tie- in joint in piping system 4

[petro84]

hi everybody
I work an inspector of construction project of a refinery plant.Due to wrong ETA(Estimated Time Arrival) of piping components; shortage of material in stock is going to make unacceptable delay in time schedule of construction plan, therefore managers are going to increase the number of tie-in joints up to 50 joints in a test package, and the contractor QC Manager believes that if one golden joint is acceptable by radiography test after installation of missed component with out hydro static test, then it is not rational to put any limit on this matter, now I request you to help me to find the reason of necessity of limiting the tie-in joint. I have considered the following reason:
- Tie-in joint is a concept of ASME B31.8 and it was considered as a factor in some design aspects and we use it in piping (designed based on ASME B31.3) for separating boundary of different subcontractor's in test packages.
If you are agree with the QC manager point of view, then why we hydro test piping or pipelines which their NDT percent is 100 ?(all joints were radio graphed.)
I will be so appreciated if you can help me with this question.
thanks for your consideration

 

[pennpiper]

I have to ask at this point,
a. where is this Refinery project?
b. when are they going to start-up the plant?

I want to make sure I am far, far away when the plane is started up.

My other comment is:
Hydrotest every Tie-In point individually.

prognosis: Lead or Lag

 

[BigInch]

Stay out of the decision making process, if you can.

Actually a case can be made for doing everything, or ... nothing, however weak nothing may be.
You'll want to review this thread,

http://www.eng-tips.com/viewthread.cfm?qid=332470

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[ardicool83]

Hi pedro.

To reduce the tie-in with golden joint, you can use flange connection, or you can parallel/joint the hydrotest if the same class (preesure test).
AFAIK Golden joint is accepted without hydrotest if NDT 100% for special case (tie-in).
You must to know that the fuction of hydrotest is not for test the welding quality, but for test piping material to handle the overall system.
In some case, hydrotest failed not happen in the welding, but in the pipe/fitting material.
Correct me if i wrong.

Thanks,
Hardi

 

[DLite30]

The main purpose of hydrotesting is to ensure the integrity of the pipe, not necessarily the welded joints. As long as the joints were weleded, inspected, and NDT'd correctly, then a joint failure is unlikely.

 

[austsa]

Every golden weld involves a very small incremental risk. Therefore, more golden welds equate to more risk. The increased risk may be very small, but it is not zero.

 

[pennpiper]

Am I the only one here that sees the "contradiction"(*) in the discussion above.
- purpose of hydrotesting is to ensure the integrity of the pipe
- 100% RT of all joints means you do not need to hydrotest

Are you saying:
if all my pipe is Seamless
and
if all my fittings are seamless
and
if I RT 100% of all butt-welds, then I do not need to Hydrotest.
Is that correct?

I do not believe the ASME B31 Codes support this.

(*) contradiction:
1). a statement or proposition that contradicts or denies another or itself and is logically incongruous.
2). in direct opposition between things compared; inconsistency.

prognosis: Lead or Lag

 

[Kiwi2671]

Pedro,
Firstly, to be eligible for consideration as a Closure Weld in accordance with clause 345.2.3 (c)the weld must be subject to "In process examination" as per 344.7.
Has this happened ?

The only exemption from hydrotest is the actual closure weld (or Golden Weld) - if the pipe, fittings and welds on two sub-assemblies have been previously tested then the closure weld receives 100% RT or UT - no problem.
Not sure if that applies to your situation as you are talking about missing components ?
Regards,
Kiwi

 

[BigInch]

Pennpiper,
No.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[petro84]

Thanks great guys
I always says to managers do not ask me what will happen if we neglect a clause of a standard, because I don't know what was discussed in relevant committees and which aspects were considered, but here I should be directed to a conclusion which was made by Pennpiper. All you guys believe that hydro-test is a test for checking integrity of piping system,that I'm agree with it, and we know pipes were hydro-tested at mill but only samples of other piping components were tested in mill. Therefore if we increase the number of tie-in joints, then susceptible to failure parts of our piping system will be those piping components which were not hydro-tested in mill neither on site; if we do in-process examination of tie-in joints weld and then radio graph the welded joint.But Dear Big inch is not agree with the conclusion of Pennpiper. Please if you can talk about this matter more and make it clearer to me.
thanks for your time

 

[waterpipe]

well, I think BigInch agrees with Pennpiper:

Am I the only one here that sees the "contradiction"(*) in the discussion above?

No.

But let BigInch clears this.

Anyway, I’m interested in the discussion brought in by Penpiper:
If one RT 100% of all butt-welds then could he argue that the hydrostatic test is not needed (assume that the pipe itself (seamless or spiral) is mill tested at higher pressure than that of the site)?
Apart from referring to a clause of a Standard, I am interested in reasons against this argument in order to mandate the field hydro test.

 

[BigInch]

I agree with Pennpiper. If all the components have been previously hydrostested and then you 100% radiograph all welds, then the radiographs are validating the welds only.

The clause is 345.1, Each piping system shall be tested to endure tightness. The test shall be a hydrostatic leak test in accordance with 345.4 except as provided herein.

The other reasons to do a hydrotest are those of Dr. Becht that I posted in the referenced thread, plus, the code only gives minimum requirements. If you are acting, deciding, or directing on the owner's behalf, and you think that a hydrotest is justified (even though perhaps not specifically required by the code), you have the right to demand it. The code only states the minimum requirements.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[rconner]

Not wanting to step on any of the prior comments, nor good advice of Dr. Becht. However, I have seen accounts that sometimes not all pipes of all piping material types are necessarily the best quality, nor even in some cases are all pipes actually hydrostatically tested at pipe factories. There are furthermore likely some other good reasons to hydrostatically even the best quality of properly factory tested and field-welded pipelines, due to potential damage somewhere along the road or even less obvious reasons. IMHO (maybe worth little more than that), a properly run field hydrostatic test of installed piping to all extant possible protects ALL parties to a piping installation project, not only the eventual Owner.
I heard a story once upon a time of a cross-country pipeline project many years ago that was plagued in required hydrostatic testing by some small and quite unusual leaks, that unfortunately took a good deal of effort and time to find. The cause of the leaks was a great mystery to some, and the quality of the pipe even questioned, i.e. until one was dug up with the drill bit broken off in same (incidentally, away from a joint/weld)!
I am alas aware there are compelling arguments made to avoid hydrostatic testing or complete testing of pipelines, not the least of which is the water, logistics, time and expense involved to do so (or to nod along with Contractors that want to avoid all that). While I suspect some pipelines have probably gotten by without testing or complete testing, I hope this post helps to explain there are potential risks that perhaps should be kept in mind. Everyone have a good weekend.

 

[BigInch]

The list of excuses is longer than a gorilla's arm.

Pipelines (B31.4 & .8 code construction) are required to be pressure tested. No escape clauses.


"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek