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[Troy]

Hello,

I am currently looking at installing an emergency vent on a 24 inch manhole cover as a fire contingency on an atmospheric tank. There are existing safety valves and emergency valves on the tank but at present the relieving capacity is far from what is needed.

In addition to the manhole cover emergency vent I require an additional vent to meet the API 2000 standards for fire. Due to the cost of installing a new flange on the roof of the tank I would like to place the additional vent on an existing pipe which already has a vent and vacuum breaker.

I would like to know how to ensure the inlet pressure drops for PSVs on the proposed piping manifold are low enough to prevent chatter.

Details of the situation are as follows:

Tank dimensions 26 ft diameter, 36 ft high
Current relief 3736m3/hr

Existing piping manifold:
6 inch diameter
Straight pipe of approximately 1m to a pressure vent with a T piece. T piece extends approximately 0.5m to a vacuum breaker.

Proposed piping manifold:
Straight pipe of approximately 1m to pressure vent with a cross piece. On one side have the vacuum breaker and on the other have the additional pressure vent.

All vents discharge to atmosphere.

Thanks in advance,

Troy