ASME B31.5 threaded joints are allowable in natural gas piping?

[wangzh2k]

Hi all,

I am wondering if ASME B31.5 threaded joints are allowable in natrual gas piping.


Thanks in advance

 

[pennpiper]

wangzh2k

A lot depends on what pressure you are going to be using. Is this high pressure pipeline gas or is this the very low pressure household natural gas?

 

[wangzh2k]

pennpiper,

Thanks for your message. It is a fuel gas piping line, the design pressure is around 280 psig. Since I do not have ASME B31.2, I misunderstood that should be B31.5.

I am wondering if there are limits of threaded joint in B31.2.

Thanks,

 

[gr2vessels]

wangzh2k,
This is an excerpt from B31.2:
Note the limit of 4" NB pipe for threaded connections.

Clause 214 THREADED JOINTS
Threaded joints may be used for joining piping components of steel, copper or aluminum pipe having at least the nominal wall thicknesses specified in Table 204.1. All pipe threads shall be taper pipe threads in accordance with USAS
B2.1 except that pipe threads other than taper pipe threads may be used for piping components, where tightness of the joint depends upon a seating surface other than the hreads, and where experience or tests have demonstrated that such threads are suitable for the conditions. Threaded joints shall not be used in aluminum pipe in the annealed temper.
It is preferred that threaded piping not be used in sizes larger than 4inch, nor where the joints are not visible for inspection. The use of threaded joints where severe crevice corrosion or erosion may occur should be avoided.
cheers,
gr2vessels

 

[JohnBreen]

Hello,

ASME B31.2 was withdrawn by ASME in 1988 and fuel gas piping is now addressed by the ANSI/NFPA Z223.1 National Fuel Gas Code. When you think about consensus National Codes and Standards it is important to understand that they are voluntary until they are specified by the municipal, State or Provence Building Code. If so specified, the specific consensus National Standard becomes "the law" (has the force of law). So your first step is to communicate with the local jurisdiction (or read the applicable local Building Code) to determine what Codes and Standards are mandated.

ASME B31.2 is still available from ASME as a "Guide Document" and of course it is widely (unlawfully) available on Internet "ebook file sharing" sites. The ANSI/NFPA Z223.1 National Fuel Gas Code is part of the NFPA National Fire Code so if that document is invoked by local jurisdictions (via their Building Code) then Z223.1 is the applicable Code for fuel gas piping.

As Pennpiper has advised, there are pressure / temperature break points in all these Codes that sets limit upon the maximum pressure and maximum temperature for the application of the Code. The Code user should always read (study) the scope paragraph in the applicable Code to determine what piping is explicitly included by the scope and what piping is explicitly included by the scope.

Regards, John

 

[gr2vessels]

Hi John,
You are absolutely correct, the ASME B31.2 has been replaced by Z223.1 (in United States). However, many other countries, like China perhaps, found Z223.1 not quite applicable and since B31.2 is still valid, it is used to complement their national standards for the natural gas piping, even if it is applicable only for the pipe stretched between the meter and the backyard BBQ.
cheers,
gr2vessels

 

[JohnBreen]

gr2vessels

Thanks for that, I wasn't aware that B31.2 was still in use anywhere. Actually I am glad that it is being used as I believe that it is still quite good.

Regards, John