ASME Sect 1: Pneumatic Test in Lieu of Hydrostatic Test 1

[RPRad]

Hi

Does anybody know whether there have been any interpretations issued in ASME Sect 1 which address whether you are able to do a pneumatic test in lieu of a Hydrostatic.

I have a horizontal vessel built to ASME 1 which is very difficult to vent because of an internal coil tube configuration. It is too big (45 feet long) and too heavy (weighs over 120,000 lbs dry) to stand vertically, need to explore the possibility of doing a pneumatic test or.....some other option

 

[puigi]

New construction or in-service, what is the test for? Pneumatic test or volumetric NDE may be acceptable, have you consulted with your AI?

 

[metengr]

Section I deals with only new construction. Unless this vessel is being fabricated in a shop or in the field, Section I for an in-service object is not applicable.

If the vessel is in-service and you have replaced internal components or performed other work, the National Board Inspection Code should be followed for guidance regaridng post repair pressure testing.

 

[RPRad]

Unfortunately its new Construction...yes....I am weighing my options before I have a chat with my AI

 

[RPRad]

If we propose pneumatic we are proposing 1.1 times, with the max being 1.2....MAWP is 400 psig

 

[racookpe1978]

A pneumatic test - regardless of MAWP "margins" used! - is extremely dangerous because of the stored energy inside the PV.

A water-based test - and horizontal or vertical makes no difference to hydrostatic pressure testing - is much safer, more reliable as well.

Now, if you were worried about the "weight" involved (for example, trying to test a rocket fuel tank that could not be filled with water without bursting the walls), you'd have a reason to use a air test. But on a heat exchanger? Why potentially build a bomb?

 

[RPRad]

No disagreement there. However standing it vertical to vent it properly is not structurally possible nor logistically possible.

So if we hydrostatically test it horizontally, without proper venting...whats my downside...smaller bomb...will I have a problem getting a stable test pressure

 

[puigi]

Is this a re-boiler for a CVN?

 

[metengr]

RPRad;
Since this is new construction, the Code is clear on your options -

1. Hydrotest

 

[davefitz]

Either way, winter time tests raise the issue of adequate ductility- make sure you meet the code required minimum permitted metal temperature at all points. But it sound like you will need to add a vent connection to facilitate hydro.

 

[RPRad]

No not a re-boiler..ginormus glycol heater

Yes well you can always strike a deal with the AI where you have a square peg and a round hole...although you dont want to go down that road too many times

Now thinking more along the lines of hooking up a diaphram vacuum pump to one end, pulling a vacuum, filling slowly with water, flushing after filling while maintaining a back pressure, isolate and squeeze...not going to get it all out but enough to do a safe test.

 

[SNORGY]

We were recently faced with something like this. We came to the conclusion that we would hopefully be able to achieve a successful hydrostatic test by maximizing our liquid velocities in the tubes durng the flush+fill process; the idea being to carry enough velocity to force as much entrapped air through the system as we could without too much of it getting hung up at the top bends in the tubes. That worked in our case.

Regards,

SNORGY.

 

[Duwe6]

snorgy is right, using a fire-hose to fill the tubes will evacuate almost all of the air -- it makes a solid tsunami-like wavefront that pushes the air our ahead of it. You will need a BIG vent outlet.

 

[RPRad]

Yes..a firehose without pulling a vacuum has been discussed... the big problem is the physical size of this thing...10' overall coil dia and 6" & 5" dia piping is utilized for each of the coils (nested configuration)...plus an overall coil length of 45'...so it might be a bit large for a firehose alone

 

[SNORGY]

Can you push a plug through the tube sections or are there just too many parallels, etc.? You'd need to look at the actual configuration.

Regards,

SNORGY.

 

[RPRad]

The coils are in a helical arrangement so its a relatively clear path...but logistically its probably not possible, more because of the size and length....although I am listening

 

[SNORGY]

If you can flange up and de-flange in such a way as to push a hydro plug or foamie pig where you want it to go, you can ensure a pretty good liquid pack behind it. The problem, of course, is collecting the plug or pig and isolating it when it comes out the other end of the tube(s). In our situation, we concluded that it wasn't practical, and the answer was in the fill velocity.

This is one of those cases where I would be inclined to negotiate a pneumatic test with the A.I., if I was confident in the weld quality, etc. that went into fabrication. I have successfully pneumatically tested units that were much bigger than the one described here; a chrome-moly steam-methane reformer, actually. It was a quiet evening and there was lots of caution tape all over the place, with people walking very quietly around with their Snoop solution. I honestly thought that they didn't want to "wake up" the furnace.

Regards,

SNORGY.

 

[doct9960]

I think SNORGY is right on track with the foam pig like the one in this link...

http://www.girardind.com/products.cfm?cat=9

If the ends of the helical coil does not have vents, pipe spools with vents could be connected. To isolate the pig at the end of run, a gate valve would be needed.

A drastic option is to add some lifting lugs on the vessel and lift it in the vertical position. Then hydro the coils.

There is no mention of pneumatic test in Section I, so hydrotest is the only option.

 

[SnTMan]

Well, this is a reach but....

Elevate one end a bit, and roll the vessel while filling the coil.

Regards,

Mike

 

[SNORGY]

That would take a pretty sophisticated shop to do successfully, but the idea is intriguing.

Regards,

SNORGY.