PSA 9.5 — PSV Reaction Forces: API 520/521, the DLF Method, and What to Model
A steam relief valve sits on a header. It is sized to pass 25 000 kg/h at relieving conditions, and it discharges to atmosphere through a 6″ tailpipe: 2.5 m horizontally from the valve outlet flange to an elbow, then vertically up and out through the stack.
The process engineer hands you a number: the reaction force is about 4.2 kN. Four kilonewtons is less than half a tonne. The tailpipe weighs 28 kg/m.
Commit to an answer before reading on: is 4.2 kN a problem?
The force is not the problem. Its lever arm and its suddenness are.
The…
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