SPECIAL SERVICE FOCUS ________________________
______________________TESTING - Flexible Metal Hose
There are a variety of non-destructive tests available that will assure that the hose and/or assembly is leak free and capable of withstanding the pressures for which the hose/assembly is rated. The application in which the assembly will be used is the typical determinant when specifying a certain type of non-destructive test. While certain tests provide much more sensitive and leak-seeking potential, the length of time to conduct some of these tests is quite considerable and the cost of these tests is also more expensive.
* Pneumatic Pressure Test ____________________________
This
test consists of pressurizing the hose assembly with air or other gas,
submerging the assembly under water and watching for bubbles which
would indicate a leak site. The media which is used to pressurize
the assembly can be varied as can the duration of the test depending on
the sensitivity of the test required. Pressurized air is suitable
for most applications and is the standard test every Hose Master
assembly is subjected to if no other testing method is requested.
The test pressure is predicated upon the diameter of the assembly.
* High Pressure Gas Test _____________________________
When
more stringent testing is required, high pressure gas (either Nitrogen
or Helium) can be substituted for air when testing under water.
As these media (Helium and Nitrogen) have smaller molecules than
standard air, they can detect and reveal a smaller leak path. In
addition, the higher pressures offer a type of "proof test" of the
integrity of the assembly.
* Hydrostatic Testing __________________________________
While
both the High Pressure Gas and the Pneumatic Pressure Tests are
designed to identify leaks in the hose assembly, a Hydrostatic Test is
designed to prove the strength and integrity of the assembly. A
Hydrostatic Test is performed by filling the assembly with water and
evacuating all the air. The assembly is then pressurized to a
specified test pressure for a pre-determined period of time.
Hydrostatic Testing is a safe way to ensure the integrity of a hose
assembly. While this is a proof test of the integrity of the
assembly, minute leaks may go undetected.
* Dye Penetrant Testing __________________________________________________
Dye
Penetrant Testing is an excellent way to determine the integrity of the
weld and/or the fittings. Where an assembly may otherwise pass a
Pneumatic, High Pressure or Hydrostatic Test, a Dye Penetrant test will
reveal flaws in the material or the weld that otherwise may not be
identified through standard leak testing methods. This inspection
method identifies surface-breaking defects in all non-porous
materials. Dye Penetrant Testing is based upon capillary action,
where a low surface tension fluid penetrates into clean and dry
surface-breaking discontinuities. Penetrant may be applied to the test
component by dipping, spraying, or brushing. After adequate
penetration time has been allowed, the excess penetrant is removed and
a developer is applied. The developer helps to draw penetrant out of
the flaw which becomes visible to the inspector. Inspection is
performed under ultraviolet or white light, depending upon the type of
dye used. Please be aware that Dye Penetrant Testing is not a
"proof test" of the integrity of the assembly
* Helium Mass Spectrometer Testing _______________________________________
Helium
Mass Spectrometer Testing, sometimes referred to as a Helium Leak
Test (HLT), is arguably the most sensitive and seeking leak detection
method available. The test is conducted by attaching the assembly
to a mass spectrometer and using a pump to draw a vacuum on the
interior of the assembly, evacuating all of the air. The exterior
is then sprayed with helium. If the assembly has a leak, the
vacuum pulls the helium into the assembly and into the mass
spectrometer where the amount of helium is recorded and reported.
An alternate method of testing is to pressurize the assembly with
helium. The mass spectrometer is fitted with a special device, a
sniffer probe, that allows it to sample air (and tracer gas when
confronted with a leak) at atmospheric pressure and to bring it into
the mass spectrometer. This method is more appropriate for larger
diameter assemblies where drawing a vacuum would not be practical,
however the sniffer method is not quite as sensitive as the vacuum
method. While the Helium Mass Spectrometer Test can be extremely
sensitive, it is not a "proof test" of the integrity of the
assembly.
Please consult one of Hose Master's highly
trained Customer Service Representatives for recommendations on the
type of testing or combination of tests that may be most suitable for
your application.
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