Leak Testing: Different Types Of Leak Testing Methods | Helium Leak Testing

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What Is Leak Testing? Methods Of Leak Testing
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What Is Leak Testing?
Leak testing is the method of checking a
structure for leaks. Leak testing can be
achieved using a range of leak detection methods
and is working to test for defects in products
and to ensure the proper function and maintenance
of industrial systems and pipelines.
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Methods Of Leak Testing
1 Water immersion bubble test method 2 Soap
solution bubble test 3 Pressure decay test 4
Vacuum decay test or Pressure rise test 5 Tracer
gas leak testing 1 Sniffing 2 Accumulation
leak testing 3 Vacuum chamber inside-out leak
testing 4 Outside-in leak testing
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Water Immersion Bubble Test Method
The Bubble Immersion leak test method is the
simplest and lowest cost leak test method. It
can be used on test parts that can be internally
pressurized with air and will not be damaged by
contact with water. This method, however,
suffers from the disadvantage that an operator
must pay close attention during the test to
visually detect bubbles emitting from the part.
Additionally, this method has no way of
reliably calibrating the test because operators
are typically instructed to reject a test part if
bubbles are seen emanating from it.
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Soap Solution Bubble Test
Instead of submersing the part in water, the
pressurized unit to be tested is sprayed with a
soap solution and the operator is able to see the
bubbles formed by gas escaping from where the
leak is.
Soap solutions are available in many different
types. Some brands may have a spray applicator
to quickly cover large areas of tubing in a short
amount of time.
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Pressure Decay Test
Pressure decay is an older technology that has
existed for many years. It is an indirect leak
flow measurement with a leak rate based on decay
rate and test pressure. Test volume is
calculated for every set up. It is sometimes
called calibration. Differential pressure
decay offers a higher resolution and cost when
compared to pressure decay.
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Vacuum Decay Test Or Pressure Rise Test
Pressure testing can be used to detect larger
leaks requiring correction prior to the component
undergoing a more sensitive, Mass
Spectrometer/Leak Detector test.
Unless there is significant time available,
Pressure Decay is the least sensitive of all the
techniques discussed here but does have a very
valuable role to play in the production scenario.
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Tracer Gas Leak Testing
In the past several different tracer gases have
been used to find leaks and to measure leak
rates, for example Ammonia or halogen gases.
But since the leak test method with the tracer
gas helium and the detection of this gas with a
mass spectrometer was developed, all other
methods became less significant compared to the
superior sensitivity of the helium method.
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Types Tracer Gas Leak Testing
1 Sniffing 2 Accumulation leak testing 3 Vacuum
chamber inside-out leak testing 4 Outside-in
leak testing.
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Sniffing
Helium sniffing is a method of leak detection
that uses helium as a tracer gas in combination
with instrumentation that can detect presence of
helium in the environment and more specifically
an increase in helium due to a leaking part.
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Accumulation Leak Testing
Accumulation Tracer Gas Systems use the same
instrumentation as Atmospheric Sniffing but use
an enclosure to isolate the part from ambient
background and contain the tracer gas.
Accumulation Tracer Gas Systems provide an
alternate type of tracer gas leak testing when
atmospheric background is controlled.
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Vacuum Chamber Inside-Out Leak Testing
The component to be tested is pressurized with
test trace gas, typically Helium, either
pre-charged and inserted in a vacuum chamber or
charged during evacuation.
Any leak in the system will allow the trace gas
to leak into the vacuum chamber where it will be
detected by the leak detector.
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Outside-in Leak Testing
The component to be tested is connected to a
vacuum pump and Leak Detector and evacuated. The
part is held in a chamber or hood which is filled
with a known Tracer Gas typically Helium.
The system (Leak Detector) then monitors for the
ingress, hence the term Outside-In, of Tracer Gas
to the part indicating the presence of a leak.
This type of test is easily automated and, time
permitting, can be more sensitive than sniffing.
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is widely used in the industry.
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