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valco valves
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VICI AG International Sales: + 41–41–925–6200 Fax: + 41–41–925–6201
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Leak Testing
The standard test methods for cross-port and outport leakage insure valve
performance at pressures and temperatures up to the specifications listed.
For valves used on mass spectrometers or for ultra-trace fixed gas analysis,
we recommend an optional test method utilizing a helium mass spectrometer,
which provides data on mechanical leaks and on those due to seal porosity and
permeability. With this method, we can certify leak rates as low as 10
-10
cc‑atm/sec.
Please consult the factory prior to ordering, since the minimum leak rate will vary
widely depending on valve configuration.
Leak Rates for
Gas Sampling Valves
The actual minimum leak rates attain-
able vary widely with seal material and
valve type. In general, the acceptable
leak rates fall into three ranges. (See
chart below.)
In order to seal to less than 10
-7
, the
valve loading tension is increased,
which somewhat lowers the maximum
operating temperature and the valve
lifetime. Currently, only select material
can seal to 10
-8
in most valve styles.
Valcon M rotor material can seal to 10
-10
,
but has a temperature limit of 50°C.
Not all valves can achieve these leak
rates. As a general rule, the larger the
valve seal and port size, the higher the
leak rate.
optional leak
testing
with HeliumMass
Spectrometer
To order a valve certified
to have helium leak rates
less than 10
-7
cc‑atm/sec,
add the suffix "Z" to the
valve product number
and $175 to the price.
Certified valves are
supplied with gold-plated
stainless steel ferrules.
We can generally tell
you what leak rate
is possible prior to
manufacturing the valve.
Test Method for
Liquid Sampling Valves
The standard test method for liquid
valves is a pressure drop over time for
both crossport and outport leakage,
using isopropanol at the specified
test pressure. This test is designed
to ensure proper performance at the
specification limit.
ranges for acceptable leak rates
10
-4
to 10
-5
cc‑atm/sec
Commercial use
Not normally sold by VICI
10
-6
to 10
-7
cc‑atm/sec
General GC use
Standard tension and components
10
-8
to 10
-10
cc‑atm/sec
Ultra trace gas analysis
(ppb range)
Higher tension and specially
processed stator and rotor material
CHROMalytic TECHnology Pty Ltd AUSTRALIAN Distributors e-mail: sales@chromtech.net.au Tel: 03 9762 2034