Rupture disk burst pressure

Note When rupture disk devices are used, it is recommended that the design pressure of the vessel be sufficiently above the intended operating pressure to provide sufficient margin between operating pressure and rupture disk bursting pressure to prevent premature failure of the rupture disk due to fatigue or creep. 

The burst pressure maximum cannot exceed the MAWP of the vessel. Depending on the situation, it may be necessary to work backward to the operating pressure maximum to see if this is usable. Table 7-9 summarizes t) pical rupture disk characteristics noting that the maximum normal operating pressure of the system is shown as a function of the rupture disk bursting pressure, P. ... 

Pb-jnin = 105/0.7 = 150 psig mm rupture disk burst pressure... 

Figure 7-32. Establishing stamped rupture disk bursting pressure at coincident temperature, Method 2. By permission, Fike Metai Products Div., Fike Corporation.

Used to indicate the inlet pressure and temperature of a pressure relief device at a specific overpressure. The relieving pressure is equal to the valve set pressure (or rupture disk burst pressure) plus the overpressure. The temperature of the flowing fluid at relieving conditions may be higher or lower than the operating temperature. 

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. 

For unexpected runaway or process overpressure not subject to exteimalfire, the rupture disk set pressure, which is the bursting pressure, should be sufficiently higher than the expected under acceptable control conditions for the operation to avoid the frequent burst and shut... 

When water started to react with MIC, no control of the temperature/pressure started, because it was late at night and the operational staff was reduced to a minimum, and the MIC tank s alarms had not worked for 4 years. The gas leakage followed, for the first 30 min, approximately the inverse route of water entrance (Figure 1.6), except that which reached the atmosphere through the vent collection system (VCS). However, the flare tower and the vent gas scrubber (Figure 1.7) had been out of service for 5 months before the disaster. After the first 30 min, the rupture disk bursts and this increased the rate of release of MIC. 

The hydrogen gas from the chemical reaction increases the pressure within the vessel. When the pressure within the SG reaches a predetermined higher level, the rupture disks burst and the sodium within the SG drains rapidly into a sodium dump tank. For such large sodium/water reaction events, it is also necessary to seal off the reactor/SG system for the purpose of containment isolation. An SG isolation system (SGIS) is provided to terminate a sodium/water reaction (by rapidly removing the water from the SG) and to isolate the water side with safety-related isolation valves which serve a safety-grade barrier for the purpose of containment isolation. 

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. 

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. 

A rupture disk is a non-reclosing thin diaphragm (metal, plastic, carbon/graphite (non-metallic)) held between flanges and designed to burst at a predetermined internal pressure. Each bursting requires the installation of a new disk. It is used in corrosive service, toxic or leak-proof applications, and for required bursting pressures not easily accommodated by the conventional valve such as explosions. It is applicable to steam. 

Maximum allowable burst pressure for supplemental (fire exposure) rupture disk device (see Note 6)... 

The stamped burst pressure of the rupture disk may be any pressure at or below the maximum allowable burst pressure. 

Rupture disks must have a specified bursting pressure at a specified temperature. There must be complete iden-... 

A single rupture disk can be used as the only overpressure protection on a vessel or system (Figure 7-10). The disk must be stamped by the manufacturer with the guaranteed bursting pressure at a specific temperature. The disk must rupture within +5% of its stampied bursting pressure at its specified burst temperature of operation. The expected burst temperature may need to be determined by calculation or extrapolation to be consistent with the selected pressure. 

Users are warned that a rupture disk wdll not burst at its design pressure if back pressure builds up in the space between the disk and the safety or safety relief valve which will occur should leakage develop in the rupture disk due to corrosion or otlier cause. 

Rupture disks are often placed below a safety valve to prevent corrosive, tarring or other material from entering the valve nozzle. Only disks which do not disintegrate when they burst (Figures 7-10, 7-11, 7-12, 7-18) can be used below a safety valve, as foreign pieces which enter the valve might render it useless. This is acceptable to certain code applications [1]. These disks are also used to pro dde secondary relief when in parallel tvith safety valves set at lower pressures. They can also be installed on the discharge of a safety valve to prevent loss of hazardous vapors, but caution should be used in anv serious situation. 

The manufacturing range is defined as the allowable pressure range within which a rupture disk is rated. It is based upon the customer specified burst pressure. The manufacturing ranges for Continental s standard rupture disk are outlined in Table 7-2. 

After the disk has been manufactured and tested, it is stamped with the rated burst pressure. The rated (stamped) burst pressure is established by bursting a minimum of two disks and averaging the pressures at which the disks burst. This average is the rated (stamped) burst pressure of the disk. Standard rupture disks above 15 psig 72°F are provided with a burst tolerance of 5% of the rated (stamped) burst pressure. This is in accordance with the ASME code. Burst tolerances for disks below 15 psig 72°F are oudined in Table 7-2. Burst tolerance applies only to the rated (stamped) burst pressure of the disk. Burst certificates are provided with each disk lot. 

The coefficient of discharge, Ko, is the actual flow divided by the theoretical flow and must be determined by tests for each type or style and size of rupture disk as well as pressure-relieving valve. For rupture disks, the minimum net flow area is the calculated net area after a complete burst of the disk, making allowance for any structural members that could reduce the net flow area of the disk. For sizing, the net flow area must not exceed the nominal pipe size area of the rupture disk assembly [1]. 

It is essential to select the type or style of rupture disk before making the final determination of the final burst pressure, and even this selection must recognize the pressure relationships betw een the disk s manufacturing range and the vessel s maximum allowable w orking pressure. (Also see Eigures 7-31A and 31B.)... 

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