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
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Posted 13 March 2019 - 11:56 PM
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
Posted 14 March 2019 - 03:41 AM
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.
Posted 14 March 2019 - 04:12 AM
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.
Posted 14 March 2019 - 10:28 PM
further PRDs are considered as ultimate safeguards and we never question their failure
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