Leakage form Main gas Transmission Line- Repair Strategy

[Nabeel Ahmed Qureshi]

Pin hole leakage occurred from a high pressure(500psig) underground gas line valve pit located in a gas well. Stagnant water accumulation inside Pit caused excessive corrosion of the line which ultimately resulted in a leakage. The pin hole leakage was temporarily addressed by installing a plidco clamp.
UT readings were taken afterwards & we found that 3 to 5 ft portion of piping was below PDT inside valve pit. To fix the issue we are planning for online sleeving of the piping portion below PDT but the well owner is reluctant from this activity & is not allowing us to carry any welding/Hot work inside the facility in running condition of line due to risk of fire/explosion & is asking for an unfordable plant shutdown.
Can some one advise if we can adopt some other means of repair like concrete sleeving over thinned out portion of line? Would it serve the purpose? If it servers the purpose then would it be a permanent repair or still temporary & we will have to replace the piping in planned Shutdown? Reference of some code / standard / engineering practice would help.
Regards
NAQ

[mechcolor]

Does the Well owner not known with hot tapping??

If really not, Mechanical clamp repair is an option to go.
It does not involve any hot work which may be objected by the Well authorities.

[ashfaqanwer]

You may look into ASME PCC-2 for more repair options and see what suits you the best.
Using a reinforcing sleeve with no welds on the piping (sealing may be done with other methods) is one option.

[ben]

Wall thinning issue is not that easy to handle. I believe main gas transmission line would be everything for you and you would never want to take any risk. Concrete sleeving, I do not know about this but it is not regarded as an authenticated repair method as per ASME PCC-2.
Composite repair I would say will solve your problem.

[Nabeel Ahmed Qureshi]

Ben you are right, this stands as our life line & we want to avoid plant shut down. Can we have some details of this composite repair like Method, Materials, machine/skills required, Life of repair etc
Regards
NAQ

[ben]

You have to contact some services providing agency who undertake composite type of repair.
This is a special technique and the method, materials etc. are extensively tested and validated according to the applicable codes and standards.
It requires certain process / procedure & personnel qualifications too.
And the life of this repair is declared / authenticated / guaranteed by the relevant agency whether long term or short term.

[mechcolor]

Have you performed MAWP calculations for the available thickness?
How much is the difference in actual operating and MAWP?

[Nabeel Ahmed Qureshi]

Hey Mechcolor,
Was away on vacations. Yes i've performed MAWP calculations.
The difference b/w MAWP & operating pressure is nearly 200psig. MAWP being on higher side.
Any advice?
Regards
NAQ

[Nabeel Ahmed Qureshi]

Ben, Have explored a local agency who performs composite repairs. They have provided following procedure.
1)- Surface preparation & have 3 options a)- Sand/grit blasting (not possible in our case due to low thickness & hig pressure natural gas inside) b)- Power brush cleaning c)- cleaning thru emery paper.
2)- Application of polymeric base to fill deeply pitted areas & to make the surface smooth.
3)- Wrapping of the build up /effected area with a multi directional woven glass fiber cloth after rinsing it in the Epoxy based resin.
4)- Curing of the wrapped glass fiber cloth for some specified time.
Would like to seek your advice that how we can make sure that the repair they are going to perform would sustain the pressure running inside pipe (if the pipe leaks after few days/weeks etc.
Also are these composite repairs to be considered Temporary or Permanent?
Regards
NAQ

[ashfaqanwer]

Nabeel,
As soon as the maximum operating pressure is below MAWP, everything is safe.
Hope you have made right MAWP calculations.