Metso Slurry Pump Sizing

METSO

Product Information

Slurry Pumps 2.0 PRODUCT INFORMATION

Page

2.1 Pump sizing ………………………………………………………....................2 - Slurry Formulas …………………………………………………………...4 - The Pipe system ………………………………………………………....6 - Laws for fixed impeller diameter ………………………………………15 - Laws for fixed Impeller speed ……………………………………….….16 2.2 Material options ……………………………………………………………….26 2.3 Pump testing …………………………………………………………………..34 2.4 Application guide ……………………………………………………………..34 2.4.1 General …………………………………………………….......……34 1. Selection of a Slurry Pump - by duty …………………........................….35 2. Selection of a Slurry Pump - by industrial Application …………………………………………………………………...35 2.4.2 Selection of a Slurry Pump - by duty ……………………......……36 2.4.3 Selection of a Slurry Pump - by industrial Application ……………………………………………………………41 2.5 Conversions and Equations …………………………………………………49 2.5.1 Table of useful conversions ……………………………………….49 2.5.2 Table of useful equations ………………………………………….50 2.6 Maximum possible vibration level …………………………………………...51 2.7 Sound level…………………………………………………………………….51 2.8 Standard allowable flange forces and moments for Metso Minerals pumps ………………………………………………………52 2.9 Pressure ratings ………………………………………………………………53

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Slurry Pumps

2.0

PRODUCT INFORMATION

2.1

Pump sizing

Modern sizing procedures for slurry pumps are computerised and easy to handle, as in Metso’s”PumpDim™ for Windows”. It is important to know the steps for sizing slurry pumps and the relationship between them, to ensure that these procedures are correctly understood. The following manual procedure is approximate and gives reasonable accuracy, except in extreme applications. For froth pumping, also see Section 9.0. Installed in a piping system a Slurry Pump must be rated against the static head, any delivery pressure requirement and all friction losses to be able to provide the required flow rate. The duty point is where the pump performance curve crosses the system curve.

Note! Never overestimate the system resistance. If over estimated, the Slurry Pump will: Give a greater flow than required Absorb more power than expected Run the risk of overloading the motor (and in worst cases suffer damage) Poor suction conditions may cause Cavitation. Suffer from a higher wear rate than expected Always use the best estimate of system head. Add safety margins to the calculated power only.

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Slurry Pumps

The sizing steps Step 1. Establish if the slurry/liquid is a: Clear liquid Non-settling (viscous) slurry (Particle size < 50 micron) Settling slurry Step 2. Set up the duty details. These vary depending on the type of liquid according to Step 1. Common details are: Slurry Flow or Solids Tonnage Static lift (head) Friction losses given or pipe system known/selected Chemical properties like pH value, content of chlorides, oil, etc. Other liquid/slurry details as below. Clear liquids When clear water - no further liquid details are required. For other clear liquids the following is needed. - Liquid S.G. - Liquid dynamic viscosity. If kinematic viscosity is given, convert using this formula : Dynamic viscosity = (Kinematic viscosity) x (Specific gravity) Slurries For slurries a number of details are required. According to the following formulas certain combinations of these data are required to be able to calculate all of them. Sm = Slurry S.G. Cv = Concentration by Volume % Cw = Concentration by Weight % S = Solids S.G. Q = Flow rate in m3/hour tph = Tonnes per hour (solids) QUS = Flow rate in US gallons per minute. stph = Short tons per hour (solids)

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Slurry Formulas:

Sm

CV =

CV =

=

C V (S - 1) +1 100

(S m - 1) x 1 0 0 (S - 1)

1 0 0 x CW

[S(1 0 0 - C W ) + C W ]

CW =

1 0 0x S 100 + (S - 1) CV

Q = t ph x [

CW = 1 0 0 -[

1 100 + - 1] m3/hr s CW

Q US = 4 x st p h x [

1 0 0 - CV ] Sm

1 100 + - 1] USgpm s CW

For non-settling (viscous) slurries also the plastic dynamic viscosity and max. particle size is required. For settling slurries max. and average particle sizes (d50 or d85) are required. Also, during the piping system analyses check that the actual velocity in the pipe is higher than the critical velocity for stationary deposition. Using particle size, solids S.G. and pipe diameter, determine this velocity from the nomographic chart on Page 9. If a pipe diameter has not been specified, the best way to arrive at one is to select the first pipe size giving a velocity above 3 m/s (10 ft/s). This pipe size should be checked to ensure that the actual velocity is greater than the critical velocity. The diagram on Page 10 can be used to find the velocity and friction loss coefficient for a given pipe diameter and flow. If the actual velocity is less than, or much greater than, the critical velocity, repeat the calculation for a size of pipe smaller, or bigger, to check that the largest possible pipe is used to ensure that settling does not take place, as well as to minimise friction losses. NOTE:!! Always use minimum anticipated flow value to calculate the pipe velocity to avoid settling problems.

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Slurry Pumps

Solids tonnage or slurry flow ? It is very important to understand the difference between”percent solids by weight” and”percent solids by volume”. Percent solids by weight are the normal way of describing a slurry. Magnetite slurry, 40 % solids by weight (solids S.G.= 4.7). Limestone slurry, 40 % solids by weight (solids S.G.= 2.6). This is due to the practice that production in general is measured in solids tons/hour (or short tons/hour), assume that for the above slurries: Magnetite and Limestone feed to the circuits are both 300 tonnes/hour (331 stph). These are not directly useful figures for a Slurry Pump man as pumps are volumetric machines and must be sized on flow. If we calculate the flow conditions of the above slurries, we will find that: The magnetite slurry gives a slurry flow of 515 m3/hour (2267 USgpm). The limestone slurry gives a slurry flow of 566 m3/hour (2493 USgpm). As tonnage, these capacities are equal; but hydraulically they are not!

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Slurry Pumps Step 3. The Pipe System

The total head in a liquid is the sum of the static head (gravitational energy), pressure head (strain energy) and velocity head (kinetic energy). The head (energy), the pump has to supply to the liquid for the required flow rate, is the difference between the total head at the outlet and inlet flanges respectively. As we do not know the conditions at the pump flanges, we must select a point on each side of the pump where we do, and then allow for pipe work losses between these points and the flanges to determine the total head at the flanges. In the diagram above the total head is known at the liquid surface in the feed tank (Point 1) and the outlet pipe exit (Point 2). At point 1

Static Inlet Head

= H1

Pressure Head

= 0 (atmospheric pressure)

Velocity Head

= 0 (practically no velocity)

Therefore,

Pump Inlet Head

= H1 – inlet pipe losses

At point 2

Static Head

= H2

Pressure Head

= 0 (atmospheric pressure)

Velocity Head

= V22 / 2g

Therefore,

V2

= Flow velocity at Point 2 in m/s.

g

= Gravitational constant = 9.81 m/s2

Pump Outlet Head

= H2 + V22 / 2g + outlet pipe losses

Pump Total Head, H

= (Outlet head – inlet head)

H = (H2 + V2 2 / 2g + outlet pipe losses) – (H1 – Inlet pipe losses) In practice is the pump suction bigger than the discharge, which makes the inlet velocity head small and is therefore often ignored. A 3.0 m/s (10 ft/s) flow velocity does only generate a velocity head of 0.46 m (1.5 ft.). Then

H = H2 – H1 + (V22 / 2 g) +outlet losses + inlet losses

The effect of pressurised inlet and/or outlet, e.g. pressurised tank or hydro cyclone feed, is allowed for by adding the pressure value, in meters (feet) of liquid, to H1 or H2 as appropriate. 2.0

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Slurry Pumps SLURRY EFFECTS ON FRICTION LOSSES

As for pump performance, slurries also affect friction losses since they behave differently to clear water. The slurry has to be treated either as settling or non-settling (viscous). Generally, slurries with particle size < 50 micron are treated as non-settling. Friction losses for settling slurries The assessment of friction losses for settling slurries is very involved, and best accomplished on computer software such as Metso PumpDim6TM for Windows. However, for short runs of pipe at higher velocities, head loss can be taken as equal to the water losses. For approximate estimations the correction factor on the bottom of Page 10 can be used.

At low velocities, head loss is difficult to predict, and there is a real risk of solids settling out and blocking the pipe. The nomogram on Page 9 will provide a safe minimum velocity. Friction loss calculations Straight pipes Similar to voltage drop in a power cable, there are friction losses in a pipe system. The friction loss in a straight pipe varies with: •

Diameter

•

Length

•

Material (roughness)

•

Flow rate (velocity)

The friction loss can either be:

2.0

1.

Looked up in a table

2.

Extracted from a Moody diagram.

3.

Calculated from semi-empirical formula, such as the William & Hazen Formula.

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Slurry Pumps Fittings

When a system includes valves and fittings, an allowance for additional friction is needed. The most common method is called the ”Equivalent pipe length” method. The fittings are treated as a length of straight pipe giving equivalent resistance to flow. See Table on Page 11. TEL - Total Equivalent Length TEL = Straight pipe length + equivalent length of all pipe fittings. TEL is used to calculate the total friction losses in the system. If software such as Metso’s "PumpDimTM for Windows" is not used then we recommend that you use the table on Page 10 to calculate the friction losses.

Friction losses for non-settling slurries Friction loss calculations for non-settling slurries are best accomplished with the aid of computer software. However, there are numerous methods of making calculations manually, although these can prove difficult with all the variables involved. Whatever method is used, a full rheology of the viscous solution is necessary for any accurate assessment. Assumptions can be made but these can prove very inaccurate.

Summary: It is very important that all the losses in a slurry system are calculated in the best way possible, enabling the pump to balance the total system resistance, operate at the correct duty point, giving correct head and capacity! Use computer software PumpDimTM for Windows.

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Slurry Pumps

Nomograph chart for minimum velocity. (Adapted from Wilson, 1976). Example :

2.0

Pipe dia. 250 mm

= 0,250 m

Particle size

= 0,5 mm (Worst case)

Particle S.G.

=3,8

Minimum velocity

= 4,5 m/s

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Slurry Pumps HEAD LOSSES IN VALVES, FITTINGS, ETC.

Resistance of Valves and Fittings frequently used on slurry pipelines. Stated as approx. length in metres of straight pipe giving equivalent resistance to flow.

Pipe Size N.B 25

R>3xN.B. Long Radius Bend 0,52

R=2xN.B Short Radius Bend

Elbow

0,70

0,82

Tee 1,77

R>10xN.B. Rubber Hose 0,30

Plug Lub Valve Rect. Way

Dia-phr. Full Open

Full Bore Valve

2,60

-

0,37

32

0,73

0,91

1,13

2,40

0,40

3,30

-

0,49

38

0,85

1,09

1,31

2,70

0,49

3,50

1,19

0,58

50

1,07

1,40

1,67

3,40

0,55

3,70

1,43

0,73

63

1,28

1,65

1,98

4,30

0,70

4,60

1,52

0,85

75

1,55

2,10

2,50

5,20

0,85

4,90

1,92

1,03

88

1,83

2,40

2,90

5,80

1,01

-

-

1,22

100

2,10

2,80

3,40

6,70

1,16

7,60

2,20

1,40

113

2,40

3,10

3,70

7,30

1,28

-

-1,58

125

2,70

3,70

4,30

8,20

1,43

13,10

3,00

1,77

150

3,40

4,30

4,90

10,10

1,55

18,30

3,10

2,10

200

4,30

5,50

6,40

13,10

2,40

19,80

7,90

2,70

250

5,20

6,70

7,90

17,10

3,00

21,00

10,70

3,50

300

6,10

7,90

9,80

20,00

3,40

29,00

15,80

4,10

350

7,00

9,50

11,00

23,00

4,30

29,00

-

4,90

400

8,20

10,70

13,00

27,00

4,90

-

-

5,50

450

9,10

12,00

14,00

30,00

5,50

-

-

6,20

500

10,30

13,00

16,00

33,00

6,10

-

-

7,30

Step 4. The next step is to select wet end wear part material. Select material from the max. particle size according to the Table 1 in Section 2.2. For clear liquids, metal pumps are the primary choice. Check chemical resistance of the selected material by referring to Tables 2 and 3 in Section 2.2. Step 5.Now we have to select the right type of pump by considering the operating costs, taking into account wear, maintenance and energy usage. Depending on the application, it can be a horizontal or vertical Slurry Pump. It could also be a pump for extreme, heavy or normal wear conditions. 2.0

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Slurry Pumps

You can see which type of pump we recommend for various industrial applications by referring to the Application Guide in Section 2.4. From this information, together with the wet-end material choice, you can select a suitable pump. From previous steps above, we know the slurry flow rate and pump total head. By referring to the appropriate tombstone charts under each pump range you can find the suitable pump size for this duty. To establish the operating pump speed and installed driver power go to the performance curve for the selected pump. Since performance curves are for clear water, corrections may be required if other liquids or slurries are to be pumped. Step 6. Clear water and Slurries with concentrations < 15% by Volume. Mark the intersection point of the duty flow and pump total head on the upper section of the performance curve, see example in figure below. From this, you can determine the required pump speed. The pump power input (P) required at this speed and duty flow is read from the lower curve.

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Slurry Pumps

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Slurry Pumps Slurries with high concentrations.

For settling slurries, consult the diagram below using average particle size d50 , solids S.G. and concentration by weight, to obtain the de-rating factors of Head Ratio (HR) and Efficiency Ratio (ER). HR and ER have the same value.

Divide the pump total head, H by the HR factor. Since the factor is