3 replies to this topic

[Paul_Needham12]

Hi, Can anyone please describe the definition of "Fails to open on demand"? When we have this issue? If If a PRD relieves above or below its set pressure, is it classified as "Fails to open on demand"? 

 

Thank you

[Sharma Varun]

normally this term is used for control valves, it simply means the respective valve doesn't open when required, for example a LV or PV acting on level or pressure should open at certain higher value of level or pressure but it doesn't due to any failure in control loop.

[fallah]

Hi, Can anyone please describe the definition of "Fails to open on demand"? When we have this issue? If If a PRD relieves above or below its set pressure, is it classified as "Fails to open on demand"? 

 

 

Hi,

 

It's mostly applied to on/off control valves such as BDVs which might be failed to open when needed to depressurize the connected pressure vessel and remains in closed stuck position. PRD that might has a relief above/below its set point is irrelevant to this matter.

[Sharma Varun]

further PRDs are considered as ultimate safeguards and we never question their failure