Servomex DF-310E, Operator'S Manual

Page: 44 / 130

40 DF-310E Sample Gas Preparation and Delivery
33 for more detail.
Contact the local Servomex Business Center for recommendations on using
the STAB-EL sensor on acid gases other than those listed.
6.4.6 Sample Gas Temperature
Gas temperature should not exceed 50 °C (122° F), nor should it fall below
0° C (32° F). Gas temperature can be controlled by passing the gas through 5
to 10 feet of metal tubing that is within the recommended sample temperature.
Because of its low thermal mass, the gas sample quickly reaches the gas
sample line temperature.
Ideally, the analyzer should be operated at a nominal temperature of 70° F.
Calibration temperature should be close to operating temperature. If the
analyzer is to be operated at an average ambient temperature outside 65° F to
80° F, it should be recalibrated at the operating temperature for optimal
performance.
NOTE
The sensor temperature can be displayed at any time by accessing
the Diagnostics Menu, Figure 56. This temperature value is updated
at intervals of 15 to 45 seconds.
6.4.7 Protecting the Analyzer from Process Upsets
The analyzer should be protected from extended exposure to high
concentrations of oxygen or hostile gases. Automatically solenoid controlled
valves should be installed to switch the analyzer over to an N
2
purge when the
process reaches some identifiable condition.
Gas line maintenance operations must also be examined for their effect on the
analyzer. For example, in many pipeline process or normal gas applications
the plumbing system is cleaned with either a liquid solvent or detergent
solution. Since either causes damage to the sensor, switch the analyzer over
to a N
2
bypass purge, or shut off sample flow and power to the analyzer prior
to initiating the potentially hazardous process.
6.5 Calibration Gas Considerations
Calibrations performed from a bottled, calibrated sample gas, may introduce
additional issues that could adversely affect the analyzer calibration.
6.5.1 Calibration Standards
Certified calibration standards are available from gas manufacturers. These
standards are available in steel and aluminum cylinders. Steel cylinders are
less expensive but do not dependably maintain a stable oxygen concentration
for long periods of time.
Calibration standards in aluminum cylinders are recommended. Servomex
has found that calibration standards in aluminum cylinders are very stable for