code question - valve changes 2

[eli73]

Our chemical plant has a plunger type valve on the drain of a pressure vessel. After repeated failures due to corrosion, they took a commercial valve and under the direction of an experience ME modified it by creating a new, sturdier valve body made from a different alloy and thicker pipe on the discharge side. It has worked well. My question is: How does that affect the legality of using that valve and are there any methods to have the valve tested and stamped to approve it for service, or is that even possible?

Thank you.

 

[metengr]

This could be a problem. Several questions;
What was the original specification for the pressure vessel drain valve - was it an ANSI B16.34 valve? Material and pressure/temperature rating?

Was the new valve modified by purchasing an ANSI B16.34 valve body with a higher pressure/temperature rating and modifying the internals?

 

[LSThill]

eli73 (Chemical)

You need to look at the Chemical General Engineering Piping Classification Specification for the System pressure vessel drains.

1). review the MSD for the System Drain.
2). The orgainal valve was not correct specificed for the valve.
3). The orginal valve trim was not correct specificed for the Valve and the stim.

The standards are:
DESIGN - API 602
ENDS - ASME B16.5
RATING - ASME B16.34
DIMENSIONAL - ASME B16.10


Note: Approved Piping Classification specification included the correct valve and manufacturing tag. the apply to the MSD.

 

[deanc]

What Codes apply in this case? What does the local jurisdiction require? Does your insurance carrier have any requirments?

You need to find out what these items are before you can answer some of the others. Do you have documents signed by the ME for the design? Suggest you have them on file as a minimum. Always practice CYA.

 

[jay165]

"Code" and "Legal" are 2 different things. As Dean says, check the jurisdictional requirements first. The greatest chance of it being a legal issue is if the vessel is in steam boiler service.

To my knowledge, noboby stamps or otherwise approves valves, unlike vessels. Valves and other components are built to standards that manufacturers voluntarily conform with.

If you're concerned about the pressure containing ability (and I would be), you could test the valve up to and beyond the MAOP of the vessel - ie the PSV setting. Just do it at a safe distance. Homemade valves are a recipe for trouble.

 

[unclesyd]

jay165,
I have to disagree somewhat with your statement concerning homemade valves. Our site designed and manufactured or modified all type of valves including the plunger type valve as mention by el173. All the design work was accomplished by the Mechanical Design Engineering Group, fabricated in our machine shop, tested in our valve repair shop, with materials recommended by our group.

When we had a process that operated at 10,000 PSIG initially, later reduced to 5500 PSIG, all valves and fittings were designed and manufactured in house. There were no valves on the market at the time. This system was a design challenge as it was highly cyclic and contained NH3 and H2. The valve design included a automatic letdown 5500 PSIG to 450 PSIG.

We designed and built 4" "0" dead space jacketed valves for operation at 2500 PSIG @ 600°F. Again no valves available of this service.

We also made many revisions to commercial valves, usually not the body or bonnet, but the remaining components were fair game for improvement in operation and function.

I’m not recommending that everyone should attempt this but with competent engineers this can be accomplished safely and economically. I’ll have to temper these statements again due to the pervasive tendency to litigate at the drop of bolt.

A more immediate and dangerous condition exist in the resurgence of supposedly repaired, rebuilt, or reworked valves along with some poor quality imports being peddled by some suppliers. This will probably get worse as the cost and non-availability of materials increases.

 

[jay165]

Syd:

I agree with your comments. When I think about it, the problems I was refering to have more to do with modifying the functionality (eg drilling a hole in a check valve) or reassembly with the wrong trim or bolts rather than beefing up the pressure capability.

 

[bozobreaker]

eli73:

I agree with deanc that it is important to determine what your regulatory and enforcement agency and insurance requirements are, if any.

If you are looking for some code rules for code valve design process, although not applicable to you, the ASME B&PVC, Section III, Articles NB-3500, NC-3500, ND-3500 provide code rules for design of valves for nuclear power plants. Section III also provides provisions for code stamping of valves for nuclear power plants.