Sonic Sealing of Copper Tubes Issues

I'm not sure what a boffin is so I don't know if I'm qualified to answer your question, but I'll give it a try. Copper tubing in high vacuum systems is sometimes sealed by a simple "pinch-off". This can be a true hermetic seal, but is very fragile and normally protected from damage after sealing. The purpose of sonic or ultrasonic sealing is to disperse contaminates and oxides on the internal surface of the tube to facilitate a true metal to metal seal. So, IMHO it depends on the nature of the internal contaminates and the effectiveness of the the sonics in dispersing them.

Hi

Are you currently using an Ultra-sonic tube sealer? What is the wall thickness of the tube? Set your "compaction" thickness equal to the wall thickness make a few samples. Cut a small portion, say 2", of the tubing. Flaten the the un-welded portion of the tubing as flat as possible so that the total thickness is double the wall thickness. Make sure that the center planes of the sqeezed portion and the sealed potion fall in the same plane.

Now file off one wall thickness from each side of this flat piece. Try to peal off by pulling the unwelded portion in the opposite directions. If the two pieces peeld of showing no sign of fusion at the suposidly fused area, you can say it did not work. I will say that it will give a good fusion if the sonics and compaction pressures are set properly.

I use an ultra sonic tube sealer in my plant. I have been using this for approximately five years for sealing off heat treated capillary tubing. I have not expreienced any problem even though they come discoloured after heat treatment. We seal-off about 2,000 comtrols a day with no rejects.

Regards,

Job Thykkoottathil

Let me explain what I'm doing, and what my problem is. We braze up and sonic seal subassemblies for HVAC systems. High volume mass production. We have been sonic sealing the charge tubes for over 10 years with little trouble.

The current supplier does a good job, and there is no heat discoloration on the charge tubes. We are trying a new supplier (cheaper) and their tubes have heat discoloration on the tube just where we sonic seal. Our leaks have increased dramatically when using these new tubes. I would like feedback about the discoloration and it's affect on sonic sealing.

Two possibilities come to mind. The first is that the discoloration of tube from your new supplier indicates something different in the processing that causes changes in properties of the tube. This may mean that the seal parameters (time, force, power) that you normally use to seal the tubes, needs to be adjusted and optimized to obtain a reliable seal on the new product. The second possibility is that the changes in tube properties are such that your sealing technology is not capable of making a reliable seal. I would approach the problem by performing an analysis of both joints to determine the difference.

Dear 39Machine,

Obviously you did not get a good seal. my suggestion is that you contact "STAPLA ULTRA SONICS". They are very good and helpful.

Good luck.