How to install safety valves and pressure relief valves

Safety valves and pressure relief valves are an important measure in order to ensure safe operating pressures. Therefore, it is important that they are installed properly. In this article, we will provide you with the needed information.

Installation guidelines

As previously stated, it is important that your pressure safety or relief valve is installed correctly. If the installation is not performed with caution it can lead to leakage or pose safety problems. In order to correctly install a safety valve onto your system, the following points should be taken into account. 

Remove dirt and debris

The valve seat can easily be damaged by dirt and debris that is present in the system. To prevent dirt and debris from passing through the valve the system must be flushed prior to installation. Additionally, the valve should be installed in places where dirt and debris cannot collect.

Mounting

  • Mount safety valves in a vertical position. Installing in a horizontal position can lead to leaks or improper functioning.
  • For flanged versions: tighten the bolts evenly. Not doing so will prevent the other bolts from being tightened correctly. Cast iron valves can crack due to the uneven pressure load.
  • Do not overtighten the valve. This could damage the valve threads and cause leakages.
  • Only apply thread sealant to the male thread. Applying it to the female thread could lead to media contamination.
  • If the valve is more than 10 ft above a vessel it should be supported. Without support, the reaction forces could damage the valve or other parts of the system. 

Inlet piping

  • The inlet piping should be short and direct. The inlet piping diameter should never be smaller than the valve inlet diameter. This will constrict the flow.
  • The inlet should not be located near high turbulence areas on a vessel.
  • Process lines should not be connected to safety valve inlet piping.
  • Install the valve at least 8 to 10 pipe diameters from Y or bending fittings.
correct safety valve inlet piping

Figure 1: Correct safety valve and pressure relief valve inlet piping

Valve operation

It is recommended that the valve’s set pressure should at least be 10% higher than the operating pressure in order to avoid leaking. Safety valves are known to exhibit leaking when it approaches 80% to 90% of the valve’s set pressure. 

Testing

Although it is recommended to test safety valves over time, this should be done about once a year. Testing too will often pose risks of dirt or other forms of contamination to get into the valve seat and lead to leaks.

Safety valve installation for steam systems

Safety valves are a common safety measure within steam systems. It is important to install the valves such that no condensate can collect on the upstream side of the safety valve’s disc. This is commonly done by installing the valve above the steam pipe. If the safety valve is installed below the steam pipe, the condensate will fill up the connection to the valve. The condensate can damage the valve seat and influence the valve operation. Figure 1 shows the correct installation for steam systems.

correct safety valve inlet piping

Figure 2: Correct vs incorrect safety valve installation for steam systems

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