NDT (radiography) and Hydrotesting

[Pipingtop]

Hi All,
In order to comply with B31.3, do I need to carry out both hydrostatic testing and NDT (radiography) for a pressure piping system (say instrument air piping) or can I eliminate NDT and carry out hydrostatic testing only?
please help

Thanks

 

[Frank1344]

Pipingtop,
Hydrotest is for making sure there is no leak in the system. And at the same time you may have welds with problems and they don't show up during the hydrotest.
Usually up to 10% random X-Ray is a common practice for making sure the welds have been performed properly (acceptable quality).

On a different note:
B31.3 is a code and not a design guide. It won't dictate all the tests that you MUST perform for a specific service.
It is up to the design body to make sure the design is safe.
Usually the piping class for the service in this case Instrument Air contains the required tests, or company specific piping installation specification may list the tests required.

Hope this helps.
Frank
Saipem

 

[stanweld]

In normal fluid service per B31.3, 5% random RT is required. Leak testing is also required per subsection 345. The 5% RT is not a substitute for the leak test. 345.1 (c) and 345.9 provide the requirements for deviations from leak testing using 100% RT or UT and MT/PT. 345.2.3 (c) permts the closure weld to be 100% RT or UT examined in lieu of leak testing.

 

[pennpiper]

It is not required and is NOT recommended to Hydro test Instrument Air (IA) systems. Instrument Air Systems falls into the same ASME B31.3 Code group that allows a "commodity test". This group also includes Plant Air, Utility Water and Domestic (drinking) Water).

 

[Frank1344]

Hello Pennpiper,
Would you please specify which part of B31.3 is talking about this?
I searched all over the 2010 edition and was not able to find it.
I really appreciate your feedback.
Thanks,
Frank

 

[pennpiper]

Well now here's the problem. I am retired and do not have access to a copy anymore. So you say, HA! he does not know what he is talking about! Well, back in the day I did have to a copy and I did know where it was. It was called "Catagory "D".
So tell you what, send me your current copy and I will look it over and if it is still there I yellow high-lite it and send it back to you.

Let me know and I will send you my address.

 

[stanweld]

Air service most likely will meet Category D. It meets the "nonflammable, nontoxic" criteria but must also meet the 150 psig max pressure at -20 F thru 366 F permissible temperature range. Per 345.7 an Initial Service Leak Test may be performed; no NDE other than visual need be performed.

 

[Frank1344]

Thanks for the feedbaack.

You are absolutely right and it is still called for Category D fluid service.

My apology.

The reason I followed up with you on this subject is I can see in if not all but most of the companies they use the same rules as applied to process lines to Cat. D lines as well.

Thanks again,
Frank

 

[engr2GW]

What if the instrument piping talked about in the question is such that produced hydrocarbon gas is used for the instrument and not air, then the Cat D talk falls off right, and the B31.3 requirement comes back in...

As much as possible, do it right the first time...

 

[pennpiper]

"hydrocarbon gas not air used for the pneumatic instruments"

I cannot even begin to imagine that some major or minor Refiner/Energy Company would consider such hair brained idea.

I cannot imagine any responsible Instrument manufacturer would allow hydrocarbon gas to be used in their instruments.

I also do not think it would pass the HAZOP Review.

 

[TD2K]

The use of natural gas or produced gas as "instrument air" isn't unheard of in remote production facilities.

I agree I wouldn't want to see it used in a Refinery or significant sized processing plant.

 

[Pipingtop]

Thank you all for your kind feedback.
The instrument air design pressure (1320kPag) in this case exceeds Category D therefore this piping system belongs to Normal Fluid hence require hydrotest. It is now clear that 5% RT (min) is also required.

 

[Tuckabag]

" "hydrocarbon gas not air used for the pneumatic instruments"

I cannot even begin to imagine that some major or minor Refiner/Energy Company would consider such hair brained idea.

I cannot imagine any responsible Instrument manufacturer would allow hydrocarbon gas to be used in their instruments."

Sales gas is used a lot over here in Aus to drive actuated valves/ESD's on remote sites, it's common practice as long as the actuators/instrument MOC are suitable for sales gas.

 

[moltenmetal]

Unless I'm mistaken, the owner must agree to the commodity (i.e. in service) test and to forego the requirement to hydrotest, even for category D lines.

For instrument air piping systems, the code-permissible alternative to hydrotesting (the pneumatic test at 110% of design pressure) is usually pretty low risk, and not all that different than the commodity test.