16 • 35-3001-01 Combustible Gas Sample-Draw Detector
Calibration Frequency
Although there is no particular calibration frequency that is correct for all sample draw detector
applications, a calibration frequency of every 3 to 6 months is adequate for most applications.
Unless experience in a particular application dictates otherwise, RKI Instruments, Inc. recommends
a calibration frequency of every 3 months.
If an application is not very demanding, for example detection in a clean, temperature controlled
environment where combustible gases are not normally present and calibration adjustments are
minimal at calibration, then a calibration frequency of every 6 months is adequate.
If an application is very demanding, for example if combustible gases are present often and in
significant concentrations or the environment is not well controlled, then more frequent calibration
than every 3 months may be necessary.
Calibration
This section describes how to calibrate the combustible gas sample-draw detector. It includes
procedures to prepare for calibration, set the zero reading, set the response reading, and return to
normal operation.
The standard calibration gas for the sample-draw detector is methane. The sample-draw detector
may be calibrated to other combustible gases such as hexane or hydrogen. Use the correct
calibration gas for your installation.
NOTE:
This procedure describes calibration using a demand flow regulator.
Preparing for Calibration
1. Follow the instructions in the controller’s operator’s manual for entering calibration mode.
NOTE:
If you can verify a fresh air environment, it is not necessary to use the zero air calibration
cylinder to set the zero reading.
2. Screw the regulator into a zero air calibration cylinder.
Setting the Zero Reading
1. Connect the sample tubing from the demand flow regulator to the sample-draw detector’s inlet
line.
This step is not necessary if you verified a fresh air environment earlier in this
procedure.
2. Allow the sample-draw detector to draw sample for one minute.
3. Follow the directions in the controller’s operator’s manual for setting the zero reading. If you
used a zero air calibration cylinder to set the zero reading, proceed to step 4. If you verified a
fresh air environment, proceed to the next section, Setting the Response Reading.
4. Disconnect the sample tubing from the inlet line.
5. Unscrew the regulator from the zero air calibration cylinder.
Setting the Response Reading
1. Screw the regulator into the combustible gas calibration cylinder.
2. Connect the sample tubing from the demand flow regulator to the sample-draw detector’s inlet
line.
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