ASME B31.8 and B31.3 3

Is that you Ben?

I think the B31.3 Code is intended for process plants (reference B31.3, paragraph 301.1 Scope). It involves the piping that is associated with those processes. In the Case of B31.3, the "processes" within the plant boundaries are intended to change the basic properties of the products processed there. I do not think it is the intension of the B31.3 Code to include any gas transmission piping as the properties of the gas are not changed.

In older editions of the B31.3 Code, a diagram was included that showed (within the plant boundaries of process plants) the intended jurisdictions of various ASME B31 Pressure Piping Codes. That digram showed that B31.8 "right-of-ways" sometimes crossed through the boundaries of B31.3 plants and when that occurred ALL the piping within the B31.8 right-of-way was to be treated as B31.8 piping.

As you know, the design philosophies of B31.3 and B31.8 are very different. Also, the types of piping covered by B31.8 (unlike B31.3 piping) is regulated by the Federal Code of Regulations. For contractual purposes, the boundaries of B31.8 above-ground facilities should be established and shown unambiguously on the facility plot plan. Within those boundaries, the rules of B31.8 and Federal Regulations (49CFR192) shall apply. Sometimes, those boundaries MAY be within the boundaries of other ASME B31 Pressure Piping Codes.

Just my opinion.

Regards, John.

I'm not on ASME's B31.x Code committee but I spent a lot of time in the B31.3 world but am spending more and more time, lately, looking at B31.8 designs (compressor packaging). I can't speak to the theoretical differences between the two but in practice I find B31.8 to be much easier (straight forward) to work with.

B31.3 makes provisions for a multitude of services through a much, much more broad library of material and material stress values as a function of temerature. I just made a quick run through B31.8 Appendix D which lists the Specified Minimum Yield Strength for Steel Pipe Commonly Used in Piping Systems...there 41 (+/-) and only one stress value for each. Sure there's a temperatrue derate variable in B31.8's functional equation but it's not material dependent. B31.8 and B31.3 both recognize pipe joint efficiences as far as seamless, ERW, etc. Something that comes into play in B31.8 but not in B31.3 is something called Location Class which is just a derate factor that takes into accound the risk/exposure of the area of installation...a pipeline running past a school is going to have versus one out in the middel of nowhere.

I've also notice a lot of B31.8's requirements (welder certs., inspection, testing, etc.) depend on operational hoop stress.

That's about all I can offer. Hope it provided some of value.

B31.8 is normally used for the applications that you described.

It might be an idea to check local rules for where the metering stations etc will be installed. What is the location in question?

Shannon

For above ground facilities like meters and interconnects you have a choice of 31.3 or 3.18. As dober alludes, the CUSTOMER may mandate you use 31.8 on his property.

We switched to 31.8 because of some of the requirements in 31.8 would not work well. The wall thickness and other basic engineering will yeild the same results and costs under each code. The most common is fillet welds on the pipe, a no-no under 31.8, but acceptable in 31.3. When bidding out our large complex meter skids, the potential vendors perfered to shop build under B 31.3.

We also switched our pig traps from ASME to fabricated piping under B 31.8.

Hello,

The fact is that it is not the responsibility of the designer to make the call on the Code that is to be used. It is the responsibility of the owner of the facility to specify which ASME B31 Code for Pressure Piping is to be used. This is important because legally, the owner is liable and responsible to the criminal and civil courts.

If the designer is to assist the owner in making that decision, the scopes of the documents would be perused (by a Professional Engineer). The other important issue is to determine what the legal jurisdiction requires. The ASME B31 Code for Pressure Piping are voluntary consensus Codes that have no legal force until they are referenced by the local building Codes or by Federal Law (Codes of Regulation). Once they are required by the local (e.g., State or Province) building Code they have the force of law to make them mandatory. To vacillate between several Code documents to suit your purpose is irresponsible and most likely a violation of the law in locations where Codes are mandated by the local jurisdiction.

In the case of gas transmission pipeline systems (in the USA), the federal Code of Regulations (49CFR192) takes precedence and B31.8 becomes a "guideline" document that supplements the Code of Regulations. The ASME has published a Guideline document that compliments the B31.8 Code document and it is well worth reading.

Regards, John.

As a pipeline owner, you can set where the pipeline begins and ends. If you do not then the regulators will and have. Conoco did not do that so the DOT went into the middle of the refinery and said the line started at the suction of the pipeline pump. They then asked to see all the maintenance and operators of that pump OQ documents. OPP, don't got any.

I always mark my drawings with a spec break between 31.8 pipeline and 31.3 plant. The spec break as the pipeline ovepressure protection and the plant has its own. This way all my plant over presssure protection and operating/maintenance falls under a different set of standards that are at my choice, not a mandated 6 month interval as required (for liquid) by DOT.

I agree with Dennis. Whether you set the pipeline riser connection to a pig launcher/receiver or further within the plant is an owner decision. Show the specification break on the P&ID's, contract documents etc. and avoid confusion.

B31.4 or B31.8 (see scopes of code in the first pages) include meters, pumps, pig, regulator, valve and compressor stations.