Section VIII Div 1 or B31.3

[dalea60]

Customer has asked about designing an item per B31.3 instead of Section VIII Div 1. Is the following a pressure vessel or piping? Here's a description: approximately 3 foot length of 8" or 12" SC 10 pipe with an elliptical head on each end, a half coupling in the center of each head & a series of six TOE nipples in the length of pipe. Media is air at up to 150 PSI @ 200 degrees F. When the item is in operation on the piece of equipment, air would be supplied to the item by one of the couplings in the head & diaphragm valves would be mounted on each of the TOE nipples. As the piece of equipment operates, the diaphragm valves would be opened one at a time to release air to the process.

Thanks,
Dale

 

[jte]

Dale-

If you change "elliptical head" to "end cap" then I'd say it sounds as though you are "...distributing, and metering or controlling flow..." and as such you fall within U-1(c)(2)(e). Read the rest of U-1 (c) to be sure, but it sounds to me as though a strong case can be made that this is a piping component. The way I understand your post, this is not an air receiver i.e. you are not using this as a compressed air tank. Flow in more or less equals flow out, and as such you are not accumulating and storing air for future delivery to the equipment.

As always, check witht the jurisdiction where this manifold will be installed if there is any doubt about the proper code to apply to its design.

jt

 

[dalea60]

JT,

That's kind of the question, whether it's an air receiver or not. I was trying to keep the description as generic as possible so as not to influence the response. Basically there is a short time delay between when one diaphram valve (1" or 1.5") opens & closes and when the next valve opens & closes. The required volume & pressure of air has to be there when the next valve opens. In my mind it seems like it functions as an air receiver tank but I'm not familiar with the application of B31.3.

The juridiction is a foreign country by way of an engineering firm so that makes it more complicated yet.

Thanks for the help.
Dale

 

[jte]

Dale-

If by "short" you mean a few seconds, I'd still lean toward B31.3. If its minutes, I'd ponder it a bit longer. Having been on the owner/operator end of the stick (as well as E&C previously), I'd push for B31.3 where possible. Simplifies things for the plant inspectors, engineers, and maintenance folks. Might even simplify your life. If its a vessel, will you be providing the relief valve? Like I said earlier, don't use SE heads, use end caps...

You may well get differing opinions, pushing VIII-1. Most will be from folks who don't deal with the equipment after it is put into service. Differing opinions are fine. If we all agreed on the answer, we wouldn't bother discussing the issue.

jt

 

[dcasto]

I'd call a distribution header and build under 31.3.

 

[dalea60]

When the piece of equipment is running there would be approximately 15 seconds between when one diaphragm opens/closes & when the next one opens/closes. The time is adjustable so it could be longer depending on the process. When the piece of equipment isn't running there would still be pressure in the "pipe" (the air isn't bled off).

Thanks for the help.
Dale