Motors Pumps and Drives - Part 1

Motor and Drive Interaction Part 1

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Hydraulic Institute / Pump Systems Matter • Pump Systems Matter (PSM) – is a non-profit educational organization established by the Hydraulic Institute, and leading utilities and energy efficiency organizations, to educate the industry on the benefits to pump systems optimization and energy efficiency to improve bottom-line savings of end-user companies. • Hydraulic Institute The mission of the Hydraulic Institute is to be a value-adding resource to member companies, engineering consulting firms, and pump users worldwide by developing and delivering comprehensive industry standards, expanding knowledge by providing education and tools for the effective application, testing, installation, operation, maintenance, and performance optimization of pumps and pumping systems, and by serving as a forum for the exchange of industry information. For more information on the Hydraulic Institute, its member companies and its Standards Partners, visit www.Pumps.org

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Meet Your Instructor • Currently the Power Generation Business Development Manager for WEG Motors • Over 40 years’ of experience in the pump industry designing, field testing, repairing and troubleshooting mechanical seals, compressors and pumping systems • An active Hydraulic Institute member for a number of years, including Pump Systems Matter Train the Trainer expert, Certified Hydraulic Institute Pump System Assessor and top PSO instructor 3

Workshop Learning Objectives As a result of this workshop, the participants will better understand: • Understand how the motor reacts to the system under VFD control • Ability to properly select a motor for VFD service • Understand the impact that motors, pumps and drives have on the pump system • Understand potential issues that one must be aware of when applying a VFD • Using a system approach to manage motor, pump and drive operations • An efficient system is a reliable system - Making the Business Case 4

Agenda • • •

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Why Efficient Pumping Systems are Important Pump Application Considerations Pumping Systems Overview • Pumping System Fundamentals; the impact on total system efficiency • Motor • Drive (Variable Speed) • Piping • Valves • End User Equipment Motor • Configuration • Selection VFD System Application Consideration Electrical System • Grounding considerations • Grounding of control system • Grounding of motor Justifying VFD • Making the Business Case Conclusion

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Benefits of Assessment – Electrical Energy Savings Potential Electrical usage with motors in municipal water systems pumping (46%) and aeration (40%) In wastewater plants, electrical usage with pumping systems account for 20-30% of consumption.

GWhr / Year

Electrical motors account for nearly 2/3rd of the North American Industrial Electricity usage with pumping systems accounting for 25%

1997 – On-site studies at 265 industrial facilities • • • •

Total facility electrical energy costs Motor system energy consumption & costs Potential energy savings Analysis by key industrial markets

Pumps Systems are Energy Intensive Source: U.S. Industrial Motor Systems, Market Opportunities Assessment, U.S. Department of Energy

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Finnish Technical Research Center Report: “Expert Systems for Diagnosis of the Condition and Performance of Centrifugal Pumps”

Evaluation of 1690 pumps at 20 process plants: • Average pumping efficiency is below 40% • Over 10% of pumps run below 10% efficiency • Major factors affecting pump efficiency: ‒ Throttled valves ‒ Pump over-sizing

• Seal leakage causes highest downtime and cost

Impact on Life Cycle Cost? 7

Conventional 75 HP Pumping System 20 Year Life Cycle Cost Initial Cost 9%

Installation Cost 8%

( $68,333 )

( $61,000 ) Operating Cost 55%

Maintenance Cost 28%

( $415,812 ) Includes Energy

( $212,000 ) 83%

Total 20 Year Life Cycle Cost = $757,145 Reference : CostWare Analysis

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Why Focus on Pumping Systems? FACT Pumping system efficiency is highly influenced by the system they are supplying

Improving pump efficiency will do little to reduce pump energy usage – the focus must be on the entire system

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Pump vs. System Standards Pump Standards Standards of design and dimensional specifications are necessary to bring unity to centrifugal pumps. Standards are provided by organizations like ISO - International Standards Organizations HI – Hydraulic Institute API - American Petroleum Institute ANSI - American National Standards Institute DIN - Deutsches Institut für Normung NPFA - National Fire Protection Agency BSi - British Standards institute Some commonly used centrifugal pumps standards ANSI/API 610-1995 - Centrifugal Pumps for General Refinery Service - Covers the minimum requirements for centrifugal pumps, including pumps running in reverse as hydraulic power recovery turbines, for use in petroleum, heavy duty chemicals, and gas industry services. The pump types covered by this standard can be broadly classified as overhung, between bearings, and vertically suspended. DIN EN ISO 5199 - Technical specifications for centrifugal pumps ASME B73.1-2001 - Specification for Horizontal End Suction Centrifugal Pumps for Chemical Process - This standard covers centrifugal pumps of horizontal, end suction single stage, centerline discharge design. This Standard includes dimensional interchangeability requirements and certain design features to facilitate installation and maintenance. It is the intent of this Standard that pumps of the same standard dimension designation from all sources of supply shall be interchangeable with respect to mounting dimensions, size and location of suction and discharge nozzles, input shafts, baseplates, and foundation bolt holes ASME B73.2-2003 - Specifications for Vertical In-Line Centrifugal Pumps for Chemical Process BS 5257:1975 - Specification for horizontal end-suction centrifugal pumps (16 bar) - Principal dimensions and nominal duty point. Dimensions for seal cavities and base plate installations.

System Standards • With few exceptions, there are no standards to guide system design • Engineering contractors and owner/operators are allowed to choose (or ignore) how to calculate system hydraulics • Specified pump operating point not subject to standards

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Motor Life Cycle Costs Purchase Price, Installation and Maintenance – 2.7%

Electricity – 97.3%

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What Does it Cost to Operate a Motor?

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What is the Value of One Point of Increased Efficiency?

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Is Choosing the More Efficient Motor the Best Solution?

Answer Later in this Webinar

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Lifetime Energy Costs of a Motor Purchase Price

Energy Cost

$5,000

$810,000 (162 X Purchase) (40 x Installed)

Installed $20,000

100 HP motor @ $0.08 / kWh Electricity ($54K / Yr) 24/7 for 15-Yr Life

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Electrical Energy Costs

100% Speed 100% Load 100 HP Induction Motor

$27,139 per year!

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Electrical Energy Costs

60% Speed 22% HP 100 HP Induction Motor

$5,970 per year! 14

Affinity Rules for Centrifugal Loads

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Annual Electrical Energy Savings 100% Speed $27,139 60% Speed $5,970 $21,169 per year!

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Estimate Efficiency and Load

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Computing Energy Costs for Pumping Systems Annual Electricity Cost (measurement formula) (measured amps) x (measured voltage) x (1.732) x pf x hours x rate 1,000 Where: Measured amps = average of three phases Measured voltage = line to line voltage PF = power factor Hours = annual hours of operation Electric Rate = electricity cost in $/kWh Get power factor (PF) from motor manufacturer performance data sheet Note - 1.732 (the square root of 3), is a constant necessary with 3 phase 1000 = Watts to kW

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Making the Business Case for Optimization

• • • •

Stake Holder Value and Profit Survival Sustainability Relate savings to the facility’s bottom line 19

Reduce Cost & Increase Profitability • Engineers, Operations and Maintenance see and approach business issues differently • Engineers: How does it work? • Operations: How does it keep my plant running? • Maintenance: How does it reduce maintenance cost? • Each group believes it makes a rational case for its thinking • The reality is it is a team effort, you must evaluate the total system when looking to reduce costs and increase profitability

$ Make the Business Case $ 20

Look Beyond Energy Savings • Energy cost is a top consideration, but there are also values for non-energy benefits:

• Higher Reliability • Increase Productivity • Less Equipment Wear and Tear • Reduced Maintenance Cost • Reduce Production Losses

• Increase Capacity Utilization • Reduce Environmental Impact

Asking the Right Questions 21

How a Centrifugal Pump Works

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Centrifugal Pump Facts • Centrifugal pumps should be selected and normally operated at or near the manufacturer’s design rated conditions of head and flow. • Any pump operated at excess capacity, i.e. at a flow significantly greater than BEP and at a lower head, will surge and vibrate, creating potential bearing and shaft seal problems as well as requiring excessive power. • When operation is at reduced capacity, i.e. at a flow significantly less than BEP and at a higher head, the fixed vane angles will now cause eddy flows within the impeller, casing, and between the wear rings. The radial thrust on the rotor will increase, causing higher shaft stresses, increased shaft deflection, and potential bearing and mechanical seal problems while radial vibration and shaft axial movement will also increase.

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Liquid Flow in Centrifugal Pumps A centrifugal pump converts Kinetic Energy (Velocity) to Pressure Energy 4. In the discharge nozzle, the liquid further decelerates and its velocity is converted to pressure according to Bernoulli’s principle.

1. The amount of energy given to the liquid is proportional to the velocity at the edge or vane tip of the impeller

Discharge

2. The faster the impeller revolves or the bigger the impeller is, then the higher will be the velocity of the liquid at the vane tip and the greater the energy imparted to the liquid. 3. This kinetic energy of a liquid coming out of an impeller is harnessed by creating a resistance to the flow.

Impeller Eye

The first resistance is created by the pump volute (casing) that catches the liquid and slows it down.

HEAD Therefore, the head (pressure in terms of height of liquid) developed is approximately equal to the velocity energy at the periphery of the impeller.

Volute

Impeller

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Pressure

Flow Pressure

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Lomakin Effect Is a support force that occurs in pumps at annular seals such as wear rings due to the action of Bernoulli's effect during the normal leakage process. The stability generated by the wear rings is generally referred to as the Lomakin Effect, which is driven by the differential pressure across the rings. The wear ring is a barrier between discharge pressure (Pd) and suction pressure (Ps). The differential pressure across this interface creates an axial flow velocity as shown in Figures 1a and 1b.

Concentric rotor side view 1b

The Lomakin Effect can sometimes be confusing because it encompasses two separate phenomena that occur at the wear rings: Damping and Stiffness

Concentric rotor end view 1a

Differential pressure (Pd) to suction pressure (Pa) produces an axial flow Damping does not directly prevent shaft deflection, but minimizes rotor response across the wear rings. to excitation forces—much in the same way that shock absorbers result in a

smooth ride in a car. Reduced clearance increases damping and results in a more stable rotor. Perhaps most important, the stiffness and damping are located at the impeller where the pump has no bearing support. This strategic location gives the Lomakin Effect a great deal of power in minimizing shaft deflection.

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Wear Ring Clearances Clearance between impeller wear ring and case wear ring should be 0.010” to 0.012” plus 0.001” per inch up to a ring diameter of 12 inches. • Add 0.0005” per inch of ring diameter over 12 inches. Use manufacturer’s guidelines when applying high-performance polymers tighter clearances are allowed. • For pumping temperatures of 500°F and over, add 0.010” to the wear ring clearance. Also, whenever galling-prone wear ring materials such as stainless steel are used, 0.005” are added to the clearance. • Impeller wear rings should be replaced when the new clearance reaches twice the original value. • Case wear rings are not to be bored out larger than 3% of the original diameter. • Metal case ring-to-case interference should be 0.002”- 0.003”, depending on diameter. 27

Consequences of Off-BEP Operation Low Flow Operation Increases: – – – – –

Vibration Axial Loads Radial Loads Suction Recirculation Discharge Pressure

BEP Low Flow

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Run-Out Flow Issues vs. BEP Run-out Flow Operation: • Increased Vibration • Increased Radial Load • High/Steep NPSHR Curve • Decreased Discharge Pressure • Reduced Seal and Bearing Life • Increased Cavitation and Potential Damage to Impeller and Case

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Specific Speed

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Pumps are Traditionally Divided into 3 Types

Radial Flow

Mixed Flow

Axial Flow

Pumps are traditionally divided into 3 types, radial flow, mixed flow and axial flow. There is a continuous change from the radial flow impeller, which develops pressure principally from the action of centrifugal force, to the axial flow impeller, which develops most of its head by the propelling or lifting action of the vanes on the liquid. Specific speed is a term used to describe the geometry (shape) of a pump impeller.

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What is Specific Speed and Why is it Important?

People responsible for the selection of the proper pump can use this Specific Speed information to:

• • • •

Select the shape of the pump curve. Determine the efficiency of the pump. Anticipate motor overloading problems. Select the lowest cost pump for their application.

Specific speed is defined as "the speed of an ideal pump geometrically similar to the actual pump, which when running at this speed will raise a unit of volume, in a unit of time through a unit of head.

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Specific Speed Where:

Example

NS = Specific Speed RPM = Speed in revolutions per minute GPM = US Gallons Per Minute H = Head in feet N = RPM Q = GPM

US gpm, ft. Ns (US gpm, ft) = (1760 rev / min) (1500 gal .75 / min) (100 ft.) = 2156

Specific Speed Specific Speed Calculator Head 100 Flow 1500 RPM 1760 Specific Speed 2156

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Specific Speed The steepness of the head/ capacity curve increases as specific speed increases. • At low specific speed, power consumption is lowest at shut off and rises as flow increases. This means that the motor could be over loaded at the higher flow rates unless this was considered at the time of purchase. • At medium specific speed the power curve peaks at approximately the best efficiency point. This is a non overloading feature meaning that the pump can work safely over most of the fluid range with a motor speed to meet the BEP. requirement. • High specific speed pumps have a falling power curve with maximum power occurring at minimum flow. These pumps should never be started with the discharge valve shut. If throttling is required a motor of greater power will be necessary. What is the Impact on Motor Selection, Horsepower?

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Specific Speed Typical Curves

Hd = Discharge head generated

P = Power Required

Q = Quantity of Liquid Pumped

n = Pump Efficiency

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Specific Speed Values for the Different Pump Designs

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Motor/Pump Electric motors maintain high efficiency Over a wide range 35% load to 120% load

Centrifugal pumps have a very narrow operating range Based on Specific Speed Acceptable Operating Range

The motor and pump react to system requirements and therefore operate based on system resistance. The pump reliability and performance is highly influenced by the system

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Efficiency Means Reliability

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Sizing Electric Motors to Pumps Using System Optimization

• Adding a service factor and additional horsepower – it can lead to maintenance problems and higher energy consumption. • The constant 3960 is obtained by dividing the number or foot-pounds for one horsepower (33,000) by the weight of one gallon of water (8.33 pounds). • BHP can also be read from the pump curves at any flow rate. Pump curves are based on a specific gravity of 1.0. Other liquids’ specific gravity must be considered. • The brake horsepower or input to a pump is greater than the hydraulic horsepower or output due to the mechanical and hydraulic losses incurred in the pump. Therefore the pump efficiency is the ratio of these two values

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Think System Use a Systems Approach to Manage Pumping System Operation

• •

Focusing solely on individual components overlooks potential cost-savings Component failures are often caused by system problems (How do you identify these problems?)

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What is System Optimization “The process of identifying, understanding and cost effectively eliminating unnecessary losses while reducing energy consumption and improving reliability in pumping systems, which while meeting process requirements, minimizes the cost of ownership over the economic life of the pumping systems.”

Source: Optimizing Pumping Systems: A Guide to Improved Energy, Efficiency, Reliability and Profitability

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Systems Optimization and Improvement Opportunities Using Variable Speed Control Defining the System by Component

Confidential and Proprietary Hydraulic Institute November 2016

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Effect of Control Valves

Impeller Size Changes • Using the affinity rules the pump head curve can be adjusted for a different diameter impeller

Efficiency Curves

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Pump Speed Changes • Using the affinity rules the pump head curve can be adjusted for a different SPEEDS.

Efficiency Curves

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Pump Speed Changes Friction-Dominated Systems

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Pump Speed Changes Mixed Friction-Static Systems

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System Efficiency

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Improving the Performance of Existing Pumping Systems with Variable Speed Control

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Six Step Action Plan 1. Screen and prioritize your pumping systems to identify good performance improvement candidates 2. Get management support for improving the highest priority pumping systems 3. Work with appropriate pumping system specialist and/or inhouse team to gather and analyze additional data 4. Identify, economically validate, and implement performance improvement opportunities 5. Document actions and report results to management 6. Repeat Action Plan process for other good candidate systems 50

Performance Improvement Opportunities - Solutions

• Eliminate unnecessary uses • Improve Operations & Maintenance (O & M) practices • Improve piping configuration • Consider alternative pump configurations • Change pump speed

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Change Pump Speed • Slower motor • Two-speed motor * • Changes to belt drives/gears * • Variable Speed Drives • Variable Frequency Drive • Magnetic Drive • Fluid Drive

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ASD? • ASD = Adjustable Speed Drive • VSD = Variable Speed Drive –Any device that can be used to change the speed of the pump shaft (E.g. VFD’s, Viscous couplings, Transmissions, Belt drives, Special motors) • AFC = Adjustable Frequency Control • AFD = Adjustable Frequency Drive • VFD = Variable Frequency Drive – Electronic solid state device with an adjustable frequency output that imitates a sine wave – A.k.a. “Inverter”

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Variable Frequency Drive System

Basic VFD Diagram

A basic variable frequency drive system typically consists of an AC motor and variable frequency drive managed through a control system (above). A method to vary/control speed is required. There are numerous control methods, both internal and external, to the VFD.

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Variable Speed Pumping • Why use a variable speed pump?

• When to use variable speed? • When not to use variable speed?

Source: Section supplied by Manitoba Hydro

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Why use a Variable Speed Pump?

% FLOW, HEAD, POWER

• Take advantage of the affinity rules of Centrifugal Pumps.

%SPEED 56

THROTTLE CONTROL

• Valve throttling increases system head resulting in excess power consumption • Excess energy noted in blue area

• Excess energy impacts equipment reliability

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BY-PASSING

• Bypass lines require more flow, which results in excess power consumption. • Excess energy impacts equipment reliability

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VARIABLE SPEED CONTROL

• No excess energy used by the system • Reliability is maximized

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When to use Variable Speed? Pump and System Curves Perpendicular

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When Not to use Variable Speed Pumps? No Variability? Use Impeller Trim or Reduced Fixed Speed

Pump and System Curves Parallel

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Conclusion of Part One Part Two • Motor design selection and application • Load Types • Grounding • Case Studies • Conclusion

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