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【Valve Knowledge】Precautions for Check Valve Installation
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1. Preparation before installation
Model and specification verification
Confirm that the type of check valve (such as lift type, swing type, butterfly type, etc.), nominal diameter, pressure level and pipeline system match to avoid leakage or failure due to specification mismatch.
Check the appearance of the valve to ensure that there are no cracks or deformations, the sealing surface is intact, and the valve disc is flexible (no jamming when manually opened and closed).
Confirm the flow direction of the medium
The check valve has a clear flow direction mark (usually marked with an arrow on the valve body). The direction of the arrow must be consistent with the normal flow direction of the medium, otherwise the valve will not be able to open or the medium will flow back.
For example: the arrow of the check valve at the outlet of the water pump should point to the water outlet direction; the arrow of the check valve of the boiler feed water pipeline should point to the boiler.
2. Installation location selection
Avoid vibration and impact
The installation location should be away from equipment with frequent vibration (such as pumps and compressors). If it cannot be avoided, flexible joints should be installed before and after the valve to reduce vibration damage to the sealing surface.
When installed vertically (such as in a vertical pipeline), ensure that the weight of the valve disc does not affect its closing performance. (For example, a swing check valve installed vertically may require a specially designed weight or spring to assist closing.)
Easy Maintenance and Inspection
Sufficient space should be left before and after the valve to facilitate later disassembly and inspection (it is recommended to reserve space at least 1.5 times the valve length).
If installed in a concealed location (such as a pipe trench or in a suspended ceiling), an inspection port should be provided to prevent subsequent maintenance difficulties.
Location Requirements for Special Scenarios
Pump Outlet
The check valve should be installed after the gate valve/stop valve (close to the outlet) to facilitate closing the gate valve during inspection and prevent backflow of media into the pump body.
Boiler Inlet
The check valve should be installed between the feedwater valve and the boiler to prevent backflow of high-pressure media within the boiler.
Vertical Pipeline
Swing check valves can be installed vertically (with media flowing from bottom to top), but lift check valves can generally only be installed horizontally, otherwise the disc seal will be affected.
3. Installation Direction and Method
Install strictly according to the flow direction
Whether installed horizontally or vertically, ensure that the arrow on the valve body aligns with the direction of the medium flow. Reverse installation is strictly prohibited (reverse installation may prevent the valve from opening and may even damage the valve disc due to excessive medium pressure).
Horizontal Installation Precautions
When installing a swing check valve on a horizontal pipe, the disc axis should be horizontal to prevent gravity from tilting the disc and affecting the sealing effect.
When installing a lift check valve horizontally, the disc should be perpendicular to the pipe axis to ensure smooth lifting and lowering.
Vertical Installation Precautions
When installing a swing check valve in a vertical pipe (where the medium flows from bottom to top), the disc should open downward, using the medium pressure and the weight of the disc to assist in closing.
Do not install a conventional lift check valve in a vertical pipe (the disc may not close tightly due to gravity, causing leakage).
Avoid reverse slopes or tilts.
After installation, the valve should be coaxial with the pipe to avoid uneven pressure on the valve flange due to pipe misalignment, which may cause leakage. When flange connection is used, the gasket material must be compatible with the medium (such as metal gaskets for high-temperature media and PTFE gaskets for corrosive media), and the gasket size must match the flange sealing surface to prevent the gasket from protruding into the pipeline and hindering the flow of the medium.
4. Coordination with other valves
Check valves are usually used in conjunction with stop valves, gate valves, etc., and the installation sequence must be reasonable:
In systems that require frequent maintenance, the check valve should be installed after the control valve (gate valve/stop valve). Closing the control valve can isolate the check valve for easy maintenance.
For high-pressure systems, it is recommended to install control valves before and after the check valve to facilitate the isolation of the valve for maintenance.
5. Inspection and debugging after installation
Sealing test
After installation, a water pressure or air pressure test (test pressure is 1.5 times the working pressure) is required to check whether the valve and flange connection are leaking.
During the test, slowly increase the pressure to observe whether the valve disc can be tightly closed (no medium backflow phenomenon) and whether it is smooth and unstuck when opened.
Remove impurities from the pipes. Before installation, remove impurities such as welding slag, rust, and sand from the pipes to prevent them from blocking the valve disc and causing seal failure or valve damage. (A filter can be installed before the check valve.)
Operational Observation: After system startup, observe the check valve's operation: no unusual noise when opening, and no severe water hammer when closing. (If water hammer occurs, it may be due to the disc closing too quickly; a slow-closing check valve or water hammer arrester may be required.)
6. Additional Requirements for Special Media
High-Temperature Media (e.g., Steam)
Select check valves made of high-temperature-resistant materials (e.g., cast steel or stainless steel). During installation, pay attention to the thermal expansion and contraction of the valve body and avoid deformation caused by overtightening the flanges.
Corrosive Media (e.g., Acids and Alkalis)
Use corrosion-resistant materials (e.g., 316 stainless steel or PVC). Ensure the sealing surface is smooth to prevent residual corrosion from the media.
Media Containing Particulates (e.g., Sewage or Slurry)
Select swing or ball check valves to prevent particles from blocking the disc. Regularly clean the valve of impurities.