RKI Instruments 35-3001-06-01 - Manual (Page 20)

16 • 35-3001-06-01 Combustible Gas/Oxygen Sample-Draw Detector
4. Reinstall the tubing routed to the sampling area.
Adjusting the Low Flow Setting
NOTE: Adjusting the low flow setting will cause a low flow alarm at the sample-draw detector
and a fail alarm at the controller. Be sure to put the controller into its calibration program
or disable external alarms before performing this test.
The factory-set low flow setting is 0.6 SCFH (±0.1). To adjust the low flow setting:
1. Use the sensor flow control valve to set the flow to 0.6 SCFH. Turn the valve’s knob clockwise
to increase the flow and counterclockwise to decrease the flow.
If the sample-draw detector goes into low flow alarm before you can adjust the flow down to
0.6 SCFH, adjust the pressure switch adjustment screw 1/4 turn clockwise, then attempt to set
the flow again. Repeat this step until you are able to adjust the flow to 0.6 SCFH.
NOTE: The pressure switch adjustment screw is accessible through a circular cutout in the
flowmeter circuit board.
2. Slowly turn the pressure switch adjustment screw counterclockwise just until the sample-draw
detector goes into low flow alarm.
3. Turn the sensor flow control valve’s knob clockwise to increase the flow until the unit is out of
low flow alarm.
4. Decrease the flow very slowlyby turning the sensor flow control valve’s knob
counterclockwise and verify that the low flow alarm is 0.6 SCFH (±0.1).
If the low flow alarm is set too low, turn the pressure switch adjustment screw slightly
clockwise. Repeat steps 3 and 4 if necessary.
5. Use the sensor flow control valve to set the flow to 1.0 SCFH.
6. Make sure the sample-draw detector’s Fail LED is off.
Calibration Frequency
Although there is no particular calibration frequency that is correct for all applications, a calibration
frequency of every 3 months is adequate for most sample draw detector applications. Unless
experience in a particular application dictates otherwise, RKI Instruments, Inc. recommends a
calibration frequency of every 3 months for the oxygen detector and every 6 months for the infrared
LEL detector.
If an application is not very demanding, for example detection in a clean, temperature controlled
environment, and calibration adjustments are minimal at calibration, then a calibration frequency of
every 6 months is adequate for the oxygen detector and every 9 to 12 months is adequate for the
infrared LEL detector.
If an application is very demanding, for example if the environment is not well controlled, then
more frequent calibration than every 3 months for the oxygen detector and every 6 months for the
infrared LEL detector may be necessary.