Correct valve type to be used with process instrumentation 1

[hull6851]

Let me preface this by saying that I am fairly uninformed in this industry as I previously was an engineer in a different industry. I have not had much luck in finding industry standard approaches on some of these issues, and my company doesn't have very good internal documents/standards, so I am hoping for some help here.

I am curious what the Oil and Gas industry experience and preference is for which types of valves shall be used with different types of process instrumentation specifically with pressure instrumentation (used on gas processing plants).

My understanding is that Pressure Gauges (Pressure Indicators) with Bourdon tubes should have a needle valve under the gauge since a ball valve, when opened suddenly, can cause damage to the Bourdon tube inside the gauge. That said, I am told that if an operator knows that they are doing, a ball valve could be opened slowly to avoid damage to the gauge, which still being preferable with regards to ease of operation when compared to needle valve (due to the time taken to operate the valve from one state to another).

Not knowing much about the instrumentation itself, can/should the above all apply also to Pressure Transmitters, Pressure Indicating Transmitters, Differential Pressure Indicators, and Differential Pressure Indicating Transmitters? How and why would the valves you would choose to use with the instrumentation differ?

I realize the answer might change for different service pressures and temperatures, but let's keep it simple and deal with only 150 pressure class and normal service temps (-20F to 250F).

If you need more information to form a quality response, please kindly ask for it, taking into consideration my ignorance and desire to learn! I am happy to entertain intelligent discussion to be better informed.

Thanks!

 

[LittleInch]

I don't know about any one else- but my normal way of attaching process instruments is a piping isolation with a ball valve then an instrument manifold valve such as the attached. Needle valves at small sizes only take a couple of turns. You also normally need a bless valve so that you can release the gas when the instrument is isolated. Typical details below

http://files.engineering.com/getfil...dc-48b1-b5a9-e03f8acca6c6&file=Cat4190_PM.pdf

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[danw2]

I think Littleinch means 'bleed' port and valve, not 'bless' valve.

The root valves that are on the piping are frequently spec'd by the piping guy, valves past that point by the instrument guy.

A couple other instrumentation valve vendors:
Hex: Link

Anderson Greenwood:
Link

Swagelock:
Link

 

[LittleInch]

The joys of predictive text.... Yes bleed, not bless. Agree with danw2.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[moltenmetal]

This varies greatly from spec to spec and industry to industry.

Generally, on piping >2" NPS, the root valve (the one connected directly to the main pipe line) is a pipe spec valve, attached by means determined by the pipe spec, at the minimum size permitted in the spec. - sometimes 1/2" NPS, sometimes larger. Generally this is a block valve giving a straight open port when open , such as a gate or ball valve. This valve is attached to the pipe by durable means per the pipe spec, so the entire instrument system can be removed/repaired/replaced without de-inventorying the line. Any manifold type block and bleed/bypass/equalization valves are located downstream of this valve (or valves, if used for differential pressure instruments). Generally, these supplementary valves are located at the instrument. Impulse lines of pipe or tubing, if required, connect the root valve to the instrument and/or its block/bleed. Those valves, where required, are often needle valves, and often they are unitized in manifolds. Sometimes they are discrete tubing valves.

Diaphragm isolated instruments when used for level, often require full port block valves of the same size of the diaphragm, ie 2 or 3". That's a huge nuisance on a small tank...but so is a diaphragm that doesn't work because a layer of sludge has built up against it because the diaphragm was served with a line of smaller diameter than the diaphragm and hence wasn't free to drain...Diaphagm seals are also sometimes fitted with a flushing ring with a drain and/or vent/flush port with plugs or with valves, gennerally again being ball or gate valves.

In smaller lines, the piping root valve is often dispensed with. A block/bleed can be mounted directly to the pipe branch. In category D services, sometimes instruments are mounted without valves.

 

[LittleInch]

Hull, you won't get much better than that explanation in a post.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[hull6851]

Thanks, all, for your responses. I haven't had much of a chance to read them today, but will read them in detail after the holiday weekend. I very much appreciate your input.

All the best to you in this New Year!