metal for sizes above .20 in. (5 mm). Recommendation: All series
HIGH PERCENT SOLIDS • Solids percentage must be below 50 percent by volume. Recommendation: All series
LOW PERCENT SOLIDS • Light-duty pump, high-efficient pump Recommendation: LCC, LCV
FIBROUS PARTICLES • Problem with particle and air blocking Recommendation: LCC or LSA with open shroud impeller
Chapter 9: Application Guides
HIGH SUCTION LIFT • Metal pumps are preferred, because of the risk of a rubber lining collapse on high suction lifts. • Maximum practical suction lift 10 - 12 ft. (3 – 3.5 m), depending on specific gravity • Priming device required. • Pump and inlet pipe must be filled with liquid before starting up the pump. Recommendation: All series
HIGH FLOW • Use parallel pumps installations. (See “Chapter 6, Slurry Pump Systems.”) • Increased cavitation risk Recommendation: All series
LOW FLOW • Use metal to avoid overheating rubber linings. Recommendation: LHD
Duties Related to Head and Volume HIGH • • •
HEAD High speed/high wear Maximum head on metal pump 410 ft. (125 m) Maximum head on rubber impeller 148 ft. (45 m) Recommendation: All series
VARYING HEAD AT CONSTANT FLOW • Use a multi-speed drive or variable drive. Recommendation: All series
VARYING FLOW AT CONSTANT HEAD • Use variable drives. Recommendation: All series
FLUCTUATING FLOW • Use horizontal pumps with variable speed drive or fixed speed vertical pumps. Recommendation: All series
Duties Related to Slurry Type FRAGILE SLURRIES • Both metal and rubber pumps can be used. • Both horizontal and vertical pumps can be used. Recommendation: All series
63
64
Slurry Pump Fundamentals
HYDROCARBON SLURRIES (OIL AND REAGENTS CONTAMINATED) • Cannot use natural rubber. • Use synthetic seals. • Use metal pumps. Recommendation: All series
Chapter 9: Application Guides
Selection by Industrial Application This general guide is provided for reference only. It contains some common slurry pump industrial applications served by GIW slurry pumps. This is a schematic of phosphate mining, a common slurry pump application.
HIGH TEMPERATURES ABOVE 212˚F (100˚C) SLURRIES • Cannot use natural rubber. • Operating limit is 275 F (135 C). Above this, bearings can overheat. Recommendation: All series
HAZARDOUS SLURRIES • Shaft sealing is critical. • Usually a closed pump system Recommendation: Horizontal series with mechanical seals
CORROSIVE SLURRIES (LOW PH) • Use Gasite® T90G. Recommendation: LCC, LSA
HIGH VISCOSITY FLUIDS (NEWTONIAN) • Pumping is critical if the viscosity is over five times the viscosity of water. Recommendation: All series
HIGH VISCOSITY FLUIDS (NON-NEWTONIAN) • Pump selection is difficult. Please consult your GIW representative.
HARD • • • • • • • •
ROCK MINING Grinding circuit pumps Floor sump pumps Tailings pumps Cyclone feed pumps Tailings pumps Thickener overflow pumps Screen discharge pumps Ball mill discharge pumps
LHD pump for tailings operation
65
66
Slurry Pump Fundamentals
Chapter 10: Computerized Pump Selection
Chapter 10:
Computerized Pump Selection
OIL SANDS • Hydrotransport pumps • Tailings transfer pumps • Cyclone feed pumps • Floatation froth pumps PHOSPHATE • Matrix pit pumps • Tailings feed pumps • Clay pumps FGD • • • • • •
TBC pump in oil sands
Most misapplications and problems in slurry pumping systems arise because the key to their successful installation and operation is overlooked.
Absorber recirculation pumps Slurry bleed pumps Additive feed pumps Spray recycle pumps Prescrubber recycle pumps Sump pumps
INDUSTRIAL PROCESS • Wash water pumps (sand & gravel) • Sand transportation pumps • Tunnel dewatering pumps • Drainage pumps • Dredge pumps
The key lies in understanding the relationship between the system and the pump. The two must be matched carefully to ensure efficient, trouble-free operation.
Pit pump in phosphate
Slysel, GIW’s proprietary pump selection program, allows a sales representative to calculate the system and pump curves, chart their intersection and select just the right pump for your slurry system.
Slysel How Slysel can help:
…And virtually any hydrotransport application you can think of.
• The Slysel program for personal computers helps design Newtonian liquid, settling slurry and non-settling slurry pipelines.
LSA pump in dredge
• A specific pump or series of pumps can be evaluated at desired operating conditions. • The software selects the pump that delivers the maximum efficiency for the pipeline system specified and plots the system curve and selected pump curve. Other pump and slurry characteristics are calculated and displayed.
67
68
Slurry Pump Fundamentals
Chapter 11: General Maintenance
Chapter 11: Slysel is available to GIW customers only. Slysel’s pump file contains information on over 2,500 centrifugal slurry pumps. Branch diameters vary from 2 inches (51 mm) to 44 inches (118 mm). The tested water performance for the pumps on file may be modified automatically for slurry solids effect using algorithms based on tests run in the GIW Hydraulic Testing Laboratory.
General Maintenance
Maintenance SOFTWARE AND HARDWARE REQUIREMENTS • Windows 98, ME, NT, 2000 or XP • X86 processor or better • CD-ROM drive ORDER INFORMATION To order Slysel: • E-mail
[email protected]. • Call our Order Entry Department at 706.863.1011. • Fax requests to 706.855.5151, Attention: Order Entry Department.
A pumping system’s reliability is of critical concern, but pumps are often poorly maintained and aren’t given attention until they start causing problems or stop working altogether. Maintenance practices, at their simplest level, include a periodic walk around a site, listening to and feeling for unusual vibration from pumps to identify which pumps are starting to wear. At an advanced level, they include monitoring and recording vibration using sensors and alignment with conventional techniques or laser.
An unmaintained pump can fail
catastrophically.
Whether simple or advanced, good maintenance practices reduce the deterioration in efficiency and improve the reliability of pumps. (Without maintenance, a pump can eventually lose about up to 15 percent of its original efficiency.) RECOMMENDED MAINTENANCE SCHEDULE Establish a maintenance schedule based on your application and internal procedures. Use the following as a guide only:
69
70
Slurry Pump Fundamentals
DAILY
Chapter 11: General Maintenance
Impeller Removal Keep consistent, accurate records. Re-adjust the impeller of a new pump after the first day of operation. Check the oil level when the pump isn’t operating. Check the bearings for sudden temperature changes. Check the stuffing box operation and make necessary adjustments. Regularly monitor pressure gauges, flow indicators, recording instruments and ammeters. Check the pump immediately if its normal running sound changes. Check for leakage from weep holes in the pump casing that indicate liners need to be replaced. Gland service pressure can sometimes indicate if pipes are blocked or if the stuffing box needs attention. Check the v-belt drive for correct operation. New belts require retensioning after the first few days because they stretch.
WEEKLY Re-adjust the impeller until the optimum amount of time required is determined. Highly abrasive applications may require weekly adjustments while lighter duty applications need less. Record gauge readings.
• Use proper removal techniques. • Install a break loose jig or use drop arm. • Do not reverse the motor. This can force impeller into the casing and damage pump. • Use anti-seize on plug threads, but not on hub face, when installing Putting a new impeller on worn the impeller. threads results in rapid failure and • Use two release gaskets between damage to other wet end parts. hub and sleeve for proper sealing. • Inspect plug threads. • Make sure mating parts are suitable during rebuilds. • Never use heat to remove an impeller. Moisture and air trapped inside can expand and explode. GIW Impeller Lift Jigs are available from Part Sales and are built to order for all standard and custom pumps.
If the threads on the shaft
QUARTERLY look like this, the shaft Drain and refill oil. should be scrapped. Adjust v-belt tension and check for signs of wear. Clean the pulley grooves and v-belts. Clean and oil studs and threads on motor base and gland where applicable. Repack the stuffing box and check for wear. SEMI-ANNUALLY Thoroughly inspect the pump. Clean bearings and bearing housings and refill with fresh oil. Check drains and sealing water piping and flush. Check pump and motor alignment.
Impeller Lifting Jigs are finished in bright safety yellow paint. They’re CAD designed according to ASME B30.20 with welded steel plate construction. Multiple lifting points and a threaded leveler align the impeller for easy installation. Each lift jig is marked with the Working Load Limit and GIW part number for fast identification. Impeller part numbers and pump serial numbers are required to select the correct lift jig for each application. Impeller Lifting Jig
IMPELLER BALANCING All GIW impellers and expeller rotors are balanced at the factory. The standard is ISO 1940, “The Balance of Rotating, Rigid Bodies.” Grade G25 is used based on the slower speed and more rugged frames of slurry pumps. The majority of slurry service can use single plane static balance methods.
71
72
Slurry Pump Fundamentals
Fastener Torque • • • • • • • •
Torque is the most important part of assembly. “As tight as the gun gets it” is not the correct torque. Use the correct bolt grade and torque chart. Force on the wrench, thread pitch and lubrication produce clamp load at the joint. 85 - 95 percent of the force applied is used to overcome friction. Incorrect clamp load can cause leaks and vibration, or allow bearing housing to move. Never reuse fasteners in critical applications such as impeller release rings. Manual, air and hydraulic torque wrenches and impact guns need to be checked and calibrated frequently.
TORQUE ACCURACY Torque Charts
Torque charts show values for different thread diameter, pitch and lubricants. • • • • •
70 percent yield value is typical. Anti-seize requires less torque than oil. Moly lube is not recommended. Never use “dry” in assembly or value. Use anti-seize on stainless steel fasteners or threads will be damaged.
Mechanical Seals Mechanical seals are selected based on shaft diameter and duty conditions. • • • •
Installation and adjustment are critical. Seal faces must be 100 percent clean. Mechanical seals must never be run dry. They require a minimum axial and radial shaft deflection (Limited End Float CBA). • Refer to manufacturer’s instructions.
Chapter 11: General Maintenance
Bearing Temperatures Depending on the application, normal operating temperatures in pumps range from 100 - 180 F (38 - 82 C) with most running between 140 - 160 F (60 - 71 C). Although grease is used in some pumps, oil is the preferred lubricant in the majority of pump applications. Standard bearing oils remain effective to approximately 180 F (82 C). If normal operating temperatures are higher, synthetic oil should be used. If temperatures exceed 200 F (93 C), a circulating oil system is recommended. Higher than normal operating temperatures in pumps can be caused by excess oil level or too much grease. Overheating can also be caused by bearing or drive misalignment, hot process fluids and elevated ambient temperature. Bearings normally run Whether simple or advanced, good maintenance slightly hotter during the practices reduce the deterioration in efficiency initial break in period. This and improve the reliability of pumps. varies depending on pump size and speed. Bearing temperatures in pumps, especially those in critical applications, should be monitored regularly.
73
74
Slurry Pump Fundamentals
LUBRICATION – OIL OR GREASE? Bearing lubrication is one of the most critical aspects of pump operation, and the type of lubricant selected impacts routine maintenance requirements. Small pumps with light loads can be operated on grease, while heavy-duty units require oil. The GIW LCC Series was designed to use either lubricant. Grease fittings and a retainer ring in the housing keep the grease near the bearing rollers. Oil-filled units have internal grooves to help circulate the oil plus a sight gauge and temperature gauge. The larger GIW LSA bearing assemblies are designed for use only with oil. GIW recommends the GIW Blue Synthetic Oil for use in all pump sizes and all manufacturers. This offers lower operating temperatures, better protection and extended change intervals. GIW’s heavy-duty units are available with the optional recirculation kit to lower temperature by reducing the volume of oil in contact with the bearings while returning hot oil to the center of the housing for heat dissipation. Oil lubrication is selected for a number of reasons: Bearing Suppliers – Most major bearing manufacturers state that spherical roller thrust bearings should be oil lubricated. Grease lubrication can be used in special cases, for example, under light loads and at low speeds. The thrust loads in slurry applications can be very significant and cavitation must be considered. In addition, bearing speeds are lowered when using grease. Maintenance – Oil-filled units do not require frequent relubrication. Draining the oil at change intervals removes contaminants and provides a visual indication of potential wear problems. Contamination – Oil tends to wash through the bearings and carry the contaminants into the reservoir, while grease holds dirt close to the rolling elements.
Chapter 11: General Maintenance
Temperature – The oil helps carry the heat from the bearing into the casing where it can be dissipated. Lubrication – In pump applications, it’s difficult to keep grease in contact with the rolling elements in adequate quantity to replenish the oil film without a continuous supply.
The key to long bearing life is using the correct amount of a top-grade lubricant with the right properties along with a strict maintenance schedule. CAUSES OF BEARING FAILURES Contamination causes most premature bearing failures. This can be the result of excessive wear, abnormal surface stresses caused by debris or corrosion from water or slurry contamination. Poor lubrication practices or wrong bearing selections cause about one third of premature bearing failures. Any bearing deprived of proper lubrication will fail long before its normal service life. Failure can be the result of using the wrong lubricant type, mixing lubricants, improper relubrication quantity or maintenance, and improper additives. Fatigue accounts for 34 percent of early bearing failures. Whenever machines are overloaded, unbalanced or misaligned, bearings suffer the consequences. These abnormal conditions cause unintended loads on the bearing that can quickly add up to a dramatic reduction in service life. Premature failures from fatigue may appear to be the result of lubrication problems. Poor installation causes about 16 percent of all premature bearing failures. Service personnel need to be aware of which tools to use and trained in using them. For example, a bearing may require mechanical, hydraulic or heat application methods for correct mounting or dismounting. Using the wrong method can damage the bearing and shaft.
75
76
Slurry Pump Fundamentals
Chapter 11: General Maintenance
Monitoring bearing conditions using predictive or condition monitoring techniques can detect problems before failure occurs. A thorough analysis and corrective action can often be applied before catastrophic failure, pump damage or production losses occur, saving the customer time and money.
Occasionally, oil leaks out of the seal. The most typical causes are worn or missing v-rings and incorrectly adjusted flingers. An overfilled oil level or incorrect lubricant could also allow some oil to migrate past the seal. Correcting these conditions normally eliminates the leakage.
Vents and Breathers
GIW eliminated the use of vents for the majority of pump bearing assemblies. Unless the unit is equipped with a breather from the factory, you don’t need to install one. Breathers generally create more problems than they solve.
During operation, all powered equipment generates heat. This expands the lubricant and air inside the housing which creates a positive internal pressure. In most industrial machinery this escapes out through a vent or breather device to the atmosphere. As the unit cools, the oil/air volume contracts and outside air is drawn back into the housing. This process is repeated for each start/stop cycle. Eventually enough airborne moisture is drawn in and condensation can actually form on internal components. This can create rust on shaft and bearing surfaces while the pump is idle. In most slurry applications, the atmosphere surrounding the pump is generally one of high humidity and contamination generated by stuffing box flow, plant processes and the area environment. This can migrate past the vent and contaminate the inside of the bearing assembly. It only takes a small amount of water to reduce dramatically the lubricating property of the oil. By using a labyrinth seal design at each end of the shaft, GIW eliminated the need for an external vent or breather. Lab testing indicated that the internal pressure rise is small and is normally equalized by bleeding out past the vring seal. After the pump is stopped, the cooling cycle is very slow and results in a slight vacuum inside the housing. This pulls the v-rings against the end cover to further prevent contamination from spray or wash down. When the pump resumes operation, the internal pressure simply normalizes. Where Inpro® seals are used, this internal pressure can escape between the stator and rotor while the pump is running. The use of synthetic oil such as GIW Blue 150 reduces the overall temperature of the unit, thus lowering the internal pressure change. This type of oil is also more tolerant of normal contamination and provides longer maintenance intervals.
77
78
Slurry Pump Fundamentals
Chapter 12: Total Cost of Ownership
Chapter 12:
Total Cost of Ownership
Buying a slurry pump is similar to purchasing a car: buyers who consider the sticker price alone may be in for a shock down the road. Once your pump is operating, several expenditures must be considered: • • • •
Power bills Cost of replacement parts Downtime costs Capital expenditures
Those expenditures comprise the Total Cost of Ownership (TCO). TCO is the total yearly cost of the pump and driver including capital, power expenses, price of replacement parts and downtime costs evaluated over five years. In the past, buyers didn’t consider TCO when making their selections. They considered only the lowest purchase price and perceived benefits described by the salesperson. We know now that the initial price of a pump is typically less than 15 percent of the total cost of ownership, and over a 20-year period, the combined energy and maintenance costs may exceed 10 times the initial pump purchase price.
Importance of making Smart Pump Purchases It’s important to make a smart pump purchase because: • • • •
Energy costs are rising daily. Capital budgets are being reduced. Profitability must be maximized. Productivity must be increased.
79
80
Slurry Pump Fundamentals
Chapter 12: Total Cost of Ownership
How GIW Can Help GIW developed proven tools to help customers select the type, size and operating speed that deliver the best TCO. GIW conducted TCO studies on many pumps in different applications. These findings show that the purchase price of a pump can be offset quickly by common operating factors: • • • •
Energy consumption Wear life Replacement part cost Downtime
numerically models slurry velocities within the shell. This predicts the wear around the hydraulic path inside the shell at the defined conditions. This powerful program is used extensively during GIW research and design work to test various pump shapes and determine the optimum geometry for a particular service. Recently, GIW expanded this program to include the impeller and suction liner. Tools are available to model the wear of the entire wet end. These tools allow GIW to recommend the combination of parts that provide the best overall wear at the lowest TCO.
Predicting Wear
Calculating Energy Costs
Predicting wet end wear life expenses used to be difficult. As a general rule, users followed the 3-2-1 rule: “Three suction liners and two impellers are normally replaced during the life of one shell.” Of course, this rule varies with operating conditions, maintenance procedures and the contents of the actual slurry.
Most pump manufacturers can estimate energy costs. GIW takes this one step further by actually testing pumps with different slurries in our Hydraulic Test Lab. From these tests and computer models, customers can know how much power will be required for a specific set of operating conditions.
Read the July 2002 article, “Wear and the Total Cost of Ownership of Slurry Pumps,” by Anders Sellgren, Graeme Addie and Krishnan Pagalthivarthi.
Working with Dr. Mihail C. Roco, senior advisor for Nanotechnology National Science Foundation, GIW developed the industry’s first computer program to predict wear in pump casings and shells accurately. Using operating parameters including flow rate, concentration, size of solids and specific gravity, the program
GIW’s Hydraulic Testing Laboratory is the largest lab of its kind in the world.
81
82
Slurry Pump Fundamentals
Chapter 13: Troubleshooting
Chapter 13:
Troubleshooting
Why Isn’t My Pump Pumping? More than 80 percent of all pumping problems are problems with the system—not the pump. System problems are typically related to the suction side of the installation. Mechanical problems such as overheating of the bearings, noise or vibration are easily detected. System problems are sometimes complex and are often incorrectly attributed to the pump.
Warnings Excessive Pump Discharge Pressure
• Pump may be running too fast. Excessive Leakage at Shaft Seal
• Cavitation/vibration (For more information on cavitation, see “Chapter 4: Wear Protection.”) • Packing, lantern ring • Worn shaft sleeve • Pressure • Seal water Pump Delivers Insufficient Flow Rate
• Verify that the pump is correct for the head and flow system parameters. The pump curve can be used to determine the output, power and speed.
83
84
Slurry Pump Fundamentals
• Depending on the age and service of the pump, parts could be worn sufficiently to reduce performance. • Verify that the motor has the correct power and voltage required for the system and is operating properly. • Verify that the pump is running at the correct speed. • Verify that the suction side has adequate Net Positive Suction Head (NPSH) available from the system. • Check the suction pipe for air pockets, leaks, partially closed valves or other restrictions. • Be certain that the suction inlet and impeller are not clogged. • Verify that the discharge valve is fully open. Increase in Bearing Temperature
• During the initial break in period, the bearings normally run hotter. • Excess temperature may be attributed to hot process fluid. • Verify correct oil level. Overfilling causes viscous drag, which builds heat. • Verify oil viscosity. High viscosity and mineral oils cause drag and build heat, especially at higher speeds. • Misalignment of the motor or coupling can create excess bearing load and increased heat. • Insufficient coupling clearance between the pump shaft and motor shaft can add axial loads to the thrust bearings. • External pipe forces can distort the pump and bind the bearings. • Worn or damaged bearings may generate excess heat before failure. • Drag from external parts such as coupling guards can increase bearing temperature. Bearing Contamination
• • • • •
Flinger missing or incorrectly installed V-ring seal damaged or missing Excess leakage at stuffing box Damaged bearing isolator Improper maintenance
High Temperature or Leakage at the Stuffing Box
• High temperature caused by packing that’s adjusted too tightly. • High temperature caused by hot process fluid. • Leaking caused by excess flush pressure.
Chapter 13: Troubleshooting
• Leaking caused by a wrong adjustment. • Leaking caused by worn parts. • Excess wear of packing or sleeve: • Adjusting the packing too tightly • Insufficient flush flow or pressure • Contaminated flush water • Poor quality packing • Failure to lubricate new packing • Excess seal water pressure Overheating of Pump Casing
• • • • •
Prolonged running against shut head or blocked discharge Blocked suction? Warning! This is could create a very dangerous condition. Insufficient NPSH available from the system Air pockets in suction pipe or pump Hot process fluid being pumped
Pump Casing Leaks
• Casing or liner worn through • Normal or excess stuffing box flow • Defective seal between pump casing, liner or housing Pump Flange Leaks
• Defective gasket at pump flange • Incorrect flange bolt torque Motor Overload
• Verify that the motor has the correct power and voltage supply, and is operating properly. • Verify that the motor is correct for the pump. The pump specifications and curve can be used to determine the power and speed required. • Verify that the pumped fluid matches the system design viscosity and specific gravity. • Coupling misaligned • Gland adjusted too tight • External pipe forces can distort the pump and bind the motor and pump bearings. • Drag from external parts such as guards
85
86
Slurry Pump Fundamentals
Vibrations or Abnormal Noises
• • • • • • • • • • • • • •
Cavitation caused by low NPSH or blocked suction. Impeller rubbing caused by incorrect nose adjustment. Impeller is out of balance. Debris jammed in impeller vanes. Pump or motor mounting bolts are loose. Air in system Large solids in pumped fluid Coupling is misaligned. Belts are misaligned or incorrectly tightened. Insufficient clearance between the pump shaft and motor shaft at coupling Worn bearings in pump or motor Gland adjusted too tightly Vibrations from system transmitted through piping. Damaged or bent shaft in pump, speed reducer or motor
Help Is Here All operators should receive proper instruction on maintaining and troubleshooting of pumps. In many modern plants, the operator and the maintenance mechanic are often the same person. If the operators know how the pump works, they will have no trouble figuring out the solution to most problems. All too often, the only instruction given is “Keep the flow gage at a certain point.” What is actually happening with the equipment isn’t understood. GIW offers training for all skills and levels. Our REGEN service center can service your pumps at our Grovetown, Ga., location or at your facility. We also have service centers in Florida and Canada. Please see “Chapter 17: Where It All Comes Together” for specific information. Your local regional sales manager can arrange on-site or off-site training. Visit www.giwindustries.com for a complete list of GIW authorized representatives. GIW offers an annual hands-on slurry course, “Transportation of Solids Using Centrifugal Pumps,” at our Grovetown facility. Visit our Web site for additional information.
Chapter 13: Troubleshooting
87
88
Slurry Pump Fundamentals
Chapter 14: Appendix
Chapter 14:
Appendix
Temperature Conversion Chart °C = (°F -32)/1.8 °C = °K -273.15 K = °C +273.15
°F = (°C *1.8)+32 °F = °R -459.67 °R = °F +459.67
Mass Conversion Chart Kilogram
Grams
Pounds
Ounce
kg
g
lb
oz
kg
1
1000
2.20462
35.274
g
0.001
1
0.00220462
0.035274
lb
0.453592
453.592
1
16
oz
0.0283495
28.3495 0
0.0625
1
Velocity Conversion Chart
ft/s m/s
Feet Per Second
Meters Per Second
ft/s
m/s
Kilometers Per Hour Miles Per Hour
kph
mph
1
0.304800
1.097280
0.681818
3.28084
1
3.60000
2.23694
0.911344
0.277778
1
0.621371
0.447040
1.609344
1
kph mph 1.466667
89
90
Slurry Pump Fundamentals
Chapter 14: Appendix
Flow Conversion Chart
l/s
Cubic Meters Per Hour
Length and Distance Conversion Chart
Liters Per Second l/s
Cubic Feet Per Minute
m 3/h
f3/m
Gallons (US) Per Minute gpm
1
3.60000
2.11888
15.85032
Feet
Inches
Yards
Miles
Centimeters Meters
Kilometers
ft
in
yd
mi
cm
km
ft
1
12
in
0.08333 1
m
0.333333
1.893939e-4
30.4800
0.304800 3.04800e-4
0.0277778
1.578283e-5
2.54000
0.025400 2.5400e-5
m 3/h 0.27778 f3/m 0.471947
1
0.58858
4.40287
yd
3
36
1
5.68182e-4
91.4400
0.914400 9.14400e-4
1.69901
1
7.48052
mi
5280
63360.0
1760.000
1
160934.4
1609.344 1.609344
gpm 0.630902
0.2271
0.1336806
1
cm
0.03281 0.393701
0.01093613 6.21371e-6
1
0.01
10e-6
m
3.28084 39.3701
1.093613
6.21371e-4
100
1
0.001
km
3280.84 39370.1
1093.613
0.621371
100000
1000
1
Volume Conversion Chart
l cc m
3
gal in
3
ft3
Liter
Cubic Centimeters Cubic Meters Gallons (US) Cubic Inch
l
cc
m3
gal
in3
ft3
1
1000
0.001
0.264172
61.0237
0.0353147
0.001
1
1e-6
2.64172e-4
0.0610237
3.53147e-5
264.172
61023.7
35.3147
3.78541
1e6 3785.41
1 0.00378541
1
231
0.13368
0.016387
16.38706
1.63871E-05
0.004329
1
5.78704e-4
28.3168
28316.8
0.0283168
7.48052
1728
1
1000
Cubic Feet
1 foot = 12 inches
1 inch = 2.54 centimeters
1 meter = 100 centimeters =1000 millimeters
1 centimeter = 10 millimeters
91
92
Slurry Pump Fundamentals
Chapter 15: Glossary
Chapter 15:
Glossary
ABRASION Abrasion is wear produced by hard particles that are moving and forced against a solid surface. AVERAGE PARTICLE SIZE The average particle size represents the behavior of a mixture of various particle sizes in a slurry. This designation is used to calculate system requirements and pump performance. BEP At a given speed, slurry pumps can be operated at a variety of flow rates. However, only one specific flow rate achieves the maximum efficiency. This is called the Best Efficiency Point. BEP is the point where the brake horsepower going into the pump is the closest to the water horsepower coming out of the pump. CAPACITY Capacity is the gallons per minute a pump puts out. CAVITATION Cavitation is more than air bubbles in the liquid. In most cases, cavitation is the liquid boiling at ambient temperatures because of the reduction in pressure.
93
94
Slurry Pump Fundamentals
CENTRIFUGAL PUMP A centrifugal pump is a machine in which water or other fluid is lifted and discharged through a pipe by the energy imparted by a wheel or blades revolving in a fixed case. Some of the largest and most powerful pumps are centrifugal pumps. CENTRIPETAL FORCE Centripetal force deflects a body from its linear path and compels it to move along a curve. CIRCULAR CASING A circular casing is a type of design used with centrifugal pumps that pump a high liquid volume rather than pumps that build a high head or pressure. In this design, the impeller has a constant clearance between its outside diameter and the casing CORBRASION™ Corbrasion is GIW’s trademarked term for the combination of abrasion and corrosion that creates unique wear conditions in slurry pumps. CORROSION Corrosion is the loss of material caused by the interaction between the pump material and chemical products within the slurry. DUTY POINT The duty point is where the pump performance curve crosses the system head curve. It represents the capacity where the energy required to move the liquid through the piping system equals the energy transferred to the liquid by the pump. HEAD This is the term centrifugal pump people use in place of the word pressure. It is also called Total Dynamic Head. KINETIC ENERGY Kinetic energy is the energy of a moving object.
Chapter 15: Glossary
MAXIMUM PARTICLE SIZE This is the largest (maxiumum) particle size in a slurry under normal conditions that’s expected to pass though the pump. NEWTONIAN FLUID Fluids, like water and gasoline, that behave according to Newton’s model are called Newtonian fluids. Newtonian fluids have a constant viscosity at a given temperature. NOMOGRAM A nomogram is a chart representing numerical relationships. NON-NEWTONIAN FLUID Non-Newtonian fluids have a variable viscosity at a constant temperature. The viscosity varies with the shear rate of the fluid. Multigrade motor oils, ketchup, blood, yogurt, gravy, pie fillings, mud and cornstarch paste are non-Newtonian fluids. NON-SETTLING SLURRY A non-settling slurry is a slurry in which the solids won’t settle to the bottom of the containing vessel or conduit. They instead remain in suspension without agitation for long periods of time. NPSH Net Positive Suction Head is the difference between the suction pressure and the saturation pressure of the fluid being pumped. NPSHA The Net Positive Suction Head Available is the difference between the pressure at the suction of the pump and the saturation pressure for the liquid being pumped. NPSHR The Positive Suction Head Required is the minimum net positive suction head necessary to avoid cavitation.
95
96
Slurry Pump Fundamentals
Chapter 15: Glossary
PERCENT SOLIDS BY VOLUME Percent solids by volume is the actual volume of the solid material in a given volume of slurry divided by the given volume of slurry and multiplied by 100.
SPECIFIC GRAVITY Specific Gravity (SG) is the ratio of the density of a substance to the density of water. Don’t confuse specific gravity with viscosity, which is a measurement of a fluid’s resistance to pouring.
PERCENT SOLIDS BY WEIGHT Percent solids by weight is the weight of dry solids in a given volume of slurry divided by the total weight of that volume of slurry and multiplied by 100.
STATIC PRESSURE Static pressure is usually stated in inches of water (H2O) or in millimeters of water (mmH2O). It’s essentially a measure of the differential air pressure between the air pressures inside an application compared to the ambient air pressure outside of an application.
PERFORMANCE CURVE A pump performance curve is a graphical representation of the head produced by the pump for various flow rates at a given speed. The curve is always downward sloping, which means head decreases as flow rate increases. PRESSURE Pressure is the force of the fluid in a hydraulic system. SETTLING SLURRY A settling slurry is a slurry in which the solids move to the bottom of the containing vessel or conduit at a discernible rate, but remain in suspension if the slurry is agitated constantly. SHEAR RATE Shear rate is the difference between velocity of parallel faces of a fluid element divided by the distances between the faces. SHUT OFF HEAD Shut off head is the maximum head that the pump can generate with a given impeller outside diameter and horsepower driver. SLURRY Slurry is a mixture of something solid and a liquid. SLYSEL Slysel is GIW’s proprietary pump selection program.
STUFFING BOX The stuffing box is the portion of the pump that holds the packing and the mechanical seal. SUMP PUMP The sump pump does just what the name implies: it pumps out a sump or pit. SYSTEM CURVE A system curve is a graphical representation of the head (energy) required to move slurry through a piping system (including process equipment) at various flow rates. TCO Total Cost of Ownership is the total yearly cost of the pump and driver including capital, power expenses, price of replacement parts and downtime costs evaluated over five years. TDH Total Dynamic Head is the sum of kinetic and potential energy per unit of fluid transferred from the impeller vanes to the fluid. In pumping terminology, “head” is often used when referring to TDH. Head is usually expressed in meters or feet. TEL Total Equivalent Length is the most common method for calculating an allowance for additional friction.
97
98
Slurry Pump Fundamentals
Chapter 16: References
Chapter 16: VAPOR PRESSURE The lowest possible pressure of the pumped liquid is called the vapor pressure. If the suction pressure is too low, the pressure in the suction area decreases to the vapor pressure of the pumped liquid. If vapor pressure is reached, vapor bubbles form and follow the liquid into the impeller to areas with higher pressure. The vapor bubble then collapses or implodes in these areas. This creates extremely loud noises. These small implosions are called cavitation. VISCOSITY Viscosity is a measure of the thickness of the liquid. Thick liquids have a high viscosity and thin liquids have a low viscosity. Like specific gravity, viscosity can be altered by a change in temperature, but unlike specific gravity, it can also be altered by agitation. VOLUTE CASING The volute casing gets its name from a spiral-shaped casing surrounding the pump impeller. The purpose of the volute is to convert velocity energy to pressure energy. WATER HAMMER Water hammer is a destructive pressure surge that takes place in piping systems when the rate of flow changes suddenly.
References Dr. Mihail C. Roco Senior Advisor for Nanotechnology National Science Foundation Chair, National Science, Engineering and Technology Council’s Subcommittee on Nanoscale Science, Engineering and Technology (NSET)
99
100
Slurry Pump Fundamentals
Chapter 17: Where It All Comes Together
Chapter 17:
Where It All Comes Together
Capabilities GIW’s pumps move just about any material, and they move it quickly and efficiently. We’ve learned our most valuable lessons through down-and-dirty applications that have taken us around the globe, wherever mining, dredging and industrial companies demand systems that expand the limits of moving slurry.
TESTING AND DEVELOPMENT GIW’s Metallurgical Laboratory performs research and development, and materials quality control and investigation. GIW’s Hydraulic Laboratory has performed over 350 pipeline tests using actual slurries to predict real-world performance. Lab testing is available on a contract basis to customers. DESIGN ENGINEERING GIW engineers are experts at finding solutions. They have published more technical papers and produced more new designs than any other slurry pump manufacturer. Processes include: • Advanced three-dimensional solid CAD computer design software
GIW’s engineers use advanced three-dimensional CAD computer design software.
101
102
Slurry Pump Fundamentals
Chapter 17: Where It All Comes Together
• Sophisticated computer programs to simulate the multiphase flow in impeller and shell to ensure high pump performance with minimized wear • Working closely with academic and industrial partners the world over to put the most advanced methods into practice MANUFACTURING GIW employees are trained in quality control techniques and the facilities operate under certified ISO9001 Standards. GIW uses the latest casting technology and equipment.
GIW’s corporate headquarters is located in Grovetown, Ga.
PRODUCTS GIW strives to offer the lowest total cost of ownership on all projects. Our pumps deliver excellent suction performance, high sustainable hydraulic efficiency and long wear life with flows of 50 - 100,000 gpm (11 - 23000 m3/h).
• Mineral processing: coal, copper, gold, iron ore, nickel, oil sands, phosphate • Power generation: FGD systems and ash handling • Aggregate: sand and gravel • Industrial process: alumina, cement, chemical, potash, wastewater • Dredge: marine, sand and gravel
History GIW Industries began as a small foundry and machine shop in Augusta, Ga., in 1891. Over the last century, GIW has made its way to the forefront of the slurry pump industry. Today, the company is comprised of two manufacturing facilities, one in Grovetown, Ga., and the other in Thomson, Ga. These foundries and machine shops are used for manufacturing and assembling pumps and for casting a variety of abrasion-, corrosion- and heat-resistant alloys, polyurethane and rubber elastomers.
Ownership As a subsidiary of KSB AG of Germany, one of the world’s largest pump and valve manufacturers, GIW has the infrastructure to supply and support a world market. GIW and KSB together have more than 125 years of experience in pumps and hydraulics.
Our expert service and sales staff are readily available to diagnose and solve field problems.
When you’ve got a complicated problem to solve, GIW/KSB is the answer.
GIW serves the following industries:
GIW’s Hydraulic Laboratory has performed over 350 pipeline tests using actual slurries.
How To Contact GIW GIW has two manufacturing facilities, one in Grovetown, Ga., and the other in Thomson, Ga.
For additional information or to find a sales representative in your area, visit www.giwindustries.com. Call, write or fax us at:
103
104
Slurry Pump Fundamentals
GIW INDUSTRIES 5000 Wrightsboro Rd. Grovetown, GA 30813 Phone: 706.863.1011 Fax: 706.863.5637 Toll-Free for Pump Emergencies: 1.888.TECH.GIW (8324.449) SERVICE CENTERS GIW REGEN Service Center
5000 Wrightsboro Rd. Grovetown, GA 30813 Phone: 706.863.1011 Fax: 706.434.0770 Arroyo Process Equipment Inc.
1351 S.R. 60 West Mulberry, FL 33860-8571 Web: www.arroyoprocess.com Phone: 863.425.1145 Fax: 863.425.2936 Ft. McMurray Service Center
155 MacMillan Rd. Fort McMurray, Alberta T9H 4G3 Canada Phone: 780.713.3457 Fax: 780.713.3458
Chapter 17: Where It All Comes Together
105
106
Slurry Pump Fundamentals
Slurry Pump Fundamentals is an easyto-understand introduction to slurry pumps and systems. GIW engineers understand stuff like: “The algebraic sum of the suction gauge head plus the velocity head at point of gauge attachment plus the elevation head from the suction gauge centerline to the pump datum,” but, frankly, we don’t. And—we’re sure we don’t want to. If you feel that way, too, you’ll like the book’s straight-forward, friendly approach. (Don’t worry. Our engineers didn’t write this book. We did, however, ask them to proofread it for us.) We use simple language to teach you about wear protection, cavitation, vane design and viscosity. We tackle the most complex topics (efficiency, hydraulics and slurry pump systems) with all the care, kindness and clarity and we can muster. We also: •
Remind you (over and over again) that a pump always operates at the intersection of the system curve and the pump curve.
•
Explain why paying attention to the design of the system in which the pump operates can achieve significant savings.
•
Cover maintenance practices that reduce the deterioration in slurry pump efficiency and improve the reliability of the system.
•
Include an appendix full of conversion charts and a glossary of common terms associated with slurry pumps and pumping systems. We doubt this will be your favorite book, but we hope you’ll use it to find basic answers to questions about pumps and systems. We worked hard to make sure our explanations are clearer than, ummmm, slurry.
www.giwindustries.com
