Preventing Backflow in Pumps: How to Choose the Right Check Valve？

As a key component of the fluid control system, the check valve plays an irreplaceable role in ensuring the safe and stable operation of the system. The valve can effectively prevent the backflow of the medium through the one-way flow characteristics, thereby protecting important equipment such as pumps and compressors from water hammer impact and reverse pressure damage, while preventing the pipeline system from being contaminated by the medium. Whether it is a large-scale industrial pipeline project or a civil water supply and drainage facility, the reasonable configuration of the check valve significantly improves the system reliability, prolongs the service life of the equipment and greatly reduces the operation and maintenance costs.

 

In the previous chapter, we introduced the definition and use of the check valve. This article will systematically analyze the mainstream check valve types from the dimensions of structural principles, performance characteristics, etc., and put forward targeted selection suggestions and technical solutions based on different working conditions.

 

Factor	Recommended Check Valve Type
Clean Fluids	Lift, silent check, nozzle check
Dirty/slurry Fluids	Swing, ball, duckbill, diaphragm
High Flow Rate	Swing, nozzle check
Low Flow Rate	Ball, diaphragm, tilting disc
Pulsating Flow	Tilting disc, silent check, nozzle check
High Pressure	Lift, nozzle check, dual plate
Low Pressure	Duckbill, swing, ball check
Vertical Flow (UP)	Ball, diaphragm, spring-loaded
Compact Space	Wafer type, ball type
Water Hammer Prevention	Silent checks, nozzle checks, tilting disc, spring-assisted
Corrosive Fluids	Duckbill, diaphragm, PVC and stainless steel valves
Low Maintenance	Ball, duckbill, swing checks

Recommended check valve types for different applications

 

• Key factors to consider when selecting a check valve

 

1. Match valve size to operating conditions

1) The valve size should always be determined based on the application, not just the line size. The valve size should match the actual flow conditions of the system to ensure that the valve remains fully open under normal operating conditions.

2) When the flow is insufficient, an oversized check valve will produce chatter and accelerate wear.

3) An undersized check valve will wear prematurely due to excessive pressure drop and excessive flow rate.

4) Always refer to the valve manufacturer's flow curve or valve flow coefficient (Cv) data to match the system flow and make an informed decision.

 

2. Fluid type

1) It is necessary to clarify whether the medium is liquid, gas or slurry.

2) The selection criteria for check valves for compressible fluids and incompressible fluids are different.

3) Clean media can choose a wider range of valve types.

4) Media containing impurities or abrasive media require more robust and professional valves, such as swing check valves or duckbill check valves with external levers and springs.

 

3. Pressure, temperature ratings, and material compatibility

1) Always select a check valve with a pressure/temperature rating suitable for the operating conditions.

2) The valve should be able to withstand the system's operating conditions and test pressure requirements to ensure a safety margin and prevent unexpected pressure spikes.

3) Check that the valve material is compatible with the flowing fluid medium. Typically, the valve material matches the system piping material.

4) The sealing material should be compatible with the fluid flowing through the valve.

5) Material compatibility is critical to ensure the life and performance of the valve.

 

4. Valve position and installation direction

1) When installing the check valve, be sure to maintain a reasonable distance from the pump and pipe fittings to ensure stable flow and prevent turbulence.

2) Standard installation distance: ≥5 times the pipe diameter downstream of the elbow, ≥10 times the pipe diameter downstream of the tee/control valve (according to MSS-SP-92 standard). Please consult the valve manufacturer when shortening the distance in special circumstances.

3) Make sure that the valve flow arrow is consistent with the medium flow direction.

4) Most check valves are suitable for horizontal pipes, but only axial flow check valves (such as spring-assisted silent check valves and nozzle check valves) are suitable for vertical upward flow. Swing check valves are prone to water hammer due to the impact of the valve disc on the valve seat in vertical upward flow.

5) Horizontal installation should be preferred.

5. Space constraints

1) The installation space available on site needs to be comprehensively evaluated. 2) Ensure that the valve size is compatible with the system layout. 3) Wafer check valves and other compact structures are particularly suitable for installation scenarios with limited space.

6. Compliance with industry standards

1) Comply with industry standards to ensure safety, durability, and compliance.

2) Water applications: AWWA C5083) Oil and gas pipelines: API 6D, API 5944) High-pressure industrial applications: ASME B16.345) General testing and performance: API 598, ISO 5208

7. Maintenance and life cycle costs

1) Prioritize valves that are easy to inspect and maintain. Valves with fewer moving parts are generally more reliable.

2) Consider replacement costs and potential downtime losses. Although the initial investment is higher, the selection of high-quality valves can achieve long-term cost optimization by reducing maintenance requirements and improving system efficiency.

 

Check valves are an integral part of fluid systems. By fully understanding the characteristics of various check valves and their applicable scenarios, engineers and operators can make wise selection decisions. Correct selection and installation of check valves can help improve the reliability and service life of fluid control systems, making them an important component in industrial applications.