This invention relates to a leak detection apparatus and more particularly to an automated means for detecting leaks via liquid immersion testing.
Numerous components are manufactured which must meet a standard for a "leak tightness". Leak tightness is a relative term, as nothing can ever by completely free of leakage. A balance must be made between the increasing cost of finding smaller and smaller leaks and their importance to the functioning of the unit over its useful life. Leak tightness is the practical leakage that is acceptable under normal operating circumstances.
Components which require some degree of leak tightness, for example, include fuel tanks, radiators, fuel system components, water pumps, refrigeration components, heater cores, torque convertors, hydraulic and pneumatic components etc. The acceptable leakage will depend upon the usage of the component with respect to the type of fluid which must be contained, i.e. a gas or a liquid, and whether or not the contents will be pressurized.
Several leak detection methods are commonly used in industry. Each method has its own advantages, limitations and sensitivity range. As a result, not all methods are useful for every application. The correct choice of the leak detection method should optimize cost, sensitivity and reliability of the test.
Liquid immersion testing is one of the oldest documented methods used to detect leaks. Liquid immersion testing operates on the basis of a differential pressure at the leak creating a flow of a gas from within the component to the liquid outside. The part being tested is pressurized with a gas and then immersed in a liquid medium, generally water. The gas escaping the pressurized component produces one or more bubbles in the liquid which then rise to the surface of the water. The component being tested is allowed to remain in the liquid for a period of time while the liquid test medium is examined for the presence of bubbles. The location of bubbles indicates the location of a leak and the frequency and size of the bubbles can be used to estimate the leakage rate.
Liquid immersion testing has several advantages which include, low equipment cost relative to other methods, location of the leak can be determined, the equipment can easily be made durable enough for factory floor applications, and various size and shape components can be tested utilizing one test apparatus.
The primary disadvantage with liquid immersion testing is the requirement of an operator to visually inspect the water for bubbles of leaking gas. This adds subjectivity to the test and, in addition, research has shown that an operator's ability to accurately identify leaks decreases during the course of a typical eight hour work shift.
Accordingly, it is an object of this invention to provide a liquid immersion leak testing apparatus which includes an automatic means for detecting the presence of bubbles of gas leaking from the component being tested.
It is an advantage of this invention that a low cost liquid immersion testing apparatus can be equipped with an automatic sensing means which provides increased accuracy in detecting leaks without significantly increasing the cost of the device.