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In the plant that I am working on it. we had a water blow-down drum. This drum connected with 3 PSVs with set point of 3.84, 3.66 and 3.5 BARG respectively and connected with bypass PSV. The main job of bypass PSV is to maintain the pressure inside the drum between 0.5-0.6 BARG. I was thinking about adding PCV to play this role instead of bypass PSV.
I need you opinions and recommendations in this suggestion?
I am looking forward to hearing from you.
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Psvs And Pcv
Started by hardiskuae, Mar 21 2006 01:14 AM
3 replies to this topic
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#2
gvdlans
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Posted 21 March 2006 - 02:56 AM
You mean that a Pressure Safety Valve was used to control the pressure? That sounds interesting....
#3
Art Montemayor
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Posted 21 March 2006 - 06:42 AM
hardiskuae:
I, like gvdlans, also interpret what you wrote as meaning that your plant is employing a Pressure Safety Valve as a back pressure controller. If so, this is positively ridiculous and a major safety concern.
I don't make this remark to demean the use of the PSV; my point is that PSVs are designed and meant to activate to ensure a safe relief of untimely pressure increases. They are SAFETY DEVICES - not process control devices. For what you are describing, a Pressure Control Valve (PCV) is employed - not a PSV. Are we on the same page?
Never, but never should a PSV be used as a "bypass" valve - whatever that means. It is designed to only relieve pressure --- and nothing else.
And what is the reason for the multiple PSVs? Multiple PSVs are not unknown; however, there has to be a good reason to employ more than one PSV.
Perhaps you are not explaining the situation accurately ...
(This thread should really belong in the Relief Devices Forum instead of here)
I, like gvdlans, also interpret what you wrote as meaning that your plant is employing a Pressure Safety Valve as a back pressure controller. If so, this is positively ridiculous and a major safety concern.
I don't make this remark to demean the use of the PSV; my point is that PSVs are designed and meant to activate to ensure a safe relief of untimely pressure increases. They are SAFETY DEVICES - not process control devices. For what you are describing, a Pressure Control Valve (PCV) is employed - not a PSV. Are we on the same page?
Never, but never should a PSV be used as a "bypass" valve - whatever that means. It is designed to only relieve pressure --- and nothing else.
And what is the reason for the multiple PSVs? Multiple PSVs are not unknown; however, there has to be a good reason to employ more than one PSV.
Perhaps you are not explaining the situation accurately ...
(This thread should really belong in the Relief Devices Forum instead of here)
#4
Guest_Maverick_*
Guest_Maverick_*
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Posted 23 March 2006 - 04:48 PM
hardiskuae:
Your thinking is absolutely correct.It is inappropriate to use PSV to do pressure control.vaiations in header/vessel pressure causes PSV to constantly chatter and its PFD(probability of failure on demand) increases by this phenomenon.You can no longer justify its use as a part of safety system.
Apart from reducing the life of teh PSV it can cause major operational and safty concerns.
yes agreed ,you have backup relief valves to lift in case of emergency,but a good operating practice is to use PSV as a last resort.There life span reduces with everyt lift and they will have to be callibrated more often.
i strongly reccomend that you change the PSV to PCV .
Your thinking is absolutely correct.It is inappropriate to use PSV to do pressure control.vaiations in header/vessel pressure causes PSV to constantly chatter and its PFD(probability of failure on demand) increases by this phenomenon.You can no longer justify its use as a part of safety system.
Apart from reducing the life of teh PSV it can cause major operational and safty concerns.
yes agreed ,you have backup relief valves to lift in case of emergency,but a good operating practice is to use PSV as a last resort.There life span reduces with everyt lift and they will have to be callibrated more often.
i strongly reccomend that you change the PSV to PCV .
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