spiral pipe for gas pipeline of sour service 7

Pressure and temperature count a lot so you need to be more specific.

API 5L also needs the grade added as this makes a difference.

Co2 and H2S with free water are bad news.

You really need to talk to a metallurgist about your specific issue as weld material / HAZ can be problematic so a spiral welded pipe has some more, but then so does welded pipe.

The internal contents make no difference to the outside corrosion.

Can you explain your role and position here.

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Thank you for your comments

my position is project manager and the role in this case to find with my team the root cause for what happened which pushed us to ask our self about the effectiveness of API standard ?

it seems that the extensive internal corrosion caused by the presence of water, CO2 and H2S gases, suggesting that the dehydration plant, which was the main source of internal corrosion mitigation in this pipeline, was not functioning adequately.


the internal corrosion developed crack along a spiral weld.

the media temperature is 55 degree. The Grade of the pipes is X52.

The problem with SAWH is that it is not cold expanded like SAWL which, for the latter, helps to relieve residual stress in the seam weld. Thus, there is a high level of residual stress locked into the helical seam increasing the likelihood of H2S cracking. Example from Kuwait: NACE Corrosion 2014, Paper 3835

Steve Jones
Corrosion Management Consultant


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

use seamless pipes in that service

Even for large diameters, you are getting seamless piping now-a-days.

Also, you need to carry out PWHT for all the welds (a service requirement). Keep that in mind while preparing WPS.

DHURJATI SEN
Kolkata, India

Well 55C wet CO2 and H2S, a 5L pipe doesn't sound like a a good idea to me.

Preferential weld corrosion is seen sometimes, but spiral weld seems to be a poor choice for sour service.

For CO2 corrosion injection of corrosion inhibitor would normally be required / considered if the u/s unit cannot dry the gas reliably.

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

I think you should do an analysis of the well stream, contact a corrosion and materials expert and select your pipe according to their advice. Certain stream contents and operating temperatures just can never be compatible with 5L, spiral or seamless. You do not say what chemicals, concentrations, pressures,or operating temperatures you have to deal with and all can make a difference in what pipe you should be using and if you should consider linings, or further stream cleanup. Water usually means salt too. You should also mention other critical factors, such as age of the existing pipe, how long a pipeline you are considering. I might select one method of corrosion protection over another, if it was a long pipeline where your 55° temperature changes, pressures are high or low and the investment is 6 billion dollars, or maybe just extra wall thickness if it is for just a few hundred meters inside a plant. This can be next to nothing, or a huge very expensive problem that never goes away, if you make the wrong decision. We really do not have much of a clue at all exactly what kind of trouble you might be getting into. If it's serious, at least get a proper stream analysis done and post that and your detailed operating conditions. Otherwise, yes, it can be a huge problem, or just as equally, nothing.

The root cause is: the misplaced belief that dehydration is 100% reliable, with 100% availability.


Steve Jones
Corrosion Management Consultant


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

Or that the equipment is running within operating range. Owner of a company I once worked for called me and asked who was stealing all the glycol. After checking all the field dehys, I found one that designed for 100 MMSCFD, but running at 140 MMSCFD.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."