Overpressure rupture disc

A rupture disc may also be used in some cases for proteetion against internal explosion overpressure. However, this is a matter of special design and the appropriate safety group should be consulted. 

Rupture disc Prevents system from exceeding specified overpressure. Effectiveness of this device can be sensitive to service and experience. 1 x 10 to 1 x 10 5 1 x 10 2... 

The process is run in a semi-batch mode, and multiple reactors are used. There are several possible causes for a loss of control such as insufficient heat removal and loss of agitation. Overpressurization leading to the bursting of rupture discs takes place several times per year, indicating both the clear need for containment but also a need to consider design and control improvements. The reference describes the autoclave rupture disc assembly, procedures for replacement of the discs, the cleaning of the containment vessels, and the routine maintenance procedures for the containment vessels. 

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. 

Some method of pressure relief is required on all pressure vessels and for other process equipment where increasing pressure might rupture the vessel. Much of the piping used in modern chemical operations also requires overpressure protection. Safety relief valves or rupture discs are employed for pressure relief. In many cases, either a rupture disc or a safety relief valve can be used. Safety relief valves are usually used for process protection and rupture discs are used for vessel protection. The safety relief valve or rupture disc must be designed to operate at a known pressure and prevent the pressure within the system from increasing. Therefore, it is important to consider the flowrate the valve can handle. 

Operations supervisors should provide procedures to ensure proper isolation of flammable, toxic, or environmentally sensitive fluids in pipelines. Typically these procedures must be backed up with the proper overpressure device. If the trapped fluid is highly flammable, has a high toxicity, or is otherwise very noxious it is not a candidate for a standard rupture disc or safety relief valve, which is routed to the atmosphere. Those highly hazardous materials could be protected with standard rupture disc or safety valve if the discharge is routed to a surge tank, flare, scrubber, or other safe place. 

The simple error of installing a rupture disc upside down is easy to do in a minute or two and can jeopardize the integrity of the overpressure protection system. Rupture disk manufacturer s representatives are available to discuss proper rupture disk handling with engineers and craftsman. Such training can be very helpful. 

Reactors should be protected against overpressuring by the use of a rupture disc or a relief valve. A rupture disc is a metal diaphragm supported between two steel flanges which are part of a pi line leading directly from the autoclave to a vent. The discs, which may be stainless steel (Type 304), platinum, steel, tin, or nickel, are designed to burst at a predetermined pressure. 

A mechanism that vents fluid from an internally pressurized system to counteract system overpressure the mechanism may release all pressure and shut the system down (as does a rupture disc) or it may merely reduce the pressure in a controlled manner to return the system to a safe operating pressure (as does a spring-loaded safety valve). 

Corrosive fluids are less likely candidates for the use of pressure relief valves. Whether by corrosion of the valve itself or of surrounding pipework, they often create a problem with deposits on the valve element or its seat. These deposits can prevent proper sealing and allow the slow escape of fluid. To combine the advantages of rupture discs and relief valves, the two devices can be installed in series, with the disc before the valve. Even if the valve is not precisely seated, there is no release from the system until the disc bursts. The same overpressure then also opens the valve. Once the piessme has dissipated and dropped below its set point, the valve reseats and prevents further release. 

There are several overpressure devices, each with particular applications. Some devices are suitable for gas and some for steam, others for liquids. Some work for combinations of gases, vapors, or liquids. Some require more maintenance and testing than others to ensure they operate correctly and reliably. Some are subject to corrosion, scale buildup, and other problems that could render them inoperative or make them operate poorly. Valves are suitable for clean materials, because they must reseat after relieving pressure. Valves minimize loss of material. Rupture discs are better for... 

Tightness control Filtered voit astern ensures confinement also at high pressures passive At overpressure the gas compression chamber in weiwell will vent via rupture disc to the filter system, protecting the rest of the containment against rupture A valve arrangement permits reclosure of the vent path... 

As the accident continued, the water and steam mixture leaving the open PORV had been collecting in the Pressurizer drain tank. About 15 min into the accident, the rupture disc on the pressurizer drain tank, which was designed to limit tank overpressure, blew and allowed additional radioactive water from this tank to run down to the containment sump (Kemeny, 1979). The water was periodically pumped from the sump into a storage tank of the auxiliary building, adjacent to the containment. 

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