The test for leak tightness with helium and helium leak detectors becomes more and more important. The practice of leak detection on heat exchangers is described in this article. Three possible methods are discussed.
The integral leaktest with vacuum in the volume around the tubes and helium at atmospheric pressure in the volume of the tubes
The preparations prior to the test, the correct procedure during the test, the pumpdown and the response time are discussed, also problems and suitable gaskets and seals. Problem solving for negative test are described.
The integral leaktest with helium pressure in the volume around the tubes and vacuum in the tubes
This test is sometimes necessary, when the volume around the tubes has had a helium filling in the past, for example for a leaktest with the sniffer probe. The changes in test conditions are decribed. Also the calculations of the leakrate according to pressure changes are discussed and the possibility of cost reduction by reducing the helium concentration as a result of pressure increase is pointed out.
The integral leaktest with helium pressure in the volume around the tubes and atmospheric pressure in the tubes
This test requires long waiting times and is used only, when other methods are not possible and when the safety conditions allow a higher testgas pressure in the volume around the tubes. The test is carried out by measuring the helium concentration in the volume of the tubes. The value of the leakrate must be calculated. The procedure of this test, the calculation of the waiting time as well as the leakrate are described.