Pin-actuated pressure relief device

Pressure relief device (PRD) is a safety device to protect equipment or piping from damage due to overpressure or vacuum, but in this chapter, we wiU discuss FRD to provcfit overpressure only. Commonly used pressure relief devices are spring-loaded and pilot-operated pressure relief valve (PRV), rupture disk, or pin-actuated pressure relief device. For equipment, it is installed cither directly on the equipment or at its inlet/outlet piping. When the equipment or piping pressure reaches the pressure relief de vice set pressure, it will open to relieve fluid inside the equipment or piping to avoid overpressure. The relief fluid can be vapor, liquid, or two phase mixture. The relieved fluid is either sent to floic system to be disposed or relieved to atmosphere. 

II1.2 Characteristics of rupture disk and pin-actuated pressure relief device They are either close or open, depending on the system pressure is below or above its set pressure. 

For pin-actuated pressure relief device, maximum operating pressure can be 95% of set pressure. 

Breaking pin device in combination with pressure relief valve. This style of pressure relief device, as illustrated in Fig. 8-19, is very similar to the rupture disk and relief valve combination, except that a breaking pin is used in place of the rupture disk. The breaking pin device is a nonreclosing pressure relief device actuated by inlet static pressure and is designed to function by the breaking of the load carrying section of the pin. 

Among the relief devices mentioned above, spring-ioaded and pilot-operated pressure relief valve (PRV) are the ones used most fiequently, PRV is a reclosing pressure relief device, since after it is opened and relieved, it will be reclosed, when equipment or piping pressure is dropped below PRV set pressure. Once it is dosed, h will continue to protect the equipment or piping from overpressure- Rupture disk or pin-actuated relief device is the non-reclosing pressure relief device, since it cannot be reused after it is ruptured or actuated - its rupture disk or pin needs to be replaced. 

Set pressure is the pressure at which the device begins to relieve, e.g., lift pressure of a spring-actuated relief valve, bursting pressure of a rupture disk, or breaking pressure of a breaking pin device. 

---