Meaning of "open to atmosphere" as quoted from B31.3 1

[Naidooru]

Hi all,

Please advise on the meaning of open to atmosphere.

Scenario: If i have built a drain line with two spools. One is a flanged on both ends and the other flanged on one side with an open end on the other that goes into a drainage system.

Question: If the two of them are bolted to an isolation valve, and as per ASME B31.3 345.1.2 (d) (Unless specified in the engineering design, lines
open to the atmosphere, such as vents or drains downstream of the last shutoff valve, need not be leak tested) is this line regarded as open to atmosphere, or is it not considered to be due to the fact that it can be still isolated at the flanges and thus the open end can be exempted from pressure testing.

Please advise me on the correct understanding

 

[LittleInch]

Interesting.

IMHO, if it's open to atmosphere then it's open to atmosphere regardless of what it has on the end, though why you want to waste a flange I don't know....

So long as it is shown this way (open, no connections) on the P & ID, has a line number and designation in the line list showing that it was not subject to a pressure test then if anyone in the future decided to do something, they should pick this up in the Mgt of change procedures. The P & ID may need a note to say no flange to be fitted, but that's probably going overboard a bit.

I've seen drain lines fitted with flanges so that a hose could be connected to drain the contents before now, but otherwise I would just cut the flange off....

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

 

[Naidooru]

Thank you LittleInch,

The reason for the flanges is that the line goes through grating to lower levels and then into the drainage system, and due to the configuration they must put the flanges on in the shop as they do not want to weld on site due to permit conditions. So what i would like to clarify is whether the section where they have flanges(since they can be isolated) be regarded as "Open to atmosphere" or is the spool from after the last flange regarded as the open to atmosphere portion

 

[Naidooru]

In my opinion, if the equipment has any means of isolation then it isn't really open to atmosphere, but anything after the isolation whether it may be valve or flange is regarded as open to atmosphere as long as there isn't anything that encourage positive isolation.

 

[Duwe6]

If they "needed the flange", then they are planning to use it for isolation. Thus, NOT open to atmosphere. If it is built w/o that flange, then it meets the B31.3 criteria for 'open'.

Tell 'em to shut up and hydro that piece; having flanges, it can easily be bolted into any other similar test assembly and get a shop hydro.

 

[mbt22]

as long as there isn't anything that encourage positive isolation.

I would go further than that and say as long as you can ensure that through the life of the facility no-one will ever try to blind at that flange. That's down to site systems enforcing a design pressure of effectively nothing.

In five years time if the drain valve starts passing and someone wants to stop the line dripping, that flange will suddenly look like an excellent place to slip a blind in even if it is difficult to get at, potentially followed by a nasty surprise.

Matt

 

[LittleInch]

Naidooro,

On the basis that the flange is only there for construction issues

Looks to me like you have a few options here:

1) Do nothing other than note the relevant information on the design drawings - but you and others are clearly concerned about the future idiot scenario
2) Pressure test the flanged spool - should be fairly easy as you have a flange on it
3) Consider using something like a screwed union if you don't want to weld - much harder to blank these off
4) find some other means of cold jointing the pipe sections which can't be undone (glue?)

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

 

[Naidooru]

DUWE 6: Thanks buddy, you made my day. I have the same idea as you

MBt 22: I have the same thought as well, with all that i have seen there isn't any guarantee that this will not be left in place as is or isolated.

Littleinch: Thank you, the manufacturer has agreed to pressure test the flanged spool.

Thank you for the insight guys.