Rupture, disk

Rupture disk is used for overpressure and/or vacuum protection. It is a simple, less e7q ensive device to provide a fast pressure relief. Per ASME code, it can be used at PRV inlet to protect PRV from corrosive fluid, to reduce emission or PRV maintenance. Sometimes, it is used as a redundant relief device. Its burst pressure is temperature sensitive. Ther ore, both temperature and pressure should be specified fm its bursting service. 

For rupture disk u.sed at PRV inlet, it should be non-fragmenting design to avoid damaging PRV. Rupture disks, such as forward-acting solid metal disk and graphite rupture disk are of fragmenting design, should not be used at PRV inlet. 

For some very corrosive service, two rupture disks installed In series may be required. 

Rupture pin technology is patented in t9K7-I990. Commercial production is started from 1990. Basically there are two types of products. One is rupture pin relief valve, which is like rupture disk, that its pin will buckle at set pressure to open the valve to relieve fluid. The other is buckling pin relief valve, which is like an emergency shutdown Valve, that its pin will buckle at Set pressure to close the valve to Slop fluid flow. This chapter will discuss the ruptiue pin valve oitly. 

The advantages of rupture pin relief valve over rupture disk are 1) Rupture pin will buckle at 5% set pressure by standard. Actually, most times it buckles at of set pressure. 2) Pin is external, not contacting process fluid. Therefore, it will not experience fatigue and is a good candidate for corrosive service. 3) No tempeiatuie correction is required. 4) It will buckle in millisecond, since it buckles at elastic point, not rupture point tike rupture disk. 5) It is easy to replace buckled pin. Only one person can do the job in less than 30 minutes. 6) Operating pressure can be 95% of set pressure. 7) Unlike rupture disk installation, there is no possibility of mistakes in rupture pin installation. [6] 

One advantage of the rupture disk that it has no moving parts and reacts quickly enough to relieve some of the pressure spikes. The quick-acting characteristics of the rupture disk have made it popular for applications in which pressure buildup is instantaneous, e.g., nmaway reaction and exchanger tube rupture. 

The rupture disk operates through differential pressure and may not work satisfactorily if there are large variations in back pressure. This disk is also temperature sensitive. Burst pressme can vary substantially with temperature. With increase in temperature, the bmst pressme decreases, simply because with increase in temperature the mechanical strength of the disk is reduced. Rupture disks are generally designed for a particular differential pressure and temperature and are not recommended if the design differential pressure and temperature vary substantially. 

---

Pressure reducing valves should be of steel constmction, designed for minimum and maximum operation conditions. Pressure gauges should be of ak-kon constmction. Pressure rehef valves should be of the spring-loaded type. Rupture disks may be used only as auxkiary equipment. Differential pressure measurements using mercury manometers should be avoided in ammonia service. 

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. 

Some vessels may be exposed to a runaway chemical reaction or even an explosion. This requires relief valves, rupture disks, or, in extreme cases, a barricade (the vessel is expendable). A vessel with a large rupture disk needs anchors designed For the jet thrust when the disk blows. 

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 Disks A rupture disk is a device designed to function by the bursting of a pressure-retaining disk (Fig. 26-15). This assembly consists of a thin, circular membrane usually made of metal, plastic, or graphite that is firmly clamped in a disk holder. When the process reaches the bursting pressure of the disk, the disk ruptures and releases the pressure. Rupture disks can be installed alone or in combination with other types of devices. Once blown, rupture disks do not reseat thus, the entire contents of the upstream process equipment will be vented. Rupture disks are commonly used in series (upstream) with a relief valve to prevent corrosive fluids from contacting the metal parts of the valve. In addition, this combination is a reclosing system. 

The burst tolerances of rupture disks are typically about 5 percent for set pressures above 40 psig. 

FIG. 26 13 Typical pressure relief system configurations (a) rupture disk system (h) pressure relief valve system. 

Introduction In determining the disposal of an effluent vent stream from an emergency relief device (safety valve or rupture disk), a number of factors must be considered, such as ... 

There are usually several reactors hnked to a single catch tank. To ensure that rupture of a disk on one reac tor does not affect the others, each reactor is fitted with a double-rupture-disk assembly. The use of double rupture disks in this apphcation requires installation of a leak detection device in the space between the two disks, which... 

While either rupture disks or relief valves are allowed on storage tanks by Code, rupture disks by themselves should not be used on tanks for the storage of highly hazardous toxic materials since they do not close after opening and may lead to continuing release of toxic material to the atmosphere. 

Do not use rupture disks in series, unless the space between them is vented to air or a telltale is installed to warn of pressure buildup in that space. 

Set the release pressure of a rupture disk or other vent closure as close to the operating pressure as practical. Note that the maximum overpressure in a vented explosion will exceed the opening pressure of the vent closure. 

Rupture disks or explosion doors may be used as venting devices. Safety valves are not suitable for this purpose. Obviously, the static-activation overpressures Ps at of he venting devices have to be equal to or smaller than the strength of the equipment to be protected (c-orre-sponding to the Pred.max)-... 

The venting capabihty EF and therefore the effective vent area of the explosion door is normally smaller than the capabihty of a plastic or aluminum foil rupture disk with the same area. Therefore, such devices need testing to determine the mechanical strength before actual use, and the venting capability or the pressure rise, respectively. 

FIG. 26-39 Definition of the venting capability EF of an explosion door in comparison with a plastic foil rupture disk. 

Use rupture disks alone or in combination with safety valves with appropriate rupture disk leak detection... 

Vapor recovery vapor incinceration rupture disks ... 

An 800-gal reaetor eontaining a styrene mixture with a speeifie heat of 0.6 eal/gm °C has a 10-in. rupture disk and a vent line with equivalent length = 400. The vessel MAWP is 100 psig and the rupture disk set pressure is 20 psig. The styrene mixture had a self-heat rate of 60°C/min at 170°C as it is tempered in a DIERS venting test. Determine the allowable reaetor mixture eharge to limit the overpressure to 10% over the set pressure. 

The following eonsiders a situation that involves all vapor relief. The size of a vapor phase rupture disk required is determined hy assuming that all of the heat energy is absorbed by the vaporization of the liquid. At the set temperature, the heat release rate q is... 

Explosion rupture disk device A rupture disk deviee designed for use at high rates of pressure rise. 

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. 

Maximum allowable scrubber pressure of 15 psi while the rupture disk allowing gas to come into the scrubber was rated 40 psi. 

Rupture discs are also used below relief valves to protect them from corrosion due to ves.sel fluids. The rupture disc bursts first and the relief valve immediately opens. The relief valve reseals, limiting flow when the pressure declines. When this configuration is used, it is necessary to monitor the pressure in the space between the rupture disk and the relief valve, either with a pressure indicator or a high pressure switch. Othei-wise, if a pinhole leak develops in the rupture disk, the pressure would equalize on both sides, and the rupture disk would not rupture at its set pressure because it works on differential pressure. 

Vessel is final scrubber in a flare, relief, or vent system, i.s designed to withstand maximum built-up back-pressure, and is equipped with a rupture disk or safety head (PSE) to bypass any internal or external obstructions, such as mist extractors back-pressure valves, or flame arrestors. 

F. N. Nazaro, Rupture Disks , Chemical Engineering Magazine, McGraw-Hill, New York, June 20, 1988. 

An important case of gas discliarge is tlie flow from pressure relief valves and rupture disks. Wlien relief is required due to fire exposure in a nonreacting... 

---