PSV/PRV vs. PCV
PSV/PRV vs. PCV
(OP)
Hi, first time poster.
I know there is a lot of discussion of PSV vs. PRV, which is not what I want to discuss.
I have the following situation at the plant I work at:
The client is re-certifying their PSVs. We have come across several PSVs (labeled as PCVs on the vendor P&ID) on the discharge of lube oil pumps for several compressors.
A previous engineer on the project changed the P&ID to read PCV instead of PSV, so I am bit confused...
Isn't there some guidance somewhere where a PSV is not supposed to be used as a PCV? Or am I mistaken? Some of these lube oil PSVs are tight shut off, as expected from a PSV. However I know of some others that are not... Maybe the lack of tight shut off is why it was labeled as a PCV?
The configuration is as follows:
Lube oil pump, circulates oil, PSV/PRV/PCV dumps it back into the reservoir if the pressure exceeds 100psi
So in this case is it a PSV/PRV or a PCV?
For the record I am Mechanical Engineer tasked with getting these valves out to their third party calibrator for repair and put back. Since it is coming off the discharge of a pump, I am of the opinion that IT IS a PSV/PRV, even though the P&ID says other wise...
I know there is a lot of discussion of PSV vs. PRV, which is not what I want to discuss.
I have the following situation at the plant I work at:
The client is re-certifying their PSVs. We have come across several PSVs (labeled as PCVs on the vendor P&ID) on the discharge of lube oil pumps for several compressors.
A previous engineer on the project changed the P&ID to read PCV instead of PSV, so I am bit confused...
Isn't there some guidance somewhere where a PSV is not supposed to be used as a PCV? Or am I mistaken? Some of these lube oil PSVs are tight shut off, as expected from a PSV. However I know of some others that are not... Maybe the lack of tight shut off is why it was labeled as a PCV?
The configuration is as follows:
Lube oil pump, circulates oil, PSV/PRV/PCV dumps it back into the reservoir if the pressure exceeds 100psi
So in this case is it a PSV/PRV or a PCV?
For the record I am Mechanical Engineer tasked with getting these valves out to their third party calibrator for repair and put back. Since it is coming off the discharge of a pump, I am of the opinion that IT IS a PSV/PRV, even though the P&ID says other wise...





RE: PSV/PRV vs. PCV
Per ISO, only the term Safety Valve is used regardless of application or design.
RE: PSV/PRV vs. PCV
However, I am still digging around. Below is the information you requested.
Manufacturer: FulFlo
Inlet: 1-1/4" Class 300
Outlet: 1-1/4" Class 300
Assembly Number (Confirmed between paper and what is in the field)
V-S-F-6-R/HS/XS
Vendor catalog here:
http://www.fulflo.com/pdf/FulfloVSeries.pdf
RE: PSV/PRV vs. PCV
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist
RE: PSV/PRV vs. PCV
Per ISO, only the term Safety Valve is used regardless of application or design.
RE: PSV/PRV vs. PCV
RE: PSV/PRV vs. PCV
In most cases these lube oil skids are servicing the bearings on machinery that is very expensive and very critical to the plant. Thus, the machinery needs a highly-reliable lube oil supply. For that reason, modulating relief valves are used in this service. A pop-acting relief valve could potentially cause a significant disturbance in the flow rate of oil to the bearing. By diverting the flow, a pop-valve could even starve the bearing of oil.
These are indeed relief valves, but since they are different from common relief valves, they are sometimes given different tag names. Maintenance/testing of these lube oil relief valves is commonly done at the same time that PM is performed on the skid itself, in which case these valves are not listed in the plant's overall PSV service program. That's another reason these lube oil relief valves are commonly given a different tag name. Doing so distinguishes them from the general population of plant PSVs.
RE: PSV/PRV vs. PCV
Without a PSV in parallel, risk of an overpressure is relatively higher, and the attendant consequences should be weighed up and checked for acceptance for this lube oil service case.
RE: PSV/PRV vs. PCV
On the basis that your particular valves are in fact in continuous service / flow, then labeling them PCVs, whilst a little odd for a spring type valve is more in line with its mode of operation and I can see why this was changed.
If, on the other hand, these valve operate rarely, then Pressure Relief valve would seem to be a more accurate description of this valve
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