Servomex DF-310E, Operator'S Manual

Page: 41 / 130

Sample Gas Preparation and Delivery DF-310E 37
If a pressure change causes the flow rate to move outside the recommended
range, an adjustment of the flow control valve must be made. If the
adjustment is not made, and the flow rate remains outside the recommended
range, the analyzer may not be operating within its stated accuracy.
6.3.5 Pressure Regulator Purge
Regulators used on bottled calibration standards are typically equipped with 2
Bourdon pressure gauges, one to measure the cylinder pressure, and the other
to measure the outlet pressure. The regulator must have a metal (preferably
stainless steel) diaphragm. It is good practice to install a flow control valve to
adjust the flow after the regulator.
All user-added upstream plumbing should be consistent with the instrument
gas delivery components so that the highest level of integrity can be
maintained. All connections should be welded or include metal face-seal
components.
Pressure gauges are not recommended on regulators used on process sample
lines because they add measurement delay time and offer opportunities for
leaks.
6.3.5.1 Regulator Purge Procedure
Before the gas is connected to the analyzer follow the procedure listed below
to purge ambient air from the regulator
:
After securely attaching the regulator to the cylinder,
1. Open the regulator flow control valve slightly.
2. Open the cylinder valve.
3. Set the regulator to its maximum delivery pressure.
4. Adjust the flow control valve to allow a modest flow rate (hissing
sound).
5. Close the cylinder valve until the cylinder pressure falls to zero. If
equipped with gauges, allow the secondary (output) gauge to approach
zero. Otherwise wait for the hissing to nearly stop.
6. Immediately open the cylinder valve to restore full delivery pressure.
7. Repeat steps 5 and 6 five to ten times to thoroughly purge the regulator
and gauges.
8. Close the shut off valve on the outlet side of the regulator to isolate the
purged regulator from atmospheric contamination.
Set the delivery pressure to 5 psig (15 psi for welded sample line with
VCR connection.
The above procedure insures that any ambient air trapped in the pressure
gauges and cavities of the regulator is purged prior to use. Once the
regulator is mounted, do not remove it from the cylinder until a fresh
cylinder is required.
6.3.6 Pressure Effects on Sensor Performance
If the analyzer is not vented to atmosphere, the sensor pressure is influenced
by the conditions downstream of the analyzer. A recalibration under your
operating conditions may be desirable to remain within the stated accuracy