Fire contingency

The coldest and hottest relieving temperature, whether resulting from ambient conditions, operational Mure or fire contingency, is used for the purpose of designing for thermal eiqiansion in the complete system of piping and headers. Credit may be taken for temperature rise or drop in the system, as described above. 

Accumulation The rise of pressure above the MAWP of the protected system, usually expressed as a percentage of the gauge MAWP. Maximum allowable accumulations are established by applicable codes for emergency operating and fire contingencies. 

Accumulation The pressure increase over and above the MAWP (maximum allowable working pressure) during the discharge of the pressure relief device. Expressed in pressure units or as a percentage of set pressure. Maximum allowable accumulation is established by applicable codes for operating and fire contingencies (see Section 3.6). 

If the liquid content of the vessel is above the critical point, a minimum latent heat of 116 kJ/kg is to be used to estimate the fire contingency. Liquid thermal expansion can also be used to eshmate the contingency if reliable data are available. Normally, physical properties estimated through simulation packages are not very reliable when the liquid is above the critical point. 

A three-phase separator, operating at 4000 kPaG and 25°C, has a total lengffi (T/T) of 8000 mm and an inner diameter of 2134 mm. The normal liquid level (NLL) of the condensate is 900 mm from ffie bottom of the vessel. The vessel PRV is to be designed for a fire contingency based on ffie following informahon ... 

Vessel V-001 is protected by a PRV. To reduce the flare load, the PRV has been designed only for a fire contingency, and it is expected that block discharge will not be a design contingency for the inlet separator. 

Adequate cash and a history of prompt payment of accounts strengthen the credit standing of a company and make it easier to obtain bank loans, etc. A company needs additional cash as a contingency against fires, floods, strikes, etc., as well as for additional adver-... 

Drums and towers, 6 m and less in diameter, constructed of pipe, pipe fittings or equivalent, do not require PR valves for protection against fire, on the basis that piping is not provided with protection against overpressure from this contingency. PR valves are required on such vessels, however, if overpressure can result from contingencies other than fire. 

If a situation occurs which involves more than one fire risk area simultaneously (such as an entire Refinery or Chemical complex), it would be classed as a remote contingency event, and the 1.5 Time Design Pressure Rule may be applied. 

In cases where vessels are provided with PR valves for protection against overpressure from fire exposure or an operating failure contingency, additional thermal expansion protection is not required. 

As the vessel pressure continues to rise above set pressure, the spring is further compressed until the disc is at full lift. The valve is designed to pass its rated capacity at the maximum allowable accumulation (10% for contingencies other than fire, 16% if multiple valves are used or 21 % for fire exposure). 

Conventional PR valves and discharge systems should be designed such that built-up back pressure does not exceed 10% of set pressure (both measured in psig), to avoid chattering problems. In the case where a pressure relief valve system is sized for fire conditions, with 21 % overpressure, built-up back pressure up to 21 % of set pressure is permissible. However, the lower rates resulting from other contingencies still must meet the 10% limitation. 

The "critical condition" in the specification sheet is entered as the contingency which determines the valve size, i.e., fire or operating failure. 

PR valve risers in flammable service should also be sized such that exit velocities are at least 30 m/s under all foreseable contingencies (except fire) which would cause the valve to release. On the basis of experimental work and plant experience, this minimum velocity, in conjunction with the riser elevation requirements, has been shown to ensure effective dispersion. Entrainment of air and dilution result in a limited flammable zone, with a negligible probability of this zone reaching any equipment which could constimte an ignition source. 

The fluid boiling point at relieving pressure is used for sizing a PR valve orifice for die contingency of fire. 

Under RCRA. each facility must contain a contingency plan designed to minimize hazards to human hetiltli or tlie enviromiient from fires, explosions, or tuiy unplanned sudden or nonsudden release of hazardous w aste or hazardous waste constituent to air. soil, or surface water. The items tliat follow are applicable to each contingency plan. 

The contingency plan must include an evacuation plan for facility pcrsoiuicl if the possibility exists that c acuation might become necessary. The evacuation plan must describe signal(s) lo be used to begin evacuation, evacuation routes, and alternate c acuation routes (in cases where prinuiry routes could be blocked by releases of hazardous wastes or fires) ... 

Copies of the contingency plan and all its revisions must be maintained at the facility as well as submitted lo all local police departments, fire departments, hospitals, and slate and local emergency response teams. 

Contingency Plan A pre-planned document presenting an organized and coordinated plan of action to limit potential pollution in case of fire, explosion or discharge of hazardous materials which defines specific responsibilities and tasks. 

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