Material for large pipe- No corrosion 1

[nickypaliwal]

Our client is installing a new pipeline very long and the corrosion rate calculation comes out to be zero.

Client is an Oil & Gas customer however the fluid is processed natural gas liquid so we do not expect H2S even in the long run. Should we still go for NACE compliance and corrosion allowance just because the pipeline is too long.

 

[brimmer]

NACE compliance to what? Your service conditions are non-corrosive.
You will find that in the construction of long transmission pipelines corrosion allowance is not normally built in.

 

[nickypaliwal]

Noted your point about corrosion allowance however one more concern is that pipeline will run through very remote areas and sort of non-accessible easily. DO you still maintain your view?

 

[brimmer]

yes - pay attention to environmentally sensitive areas, river crossings, HDD, etc. you may want to design with heavier wall in these areas

 

[OGMetEngr]

It all comes down to risk the customer is comfortable with. Corrosion allowance may be added if risk is high, which could be due to non-accessibility and/or high costs for replacement, high consequence of failure, etc. It doesn't sound as if NACE compliance is an issue here, unless trace H2S may remain in the gas.

 

[nickypaliwal]

H2S is present but the content is 0.00001 mol % and around..

So we assume no H2S at all..

 

[OGMetEngr]

This may not be a safe assumption depending on product form. You state large pipe. If this is constructed from plate, there is a specific clause in NACE that warns about trace amounts of H2S and steel chemical composition. Take a look at section 2 clause 8 of the NACE document. If the customer is not aware of this it should be mentioned and considered.

 

[EdStainless]

And then there is external corrosion.....

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[moltenmetal]

Is there any chance this very long pipeline will be used in future for some other purpose? Sounds like a big investment- it would be a shame to limit its usefulness for other purposes if its current purpose comes to an and before the lifetime of the pipe is up. They're re-purposing pipelines here after many decades of service.