Pressure Rupture Disk

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. 

Figure 7-11. Safety valve and rupture disk installation using pressure rupturing disk on inlet to safety relief valve, and low pressure disk on valve discharge to protect against back flow/con-osion of fluid on valve discharge side, possibly discharge manifold. By permission, Fike Metal Products Div., Fike Corporation, Inc.

In designing a reactor, the vessel must be able to withstand both vacuum and a very slight positive pressure. The reactor must be fitted with a blow-off valve to vent any excess of nitrogen padding gas. In case the reaction runs out of control, the lid of the reactor also must be fitted with a pressure rupture disk. The fumes and product must be trapped safely. 

Processing equipment has standard procedures to operate and meet safety requirements. Safety information and standards are available from various sources that include the equipment suppliers. Society of Plastics Industry (SPI), and American National Standards Institute (ANSI). For the past century we have observed increasing activity on the part of manufacturers to upgrade safety in fabricating plants. Examples of safety features are many and differ for the different equipment in the lines. Safety interlocks ensure that equipment will not operate until certain precautions have been taken. Safety machine lockout procedures are set up for action to be taken in proper lockout of the machine s operation such as electrical and mechanical circuits. There are preloaded pressure bolts around dies, pressure rupture disks on barrels, and so on. The operating environment is continuously upgraded with reduced sound and noise in the operating areas. 

Rupture disk n. A thin metal disk, contained in a rupture-disk fitting, that, when subjected to a known high fluid pressure, will tear, permitting outflow of fluid and rapid relief of pressure. Rupture disks are now used routinely on extruders and gear pumps to protect both personnel and... 

A rupture disk is located in the extruder barrel just before the breaker plate. When the extruder pressure exceeds the disk s rated value, the rupture disk opens, thereby reducing the pressure. Rupture disks are typically rated for 34.5, 51.7, and 70.0 MPa (5000, 7500, and 10,000 Ib/in ). They are required for operator safety... 

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. 

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. 

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. 

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. 

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. 

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. 

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. 

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... 

Consider now tlie following hypothetical example of a more complicated fault tree involving eight basic events leading to tlie rupture of a pressure release disk, tlie top event T. Tlie fault tree is shown in Fig. 20.7.2. Let tlie basic events be defined as follows ... 

Most reactors are equipped with safety rupture disks to protect the operator and equipment from destructive pressures. The operating pressure in a vessel should never exceed 70% of the range covered by the rupture disk. Similarly, gauges should not be stressed beyond about 70% of full-scale readings for safety and to ensure reliable readings. 

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