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What is the discharge head of a Progressive Cavity Pump?

by brian•

In the world of fluid handling, the progressive cavity pump stands out as a reliable and versatile solution for a wide range of industries. As a supplier of progressive cavity pumps, I’ve had the privilege of working closely with customers to understand their unique needs and provide them with the most suitable pumping solutions. One of the most frequently asked questions I encounter is about the discharge head of a progressive cavity pump. In this blog, I’ll delve into what the discharge head of a progressive cavity pump is, how it’s determined, and why it’s crucial for the proper operation of your pumping system. Progressive Cavity Pump

Understanding Discharge Head

The discharge head of a pump refers to the total pressure that the pump must generate to move the fluid from the suction point to the discharge point. It’s a measure of the energy required to overcome the various forces acting against the flow of the fluid, including gravity, friction, and static pressure. In the context of a progressive cavity pump, the discharge head is a critical parameter that determines the pump’s performance and its ability to handle specific applications.

Components of Discharge Head

The discharge head of a progressive cavity pump is made up of several components, each contributing to the total pressure that the pump must overcome. These components include:

  1. Static Head: This is the vertical distance between the suction level and the discharge level of the fluid. It represents the energy required to lift the fluid against gravity. For example, if you’re pumping water from a well to a storage tank located on a higher elevation, the static head would be the difference in height between the water level in the well and the level of the storage tank.
  2. Friction Head: When fluid flows through a pipe or a tubing, it encounters resistance due to the friction between the fluid and the pipe walls. The friction head is the pressure loss caused by this friction and is dependent on factors such as the pipe diameter, length, roughness, and the velocity of the fluid. A larger pipe diameter or a smoother pipe surface will result in lower friction losses, while a longer pipe or a higher fluid velocity will increase the friction head.
  3. Vapor Pressure Head: In some applications, the fluid being pumped may be close to its boiling point. When this happens, the vapor pressure of the fluid can cause the formation of vapor bubbles, which can disrupt the flow and reduce the pump’s performance. The vapor pressure head is the pressure required to prevent the fluid from vaporizing and is related to the temperature and the vapor pressure of the fluid.
  4. Pressure Head at Discharge: This is the additional pressure required at the discharge point to meet the specific requirements of the application. For example, if the fluid is being pumped into a pressurized system, such as a boiler or a pressure vessel, the pump must generate enough pressure to overcome the system pressure.

Determining the Discharge Head

Calculating the discharge head of a progressive cavity pump involves a detailed analysis of the pumping system and the specific requirements of the application. Here’s a step-by-step guide on how to determine the discharge head:

  1. Measure the Static Head: Use a level or a surveying instrument to measure the vertical distance between the suction and the discharge points. Make sure to account for any changes in elevation along the pipeline.
  2. Calculate the Friction Head: Use the Darcy-Weisbach equation or other friction loss formulas to calculate the pressure loss due to friction. You’ll need to know the pipe diameter, length, roughness, and the flow rate of the fluid. There are also many online calculators available that can simplify this process.
  3. Determine the Vapor Pressure Head: Refer to the fluid’s properties data to find its vapor pressure at the operating temperature. Calculate the vapor pressure head based on the difference between the system pressure and the vapor pressure of the fluid.
  4. Identify the Pressure Head at Discharge: Determine the required pressure at the discharge point based on the application’s needs. This may involve consulting with the end-user or referring to the system’s specifications.
  5. Sum up the Components: Add up the static head, friction head, vapor pressure head, and pressure head at discharge to get the total discharge head.

Importance of Discharge Head in Progressive Cavity Pump Selection

Selecting the right progressive cavity pump for your application requires careful consideration of the discharge head. Here’s why the discharge head is so important:

  1. Pump Performance: The discharge head directly affects the pump’s performance. If the discharge head is too high for the pump’s capabilities, the pump may not be able to generate enough pressure to move the fluid, resulting in reduced flow rate or even pump failure. On the other hand, if the discharge head is much lower than the pump’s rated capacity, the pump may operate inefficiently, consuming more energy than necessary.
  2. Pump Life and Reliability: Operating a progressive cavity pump at or near its maximum discharge head can put excessive stress on the pump components, leading to premature wear and failure. By selecting a pump with the appropriate discharge head for your application, you can ensure that the pump operates within its designed limits, maximizing its lifespan and reliability.
  3. Energy Efficiency: A pump that is correctly sized for the discharge head will operate more efficiently, consuming less energy per unit of fluid pumped. This can result in significant cost savings over the life of the pump, especially in applications with high flow rates or long operating hours.

Factors Affecting Discharge Head in Progressive Cavity Pumps

Several factors can affect the discharge head of a progressive cavity pump, including:

  1. Pump Design: The design of the progressive cavity pump, including the number of stages, the pitch of the rotor and stator, and the material of construction, can have a significant impact on its discharge head capabilities. Pumps with more stages or a finer pitch generally have a higher discharge head capacity.
  2. Fluid Properties: The properties of the fluid being pumped, such as viscosity, density, and temperature, can affect the discharge head. Higher viscosity fluids require more energy to pump and can increase the friction head, while changes in temperature can affect the vapor pressure and the viscosity of the fluid.
  3. System Configuration: The layout of the pumping system, including the pipe diameter, length, and the number of fittings and valves, can also affect the discharge head. A more complex system with many bends, elbows, and valves will have higher friction losses, resulting in a higher discharge head requirement.

As a supplier of progressive cavity pumps, we understand the importance of selecting the right pump for your application. Our team of experts can work with you to analyze your pumping system, determine the required discharge head, and recommend the most suitable pump for your needs. Whether you’re pumping thick slurries, abrasive fluids, or viscous polymers, we have the experience and the expertise to provide you with a reliable and efficient pumping solution.

Hydraulic Diaphragm Metering Pump If you’re in the market for a progressive cavity pump and need help with pump selection or have any questions about discharge head, we’d love to hear from you. Feel free to reach out to us to discuss your requirements and start a conversation about how we can help you find the perfect pumping solution for your application.

References

  • Karassik, I. J., Messina, J. P., Cooper, P., & Heald, C. C. (2008). Pump Handbook. McGraw-Hill Professional.
  • Stepanoff, A. J. (1957). Centrifugal and Axial Flow Pumps: Theory, Design, and Application. John Wiley & Sons.
  • Hydraulic Institute. (2012). ANSI/HI 9.6.7-2012 Rotodynamic Pumps – Guideline for NPSH Margin.

DEPAMU (Hangzhou) Pumps Technology Co., Ltd.
DEPAMU (Hangzhou) Pumps Technology Co., Ltd. is one of the leading progressive cavity pump manufacturers and suppliers in China, with professional factory we are able to produce Chinese best progressive cavity pump at both low price and good quality. If you are looking for Germany technology or famous brand progressive cavity pump, please feel free to contact us.
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