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ASME Sect 1: Pneumatic Test in Lieu of Hydrostatic Test Helpful Member! 

RPRad (Mechanical) (OP)
5 Jan 12 13:23
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 (Mechanical)
5 Jan 12 13:49
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 (Materials)
5 Jan 12 14:01
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 (Mechanical) (OP)
5 Jan 12 14:05
Unfortunately its new Construction...yes....I am weighing my options before I have a chat with my AI
RPRad (Mechanical) (OP)
5 Jan 12 14:07
If we propose pneumatic we are proposing 1.1 times, with the max being 1.2....MAWP is 400 psig
racookpe1978 (Nuclear)
5 Jan 12 14:14
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 (Mechanical) (OP)
5 Jan 12 14:34
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 (Mechanical)
5 Jan 12 14:59
Is this a re-boiler for a CVN?
metengr (Materials)
5 Jan 12 15:04
RPRad;
Since this is new construction, the Code is clear on your options -

1. Hydrotest
davefitz (Mechanical)
5 Jan 12 15:30
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 (Mechanical) (OP)
5 Jan 12 15:38
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 (Mechanical)
5 Jan 12 16:05
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 (Industrial)
5 Jan 12 16:20
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 (Mechanical) (OP)
5 Jan 12 16:32
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 (Mechanical)
5 Jan 12 19:54
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 (Mechanical) (OP)
5 Jan 12 20:33
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 (Mechanical)
6 Jan 12 1:35
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 (Mechanical)
6 Jan 12 2:19
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 (Mechanical)
6 Jan 12 11:25
Well, this is a reach but....

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

Regards,

Mike
SNORGY (Mechanical)
6 Jan 12 12:09
That would take a pretty sophisticated shop to do successfully, but the idea is intriguing.

Regards,

SNORGY.

RPRad (Mechanical) (OP)
6 Jan 12 12:19
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 (Nuclear)
6 Jan 12 16:52
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.
Helpful Member!  RPRad (Mechanical) (OP)
6 Jan 12 17:11
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 (Mechanical)
7 Jan 12 18:45
RPRad,

Quote:

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 (Mechanical)
9 Jan 12 9:14
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 (Mechanical) (OP)
9 Jan 12 12:42
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 (Mechanical) (OP)
9 Jan 12 12:43
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 (Materials)
9 Jan 12 14:02
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 (Structural)
9 Jan 12 15:16
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 (Mechanical)
14 Jan 12 14:36
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 (Mechanical) (OP)
14 Jan 12 16:11
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 (Mechanical)
14 Jan 12 17:55
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 (Mechanical) (OP)
14 Jan 12 20:27
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 (Mechanical)
2 Feb 12 9:52
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 (Industrial)
2 Feb 12 11:15
" .  .  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 (Mechanical) (OP)
4 Feb 12 14:40
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 (Mechanical)
14 Feb 12 2:22
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 (Mechanical)
15 Feb 12 8:51
When negotiating with your AI, what insider knowledge about the structual integrity of this particular vessels welds does he have that you don't?  smile

Shouldn't it be 'co-ordinating' absolute safety with your AI rather then 'negotiating'.
RPRad (Mechanical) (OP)
5 May 12 12:47
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 (Mechanical)
5 May 12 16:01
You're welcome.  What did I win?  If you are ever in the pub, I like Rickards Dark.

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