Pressure adjustment issue of the safety valve behind the pressure relief valve

The function of the safety valve on the steam distribution cylinder is to protect it; of course, the safety valve is set based on the operating pressure of the steam distribution cylinder

The safety valve ensures that the downstream equipment does not experience pressures exceeding the designed level, and it is adjusted accordingly to the pressure of that equipment.

Safety valves are generally based on the operating pressure, to which a safety factor is applied. The set pressure of the safety valve on the cylinder should be adjusted based on 0.3 of the regulated pressure. However, the piping system should also take into account the possibility of an increase in pressure due to pressure regulation failure. So sometimes a shut-off valve is installed. When pressure regulation fails, the outlet pressure continues to rise; once it reaches a certain safety factor, the safety valve activates to cut off the pressure downstream, preventing further increase and ensuring the structural safety of the downstream pipelines.

It is necessary to take into account the design pressures of all the devices and pipelines downstream of the pressure relief valve; the setting pressure of the safety valve must not be higher than the highest design pressure of the subsequent system, in order to ensure the safe operation of the system.

A safety valve is used to protect the cylinder assembly, or rather, the system behind it.

The set pressure of the safety valve must not be higher than the highest design pressure of the subsequent system

To protect the split cylinder and the equipment and pipelines behind it, use the design pressure that is lowest; go by that value

The experts upstairs are all very professional. The safety valve has its setting pressure determined based on the normal (safe) operating pressure of the equipment downstream ； The nominal pressure is determined based on the highest operating pressure and operating temperature upstream.

Proper setting of steam safety valves: For most types of steam safety valves, it is permissible to use air or gas for their adjustment. A specially designed test platform is typically used to facilitate the quick installation of safety valves, enabling their calibration at the desired set pressure, as well as subsequent locking and sealing. Apart from general safety considerations, the most important requirement for steam safety valves is the use of quality-approved instruments and instruments and regularly calibrated on-site systems. The standards for all steam safety valves specify the allowable deviation of the set pressure (typically around ±3%), and this requirement must be adhered to. Furthermore, the testing environment should be clean, free of dust, and relatively quiet. The sources of the fluid used for tuning vary, ranging from compressed gas cylinders to enhancement devices and collection containers connected to industrial compressed air main lines. In the case of the latter, the air must be clean, free of oil and moisture. It should also be noted that there are no special requirements for the displacement test. The test platform merely meets the requirement of reaching the set pressure. Normally, at the set pressure, one listens for any “hissing” sounds. During adjustment, whether it is a safety valve with a metal valve seat or one with a soft-sealed valve seat, the valve disc must not come into contact with the valve seat or nozzle while rotating; otherwise, damage will occur easily, and proper sealing will not be achieved. Therefore, to prevent the above situation from occurring, the adjustment screw should be rotated while clamping the valve stem. The allowable setting procedures for ASME I steam boiler safety valves differ in one fundamental aspect: in order to obtain certification for these special equipment items and to have a ‘V’ mark stamped on the valve body, they must be tested using steam on a test bench. Not only must they reach the required set pressure, but they must also exhibit sufficient discharge capacity to show the valve’s opening point and closing point. This process must comply with the approved and controlled quality procedures. For ASME VIII safety valves (marked with ‘UV’ on the valve body), if the installer has steam testing facilities, these safety valves must also be tested on a test bench using steam. If not, it is also permissible to use air or gas for setting. When safety valves that meet ASME VIII standards are used in liquid systems, an appropriate liquid, usually water, must be used for setting purposes. When the safety valve is equipped with an adjustment ring, the setting position should be determined in accordance with the recommendations provided by the manufacturer, and the sealing locking pin should be used. If a safety valve does not specify any applicable standards, and there are no standard references on its nameplate or supporting documents, then there are no restrictions on those who set it. Such valves are usually used to indicate a certain pressure that has been reached, and they are not used as safety valves. If a safety valve has been independently certified by a competent authority as meeting a certain standard, then the setting and lead sealing of the safety valve also constitute part of the certification. In this case, it must be set by the manufacturer or an agency approved by the manufacturer that operates in accordance with quality procedures agreed upon by both parties, and test equipment approved by the manufacturer or a certification body must also be used. To prevent unauthorized changes or damage, most standards require sealing after the safety valve is set. The most common method of sealing is to use sealing wire to connect the valve cap and the spring housing (bonnet), as well as the bonnet and the valve body. The adjustment ring pin can also be locked using sealed wire. Then the wire is lead-sealed, so that the trademark imprint of the setting mechanism can be marked on it.