Rupture Disc Info

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Defi nition of a Rupture Disc

A rupture disc is installed on a pressure vessel or a pipe line and gets ruptured when the pressure exceeds the safety limit or the regulatory limits, so that the overpressure can be discharged to a safe place and the pressure vessel and the pipe line can be protected from damages

The installation requirements for rupture discs

1. Where it is feared that the reaction gets out of control and the pressure increases too fast for a spring-type safety valve to catch up.

2. Where a large discharge volume is required over a shorter time

3. Where the nature of the reaction product prohibits installation of a safety valve

① In case the material inside is a mixture of powder and liquid or where it is required to handle or store materials with higher viscosity

② In case the material to be stored or handled is prone to polymerization

4. Where even a small amount of leakage is not permitted due to possible hazards to the working environment, such as toxic materials leakages

5. Where selecting the material for the safety valve can be problematic since the liquid is highly corrosive.

6. Where it is intended to protect the expensive safety valve from corrosion

7. Where leakage should be prevented in order to meet the environment requirements

8. Where it is intended to save the energy by preventing natural evaporation of the stored material

Rupture Discs' Pros

1. Reduces leakages that are beyond control (The disc is completely sealed and there is no leakage until the disc is ruptured.)

2. Provides corrosion-resistance at a low cost (to prevent corrosion of the safety valve and piping)

3. Protection from an abrupt increase of pressure due to a rupture of the tube in a heat exchanger or the internal, explosive combustion.

4. Provides protection of the pressure and a relief from it at the same time

5. Provides a secondary protection with lower contingency that require a wider leakage range.

6. Almost no limitation on the environment of usage and sizes

The Application Code of the Rupture Disc

ASME Sec. Ⅷ, Div.1

API RP 520

ISO 6718

ISO 4126-2~6

KOSHA Code

Rupture Discs' Installation

1. Can be mounted on both horizontal and vertical pipe lines.

2. Should be installed along the direction of the liquid fl ow.

3. Should be mounted using a holder. (However, the POPF types can be mounted without holder.)

4. A rupture disc should not be installed if there is any damage on it.

5. When installing a rupture disc, the fastening planes on the holders of both sides should be cleaned thoroughly. Then, after checking for any dust or oil, the disc should be mounted. The bolt should be fastened in a symmetrical pattern to prevent only one side from getting fastened too much.

The Application Method of the Rupture Disc

If the rupture disc is to be used as the primary or a singular pressure reliever, it can be used as a complementing means to protect the overpressure. The pressure setting should not exceed the maximum allowable working pressure (MAWP.) It should also be capable of preventing the pressure vessel from developing a pressure that exceeds 10% of the maximum allowable pressure or 3psi

Secondary (Multiple) Relief (Used as the two or more safety devices)

A rupture disc device may be used as a secondary relief for other rupture discs or safety valves. When a multiple number of reliefs are used, the burst pressure should not exceed the MAWP of a single pressure vessel. The rest should not exceed 105% of the MAWP except for the external fi re reliefs. Also, it should be possible to prevent the pressure from rising by 16% or 4psi beyond the MAWP of the pressure vessel.

Combination Relief (Used in combination with the safety valve)

The rupture disc device can be installed between the safety valve and the process. It is done to prevent the leakage and water leak through the safety valve and protect the safety valve from corrosion. In case a safety valve is mounted between the inlet for the safety valve and the vessel along with the rupture disc, the confi rmed capacity by the safety valve is either recognized as to be 90% of the rated fl ow rate of the valve or as the actual value confi rmed after assembling the valve and the disc. There are a number of monitoring instruments, such as a pressure gauge, mounted between the rupture disc device and the safety valve. Such devices make it possible to monitor the disc for any ruptures or leakages.

External Fire Relief (Used as the external re safety devices)

In case the pressure vessel is exposed to additional risks due to unexpected external heat, including a fire, the pressure reliefs should be installed in order to protect the equipment from overpressure. In this case, the pressure reliefs added on should be capable of preventing the pressure from rising beyond 21% of the MAWP. The pressure setting shall not exceed 110% of the MAWP. Pressure reliefs, which are mounted on the vessel without a permanent supply connector, used for storing liquefi ed, compressed gas in ambient temperature, and with the primary purpose of protecting the pressure vessel from leakage due to external heat, should be capable of preventing the pressure from rising beyond 20% of the MWAP of the vessel.