Vent tail pipe

Relief valves vented to the atmosphere should have tail pipes equal to or larger in diameter than the relief valve outlet that extend vertically a minimum of one foot above building eaves, or eight feet above adjacent platforms on operating areas. The tail pipes should be provided with a drain located such that the exhaust through the drain hole does not impinge on vessels, piping, other equipment or personnel. 

SRV noise is primarily radiated from the associated piping, supports and equipment as well as from the wall of the SRV itself. In case of open-vent systems, the majority of the noise exists at the open vent and at the end of a tail pipe. Noise may also be generated due to the mixing of high-velocity gas with surrounding air. 

The calculated PWL of the valve can be thought of as that part which goes down the tail pipe. Where the exit pipe leads to an open vent, we may need to evaluate a safe distance or a distance before a community or environmental limit is reached. 

The final vent from the system should be regarded as a point of possible chlorine emission. It should be at a high level and away from personnel traffic and ventilation system intakes. Particularly when the low-pressure scrubbing device is a packed bed, booster fans may be added on the tail pipe. The piping arrangement around the fans then should avoid low points that could collect liquid. As with any vent manifold, the designer of a system serving several different units should take precautions to avoid mixtures in headers that may lead to undesirable side reactions. 

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