3 replies to this topic

[Tween]

Hi,

 

For Creep relief(gas) valve designing, 1% of maximum design flow is considered as required flow.But i could not able to check in API 521 the same.I can see only blocked outlet case and other cases except creep relief case.

 

Anyone please help in this.

 

Thank you

[fallah]

IROBOT,

 

As far as i know, the creep relief valve maintains the line pressure downstream of a PCV during PCV failure in wide open position by relieving the excess pressure above a preset value. Then its required relief would be the difference between the maximum flow passing through the PCV in wide open position and normal passing flow. Is your case other than what i mentioned?

[aroon]

As per my knowledge, creep is equivalent to failure of automatic controls mentioned in API-521. Here, we should understand the occurrence rather than the terminology. The creep relief valve has to be sized based on the difference between maximum Cv and normal Cv as mentioned by Fallah. Excess flow due to failure opening of upstream control valve/regulator should be the basis of relief requirement. 1% might be the design practice for some cases but may not be true in all. Realistic scenario is the better approach.

 

Hope this may be useful.

 

Regards,

Aroon

[Tween]

Thank you Fallah