Pressure relief devices rupture disk

Unlike other pressure relief devices, rupture disks do not fall back to the original position when the pressure is reduced. The rupture disk is of the nonclosing type and needs to be replaced manually. 

If a rupture disk is used as the primary pressure-relief device, then when it bursts the operators have no option but to shut down the plant so that the disk can be replaced before the vessel is repressured. Rupture disks are therefore most commonly used at the inlets of relief valves or as secondary relief devices. Rupture disks can be sized using equation 13.105 for compressible gases in sonic flow, with a value of Kd = 0.62. 

Pressure-relief-device requirements are defined in Subsec. A. Set point and maximum pressure during relief are defined according to the service, the cause of overpressure, and the number of relief devices. Safety, safety relief, relief valves, rupture disk, breaking pin, and rules on tolerances for the reheving point are given. 

Pressure Relief Devices The most common method of overpressure protection is through the use of safety rehef valves and/or rupture disks which discharge into a containment vessel, a disposal system, or directly to the atmosphere (Fig. 26-13). Table 26-8 summarizes some of the device characteristics and the advantages. 

Rupture disk device A non-reclosing pressure relief device actuated by inlet static pressure and designed to function by the bursting of a pressure containing disk. 

The capacity of the combination of the rupture disk device and the spring loaded safety or safety relief v alve may be established in accordance with the appropriate paragraphs of UG-132, Certification of Capacity of Safety Relief Valves in Combination with Non-reclosing Pressure Relief Devices. 

Never place a block valve on the inlet side of a pressure relief device of any kind, unless it conforms to the code practice for rupture disks or locking devices. See [1] Par. UG-135(e) and Appendix M, ASME code. 

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. 

Figure 10.6 Schematic of two pressure-relief devices that are installed improperly a) the stem on this device may be too long, causing the polymer to solidify in the stem during a rupture, and b) the rupture disk should be flush with the flow surface and not recessed as shown...

Relief valves are preferred for use on clean materials, because automatic closure prevents excessive discharge once excessive pressure is relieved. Rupture disks are less susceptible to plugging or other malfunctions but may allow complete emptying of the vessel, thus creating a safety or environmental hazard. Where fluctuating pressures or very corrosive conditions exist, or where polymerizable materials could prevent proper operation of a relief valve, some designers install two safety devices in series, ie, either two rupture disks or an upstream rupture disk followed by a relief valve. With either arrangement, it is imperative that the space between the two relief devices be monitored so that perforation or failure of the relief device closest to the vessel may be detected (86). 

Alternative energy processes, just like any others, need to be protected from excessively high or low pressures. The methods of protection include pressure regulation, alarm, or safety interlock actuation when preset pressure limits are violated, and providing pressure relief devices, which need to be replaced after each operation (rupture disks) or can automatically reclose (relief valves). The features and characteristics of these devices are discussed in the following subsections. 

Pressure-relief devices include direct spring-loaded and pilot-operated relief valves that close or reseat if the vessel pressure is brought back into a safe condition, as well as non-reclosing devices such as rupture disks and breaking-pin devices. 

Two types of non-redosing pressure-relief devices are used rupture disks and breaking-pin devices. 

Both rupture disks and breaking-pin devices are sensitive to temperature. The manufacturer should always be consulted for applications that are not at ambient conditions. Since non-reclosing pressure-relief devices can be used only once, the set pressure is determined by testing a sample of the devices out of each manufactured batch. Pressure-relief valve test methods are specified in AS ME PTC 25-2001. 

Pressure-relief Devices. Spring-loaded pressure-relief valves and rupture disks of thin sheet material are available from manufacturers (see " Chemical Engineering Catalog ). When using pressure-relief disks, a strictly noncorrosive material must be specified because of the requirement of maintaining strength in very small thickness. 

This type of installation has been shown to create a hazardous condition in the event that the rupture disk develops a pinhole leak that allows the pressure between the rupture disk and the relief valve to equilibrate with the process pressure. In order for the rupture disk to burst at its specified set pressure, the backpressure on the device needs to be low (typically atmospheric pressure). In the event of a pinhole leak, the rupture disk backpressure can rise until it reaches the equipment operating pressure, which effectively raises the burst pressure by a like amount. Depending on the set pressure of the rupture disk relative to the maximum allowable working pressure (MAWP) of the equipment, the equipment can be subjected to an overpressure that is unsafe. The typical layer of protection is to install a tell tale pressure gage between the rupture disk and the relief valve that is frequently monitored by operations. When pressure is noted, the rupture disk is replaced with a new one. 

Mechanical equipment that performs an action to relieve pressure when the normal operating range of temperature or pressure has been exceeded. Physical relief devices include pressure relief valves, thermal relief valves, rupture disks, rupture pins, and high temperature fusible plugs. 

The rupture disk is the operating part of the pressure relief device and, when installed in a... 

Type CG-4 and CG-S (combination rupture disk/fusible plug). A combination rupture disk/fusible plug pressure relief device requires both temperature and pressure in that order for it to operate and therefore provides for maximum retention of the cylinder contents. Sufficient heat is required to first melt out the fusible metal, after which the device will afford the same protection as the CG-1 rupture disk device. 

To protect the inner container from overpressurization, the unit includes a CG-7 pressure relief valve. As a secondary pressure relief device, such containers are further protected from overpressurization by a CG-1 rupture disk. The cylinder will also contain an internal vaporizer, which converts cold liquid to warm gas for gas withdrawal. The vacuum jacket is also protected by a safety device to prevent overpressurization due to leakage. 

Rupture disk device in combination with pressure relief valve. Combination rupture disk/pressure relief devices, as illustrated in Fig. 8-18, consist of a conventional reclosing pressure relief valve in series with a rupture disk. The rupture disk is located between the pressure relief valve and the container. The relief valve is... 

When this combination-type pressure relief device is installed, some regulations require that the space between the rupture disk and relief valve be vented to the atmosphere or monitored to detect any pressure buildup on the downstream side of the rupture disk, which could prevent proper functioning of the rupture disk. 

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. 

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