One of the most overlooked best practices for finding tube leaks is to clean the tubes before testing. If the tube is not cleaned before testing, tube leaks can go undetected. On the other hand, if a tube is not cleaned properly, any residue that is left in the tube can result in a false reading and potentially increase maintenance costs.
False negatives occur when tube holes are covered up by deposits. When the test gun is inserted into the tube and pressure is maintained, debris can be forced inside of a leak path, disguising the presence of a leak. This can cause issues later on once the debris is dislodged and the tube continues to leak. False positive readings can also occur if tubes are not properly cleaned. If debris or excess lubricant is present in the ID of the tube it can cause the seal to slip and not expand properly. Without proper seal expansion, the test gun would show a false positive result, resulting in tubes being plugged unnecessarily.
Another issue that can occur from not cleaning tubes has to do with the tester itself. Vacuum tube testers have a screen inside the venturi nozzle that can become clogged from the deposit and debris inside the tube. If this occurs, the test gun will not be able to create a sufficient vacuum inside the tube. Small particles can also pass through the screen and collect on the check valve, preventing it from operating correctly. If the check valve does not work, it will allow air to pass into the tube, resulting in a false reading (a leak will be indicated where in fact there is no leak).
Overall, it is important that tubes are properly cleaned prior to testing for leaks. If tubes are not clean or if an improper cleaning method is used, it can result in false readings and potentially increase maintenance costs later on.
Visit our tube cleaning section for more information about tube cleaners and how to choose the right one for your application.