4 replies to this topic

[Klara]

Hello everyone,

 

Can anyone tell me if there are any standards/requirements for intelligent pigging of MEG pipeline.

 

Briefly, we operate an offshore MEG pipeline for injecting it into multiphase pipelines to prevent hydrates. During Basis of design the MEG

was considered as non-corrosive product (CA=1 mm) therefore there are currently no pig trap facilities (they were temporary provided for commissioning only).

 

The pipeline is being operated since 2009 and now I have to revaluate requirements whether or not the IP is required. It's obvious that if the line fails we are in trouble...

 

Much appreciate any answers, advice...

 

Thanks

 

Regards,

Klara

[ankur2061]

Klara,

 

100% MEG (pure) will not corrode carbon steel. Glycol-Water solutions are corrosive to carbon steel and in such applications corrosion inhibitors are injected to slow down corrosion rates and ensure that the system performs for its intended design life.

 

When the MEG pipeline was designed, there must have been a design life specified for the pipeline. What is that design life in number of years?

 

Providing a permanent pigging arrangement after 7+ years of operation doesn't make much economic sense. An option would be to inject a corrosion inhibitor in the MEG pipeline. Characteristics of the corrosion inhibitor should be to provide a protective film on the pipeline wall.

 

If you are at the end of the pipeline design life, build a new parallel pipeline using corrosion resistant alloys and after commissioning it de-commission and dismantle the old pipeline.

 

BTW, there are no specific standards or guidelines for pigging of MEG pipelines.

 

Hope this helps.

 

Regards,

Ankur.

[Klara]

Dear Ankur,

 

Thank you so much for your reply.

 

If you do not mind, let me add some additional information on this subject.

 

Well, the design life for the MEG pipeline is 30 yrs.

We do inject a corrosion inhibitor (CGW85567) and concentration was within Integrity Operating Window for this period with some little deviations.

As to MEG pH, it was within specified limits for the whole period.

But... you said that only 100% MEG will not corrode steel, but in our case we inject 85% MEG. And because of MEG regeneration we have got accumulated acids.

So... do you have anything to say now?

 

Regards,

Klara

[ankur2061]

Dear Klara,

 

Well, after your clarification about corrosion inhibitor injection, it is obvious that a pigging system needs to be installed. Whether a permanent pigging system or a temporary pigging system that can be dismantled needs installation, requires a cost benefit evaluation from your side. As mentioned earlier in my post, there are no specific standards or guidelines for pigging of MEG pipelines. Refer the attached NACE standard for pigging.

 

Regards,

Ankur.

Attached Files

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[Klara]

Dear Ankur,

 

Your answers helped me. Thank you for this.

 

Regards,

Klara