raising setpoint above nameplate rating 4

[jamesrw]

I have found an instance where many years ago our plant piping was raised to a higher pressure. I have found a relief that had the setpoint raised above the nameplate setpoint rating. There are no pressure or relieving capacity issues with this change, but I have always been under the impression that you were not to set over the nameplate. I can't find any documentation showing this is true or not. Any ideas?
Thanks.

 

[RVAmeche]

The relief valve has to be stamped for the set pressure and rated capacity of the valve.

Do you have capacity test data for the new set point?

 

[jamesrw]

I had always been led to believe that the nameplate had to show the set pressure and capacity. Can you point me to documentation that shows this? As far as the new capacity, I do have an old manual with capacity charts that show the relief is within needed capacity.
Thanks.

 

[The Obturator]

A set pressure change can very easily mean a change of spring requirement. Spring ranges are often not that great and would not cover the entire range of the valves pressure rating. Your comments suggest this was an ad-hoc site change. Wrong spring will return incorrect lift etc. You best get the serial number off the nameplate and contact the manufacture or local representative with the set pressure you require. The nameplate may also state the spring number fitted. Capacity stamping is only done for SRV's required to be "UV/NB" Code Stamped, and then with the equivalent test medium (air/steam or water). I would get the manufacturer to check out total valve suitability against current service conditions. Any earlier set pressure change should have been done by authorised personel and the valve recalibrated and "VR" stamped for "Repair".

Per ISO, only the term Safety Valve is used regardless of application or design.

 

[RVAmeche]

ASME Section VIII, Div 1, UG-129 contains marking requirements including set pressure and capacity.

If someone just "turned a wrench" and adjusted the valve it is not acceptable, as Obturator explains. Additionally, relief valves should have regular test reports to confirm set pressure/capacity and the plant should have those reports on file.

 

[jamesrw]

Gentlemen,
Thank you for your replies, you have sent the information that I have been looking for.

 

[gguliye]

Actually in ASME it is allowed to change the set pressure 5 % above/below the nameplate setting as far as i am aware of

 

[The Obturator]

Correct, but with caution. Affects capacity anyway. ASME VIII UG-126 words as per attachment.

Per ISO, only the term Safety Valve is used regardless of application or design.

 

[jamesrw]

Obturator,
I have looked in the 2019 ASME BPVC.VIII.1-2019 manual, UG-126 and I do not find your attachment in that manual. My situation is for piping overpressure, not an ASME vessel. Is there perhaps a different manual I should be looking at?
Thanks.

 

[A clark]

The 5% adjustment has been removed from Section I and section VIII

 

[The Obturator]

OK. I referenced an old ASME VIII UG-126 statement thinking it would never change.

A clark is correct. It has been taken out. However this does not give licence to simply adjust set pressure in the field.

I now attach extract for current 2019 ASME VIII UG-136. Basically the onus is for the user to obtain manufacturers or representatives approval and/or sign off for a set pressure change. if the vessel is not to ASME it is suggested to follow this advise in any case. May affect insurance etc. My original comments re spring range. capacity remain applicable.

Per ISO, only the term Safety Valve is used regardless of application or design.

 

[RVAmeche]

You should also have test reports indicating the set pressure and capacity. Pointing to a catalog value is not adequate in my experience.

 

[jamesrw]

I do have records for all of the annual test set pressures, but the capacity reviews were non-existent. That is how I found the nameplate issue.

 

[RVAmeche]

I don't think your testing meetings ASME requirements if you only have set pressure data and not capacity.

 

[jamesrw]

I do have capacity reviews, have created them over the last few years, but during a review I found the nameplate issue.