Golden Welds and Pressure Test 8

[cadiehl]

So I understand the application of Golden Welds. Let's say I am replacing a 10' long damaged segment of 3" ips piping in a 600 psi Liquefied Natural Gas system. There is no feasible way to pressure test the 2 buttwelds required to perform this task. Am I required to separately pressure test the new 10' long piping segment prior to welding into the system? This has been a topic of discussion around the office for the last couple of days, and needs to be put to rest. We have ourselves in a situation similar to the above.

 

[BigInch]

Test the new section of pipe and any fittings welded to it first, then weld it in. Lastly, NDT the golden welds.

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

 

[cadiehl]

Thanks BigInch.... what if there are no fittings welded to it... just a straight run of pipe. Does it still require testing prior to welding it into the system?

 

[mfgenggear]

straight pipe can be hydro pressure tested.

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.

 

[brimmer]

It would still need to be hydrotested whether it has fittings or not

 

[cadiehl]

I know it "can" be tested. I am asking if it is "required" to be hydroed or pneumatically tested PRIOR to welding it into the system. It's just a straight 10' long piece of stainless, no fittings. It will be buttwelded into a system that cannot be pressure tested. So, it will have 2 closure (golden) welds that will be RT'd after welding it in. But, does the 10 foot long piece of new pipe need to be pressure tested in the shop PRIOR to welding it into the system? Is it a code requirement?

 

[BigInch]

It is REQUIRED.

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

 

[cadiehl]

Thank you Biginch.

 

[Kiwi2671]

Big Inch,
Out of curiosity, where is the requirement stated ?
B31.3 Cl 345.9.1 states " Welds, including those used in the manufacture of welded pipe and fittings,which have not been subjected to hydrostatic or pneumatic leak tests in accordance with this Code,shall be examined as follows:"..... 100% RT or UT.

So, in accordance with B31.3 if you have ERW pipe you either hydrotest/pneumatic test the section of pipe or you perform 100% NDT on the longitudinal seam.
What if cadiehl has seamless pipe - what are you actually testing ?

IMHO it is a good idea to put caps on the end and pressure test if only to confirm the integrity of the pipe but again IMHO there is no code requirement for it to be performed,
Regards,
Kiwi

 

[BigInch]

345.1

But now that is unimportant, as codes represent the MINIMUM requirements, it is the engineer's opinion that sets the requirements. Your opinion has already superceeded code minimum requirements and now the system must be tested.... according to YOU, regardless of what is stated in the code, or anywhere else.

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

 

[Kiwi2671]

Big Inch,
Your post has absolutely lost me ?
Your initial post stated "It is REQUIRED"
I asked for confirmation of where this requirement is ?
You came back with 345.1 which makes no reference at at all to piping, it talks about piping systems and ensuring "tightness".
Then you have a comment with YOU which completely lost me ?
Cheers,
Kiwi

 

[cadiehl]

Now I'm lost also. I just want to know if the CODE requires this 10 foot section of new piping to be pressure tested prior to welding it into the system. I don't care about good engineering practice, client requests, etc.... that is a totally different issue. Does the CODE require it? Or not? Now I see why no one in our office can come to a conclusion on this.

 

[SJones]

Assuming that A312 is the product specification, you have the option to require a mill hydrostatic test. The thrust of the exchange above is that it would be prudent to exercise that option.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[cadiehl]

Yes Steve. I just found that the A312 spec mandates a 30 second pressure test on all piping at the factory. However, the pipe segment would require a 10 minute pressure test to meet B31.3. That can done at the mill or on site, obviously. I think I have my answer. I think. Unless someone comes on here and throws a wrench in the gears.

Thank you, everyone.
CD

 

[mfgenggear]

why not contact the original engineer or any engineer that has worked this project.
flying blind is no excuse, someone there needs to be a qualified engineer.



Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.

 

[mfgenggear]

http://www.astm.org/Standards/A312.htm

Mfgenggear
if it can be built it can be calculated.
if it can be calculated it can be built.

 

[cadiehl]

Not flying blind MF... as you can see, opinions differ across the board on this subject. The same goes with the engineers I have spoken to around here.... even if this was a hypothetical situation, the answers would not be the same from every engineer you asked. Some say that pressure testing is for the welds, others say it is for the welds and fittings, others say it is for the welds, fittings, and pipe..... so, who is right? Those answers come from very experienced engineers. That is why I tried to pose the question here. Hoping to get some clarity.

 

[BigInch]

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.

345.4.2 Test pressure in every point in a metallic piping system shall be as follows:
Not less than 1.5 x design pressure.

Is there any doubt that a piping system includes pipe, fittings and flanges?

I don't think there is any more experienced engineer than Dr. Becht.
Dr. Charles Becht's opinions;

Pressure Testing

ASME B31.3 requires leak testing of all piping systems other than Category D systems. For piping in Category D fluid service, the piping may (at the owner’s option) be put in service without a leak test and examined for leakage during the initial operation of
the system. This is an initial service leak test. For all other piping, the following options are available:

(1) hydrostatic test,
(2) pneumatic test,
(3) hydropneumatic test, and
(4) alternative leak test.

An alternative leak test is only permitted by ASME B31.3 when:
(1) exposure of the piping to water via a hydrostatic test would damage the linings or internal insulation, or contaminate a process that would be hazardous, corrosive, or inoperative
in the presence of moisture; and
(2) a pneumatic test is considered by the owner to entail an unacceptable risk due to the potential release of stored energy in the system (the danger of a pneumatic test ncreases with the pressure and contained volume); or
(3) a hydrostatic test or pneumatic test would present the dan-ger of brittle fracture due to low metal temperature during the test.

Hydrostatic Test

"A hydrostatic test is generally the preferred alternative because it is conducted at a higher pressure, which has beneficial effects such as crack blunting and warm prestressing, and entails sub-stantially less risk than the pneumatic test (alernative). These reduce the risk of crack growth and brittle fracture after the hydrotest when the pipe is placed in service. The test is generally conducted at a pressure of 1.5 times the design pressure times a temperature correction factor.

Closure Welds

In the 1996 edition, addenda c (1998), closure welds were added [para. 345.2.3(c)] as an acceptable exemption from leak testing. A closure weld is a final weld connecting piping system or component that has been successfully leak tested. The closure weld does not require leak testing if it passes 100% radiographic or ultrasonic examination and is in-process examined. Closure welds are not used in the Code in the context of a con-nection to an existing pipe, since that weld is considered to be outside of the scope of ASME B31.3 (although you could look to the closure weld requirements for guidance). Rather, it is a con-nection between new components. For example, consider a large diameter vapor line, for which providing additional support for the fluid weight in a hydrotest is impractical, and for which a pneumatic test would entail undue hazard. The line could be pres-sure tested, as a subassembly, at grade, erected, and connected to equipment with a closure weld. "




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

 

[cadiehl]

Gots me some clarity... thanks BigInch.

 

[BigInch]

Now some mud in the water.
The above said, with B31.3 the decision ultimately resides with the OWNER of the installation, but at least now WE know how to advise him and that if he thinks differently, he should contact his insurance company and his lawyer.

Note that the pipeline codes B31.4 & 8 differ. Code & USA regulated pipelines must be pressure tested. Fortunately the pipeline codes B31.4 & 8 are specific. The applicable CFRs are law. The owner has no options.

B31.4
437.1 General
(a) In order to meet requirements of this Code, it is necessary that tests be made upon the completed system and upon component parts of the finished system.
437.1.4
(2) Systems to be operated at a hoop stress of more than 20% (in 35 years I've never designed a pipeline for < 20%) of the specified minimum yield strength of the pipe shall be hydrostatically tested in accordance with para. 437.4.1.

437.1.4 (5)-b Testing Tie-Ins. Because it is sometimes necessary to divide a pipeline into test sections and install test heads, connecting piping, and other necessary appurte-nances for testing, or to install a pretested replacement section, it is not required that tie-in welds be tested; however, tie-in welds and girth welds joining lengths of pretested pipe shall be inspected by radiographic or other accepted nondestructive methods...

437.4 Test Pressure
437.4.1 Hydrostatic Testing of Internal Pressure Piping
(a) Portions of piping systems to be operated at a hoop stress of more than 20% of the specified minimum yield strength of the pipe shall be subjected at any point to a hydrostatic proof test equivalent to not less than 1.25 times the internal design pressure at that point (see para. 401.2.2) for not less than 4 hr.

B31.8

841.3 Testing After Construction

841.3.1 General Provisions. All piping systems shall be tested after construction to the requirements of this Code except for pre-tested fabricated assemblies and welded tie-in connections where post construction tie-in testing is not practical. Additionally, single lengths or multiple welded lengths of pipe previously tested in accordance with this Code
for the purposes of repair or replacement do not require a post construction retest.
(a) The circumferential welds associated with con-necting pretested assemblies, pretested repair pipe lengths or sections and welded tie-in connections not pressure tested after construction shall be inspected by radiographic or other accepted nondestructive methods
in accordance with para. 826.2.

(b) Nonwelded tie-in connections not pressure tested after construction shall be leak tested at not less than the pressure available when the tie-in is placed into service.

Furthermore, the pipeline codes/CFRs define maximum allowed operating pressure as test_pressure / test_pressure_multiplier, so if not pressure tested, pipelines will not have an operating pressure ... and therefore cannot be operated. A pipeline designed for 1460 psig, but only tested to 1250 psig can only be operated to a maximum pressure of 1250/1.25 = 1000 psig.

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