Thermo Scientific FTIR, User Manual

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Maintenance
Test for leaks
The pressure and flow controls of the MGS system require that all the plumbing connections are
sealed tightly, with no leaks.
Test the system for leaks periodically to ensure that all connections are secure. Be sure that the
procedure you use for leak testing is appropriate for your gas system configuration.
To test that the fittings are all properly tightened, you adjust the MGS settings to pull a maximum
vacuum on the gas cell and system, with all inputs closed and with outputs to the vacuum fully open.
After the internal pressure is reduced to its minimum, you close all valves, turn off the vacuum, and
monitor the gas pressure to verify that it remains stable. If there are leaks, the pressure value will drift
back towards ambient pressure (typically around 760 mmHg).
If your system includes the Alicat pressure controller, you must also set the pressure setpoint of the
Alicat pressure controller from 0 mmHg for this test.
Before you begin, plug the sample line inlet to prevent any gas from entering the system. You can test
the system for leaks without checking the sample inlet connections by turning the gas selection valve
to Nitrogen and turning the Nitrogen valve to close.
Checking for leaks requires somewhat different procedures for the automatic and Manual Pressure
Control systems.
Note The following procedure does not test any connection to the vent outlet. Test the vent
connection using another procedure that is appropriate for your gas system configuration.
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To test for leaks in the Automatic Pressure Control system
1. Turn the N2/Span1/Span2 valve to the Off position.
2. Close the CALIBRATION FLOW flowmeter dial to block any flow.
3. Turn the FTIR INLET RESTRICT Swagelok valve to the closed position
4. Turn on the SAMPLE PUMP switch to pull a vacuum onto the gas cell and system.
5. Adjust the Alicat Set Point from 650 mmHg to 0 mmHg:
58 Modular Gas System User Guide Thermo Scientific