Step by Step Guide to Rotary Pump Selection

 

1.) Determine the Capacity Required in USgal or L/min

Pump capacity required is need to determine the correct pump size and motor. Conversion to USgal or liters may be required. Click here for Volume Conversion Factors.

On occasion, the need to calculate volumes of tanks or vessels or the requirements of various processes arises in order to determine the pump capacity.

2.) Determine the Viscosity of the Liquid

The viscosity of the liquid at the lowest pumping temperature(s) is required during the selection process. Determining the correct viscosity ensures the appropriate pump is chosen. High viscosity limits the performance and can cause damage to a pump unit if not properly selected. 

Our graphs show kinematic viscosity expressed in units of Seconds Saybolts Universal (SSU) or Centistokes. Conversion to these units is needed for pump selection. Click here for Viscosity Conversion Factors.

Click here for Typical and Approximate Viscosity List for examples of liquids within a viscosity range.

 

3.) Determine the Differential Pressure of the System

Differential pressure is the difference in pressure between the suction and discharge sides of the pump. Pressure is a factor for determining the required motor horsepower.

Ensure all pressure units are expressed in the same units of measure. (Click here for Pressure Conversion Chart.) 

 

4.) Select the Pump Size

Once the capacity, and viscosity are known the pump size can be chosen. Use the chart below to select the pump size suited for your application. The letters in the chart represent the models available for selection.

 

Size Selection Procedure: By using size selection chart, locate the required capacity on the vertical scale, then move horizontally to the specified viscosity rating. The intersecting point represents the recommended pump model to be used. This chart is based on maximum recommended pump speeds. Consult individual curves for more specific details.

Click here to for more information on Vican Products.

5.) Determine the Pump Series and Characteristics

How the pump is constructed and which series to use is determined by the application characteristics. The model of the pump is followed by number indicating the series of the pump. In some cases the model is used in more than one series. (i.e. KK-32 and KK-124 The 32 series is considered a general service pump and the 124 is considered a heavy duty pump.) Determining which series to use is determined by the application characteristics. Some application characteristics that are considered are as follows.

Pressure: The working pressure helps to determine horse power requirements, relief valve setting, and adequate flange ratings.

Temperature: Liquids at 200F (94C) or more require attention to expansion of materials, mechanical seal components, packing material, and pump material. 

Suction Condition: Pumping high viscosity liquid may require larger ports or a larger pump running slow to over come high line losses on the suction end of the pump.

Abrasive Liquids: Information on particle size, hardness, and percent volume are required to determine the pump component materials to use for improving pump life.

Corrosive Liquids: This information will determine the compatibility of the pump material with the liquid.

 

6.) Determine Pump RPM and Required Horse Power

After selecting the pump model and pump characteristics, next is to look up the specific curve for the pump size. Find an example of a curve following.

 

RPM and Required Horse Power Selection Procedure: By using the example curve, locate the required capacity on the vertical scale, then move horizontally to intersect  the specified pressure determined earlier. Drop vertically to read the required pump RPM. Using the same vertical line, move up vertically to the second set of curves and intersect the specified pressure determined earlier. Now shift horizontally to the left and determine the required horse power.

Performance curves are printed with a specific viscosity noted in the "VISCOSITY" box at the top of the curve. Each model and series has from four to eight different curves that increase in viscosity. The number of curves depends on the ability of the model and series to handle high viscosity. Each curve has two sets of pressure curves. The lower set of curves is for determining the pump rpm and the top set of curves is for determining the required horse power.

 

This is what it takes to select the right pump for you.

Complete the application data on the Application Form to request a pump selection.

Click here for Application Form 

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