Servomex NanoTrace DF-760E, Инструкция по эксплуатации

Страница: 34 / 182

30 DF-760E Installation, Start Up and Shut Down
6. The state of the gas control valves for each of the sensors is indicated on the main
display. The default state of a factory-shipped instrument is isolation for both
sensors. This can be adjusted in the Power Up Default section. If the sensors are in
isolation, establish process flow via the Controls menu. See page 48 for the
Moisture valves and page 72 for the Oxygen valves.
7. Once flow has been established through the moisture cell, observe the pressure
indicator on the main display. For all gases, with the exception of helium, the
pressure in the moisture cell is only controlled by adjusting the needle control valve
on the aspirator. See Table 1 for appropriate pressure settings. In the case of
helium, the vacuum source must be off, and the needle control valve wide open.
8. It is important to ensure that a minimum of 0.2 slpm flows through the bypass loop
at all times to prevent backflow. See page 31 for additional information on back
pressure prevention.
9. The proper pressure ranges listed in Table 1 will automatically appear on the
display when the background GSF is selected.
10. Note: For light gases (hydrogen and helium), the flow indication for the oxygen
sensor will be adjusted automatically by approximately 0.3 to compensate for the
lighter gas. As a result, the flow rate through the oxygen sensor should always be
set to a reading of 1.0 slpm no matter what background gas is in use.
Background Gas Pressure Vacuum Source
N2 150 - 250 Torr ON
Ar 280 - 380 Torr ON
He 740 - 780 Torr OFF*
H2 300 - 400 Torr ON
O2 300 - 400 Torr ON
*A shut off valve must be installed at the inlet to the aspirator to disable the vacuum.
Table 1: Recommended Sample Outlet Vacuum Pressure
4.2.3 Moisture
Start the gas flow through the Moisture cell by going to the Moisture Controls Menu as
shown on page 47 and select Gas Valves. On the Gas Valves screen Figure 20, highlight
“Restore Process Gas Flow” and hit Apply, and then hit Done.
On initial start-up, after the six minute warm up process is complete, the moisture analyzer
will take a few hours to equilibrate and the concentration of moisture is automatically
shown in parts per million (ppm) or parts per billion (ppb) on the display.
If after initial start-up, the power is briefly turned off, the moisture analyzer will take
approximately six minutes to re-equilibrate.
See the section on Gas Flow and Pressure Regulation on page 29 for important information
on setting proper pressures and flow rates.