PRV Testing Qualifications 1

[Kaplin]

I'm at a hydroelectric plant in Canada. We typically send our PRV's off to be tested and recalibrated if required.

What training would be required for my mechanics so that they could test and recalibrate the PRV's themselves?

Thanks!

 

[PMarinshaw]

I would suggest you contact the manufacturer of the valves you currently have. If you have more than one manufacturer, contact anyone of the major vendors (Crosby, Dresser, Farris, etc) as they can all help you. The training itself is quite simple, and can be done in one day. And it's the same no matter who provides it - if you make sure its generic for all of the valve types you have (ie Pilot Valves, Direct Spring, Thermal, Steam, etc.) The manufacturers can and will conduct the training at your facility as well. If you have sufficient test facilities - ie a test bench capable of enough volume to adequate lift the PRV (open it), even only for a short time, then you can re-establish the set & reseat pressures for proper calibrations. Liquid valves are more difficult to determine opening and closing pressures, and the specific manufacturers definition should be followed for each type. One of the problems many end-users have is they test all of the valves on the same medium - either air or water because they only have a single medium test bench. This often translates into actual variations of the set pressures in the installations during the operational conditions. So be sure the training covers exactly how to correlate for other service media which is different from your test bench medium.

 

[sterl]

If these are tagged Safety Relief Valves the whole thing is a little more involved...Shop and Personnel capability subject to the auspices and regular inspection of the National Board to maintain a VR shop listing.

If you need to be able to requalify Safety Relief Valves, contact the National Board in Columbus Ohio before you expend money on training...The test environment investment may make the whole thing a moot point.

 

[unclesyd]

Our valve shop has the NB rating as VR shop.
As mentioned the investment is pretty heavy on the front end. For routine relief valves it is pretty straight forward, its when you get into the higher pressure steam or special process fluids that can present problems.

We test all our Steam valves that are less than 650 psig using the 650 psig steam as a test media. This requires a separate test stand due to the fact that our 650 steam at this point has about 250°F superheat.

The 650 RV's are sent out to a valve company that has steam generator that can test at the proper temperature and pressure.

We have an enormous number of RV's in vaporized Therminol service that really present a problem due to the vapor temperature of the Therminol at 70 psig. We did test with superheated steam but the AI had problems with our procedure. We went back using a cold test with temperature compensation and ended up with a lot of inservice weepers. The larger valves are now sent off to be test hot. The smaller valves are tested off the primary header into a vacuum header, normal operation. This took several meetings to resolve this problem.
The trend with the corporation now is outsourcing this type work as the experience leaves. My understanding is this is presenting some problems.


Here is one type tester we had. We had another one with multiple stations made by a company no longer in business.

http://www.caldertesters.com/products/900_2.html

 

[JAlton]

Training in PRV Repair is available. It should include ASME Code, NBIC Requirements, Nomenclature, Terminology, THeory of Operation, Namelate Data Interpretation, Disassembly, Inspection, Machining, Parts Replacement, Laing, Reassembly, Testing, Sealing and Stamping. All steps of repair should be documented, including "as found" and "as left" ring settings, test results and part dimensions. However, the comments regarding Test Equipment are correct. Unless you have Test Equipment capable of demonstrating accurate PRV set pressure performance, the best efforts of a fully qualified PRV Repair Technician are insufficient to guarantee a properly repaired PRV.

J. Alton Cox

http://www.delucatest.com