How to Install Safety Valves and Pressure Relief Valves
Figure 1: Pressure safety valve
Safety valves and pressure relief valves are essential to ensure safe operating pressures. Proper installation of these valves significantly reduces the chance of danger to people and damage to system components. This article looks closely at the installation procedures of safety and pressure relief valves.
Table of contents
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Safety valve vs pressure relief valve
Safety valve and pressure relief valves have similar installation procedures but different operations. As soon as the system’s pressure reaches a safety valve’s set pressure, the valve opens rapidly to reduce pressure in the system quickly. The safety valve does not begin closing again until the system pressure is very close to the safety valve’s reseating pressure. A pressure relief valve also begins opening when the system’s pressure reaches the valve’s set pressure. However, a pressure relief valve opens proportionally to the increase in pressure. Similarly, it closes proportionally to the system’s pressure dropping. A pressure relief valve works to relieve pressure without rapidly decreasing system pressure. Read our safety valve vs pressure relief valves article to learn more.
Installing a safety valve or pressure relief valve
Figure 2: Relief valve
This section covers guidelines for before, during, and after the installation of safety valves or pressure relief valves. The guidelines apply to both types of valves.
Rushing to install a safety valve or pressure relief valve and overlooking the following pre-installation guidance can lead to poor operation and disaster.
- Storage: If not immediately installing a valve, store it in its original container in a dirt-free environment. Check with the manufacturer for guidance on recommended storage temperatures.
- Packing: Ensure that no packing material is in the valve and prevent any from entering the valve when removing the material.
- Damage: Investigate the valve for any damage it may have taken during the shipping process.
- Nameplate: The valve’s specifications written on its nameplate should match the specifications needed for the system.
- Port covers: If the inlet and outlet ports have covers, wait to remove them until installation.
- Lifting and carrying: If the valve has a handle or lever for manual operation, do not use it to lift or carry the valve.
- Testing: It is highly recommended to have a certified technician test a safety valve or pressure relief valve’s set pressure and seal tightness before installation.
After taking sufficient precautions during the pre-installation phase, install a safety or pressure relief valve using the following guidelines.
- PPE: Wear PPE (personal protective equipment) such as gloves, eye protection, and hard shoes.
- Depressurization: Depressurize the system upstream of where the valve will be installed.
- Location: Install the valve close to the pressure source (e.g., air tank). If there is a bend or elbow between the valve and the pressure source, install the valve at least 8-10 pipe diameters from the diverter.
- Vertical position: Install valves in a vertical position with the stem facing upwards unless the valve design explicitly allows a different orientation.
- Pipe size: Ensure the piping diameter is at least equal to the diameter of the inlet and outlet ports.
- Lubrication: Avoid lubrication to prevent overtightening. Even Teflon tape provides some lubrication, so take care if using Teflon to seal a threaded connection. Also, with Teflon, leave one to two threads on the connection’s end uncovered and do not use Teflon on internal threading.
- Overtightening: Overtightening can damage the valve. Follow the manufacturer’s recommendation on how tight the connection should be.
- Flanged connections: Tighten the bolts of flanged connections in a star pattern rather than tightening consecutive bolts. The latter can lead to an improper distribution of tightening.
- Pressure fluctuations: Install the valve away from zones of pressure fluctuation—for example, turbulent areas near other valve outlets.
- Support: Ensure the valve is properly supported to avoid undue stress on the valve body.
- Steam: Install safety and pressure relief valves above a steam pipe to avoid condensation interacting with the valve.
- Testing: After installing a pressure relief or safety valve, test it by slowly delivering pressure to it until the pressure reaches the set pressure limit. Ensure the valve functions as it should.
- Adjustment: Adjusting a pressure relief valve may be necessary if testing determines that the valve opens at the wrong set pressure.
- Maintenance schedule: Ensure a schedule is in place for regularly testing the valve. Pressure relief and safety valves require testing at least once a year. Valves that operate more frequently may require more frequent testing.
Where is a safety valve usually located?
Safety valve installation needs to be near the pressure source, for example, the air tank. If the valve is too far away from the pressure source, it may not function precisely.
Is a pressure relief valve necessary?
Yes. Pressure relief valves ensure that pressure is not able to build to dangerous levels within a system.