I would like to take the time to add some comments on the method that I have used to find leaks.? I worked on vacuum systems while getting my phd and still have a interest in them. (Currently working on building my own system)
Finding leaks are not easy, a lot of time can be saved if you think ahead and build in ways to isolate the various parts of the system.? This is not always possible.? If you have ways to isolate the various parts of your system and then test each in turn you can narrow down the area where the leak is.? Sometimes this is enough, most of the time it is not.?
For the rest of the times, if you isolate the system and pressurize it.? I would pressurize the machine we used to about 50-60psi with Nitrogen (it is cheap and easy to get).? If you want cheaper, then you could use compressed air, however I wanted something dry (water was a big problem with type of chemical reactions we were trying to do, so great care was taken not to introduce any more water than necessary).? This pressure should force the gas out of the leak. Following pressurization you can take a squeeze bottle of soapy water (we used a product make by swagelock called snoop) and spray each joint and look for bubbles.? Not high tech, but a very old school and chap way to find the leaks.? And when you have around 20 meters of swagelock tubing to look for leaks in, it is fast.
We tried the Helium leak detectors and the major problems, we experienced was leak size and false positives.? For small leaks it would most of the time fail to detect them.? And the detector was sensitive in that you had to move it in just the right way.? Moving to fast and the detector would registrar a leak.??
Another note is that if you use glass in your system, like the one I used in getting my PhD, be careful not to push the pressure above what the glass can.
I hope this helps.?
