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

 

[RPRad]

I like the last suggestion, actually not as crazy as it sounds..but the unit is physically too big to roll...but sure would be interesting to see.

The foam plug actually isnt a bad idea but looking at the inlet and outlet configuration on the ends of the coil, we wont be able to get it in or out.

Taking it vertical I dont think is an option, I think there would be numerous structural loading and logistical concerns that make it impractical.

We have a good enough relationship with the AI to negotiate a pneumatic test, although they will probably opt to have a 3rd party witness the test. Given the configuration of whats being tested I am not really concerned about failure of any of the heater components, but I would be concerned about failure of the ancillary stuff (flanges, temporary supply piping hoses, fittings etc) required to carry out the test (although I would negotiate for 1.1 times.

I think that brings me back to trying to draw down as much of a vacuum as I can (shouldnt be a external pressure issue for the coils given the configuration), filling it with water and then trying to further purge it with either a fire hose or a high capacity pump. I may not get rid of all the air but its probably a lesser evil and more practical option than some of the other options.

 

[bcguy]

Interesting discussion;
There is an old interpretation (I-86-42)that would allow a pneumatic test "prior" to the "required" hydrostatic test, but unless there is a Code Case that allows pneumatic instead of hydrostatic test you have no option. Your AI would not have the authority to "negotiate" an exception to Section I requirements, only ASME have that authority.

 

[RPRad]

Yes that in itself is an interesting topic, I am sure there is precedent...

Our AI has been pretty reasonable when it comes to issues similar to this...which leads to is it an ASME issue or NBIC issue or an issue of what it says in the pressure vessel legislation of the particular state or province...

In this case all the welds have been 100% radiographed so there is less concern around the components and more around the stuff required to carry out the test..

...and then of course there is the issue of do I really want to burn some brownie points up over this...takes a while to earn them back..just like with my wife!

 

[doct9960]

RPRad,

Our AI has been pretty reasonable when it comes to issues similar to this...which leads to is it an ASME issue or NBIC issue or an issue of what it says in the pressure vessel legislation of the particular state or province...

You mentioned "new construction" in your previous posts, so it is an ASME issue. ASME Section I does not permit pneumatic testing. It is non-negotiable. There is no way an AI would approve of pneumatic testing. But then again I could be wrong.

Please do let this forum know how your negotiations with the AI went. Thanks.

 

[Fizza453]

BCGUY has noted an old interpretaion, I am copying that interpretation here;


Interpretation: I-86-42
Subject: Section I, Pneumatic Pressurization Prior to Hydrotest
Date Issued: February 19, 1987
File Number: BC86-066

Question: Does Section I prohibit pneumatic pressurization of the boiler system prior to performing the required hydrostatic test?

Reply: No. However, air or gas may be hazardous when used for pressurizing boiler systems. It is therefore recommended that special precautions be taken when air or gas is used for this purpose

Nasir
Welding Engineer
DESCON ENGINEERING LIMITED
PAKISTAN

 

[RPRad]

Thanks for the interpretation, Nasir. I think it nicely explains the logic for why ASME Section 1 does not specifically address the pneumatic testing....and I dont disagree with them

But it would be hard to argue that a pneumatic test is not as an effective test method as a hydrotest (although you are not putting the vessel components under hydraulic head (load), which might be applicable in some cases).

I am pretty sure that in cases such as the one we have before us you could successfully argue for a pneumatic test, but I also think you are going to have to prove beyond a shadow of a doubt that a hydrotest cant adequately be performed...in the case at hand I believe I am close or on that boundary.

 

[RPRad]

As indicated we are still evaluating the possibility of pulling a vacuum on it before filling...which leads to another interesting question. What is you length "L" when calculating external pressure conditions on the piping coils. The coiled length of the pipe is 45' but the overall uncoiled length would be close to 1000'.

Anybody have any experience in this area?

 

[metengr]

Your only possible option would be to explore a "state special", which means an object that is not stamped to ASME Code. Some Jurisdictions or regulatory bodies allow such objects to be installed and operated, others do not.

 

[REGRUMBLE]

We made a similar vessel(sound about the same size and weight) under section VIII and tested with nitrogen. At 400PSI one of the gaskets let go. Thankfully everyone was well back at the time but there were a lot of people headed for the floor.

 

[wikinfo]

I think it will be better to stick with the 2010 standards / ASME / if your concern is only how to feel the hely-tube,
I suggest to fabricate a hydro test kit dedicated to that specific vessel and use it with a crane lifted full water tank that contain at least 1.5 of the total tube volume of water 1.5x (1000'x3.14xr^2), choose the easy accessible flange as intake and the other one as discharge just make sure that the discharge tube-end is also elevated above the top of the vessel by at least the diameter of the vessel before it goes in a second tank to recuperate the fluid, instal a valve at the discharge side to close it gradually as soon as the fluid start coming out, you will probably have a 1-3% of air left inside, that amount of air at 400 PSI will drives out fluid for a longer time and with a velocity that can cause serious injuries.
So make sure that staff members stay away from -- blinds, valves, any area with gaskets…,--
Vacuum may damage the water tank if not properly vented.

 

[RPRad]

I will pass that on...interesting take

To update, we have talked to the AI and they will grant a variance for a pneumatic testing, however as indicated by those in the know above it cannot be "S" stamped....but would be given a design registration number for In-Province use...since this isnt going to be mass produced its an acceptable alternative.

The other legitimate option for those in Canada is to apply for a Canadian Registration Number under Chapter 10 of CSA B51, which is specifically for "Fired-Heater Pressure Coils for use in Petroleum and Chemical Plant Service"....Clearly somebody somewhere for saw the need to treat these things differently occaisionally. Under this section the coil design and inspection must satisfy both ASME B31.3 and API 530. Therefore you have your choice of doing a hydro or a pneumatic test. So theoretically everybody is happy...its been designed to ASME Sect 1...the design is re-evaluated with respect to B31.3 / API 530, it gets a pressure test prior to leaving the shop and it gets a design registration number...and it will get an inservice hyrdo when they fill this thing up on site(I wonder if they have thought of how they will vent it).

Anyway at this point there has been no decision on which route to proceed...a hydrostatic test is still not out of the question and may be done on site...should the choose a pneumatic one I will witness it by webcam

 

[rmw]

A few posts back you mentioned pulling a vacuum on it. Is it designed for vacuum? If not, I would rule this out.

rmw

 

[RPRad]

Not a full vacuum, but given this is 5" and 6" dia. piping I would want to do some calculations to determine what level I could pull and still be on the safe side. A few posts backs I was inquiring what length "L" I would use for a coiled assembly like this...the coiled assembly probably has some inherent strength with regard to external pressure...but were are still talking a total length of around a 1000 feet uncoiled

 

[GenB]

RPRAD, sect I does not allow pneumatic. if you AI accept w/o stamping... ok. I would still fill it up with water and whatever air is inside let it be. it will be a combination test, that way you eliminate the danger probably 80%.

 

[Duwe6]

" . . combination test, that way you eliminate the danger probably 80%."

Looks like an inverted factor -- probably should be 20% improvement in safety. A combo hydro-pneumatic still compresses a LOT of air. That gives a lot of stored energy waiting to blast something into pieces.
Granted, a catastrophic failure of a new boiler is probably 1 chance in 1,000,000 tests. But it still is catastrophic when any significant quantity of air is compressed.

 

[RPRad]

Yes, all good points and all have been considered.

Pulling a bit of a vacuum to get as much air out as possible and then trying to pump water at high velocity to try and clear as much of the rest as possible is probably the safest alternative...yes there may be air in it but the volume is considerably smaller and the probability that if it was to fail it probably will occur in a hydraulic section (I am guessing that most of the air pockets occur at the top of the coils...so the odds of there being a seam weld there is small).

Again to date no decision has been made, although it seems the manufacturer is still leaning toward a pneumatic test. No question this extremely risky business, although given the nature of component being tested it is a somewhat managed risk. As indicated all the circ welds have been 100% radiographed, thus I would be more worried about the tie in points (ie flanges, hoses etc) than the actual coils, however one must always cognisant of what would occur in the event of a catastrophic failure of a weld. I guess you could always haul it out into the middle of a field and have a go...maybe we should hire the Mythbusters for this one




I

 

[GenB]

Duwe6,
one have to be familiar with coil designed boilers to say that.
unlike single chamber vessels and shell boilers, coil boilers have small surface concentrations and can be safely combo tested.
you are free to believe otherwise.

 

[Karloss12]

When negotiating with your AI, what insider knowledge about the structual integrity of this particular vessels welds does he have that you don't?

Shouldn't it be 'co-ordinating' absolute safety with your AI rather then 'negotiating'.

 

[RPRad]

Hi Folks

Thanks for everyone that posted on this thread, thought I would provide an end to this tale.

The winner(s) were Snorgy and Doct9960. Based on the information provided in this post the company purchased and utilized plugs to successfully clear the air from the coils. In the end they used a high pressure water pump to force it through the tight elbows at the inlet and outlet nozzles of both coils and along the length of the vessel. It was hydro tested successfully and received it's "S" stamp and clean bill of health.

Thanks for posting

 

[SNORGY]

You're welcome. What did I win? If you are ever in the pub, I like Rickards Dark.