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Leak Testing Machines

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Leakage testing machines are a type of non destructive testing equipment that are used to test and measure the escape of liquids, vacuum or gases from sealed components or systems, such as filters, valves, pipe and fittings, radiators, taps and more. Some systems may require a separate leak detector as input, which can be often equipped with several other components such as pumps, calibrators, gauges and cases.

Leak Testing Methods
A variety of leak testing methods are available that can be used to the leakage of a filter or any other systems, including -

Bubble Testing
Calorimetric Developer
Electronic Gas Detection
Mass Flow
Mass Spectrometer
Pressure Differential / Decay
Ultrasonic Leak Detector

A brief description of the different types of leak testing methods is given below:

Bubble testing method is suitable for applications that require superior sensitivity. In this procedure, a pressurized test object is submerged in a water tank and if a bubble emerges there is a leak.
In the calorimetric technique, the surface is treated with a developer and reacts with the leaking fluid that causes a visible color change to take place at the point of leakage. Developer application method can be aerosol spray, paint or treated paper. The technique can be used for leakage testing of large single and double walled tanks, pressure and vacuum vessels, laminated, lined or double-walled parts, complex piping systems, flexible containers such as aircraft fuel tanks and glass-to-metal seals in hybrid packages.
With the electronic gas detection, the test object is pressurized with a tracer gas and a sniffer probe is applied to scan the object for the leaking gas.
In the mass flow method, inputting air into the test part compensates for any change in pressure determined by a pressure sensor. The amount of air that enters into the system is measured by a flow sensor, which directly determines the leak rate of the part. The flow of leakage is directed across a heating element. The change in temperature across a temperature transducer bridge results in an output voltage, which is proportional to mass flow.
Mass spectrometer is another technique that involves the pressurizing of the test object with a helium mixture inside an airtight pressure chamber. The air is then emptied from the chamber, which creates a pressure gradient between the vacuum and the internal volume of the part. The helium molecules start moving out of the part through any leakage. After this a mass spectrometer samples the air inside the chamber and calculates the partial pressure of helium.
The pressure differential or decay procedure necessitates the initial inflation of the object to be tested and the establishment of a reference pressure. After a specified amount of time, the pressure is calculated again and the starting and end results are compared. The change in pressure can be used to compute the leak rate given the internal volume of the equipment. Pressure decay is able to test and observe even the very small changes in pressure.
An ultrasonic leak detector, often known as sonic or choked flow or turbulent flow, is another leak detection procedure. The turbulent flow of the fluid across a pressure boundary produces acoustic waves that can be transmitted by the medium of fluid itself, through the containment structure, or through the air that surrounds the containment structure. The ultrasonic detector is used to catch up these sounds.

Output:
Leakage testing equipment can have analog voltage, current or a pulsed or frequency output. The output can also be a change in the form of a switch or an alarm. Digital outputs can be either serial or parallel or other computer signals. In a same manner, display for leak testing equipment can be digital, analog or video type readouts. Some of the popular features that are available for some leak testing equipment include timers, triggers, alarms, data logging or memory and self-calibration.

For HEPA filters, there are also available two additional types of leakage tests, namely -

Total leak test
Scan leak test

For radioactive applications, only the total leak test is allowed, while for all other Types of applications, either of the methods can be used. Both these procedures require qualification of the testing equipment so as to ensure consistency in results. The total leak test also demands the downstream sample to be qualified in order to ensure that concentration remains uniform.

Applications:
Leakage testing equipment has found variety of uses in different industrial applications, such as automotive, engineering and plastic. Given in the table below are some of the applications of leakage testing machines.

Automotive		Engineering		Plastic
Cylinder Heads	Cam Covers	Valves	Air Cylinder	Plastic Containers	Medical Devices
Clutches & Gear Boxes	Oil Sumps	Electronic Enclosures	Pumps	Filters	Pipe Work
Turbo Chargers	Radiators	Taps	Sprinklers	Pneumatic Fittings	Fuel Tanks

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