ASME VIII vs B31.3

[Kodis]

Hi guys,

I'm new here and have a very general question concerning standards;

If I am designing a piece of equipment, what are the factors that would differentiate between B31.3 & ASME VIII.

The equipment is not technically 'holding' pressure but has fluid passing through it (you might compare it to an in line heat exchanger as it is simply a chunk of plates & pipes inserted into a larger pipe. - However ideally I would like to use weldolets and end caps for the connections and would like to know what I can get away with without straying into ASME VIII territory (e.g. is it dependant on fittings or purely if it holds pressure).

Thanks in advance for any feedback.

 

[marty007]

One very basic way of differentiating the two codes is the purpose of the item. If the purpose is conveyance of fluid/gas, then it should be considered piping (B31.3/B31.1/etc...). However if the purpose is something else (exchanging heat/reacting chemicals/etc.), then it should be considered equipment.

There are a host of ways to 'bend' these definitions, but you'd have to have good reasons to bend them very far. With regards to a heat exchanger, I've seen people go either way for say a jacketed/double pipe, but I don't think I've ever seen a shell/tube exchanger called piping (and I'd have some strong opinions if someone tried).

Cheers,
Marty

 

[Ripz]

ASME Section VIII covers equipment over 14 psi. I don't think B31.3 has any limits.

But if it's atmospheric pressure, with no jurisdictional requirements, then using a code isn't mandatory. Just use good engineering judgement.

 

[jte]

Strictly speaking, VIII Div. 1 covers equipment with an MAWP (and be sure to read end note 36 in Div. 1) exceeding 15 psi, however vessels with lower MAWP's may be stamped as well. It is not unusual to specify 14 psig just to be positively certain of the intent, though you could stamp 15 psi with no U stamp.

The components from which a chunk of equipment is not relevant in the sense of assigning a code. [I was going to use the word "determining" but there is so much gray area out there that I figure "assigning" is more appropriate.] I can very easily build a Section VIII Div. 1 scope pressure vessel out of NPS 10 pipe, a couple of end caps, and a few weldolets.

jt

 

[XL83NL]

B31.3 (dont have the 2012 edt in front of me, so just checking the 2002 edt) has an exclusion for the scope

300.1.3 Exclusions. This Code excludes the following:
(a) piping systems designed for internal gage pressures
at or above zero but less than 105 kPa (15 psi),
provided the fluid handled is nonflammable, nontoxic,
and not damaging to human tissue as defined in 300.2,
and its design temperature is from −29°C (−20°F)
through 186°C (366°F)

 

[Kodis]

Thanks very much for the tips, maty007 I think you've pretty much summed up the position I'm in; the equipment I'm designing would probably be classed as a vessel but as it is 'inside' a pipe and no fluid is being stored in it I was hoping to get away with designing it to B31.3. We have done it before and I have seen other examples from other companies - but there seems to be a very grey area and dependant on how the individual inspector views the item.

You're comments have all been helpful,

Cheers!

 

[moltenmetal]

Is the device somehow a potential source of pressure to the surrounding pipe that may cause it to rupture? If not, this thing is a NOTHING- a non-code device, since it is entirely inside another piece of pipe which itself is the pressure boundary.

If it is capable of generating pressure, then something- a wire, a steam line etc., has to cross the pressure boundary.

 

[Kodis]

moltenmetal - The device does not generate pressure itself, it has a MAWP but this is relating to the pressures generated upstream.

I believe it is possible to design it to 31.3 but I am still unsure of the exact restrictions. I think I'm going to need to talk to an authority to bottom out the design.

Thank you for your help though!

 

[matt73]

Depending on how your business is contracted, which code you design by is ultimately determined by the "owner" or the "Authority Having Jurisdiction". Yes - you can force a design to be compliant with a code, but was the specific code used for the design necessary by contract?

This is a big issue we have at my facility. We are forced to use ASME BP&V, and B31 Codes, even when they are not applicable.... yet we force the applicability of the code to pressure systems that are not within the intended scope - because the pressure's are within the scope of the ASME Code.

Use a vehicle tire as an example: It's I.D. is larger than 6" and the internal pressure will be greater than 15 psig... does that make ASME Section VIII, Div 1 applicable? It sure does, but does it mean that we have to use ASME Section VIII, Div 1 to design the tire? No. However - does my contract require me to design tires in accordance with ASME Section VIII, Div 1?? Yes.

(This is an analogy - we're really not making U stamped tires).

 

[marty007]

matt73,

Whenever I design a tire I invoke U-1(c)(2)(c), i.e. a tire is an integral part of rotating equipment.

(said in jest, I have no knowledge of tire industry)

Marty

 

[jte]

No, no, no. You have it all wrong!

Clearly, the tires are transporting compressed air from one location to another. Thus, they fall into the exclusion of U-1(c)(2)(d).