Relief Valve Effluents

Quite often, a higher pressure vessel will vent, not to a flare, but to a lower pressure vessel. For example, a high pressure reactor might relieve to a low pressure fractionator to recover the liquid portion of the relief valve effluent in the larger fractionator. But then the fractionator relief valve must be sized for the vapor venting rate from the high-pressure reactor. A complex engineering problem results. 

It is certainly required to maintain a positive pressure throughout the relief valve effluent piping system to preclude the entry of air, which, at least theoretically, could cause an explosion. 

Gas pressure was maintained in the cell by placing spring loaded pressure relief valves at the outlets. The effluents were bled into lOmL graduated cylinders to collect the water effluent. Tees were placed in the outlet lines with relative humidity sensors in the dead legs of the tees. The water content of the outlet streams was measured with humidity sensors (Sensirion SHT7X). 

If water flows through the SG safety and relief valves, they may not be able to close and cut off the stream when the pressure is lowered. In this case, the accident is worsened with an effluent release to the environment. 

Once a relief valve is forced open by exceeding its set pressure, fluid flows out into the relief valve header piping. In most plants, there is a piping system that collects the effluents from various relief valves. This collection system, in turn, vents to the plant flare system. 

Introduction In determining the disposal of an effluent vent stream from an emergency relief device (safety valve or rupture disk), a number of factors must be considered, such as ... 

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