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Up Topic Welding Industry / ASME Codes / insulation stripping
- - By doyenofcastle (**) Date 05-17-2011 10:03
we are doing construction of  pipe line 31.4 offshore ,in some areas we have to remove scaffolding fast after welding , heat tracing and insulation .to keep scaffolding till the end of the line it will cost us a huge budget ,Is there any restriction  to do hydrostatic after insulation  the weld joint is already checked by random RT and 100% PT(not allow in 31.3 to insulate before hydrostatic )
in API 570 they allow after repair to not strip the insulation prior hydrostatic they accept to monitor the pressure gauge and hold pressure for longer time .
thanks
Parent - - By swsweld (****) Date 05-17-2011 12:31
We get the EOR's approval quite often to allow insulation and backfill
Prior to hydro. All welds visual and % RT but this is 31.1 and not critical
service. We agree to find and fix at our expense if there is a failed hydro.
There have been no failed hydro's.
Of course I'm comparing apples to oranges but essentially the same dilemma.
Can't look at code now but our specs normally says to hydro prior to insulation and backfill.
We get permission from the EOR and after the NDE, insulate and backfill.
Parent - - By 803056 (*****) Date 05-21-2011 13:53
The hydro test performed after insulation has been applied or after backfilling a ditch is like trying to determine if an orange is ripe in the dark.

A very small leak in a gas line or high pressure steam line can have dire consequences. Unless the hydro test pressure is maintained for a long time, a small leak path may not show up as a pressure drop on the pressure gage. A small amount of gas leaking over time can build up sufficient volume to become a problem. A small leak in a super heated steam line will get larger over time by erosion and can cut a man in half if he inadvertently walks past the leak.

These problems are always seen as minor by the contractor that will have collected his money and will be long gone months after the project is completed. 

Best regards - Al
Parent - - By swsweld (****) Date 05-22-2011 03:48
I don't disagree with your middle paragraph....:wink:

My suggestion to the OP was to run it by the EOR. If the pluses outweigh the minuses the EOR may allow insulation before the hydro. We don't know what the OP's specifications state in regards to his hydrostatic test.

I have, as a contractor, installed several underground systems (many on military projects for the USACE) and the specs may dictate that all joints remain uninsulated and not backfilled until a successful hydro has been achieved. This allows someone to visually inspect each joint if they feel like it or if its not too hot or cold or raining. A mile down the road on different project, with the pipes coming from the same boiler or chiller at the central energy plant, the specs may state that the pipes shall be backfilled before hydro, usually on gaskeded PVC joints to prevent movement. Other specs do not address the issue directly. MANY specs are just recycled from previous similar projects.

We have ran HDPE gas lines where line must be partially backfilled before pressure test per the specs.

Is it better to test a chill water PVC system before you backfill or after? You must have some backfill to test but if you test first and then backfill you may damage the pipes during the backfill and compaction. I think it is better to test after insulation and backfill. You are testing the finished product. The CHW product is usually 40F and 70PSI so not too dangerous. Hot water is always steel and welded joints on these projects and vary in temp and pressure but still not close to the dangerous super heated steam line that you mentioned and I agree with your warning on those lines.

There are systems that are way to critical to insulate or cover before the pressure test but that isn't always the case. IMHO it is a good idea to discuss it with the EOR to determine the best means and methods to achieve the best product for the customer in regards to hydro.

Not all contractors are looking to cut corners to save a buck or two. I know lots of them do but I don't want to get a call 11 months and 29 days after acceptance of completed project and hear "You need to come and fix a leak in your pipes...under the four lane highway."
Parent - By ssbn727 (*****) Date 05-22-2011 18:54
All I have to say is to remind folks of the old "Fram" oil filter commercial, and it's saying which basically alludes to either paying more now to make sure something is fixed right or working correctly by using a superior product, or pay a heck of a lot more later for taking shortcuts or using inferior products instead.:wink::cool: So what'll it be???:confused:

Respectfully,
Henry
Parent - By js55 (*****) Date 05-23-2011 11:58
You cannot insulate a piping assembly and comply with 345.2.2(a).
How do you examine all joints and connections if you can't see them?
And in ASME engineers do not have the authority to waive the code.
- By doyenofcastle (**) Date 05-24-2011 04:03
I'm sorry I forget to say the line is API 5L GR B thickness 9.5 mm line pressure is 8 bar ,design pressure 16 bar ,test pressure 24 bar  this line will be insulated .the liquid will be crud oil at 50 C degree
Up Topic Welding Industry / ASME Codes / insulation stripping

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