as knowing when to dispose of a valve

[luisfrade]

Greetings .-

I am researching valves used in natural gas distribution networks and would like to know what are the criteria for a valve is discarded and no longer be repaired, there is some Standard or document about it.

Thank you

 

[zdas04]

I started to answer this question from the Natural Gas Producer viewpoint (we rarely repair valves, the cost of shut-in gas for the repair is way more than the cost of a replacement valve), then realized that I know nothing about the distribution end and that I can't help (I posted this so that other producers who look at the thread might think about how much they know about distribution before answering).

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

 

[gerhardl]

The general answer for this is a mix of experience, engineering, regulations and economical factors. As factory-new valves differ in quality and price from brand to brand (and type to type) it is sensible to try to estimate the cost/lifetime factor before selecting any valve. This is valid also for repaired valves compared to new valves. Do not forget to include the cost both of repair, downtime and working cost included in any installation, both for new and repaired valves.

Another factor is risk and consequences if anything goes wrong with a valve, and cost of tests for the net and single valves.

Eg.: No easy way out, no general formula, but lots of gathered experience in each single valve branch. (And I also have none for gas distribution ).

 

[LittleInch]

The scope of your question "valves used in natural gas distribution networks " is very wide and hence no one solution will fit all.

Do you mean steel or plastic valves, ball valves, gate valves, plug valves, butterfly valves what sort of pressure range (could be <1 bar to >70 bar) and size (<1" to > 36")...?

The cost and availability of repair places varies just as widely therefore one company could have a policy of replacement and discard / scrap and another that they repair and replace. the same type size and rating of valve.

Most distribution system valves tend to be always open or always closed so valve repair tends to be limited, thought you may have other experience.

Why are you researching this and for whom?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[luisfrade]

Thanks for all the answers, my question specifically if there are any standard or document to know and serve me back when I decide to repair / discard a valve.

Of course the desicion repair / discard the valve was taken considering the economic, logistical and engineering factor.

We are talking about ball valves, from 2 "to 8" in steel, with a pressure up to 35bar online.

Thank you.

 

[LittleInch]

There may be company standards, but other than referring back to the original standard to which it was built / designed (API 6D?) and then throwing it away if it couldn't meet the original seat tightness tests, I don't know of one.

For gas distribution it should only really be the seats which wear out or need replacing but as repair costs have risen much faster than the cost of the original new item, the margin where you replace rather than repair gets smaller and smaller every year and hence the economic number of things which can be replaced goes down.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way