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Technical Discussions
tammatthews
tammatthews
00:37 Sep-09-2004
Helium Leak Test.

I am welding aluminum parts 15" dia. 6" thick with a 10" dia x 2" wide cavity in one end, with a 3/32" thick cap welded to it.

It has 2 standard 1/4 npt ports for in and out.

What would be the best procrdure for leak testing with Helium at
150 psig at room temperature.

I haven't gotten them to hold water yet.

Thanks..


    
 
 Reply 
 
Jim Knowles
Jim Knowles
00:43 Sep-16-2004
Re: Helium Leak Test.
----------- Start Original Message -----------
: I am welding aluminum parts 15" dia. 6" thick with a 10" dia x 2" wide cavity in one end, with a 3/32" thick cap welded to it.
: It has 2 standard 1/4 npt ports for in and out.
: What would be the best procrdure for leak testing with Helium at
: 150 psig at room temperature.
: I haven't gotten them to hold water yet.
: Thanks..
The best way is to ensure the components are clean and dry, free from any oil grease or penetrant.
Pull a full vacuum on the interior (1000mb), and apply a bag to the welded seams ensuring a tight seal around the edges, apply a helium fill to the ineterior of the bag. Connect the helium mass spec or leak testing equipment to the interior void, measure if ther is any ingress of helium into the interior void.
------------ End Original Message ------------




    
 
 Reply 
 
Dent McIntyre
Consultant, NDE Manager NDELevel III/3
NDT Consultant, Canada, Joined Nov 1998, 248

Dent McIntyre

Consultant, NDE Manager NDELevel III/3
NDT Consultant,
Canada,
Joined Nov 1998
248
09:29 Sep-17-2004
Re: Helium Leak Test.
You should not have water in vessel before helium testing! Water will plug the tiny leaks that helium would find. You will need to bake out the water beore testing with helium.
as an alternative to the hood test described you could pressurize with a helium and air mixture then sniff for leaks on the other side. This would be less sensitive than the hood test under vacuum.


----------- Start Original Message -----------
: : I am welding aluminum parts 15" dia. 6" thick with a 10" dia x 2" wide cavity in one end, with a 3/32" thick cap welded to it.
: : It has 2 standard 1/4 npt ports for in and out.
: : What would be the best procrdure for leak testing with Helium at
: : 150 psig at room temperature.
: : I haven't gotten them to hold water yet.
: : Thanks..
: The best way is to ensure the components are clean and dry, free from any oil grease or penetrant.
: Pull a full vacuum on the interior (1000mb), and apply a bag to the welded seams ensuring a tight seal around the edges,apply a helium fill to the ineterior of the bag. Connect the helium mass spec or leak testing equipment to the interior void, measure if ther is any ingress of helium into the interior void.
------------ End Original Message ------------




    
 
 Reply 
 
Min Lee
Min Lee
21:20 Jul-05-2011
Re: Helium Leak Test.
In Reply to Dent McIntyre at 09:29 Sep-17-2004 .

I know this is an old post but was hoping I'd be able to get some more information re: "tiny leaks that Helium would find". I was wondering if there was any literature/documentation I could look up to use as a basis to support that tiny leaks would be covered up by water?

    
 
 Reply 
 
Dent
Consultant, NDE Manager NDELevel III/3
NDT Consultant, Canada, Joined Nov 1998, 248

Dent

Consultant, NDE Manager NDELevel III/3
NDT Consultant,
Canada,
Joined Nov 1998
248
17:05 Jul-06-2011
Re: Helium Leak Test.
In Reply to Min Lee at 21:20 Jul-05-2011 .

I attended several leak test classes and this was fundamental. You may try the NDT Handbook for verification.

You also may want to consider reversing the test described by putting the helium inside and performing a sniff test on the outside. You still bag the seams with plastice and allow it to sit for a while, then puncture the bag with a sniffer probe to detect helium in the bag. If you detect helium you then need to slowly scan the welds to find the location. By applying the helium on the outside and applying vacuum inside you have no way to locate the leak.

    
 
 Reply 
 
Oliviero
NDT Inspector,
Quality Control srl, Italy, Joined Oct 2008, 414

Oliviero

NDT Inspector,
Quality Control srl,
Italy,
Joined Oct 2008
414
21:34 Jul-06-2011
Re: Helium Leak Test.
In Reply to Min Lee at 21:20 Jul-05-2011 .

Furthermore, water or humidity into the vessel makes it difficult to obtain the right value of void and does not permit to perform the examination.

    
 
 Reply 
 
P V SASTRY
R & D, NDT tecniques metallurgy
TAKEN VRS FROM THE POSITION OF SR. DEPUTY GENERAL MANAGER BHEL CORPORATE R&D, India, Joined Jan 2003, 195

P V SASTRY

R & D, NDT tecniques metallurgy
TAKEN VRS FROM THE POSITION OF SR. DEPUTY GENERAL MANAGER BHEL CORPORATE R&D,
India,
Joined Jan 2003
195
00:39 Jul-08-2011
Re: Helium Leak Test.
In Reply to Dent at 17:05 Jul-06-2011 .

Dear Sir,

It is was a long time ( 35 years ) since I have done this Helium tests on Cryogenic vessels. At that time we were directly sniffing along the weld seams. We were not using the plastic bagging. May be that is a more efficent method. The instrument was capable of detecting leaks of the order of ten to the power of minus seven standard cc per second. The present day instruments must be doing much better.
Pesonally I was always confortable with the inside out test( sniffing) rather the evacuation method.
Regards
PV SASTRY

    
 
 Reply 
 
S V Swamy
Engineering, - Material Testing Inspection & Quality Control
Retired from Nuclear Fuel Complex , India, Joined Feb 2001, 787

S V Swamy

Engineering, - Material Testing Inspection & Quality Control
Retired from Nuclear Fuel Complex ,
India,
Joined Feb 2001
787
16:21 Jul-08-2011
Re: Helium Leak Test.
In Reply to P V SASTRY at 00:39 Jul-08-2011 .

There are now good equipment and some new techniques have come up to take care of varied test conditions. Which is the most suitable technique depends on the size of the component to be tested, numbers to be tested, amount of helium consumed in each technique, sensitivity needed etc.

Any leak is affected by the presence of any foreign material that affects the flow of the fluid - corrosion products, sudden change of the section (leaks after all are not machine made discontinuities but are natural and thus vary in orientation, size etc. along their length), water or oil, grease etc. Thorough cleaning and baking / drying / stress relieving is recommended to open up the leaks and remove the foreign material ingress.

Regards

Swamy
Quality Consultant

    
 
 Reply 
 
John McLaren
John McLaren
07:56 Jul-10-2011
Re: Helium Leak Test.
In Reply to S V Swamy at 16:21 Jul-08-2011 .

There is a good book here on helium mass spectrometer leak detection: http://www.chem.agilent.com/Library/training/Public/Introduction_to_Helium_Mass_Spectrometer_Leak_Detection.pdf
Plugging of leaks by water and water vapor is discussed in a couple of areas.

    
 
 Reply 
 
Daniel Austin
Daniel Austin
18:24 Nov-16-2011
Re: Helium Leak Test.
In Reply to tammatthews at 00:37 Sep-09-2004 (Opening).

The replies here have been very helpful.


http://www.cmrelectrical.com/water-leak-detection.htm

    
 
 Reply 
 

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