Rupture disc failure

Correlations are needed to predict whether two-phase flow will occur after vapor venting is initiated by rupture disc failure or relief valve opening. Research is needed in this area, but for the present we recommend the following correlations to predict batch swell. For systems with low viscosity (less than 500 cp) an equation based on bubble column hold-up is used to obtain a swell ratio ... 

An important problem with rupture discs is the flexing of the metal as process pressures change. Flexing could lead to premature failure at pressures below the set pressure. For this reason some rupture disc systems are designed to operate at pressures well below the set pressure. In addition, vacuum service may cause rupture disc failure if the relief system is not specifically designed for this service. 

An important application of a rupture disc device is at the inlet of a pressure relief valve. The sizing of the pressure relief valve or rupture disc device combination requires that the pressure relief valve first be sized to meet the required relieving capacity. The normal size of the rupture disc device installed at the inlet of the pressure relief valve must be equal to or greater than the nominal size of the inlet connection of the valve to permit sufficient flow capacity and valve performance. The failure modes of rupture discs are [40] ... 

Rupture discs should be removed from service at predetermined intervals for visual inspection. Depending on the condition of the disc and recommendations by the manufacturers, they are either replaced or returned to service. The most common mode of failure is case (c), premature rupture below the minimum bursting pressure. An analysis of this mode of failure indicates that this can be the result of ... 

Incorrect specification of the disc. This includes overlooking intermittent vacuum conditions and other pressure/temperature transients, failure to predict corrosion, or operating at a pressure too close to the rupture disc pressure, resulting in fatigue failure. 

Failure of relief devices, e.g. pressure relief valves or rupture discs. 

When rupture discs are used before a spring-loaded relief, a pressure gauge is installed between the two devices. This telltale gauge is an indicator that shows when the disc ruptures. The failure can be the result of a pressure excursion or of a pinhole caused by corrosion. In either case the telltale gauge indicates that the disc needs to be replaced. 

Overpressure accidents can not only damage equipment but also cause injury or even death to plant personnel. In order to reduce the potential number of incidents or accidents, it is the job of the process engineer to analyse the process design and to determine the what can go wrong scenarios and either find a way to design out of them or provide protection against catastrophic failure in the event an accident does occur, that is, install an SRV and/or rupture disc. 

Active A reaction capable of generating 22 kPa, realized in a reactor with a 1 kPa high-pressure interlock to stop reactant feeds and a properly sized 3 kPa rupture disc discharging to an effluent treatment system The interlock could fail to stop the reaction in time, and the rupture disk could be plugged or improperly installed, resulting in reactor failure in case of a runaway reaction. The effluent treatment system could fail to prevent a hazardous release... 

Large leak signal based on gas pressure increase in the pressure compensator vessel was not put out because of burst of the rupture disc that had happened before pressure safety settings were reached in the compensator vessel. Absence of displayed information and KAV-7 gas analyzer and ITI system responses which were habitual in connection with the previous leaks, as well as unusually rapid growth of IVA-1 indications sinnlar to that in case of device failure - all this made personnel doubt in the correctness of these devices. As a result of this, personnel did not manage to understand the situation and decision on the SG shutdown was made with delay. 

In the case of a channel failure, the moderator acts as an energy-absorbing cushion, preventing failure of the calandria vessel. Even for beyond-design-basis severe core damage accidents, where a number of channels are postulated to fail, the calandria may leak (pressure relief rupture discs) but would retain its gross structural integrity. 

Diversion of flow safely All the above systems discussed are part of electronic system requiring power. As a next layer of protection there are mechanical devices (requiring no power to meet power failure situations) to divert the flow safely. Safety and relief valves are used to in case to depressurize when SIS fails to take care (e.g., say due to control power failure). Pressure relief valve diverts the fluid for safe passage. These relief valves are spring force to close so that when pressure is below setting it is closed. Many cases rupture discs are used but in that case system needs to be closed to attain the disc. To a certain extent quartz bulb in sprinkler system does the same function. 

One might note the striking similarity between Cases I and II. In both, a crucible failure allowed water to enter and mix with molten titanium. Steam (and hydrogen) formed and the pressure increased so as to bulge the crucible and rupture the safety discs. Tamping the water-metal mix by the fall of the electrode then caused a major explosion. No injuries resulted in the Case II incident because the vault walls provided protection. No data were available to allow an estimation of blast pressures, but as described, the vault construction maintained its integrity and the wave was forced to exit from the bottom. 

These composite relief devices introduce a hazard that must be catered for. A small leak, as through a pinhole in the disc, can raise the pressure between the disc and the valve to the normal operating level of the equipment being protected. The disc then will not rupture until the process pressure exceeds the pressure between the disc and the valve, not the atmospheric pressure, by an amount equal to the set point of the disc. This could result in catastrophic failure. Any gas that accumulates in the space between the two safety elements must be removed to prevent this. 

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