Short duration pressure surge

[bigthumbs]

Hi guys. The PED states:

2.11.2 Pressure Limiting Devices
These devices must be so designed that the pressure will not permanently exceed the maximum allowable pressure PS; however a short duration pressure surge in keeping with the specifications laid down in 7.3 is allowable, where appropriate.

Does anyone know what is meant by "short duration", how the duration might be determined, or if there is any precedence?

Many thanks for any responses.

 

[stanier]

ASME B3.3 and AS4041 piping codes define them by over pressure and duration. I suspect the equivalent EN standard would also so define them.