Servomex NanoTrace DF-760E, Инструкция по эксплуатации

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Installation, Start Up and Shut Down DF-760E 29
4.2.1 Gas Delivery System
The gas delivery system as shown in Figure 7 is designed to deliver a gas flow rate of 1
liter per minute to both the moisture and oxygen sensor while maintaining the highest
standards of gas purity and delivery for ultra-trace analysis. Features include a single inlet
line for the gas sample, a bypass loop to maintain constant purging, and essentially dead-
leg free delivery. The gas delivery system also allows the user to perform zero calibration
adjustments for both the oxygen and moisture cells as well as a span calibration for the
oxygen sensor.
The connections at the rear of the gas delivery system include a pneumatic gas connection
(1/8” compression), a ¼” VCR swivel connection for the process inlet, a ¼” VCR swivel
connection for oxygen span gas, a ¼” compression outlet for the moisture cell, and a ¼”
compression outlet for the oxygen sensor and bypass loop. Also on the rear of the gas
delivery system are a sample gas regulator to adjust the internal sample pressure and a
bypass flow meter.
The moisture sensor outlet will be connected to the supplied aspirator or to the vacuum
pump, if equipped. The oxygen and bypass outlet should not be connected to a high-
pressure vent such that back-pressure greater than 1psig is not placed on the oxygen
sensor.
The process inlet to the moisture analyzer, as well as the zero gas inlet, are heated to 60 C.
This is done to mitigate any effects of adsorption-desorption of trace moisture on the walls
of the tubing.
NOTE: After properly setting the flow rates, isolation of either sensor will not affect the
flow rate through the other.
4.2.2 Gas Pressure and Flow Settings
Attention to the setting of gas pressure and flow is critical to proper operation of the
analyzer. If steps 1-7 are followed carefully at the time of start up, subsequent changes to
flow or background gas will be made easier. The following procedure assumes all
electrical and plumbing connections have been made according to instructions in this
manual. In addition, this procedure assumes a Nitrogen gas background unless otherwise
noted.
1. Power up the unit. See page 28. If the unit is equipped with a Hydrogen Safety
System, no flow will enter the system until the unit is on power.
2. Ensure that the needle valve on the aspirator is fully open.
3. Completely open (turn fully clockwise) the inlet regulator on the rear of the
analyzer. For operation in Nitrogen, Argon and Oxygen the regulator is closed
(turned counter clockwise) to the approximate middle, or 50% of its range. For
operation in Helium and Hydrogen it should be closed to 80-90% of its range.
4. Open the flowmeter bypass valve on the rear of the analyzer and flow in the bypass
loop will be indicated on the flowmeter. Adjust the flowmeter bypass valve to 0.5
slpm. See Figure 4.
5. Purge for 15 minutes before opening gas valves.