Safety valve system, dual

A simple, sequential numbering system to identify SRVs may be acceptable for a small plant such as a batch-chemical processing facility with only a few dozen SRVs. However, for PPG s Lake Charles plant, a dual numbering system is used to keep up with 2,000 SRVs in service and several hundred additional SRVs in storage. The devices kept in storage onsite are used as spares or can be cannibalized for parts. Spare safety valves for critical equipment must be available. [8]... 

Each trailer is equipped with a dual safety valve and a dual rupture disc system (Figure 7). These are independent systems manually operated by the driver and can be switched to the alternate if the primary system fails. The capacities of the safety valves are designed to handle a fire on the outside of the container with a uniform surface temperature of 1200°F. 

The safety/relief valves are dual-function valves discharging directly to the pressure suppression pool. The safety function provides protection against overpressure of the reactor primary system. The relief function provides power-actuated valve opening to depressurize the reactor primary system. The valves are sized to accommodate the most severe of the following two pressurization transient cases determined by analysis ... 

The isolation process deserves special consideration (Fig. 10.4). Here, isolation refers to the secure containment of any hazards so that technicians can work on the isolated plant in safety. However, the process of isolation has a dual role not only does the isolation ensure the safety of the technicians, it also acts to ensure that the plant cannot be returned to operational status until the technicians have completed their work, and the work has been inspected and deemed ready for return to service. The isolation process ensures that all hazards are securely separated from the work to be done - this includes electrical systems, high-pressure fluid systems, and any sources of toxic or inflammable material. Any residual high pressure or high voltage must be vented or earthed. Valves are locked shut. 

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