Engineering Calculations for Designing and Building Industrial Fluid Handling Pump Systems

IN THE ZONE | Articles

Designing and building pumps and packaged pump systems involve challenging scenarios where complex pump calculations for any type of fluid handling requirements. These calculations are required for manufacturing and remanufacturing industrial pumps, as well as engineering custom fluid handling solutions.  There are several common calculations that are used for many industrial pumps that you will find in oil fields, agriculture, mine operations, and construction. 

There are calculations that apply to any pumping systems and are required for professionals and hobbyists alike. Engineering departments will use them in designing and applying equipment for mechanical applications. Testing technicians and specialists for troubleshooting current systems or when verifying new systems. Calculations are not just limited to employment. Hobbyists, enthusiasts, and students from Power Zone Technical Courses will also use calculations for projects and training.  

Calculating Friction Loss 

One of the most common pump calculations is friction loss which is applicable for any industrial pumping system which requires moving oil, gas, slurry, water, or any other type of fluid through a piping system. Industry standard uses calculations are known as Hazen Williams Equation, Darcy Weisbach Equation and Fanning Churchill Equation are industry standard for calculating friction loss.  

Friction loss is a property of a system that must be overcome by the pump. If the frictional losses of both the inlet and outlet piping are not taken into consideration, the flow rate and pressure of the system will both be less than desired. When the friction loss of the inlet piping is ignored, the pump may cavitate causing damage to the inside of the pump and a reduction in life expectancy of the equipment. While cavitating, a pump suffers a large loss in expected efficiency, pressure, and flow rate. Checking and using the calculations for friction loss can help to ensure that the selected equipment in an application will perform as expected and last for the lifetime of the system.

Friction loss should be included in calculations for any type of pump where a specific pressure, flow rate, or efficiency is expected. Friction loss calculations may be excluded in rare applications. For example, friction loss calculations would not be used when the flow rate and differential pressure across the pump are known. In this case, the friction loss would already be included in the system either through previous measurements or tests of the system.

Friction loss is usually calculated early on in the equipment selection process. The correct pump can rarely be chosen without taking the surrounding system into consideration. Friction loss calculations are also an easy way to narrow down problems when a pump is not operating as expected. Combined with other measurements, they can also be used to signal when the pump system is in need of maintenance. 

Calculating Plunger Pump and Piston Pump Flow

This Plunger Pump Flow Calculator is meant to quickly calculate the flow of a plunger pump or piston pump. By multiplying the area of the pumping chamber(s) by the RPM the pump is rotating, you can precisely calculate the flow of a reciprocating pump.

Since Positive Displacement Pumps move specific volumes of fluid with each rotation, they can be used in applications where more accurate flow rates are needed. Calculating the flow rate will provide the needed information to find how long it will take to move a specific volume of fluid, if a pump will need to rotate slower or faster in a given application, or if new plungers or a different sized pump is needed. 

The calculated flow rate is important to know during the equipment selection stage of the application process. The calculated flow rate of pump candidates can be compared with the required flow rate of the actual application. The best pump can then be selected for the application. Calculated flow rates can also be used to troubleshoot a pump’s performance and can signal pressure and fluid losses through broken valves, cracked fluid ends, and leaking system piping.

Calculating the Net Positive Suction Head 

NPSH (Net Positive Suction Head) is a term referring to fluid supply in a pumping system. NPSH Required (NPSHR) is the amount of fluid that a pump will require at a certain operating point. NPSH Available (NPSHA) is the amount of fluid that a system can deliver to the pump. If NPSHR is greater than NPSHA, meaning the pump requires more fluid than is available to be pumped, the fluid will begin to cavitate and cause damage to the pump. 

Using a NPSH Calculator simplifies the process so almost anyone can do the calculations but for applying to an operating system the calculations should be done by skilled and highly trained professionals. Miscalculating can cause severe cavitation which sounds like gravel is being passed through a pump and the damage caused by cavitation is similar. Even a small, un-audible and undetectable amount of cavitation can cause erosion to the impellers, the impeller vanes, and the volutes of a pump.

When calculating NPSHA for a reciprocating pump, you must calculate the Acceleration Head. This is the pulsating flow of the supply of a reciprocating pump will affect the calculation process. Additional margin should be built into the calculation, as well as adequate pulsation control equipment installed on the suction and discharge of the pump.

Calculating Pump Curve Speed 

This centrifugal pump curve calculator is meant to quickly calculate the different operating conditions when a centrifugal pump is sped up or slowed down. Using affinity laws, we can accurately calculate the pressure, flow and required speed and power of a pump from a specific known set point. 

The pump speed calculation uses the “Affinity Laws” for pumps to change speed, pressure, flow rate, and power for a given pump curve. It is considered to be highly accurate for all types of centrifugal pumps, and for any given centrifugal pump size. However, it would likely not be used for small pumps with loose tolerances such as fountain pumps, fuel pumps for cars and trucks, or where precise measurements are not needed. 

By using the pump speed curve calculator, it can be determined if a given pump will meet the expectations of an application. It may also be used to compare several different pump sizes and give the purchaser different options on pump models, makes, and pricing.

Calculating Centrifugal Pump Power 

This centrifugal pump power calculator by Power Zone provides you with the accurate mechanical power required for a single stage horizontal centrifugal pump or a single stage vertical centrifugal pump as well as a horizontal multi-stage centrifugal pump or a vertical multistage centrifugal pump at a set operating point.

This calculation will provide the necessary information to choose a driver such as an engine or motor. The result of the calculation is the required amount of power that the electric motor must provide to the pump shaft in order to meet the operating point.

Calculating the pump power will give a more accurate measurement of the size of the driver that is needed. Without taking this into consideration, a more costly larger driver might be selected, or a smaller driver that won’t provide the power required to meet the pump’s operating point. 

The power required to drive a centrifugal pump increases as flow increases, or efficiency decreases. Required power will also vary by the fluid being pumped. Light fluids such as oil will require less power than heavy fluids such as salt water or slurry.

Professional Calculations for Fluid Handling

This article provides basic outlines and principles when calculating your requirements when purchasing inventory, setting up your operation, or for general maintenance. Please always consults with a professional engineer or pump expert before beginning your next project. The team at Power Zone Equipment will be happy to provide any support you require.

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