ASME B31.3 Exempt Piping

[A.egis]

Hello,

I have a vendor claiming the gas piping to a burner is exempt from B31.3 due to the design pressure being 12 PSIG and stream composition being purely natural gas. I looked into the contract code, AMSE B31.3(1996) and found the following exclusion and definition for flammable.

Given that natural gas has flammability range of approximately 5 to 15 percent in air, which is not present in that stream. Could it be considered inflammable under the ASME definition due to service conditions or is that interpretation wrong.

 

[LittleInch]

I think its wrong.

Under expected operating conditions it can be ignited and continue to burn in air.

Not sure what advantage is gained by not doing this??

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

The def of flammable says "ignited and continue to burn in air", doesn't that describe NG?
It doesn't say "within the closed system".
What rules is he suggesting that work to?
Does he have the NFPA info at hand to quote?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[btrueblood]

Kinda depends on jurisdiction. Washington state requires fuel gas installations conform to IFGC, and that code states that when conflict between codes exist, the more restrictive code applies.

I've also seen NFPA 54 applied, and the introduction for ASME B31.3 states that "certain piping within a facility may be subject to other codes and standards, including but not limited to..." and calls out ANSI Z223.1 National Fuel Gas Code, which is another name for NFPA 54. I don't know if NFPA has a similar statement as the IFGC.

Like LI says, fuel gas is flammable per the definition in B31.3 section 300.2, so you don't get to waive B31.3, but you do need to consider whether the applicable fuel gas code is more restrictive. Is there something about the burner installation that you think violates B31.3? Know that anything upstream of the meter connection is not your problem, it belongs to the gas company and they have their own code to follow.

 

[A.egis]

Thanks for the responses, for closure I asked them to clarify and provided the same code section and they changed their stance on the matter.

LittleInch; I believe the advantage would be using their defined NDE percentages and having less documentation to worry about. They would treat as Class D piping.

EdStainless; The vendor was caught up on the low pressure of the system and the wording "The term thus may apply, depending on service conditions..." in the definition. They have no NFPA info on hand to back this up.

Btrueblood; The site would be under federal jurisdiction and NFPA 54 would not apply per the scope applicability section. There are no worries about the reliability and safety of the equipment, it's just a matter of having the right amount documentation and NDE for the turnover package.

Thank you again for the information, very helpful.

 

[DekDee]

A.egis,
May I ask why on earth you would be working to the 1996 edition of B31.3 ?
There have been multiple new editions issued since then.

I agree with LI and Ed - NG is flammable.
Therefore Category D is out of the question.

This piping should be designed & fabricated to Normal Fluid Service.

it's just a matter of having the right amount documentation and NDE for the turnover package.
Category D is zero NDE (other than visual) so do not expect much of that.

Cheers,
Shane

 

[A.egis]

DekDee,

The equipment is for an LNG facility in the USA. Federal code for LNG facilities, 49 CFR Part 193, incorporates NFPA 59A(2001 edition) which then incorporates ASME B31.3(1996 edition). To be compliant with federal standards we must then conform to outdated standards.