Multiple choked flow in PSV tail pipe

[nasermashti]

Dears,

Is it possible having multiple choked points in PSV tail pipe?

Thanks

[Cubeng]

Pressure drop in psv tail pipe (build up back pressure) is limited by the psv type. For example, if psv is conventional your total back pressure can't exceed 10% of psv set pressure. For balanced bellows and pilot psvs total pressure drop is higher (30-50%) of set pressure. Read API 520 and 521 and consult psv vendor for a maximum allowed back pressure for particular psv.