Any problem with threaded connection on H2S service under low pressure?

[engr2GW]

Hi,

This is grade B piping (SA 106B, and SA 105B fittings)in oil/gas service on well sites. H2S can range from 10ppm to 10,000ppm, and pressure ranges from atmospheric to 300psig. My questions are:
1. will there be any issues with threaded connections?
2. I know welding is preferred, but are there pressure and H2S conditions that can make threading (when done properly)an issue?

As much as possible, do it right the first time...

 

[SJones]

Why do you ask? Is it because company standards that you are working with, or have worked with, prohibit such connections in H2S service?

The simple fact that 'threading' is incorporated in ISO 15156-2 means that some people, at least, don't see a problem with it. Some others do find a problem with the propensity to initiate corrosion and the stresses that may promote cracking.

Who is right?

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[zdas04]

SJones,
That is the essence of the issue. I'm one of those people who have successfully used NPT threads (and machine threads with careful selection of o-ring material) in H2S service. I've stopped spec'ing them. Far too many company spec books absolutely prohibit threads in H2S service. Fighting the battle with people who would rather have a policy than an analysis is just beyond my capabilities.

If your company allows threads in this service, your success will be increased if you stay with pipe 2-inch and smaller (I've had a lot of trouble getting field crews to consistently torque 3-inch and 4-inch properly at the end of the day) and find a pipe dope that the manufacturer has tested in H2S service.

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

 

[BigInch]

Analysis didn't save lives, or prevent leaks, hence the policy.

 

[zdas04]

Analysis did indeed save lives and protected property. Applying policy inappropriately has cost more damage and injury that proper engineering analysis has ever caused.

Failure of engineers to do engineering properly was the problem. I will never stop being shocked by the amount of "engineering by wishful thinking" that goes on in Oil & Gas.

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

 

[BigInch]

I'm sure I can get somebody to do a CFD and prove 24" screwed ends work for H2S
even though such a fools errand it would be.

 

[zdas04]

LOL. I'm sure you can. Models are "proof" too, right?

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

 

[BigInch]

Just saying that I hate to have to prove something's not a good idea, even though it works, if you get my drift.

 

[georgeverghese]

For concentrations going up to 10e3 ppmv H2S, it may not be pleasant if you break away from company policy( for any reason) and you get audited by some one who goes by the rules.