Appropriate code for low-pressure piping

[McKeil]

I'm working on a project that calls for radiographic examination of field-welded pipe in the specification and no acceptance criteria is identified. When asked, the Consultant/Client is likely going to suggest ASME B31.3, however the piping system operates at between zero and 15 PSI (air recirculation piping).

Does anyone know of an appropriate code of construction for piping below 15 PSI?

THANKS.

 

[MJCronin]

McKeil...

IMHO, I believe that you do not have piping on your hands here....but you do have a "tubular structure"

I would use the AISC rules for weld inspection for these low pressure systems.

-MJC

 

[jte]

Might depend on what type of plant the tubular structure is going into. If its a refinery, they'll likely demand B31.3. They are familiar with it and all pipe is assumed to be B31.3. If you try to make an exception, it'll have to be documented, remembered, forgotten, resurected... In other words, it'll become a PITA.

As an owner's engineer a few years ago, I was once asked by some of the guys in Ops to help them design a system with ABS pipe so they could take a Shop Vac at grade and connect the flex hose to various outlets on a platform. Basically a jury-rigged whole house vacuum for a large, messy part of the plant. I killed the project when I was told I'd have to get P&ID's drawn up, make up a line class, push an MOC through, etc etc. Stupid, but reality. And I have no doubt that that platform is still hazardous from a "particle in the eye" perspective.

So, if the rest of the round stuff in the plant is B31.3, its probably easiest and likely most efficient in the long run to just treat this round stuff as B31.3 pipe.

jt

 

[Ballbearing1]

Mckiel,
Not sure what code it will fall under but pretty sure it is not B31.3.
B31.3 300.1.3 Exclusions: "This code excludes the following; (a) piping systems designed for internal gage pressure at or above zero but less than 105 kpa (15 psi)....".
Absolutely no idea why RT would be called for.
B31.3 Cat D does not require RT and that can be nearly 10 times the max pressure that you are using.
Regards,
BB

 

[McKeil]

The suggestion that this might be tubing is interesting. This pipe/tubing is stainless steel, 11 gauge, 10 gauge and 0.250" wall, and diameters range from 12" to 66". This pipe/tubing has been welded outside in position, making for difficult welding. This stuff is most of the plant. If we are forced to meet B31.3 welding acceptance criteria, I know we will have some nonconforming defects, and hence repairs. Being forced to cut into a 30" pipe that has 1 1/2" (of its 94" circumfrence) of lack of penetration (due to high-low because the wall thickness is so thin leading to the pipe being out of round), when only 12 PSI of air will ever go through it, will seem so unnecessary, and be costly.

 

[Ballbearing1]

Mckeil,
Show the consultant / client the page from B31.3 that I quoted. It clearly states that your piping is excluded from B31.3.
On another note it sounds like the piping is already welded. How can you quote on a job that you don't know what the acceptance criteria is ?
This is the thing you should clarify with the client before you start welding, not after it is finished.
Good luck,
BB

 

[BoyTNDT99]

Your should do as owner required/ determine.

 

[McKeil]

BoyTNDT99,
The Owner didn't specify what they require in the contract documents.

If you're suggesting that since we missed asking for clarification before the contract was issued, that we should follow what the Owner directs us to do now after a price is in place, what would prevent the Owner from asking for nuclear quality welding on their 12 PSI line?

 

[rodofgod]

Hi All!

McKeil,

First of all, I'm mystified how you can be expected to perform radiographic examination of field-welded pipe with no acceptance criteria??? How do you know if a weld is acceptable or not? I think this could be quite a problem for your company!
As you have stated, there is nothing to stop the client asking for 'nuclear quality welding'! If welding has already taken place and it looks like it has, then you really need to go 'cap in hand' and sort this out PDQ! Do some homework on the likely standards that are in use and, as BB states, use them in your favour to establish an acceptance level with the client!

Good Luck!

Regards

 

[BigInch]

B31.9 might be what you're looking for.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[JohnBreen]

The ASME B31 Codes for Pressure Piping explicitly EXCLUDE piping from 0 psig to 14.99 psig. For example, see B31.3 paragraph 300.1.3. Just be sure it will not exceed 15 psig and it will not have an application of external pressure (i.e., internal vacuum - perhaps use a vacuum breaker).

You have an air DUCT. See ASCE publication "The Structural Design of Air and Gas Ducts for Power Stations and Industrial Boiler Application".

http://www.asce.org/bookstore/book.cfm?book=3644

Ducting examination requirements may also be provided (yes even for circular section ducts) by SMACNA and ASHRAE Standards.

Regards, John

 

[JohnBreen]

..........On the other hand IF THE DESIGN PRESSURE IS 15 psig or more, all the rules of B31.3 apply. Have a look at Appendix M, Figure M300, and see if the rules of category D fluid service can be applied.

Regards, John

 

[LSThill]

JohnBreen(Mechanical)

Additional Anslysit for API-ASME FFS-1 APPIDENX B, LEVEL III:

Pipe Beam Modeler with 18DOF is the First Pipe Stress Program to Automatically Run Finite Element Analysis for Local Intersections for The Structural Design of Air and Gas Ducts for Power Stations and Industrial Boiler Application.

Regards

Leonard Stephen Thill

 

[McKeil]

The Engineer has confirmed that the maximum operating pressure is under 15 PSI but they're insisting on having Radiographic Examination as per contract, and they want us to go to ASME B31.3 category D.

THANK YOU to everyone who is commenting. I appreciate your help.

 

[JohnBreen]

No problem Mac.

It is the responsibility of the owner to determine (prescribe) the fluid service. You will find that Category "D" fluid service is a little less rigorous than "Normal" fluid service. You might suggest the installation of a pressure relieving device to assure that the system will not be operating at pressures above the design pressure.

Good luck with your projects.

Regards, John.

 

[BigInch]

I still think you should look at B31.9

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/