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Pump Selection Stages


DOING LIST OF PUMP SELECTION

  Corrosive Thin liquids Dark Solid Dry operating Outlet Pressure
Internal Eccentric Gear
G
G
E
P
A
G
Helical & spur gear
G
G
G
P
A
E
Lobe
G
A
E
E
A
G
Vane
P
E
A
P
G
A
E = Excellent  , G= Good  ,  A = Average  ,  P= Poor

Table : 4

 

CHARACTERISTICS OF PUMPS

Internal eccentric gear pumps
Advantages;
  1. Two moveable parts. 
  2. One piece of stuffing body   
  3. Positive suction, non-vibrating pressure  
  4. Ideal for high viscosity liquids.
  5. Operating in silence motion.
Disadvantages;
  1. Low rpm is generally needed.
  2. Medium pressure.
  3. Pump shaft bushes loaded the applied force.
Helical& Spur Gear Pumps
Advantages;
  1. Operating in high Rpm.
  2. Positive suction, non-vibrating pressure
  3. Medium pressure     
  4. Some models are ideal for high viscosity.
  5. Applied force is not existed in one bushes.
  6. Operating in silence motion
Disadvantages;
  1. Having 4 bushes that can be contacted with the liquid.
  2. Sometimes 4 stuffing body may be needed.   ( External ball bearing model)
  3. Some of models are not allowed for transmittance of solid liquids.
Lobe Pumps
Advantages;
  1. Mid-size solids can be transferred   
  2. During the liquid transfer there is not any friction among the surface materials.   
  3. You may clean the pump while it was connected to the service line.
  4. Having capability of positive suction. 
  5. Operating in silence motion.
Disadvantages;
  1. Timing gear is needed
  2. Two pieces of tightness or leakage element  is needed.
  3. High Rpm is needed in thin liquids.
  4. Repairment should be made by the factory.
Vane type pumps
Advantages;
  1. Thin and dark liquids can be transferable.  
  2. Sometimes solvents and LPG can be preferred.
  3. Dry operating for a short period.   
  4. Occurring pressure speciality is good.  
  5. Singular stuffing body (sealing) is required. 
Disadvantages;
  1. Sometimes 2 pieces of stuffing body (sealing) is needed.
  2. Medium pressure.
  3. Some models have complex bodies.
  4. Not suitable for corrosive fluids.
  5. Some models are not useful for high viscosity.

Table : 5

 

9 Simple steps for the pump selection

  1. Determine the capacity of system that is required. The need of capacity that pump will use must be identified in litter/minute or metre cubic/hour
  2. The viscosity level of the transferred liquid must be identified. Liquid viscosity is a very important factor that is both depending on and determining pump greatness, calculating pipe diameter, efficient electrical motor and redactor. Because of all above reasons, viscosity of Liquid during the transfer must be specified before in a certain position. Under the following you may find the link of viscosity conversion.

    Table 6 Click here for the conversion table of viscosity..

  3. Determine the volume (greatness) of pump. Pump volume can be selected from Table 3 in pursuant of specified capacity and volume.
  4. Specify the pump type. After choosing the greatness of pump from the above table, take care of the system requirements and determine the pump type.(Internal eccentric gear, helical & spur gear).
  5. Pipe diameter of pump suction line shall be determined. Maximum distance between pump axis and the liquid placed in tank is called as suction depth. This distance is specified by; length of suction, diameter, elbows, filters and clacks. Suction distance depends on the air pressure which system was installed. Air pressure is accepted as 760 mm Hg or 10,33 mWc at the sea level.In practise you may take this value as 10 mWc. When you have climbed 100 meters from sea level, suction distance decreases 10 cm concerning with pressure decreasing. In the other words suction distance of pump at 1.000 meter is 1 meter shorter than the pump that was installed in the sea level. Also pump placed in 2.000-meter height can be 2 meters shorter. Pump installed in 2.000 meters can suck the liquid from 6 or 7-meter depth. This distance can be change up to material density and ambient temperature.In order to suck the vacuum, suction pipe diameter must be smaller than pump inlet diameter and if it is possible fasten a clack to the suction line. If the pump works for pushing instead of sucking you have to install the pump as close as to the tank and to the bottom level of tank. Suction pipe scale must be larger than pump inlet port diameter or it must be at the same sizes.
  6. Determine the diameter of outlet pipeline. Viscosity of liquid, density and discharge distance is important for determining the diameter of outlet pipeline. You may benefit from the below table. (Table: 8-1,2,3,4 = pressure loss occurring from pipe depends on viscosity and capacity.)
  7. Motor power must be indicated. Power of the motor can be change depending on capacity of liquid (lit/h), pressure loss (mWc), density and pump productivity. Pressure (resisting) in pipes; at horizontal 100 meter for 10 (mWc meter water column) and vertical 10 meters for 10(mWc) are accepted for the fluids whose density is 1 and less than1. Even if the fluid whose density is more than 1, the pressure loss can be calculated by using the coefficient numbers shown in table 8 with the below formula. Note: When you are calculating the resisting (pressureloss), you will have to pay attention to equivalent length of pipes which   elbows, clacks, valves and etc. are coupled on the line. Equivalent pipe lengths are given in table 7.

    Pressure loss (mWc:  meter water column) = Coefficient (from table8 – 1,2,3,4) x Density of liquid x 0,226 x length of pipe.

  8. MOTOR POWER (HP)= Capacity (l/h) x power loss (mWc) x Density of liquid

                                                             3600 x 75x h(performance)

    1 kW = 1,36 hp


    Type
    1” 1¼” 1½” 2” 2 ½” 3” 4” 5” 6” 8” 10”
    Gate valve 0,2 0,25 0,3 0,35 0,45 0,5 0,75 0,9 1,2 1,5 1,7
    Check Valve 2 2,5 3 4 5 6 8 10 12 16 20
    Suction Clack 2 2,5 3 4 5 6 8 10 12 16 20
    Goose Neck 0,5 0,8 0,9 1,1 1,3 1,6 2,1 2,8 3,5 4,5 5,5
    Standart T 2 2,5 3 4 4,5 5,5 7 9,5 12 15 18
    Standart Elbow 0,8 1 1,4 1,6 2 2,5 3,5 4,5 5 6,5 8

    Table : 7 Equivalent lengths of flat pipes are given in table 7 for vanes and fittings against pressure loss.

     

    Pressure loss table of pipes concerning with viscosity and performance.
    Click on table 8 in order to download Excel format.

     

    Graghic1: Pump Performance (click on the graphic in order to see the large sized view).

     

     

  9. Identify the pump materials and specialities. Materials used during the production are changing in pursuant of the fluid, which will be transferred by the pump. As we know that every liquid has got different chemical and physical properties. Fluids always indicate different specialities when interacted with pump material. Henceforth, pump materials are selected according to liquids properties. We offer you to select bronze bushes when the liquids are having lubrication speciality, also carbon bushes must be selected when the liquid is acid or originating from acid. Beside these when the food fluids are transferred, full stainless steel or Teflon coated material must be selected for the contact surfaces of liquid. After determining the material, pump shall be selected as Jacketed or without Jacketed, according to necessaries of liquid temperature whether it will be heated or not during the transfer.
  10. Coupled position of pump is determined.

In conclusion we shall decide the pump drive situation after specifying the details as above.
Coupled positions are stated under below.

  1. Not coupled. (Bare Pump)
  2. Coupled directly to the electrical motor.
  3. Coupled to electrical motor with reducer.
  4. Coupled with reducer.
  5. Coupled with vee belt.
  6. oupled to electrical motor with reducer and variator.
  7. Coupled on chassis with pull-type (with wheel).
  8. Coupled with vee belt and reducer motor.
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