Testing of silver soldered joints

[ehestnes]

We have a large fleet of Nitrogen hoses that has a brass end connector fitted onto it. This brass end connector are silver soldered to the hose end pipe. Brass end are smallest part.
Currently we are doing this without any other means of Q.C than pressure testing and using high skilled welders.

Is there any ways we can test this?
The connector is 1-1/4" OD, pressure is up to 300 psi, medium is liquid Nitrogen (-196 degree C). so the consequences of a failure is rather worrying.

Alternative is ofcourse to start threading the connections and/or changing them with stainless steel, but the cost impact is significant

 

[Rich2001]

Take a look at Helium Leak Testing ASTM E479, E498 E499

 

[EdStainless]

You might be able to Ultra Sonic test these. If the joint is in an area of constant thickness. UT will be able to detect voids in the bond, even if the joint doesn't leak.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[btrueblood]

We used to also create a certain number of pre-braze and post-braze samples when brazing in aerospace applications. The samples were typically either "extra" production pieces or parts made to simulate (but lower cost than) production parts.

The samples would be sectioned & examined under magnification after the batch was run, if defects (voids, inclusions) beyond a certain size & number distribution were found in any sample, the entire lot would be rejected.

During braze joint development and qualification (at least partially done to determine inspection criteria) we would also do pull tests of braze joint samples to verify yield and ultimate strengths of joint.

Also, the entire lot was subjected to visual inspection at 10x or better magnification, and inspected (sometimes with a dental pick or similar probe device) to look for porosity and verify no surface pits beyond a certain size.

The above was pretty expensive and intensive, and resulted in a fair bit of Material Review Board activity. Not to mention that the development was pretty costly. Ultimately, you need to weigh the cost/benefit of extra QC.