Positive Displacement Pump

Why Does Your Positive Displacement Pump Come with a Pressure Relief Valve?

Positive displacement pumps are engineered to deliver a constant volume of fluid with every revolution of the shaft, regardless of system pressure. This characteristic makes them highly reliable in applications requiring steady flow. However, this same trait also creates the potential for overpressure when discharge flow is restricted or blocked, which is why pressure relief valves are essential.

Understanding the Role of Pressure Relief Valves

Unlike centrifugal pumps, which have a performance curve where flow decreases as pressure increases, positive displacement pumps maintain a nearly constant flow rate regardless of pressure changes. This  performance can lead to excessive pressure if the system isn’t designed to handle such conditions.

A pressure relief valve provides a crucial safety mechanism by preventing overpressurization. When pressure in the system exceeds a set limit, the relief valve opens, redirecting the fluid back to the pump inlet or to a safe discharge point.

Benefits of a Pressure Relief Valve

  1. Prevents System Overpressure: The constant flow of a positive displacement pump can easily cause pressure spikes if the discharge is blocked.
  2. Protects Piping and Components: Overpressure can cause mechanical failure of pipes, seals, and other system components.
  3. Safeguards the Driver: Excessive pressure can overload the pump driver, leading to equipment failure.
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Integrated vs. External Relief Valves

Integrated valves are compact, efficient, and reduce installation complexity. Alternatively, some systems use external pressure relief valves mounted in the piping system, offering greater flexibility in configuration.

Additional Considerations for Pressure Relief Valve Operation

When working with a pressure relief valve in your positive displacement pump, keep these points in mind:

  • Regular Testing and Maintenance: Pressure relief valves are critical safety devices and must be inspected regularly to ensure they open and close properly. Blocked or malfunctioning valves can lead to overpressure despite their presence.
  • Set Pressure Limits Carefully: The relief valve must be set to open at a pressure that is slightly above the system’s normal operating range but well below the maximum pressure the system can handle.
  • Flow Recycling Options: If the relief valve redirects flow back to the pump inlet, consider the impact on fluid temperature. Continuous recycling can lead to overheating, so additional cooling measures may be necessary.

Pressure relief valves are a vital part of any positive displacement pump system. By preventing overpressure, they protect your equipment, piping, and drivers from damage. With proper maintenance and an understanding of their function, pressure relief valves safeguard your system and maximize the longevity and efficiency of your pump.

The original article can be found on Pumps & Systems website.

For more information or for an RFQ, contact IEQ today.