ENMET ISA-RAL-M - Manual (Page 13)

ISA-RAL-M, ISA-RAH-M ENMET Corporation
9
6.0 Calibration 6.0 Calibration
The following procedure is for checking the calibration level and for recalibrating the ISA-RAL-M.
Perform A Complete Recalibration Periodically (At Least Every 90 Days) And:
•
When you replace the sensor.
•
When the sensor encounters severe conditions (i.e. gross exposure to smoke or liquid hydrocarbons).
MATERIALS:
•
Cylinders of calibration gas of known CO concentration in air corresponding with the alarm level of the unit, for
example, 20 ppm CO in air.
C AUTION : Do not use CO in a pure inert carrier gas, such as nitrogen or argon.
•
Calibration adapter, ENMET part no. 03605-001.
•
Small screwdriver for potentiometer adjustment.
PROCEDURE:
1.
Turn the switch to PURGE ON. The alarm lights go on; this is normal.
2. Leave switch in the PURGE ON position for at least one hour. Air must be flowing through the humidifier and
over the sensor during this time. Remember, if you suspect contaminated air in your compressor system, use clean
bottled air.
3. After at least one hour, turn the switch to HORN OFF. Allow the sensor to stabilize for 30 minutes before
continuing.
N OTE : Some compressor installations produce very clean air during normal operations. A medical air system is an
example of such an installation. In such situations, the purge operation before calibration can usually be
eliminated. The sensor requires purging only when the meter needle does not return to the normal “zero” area
within 30 minutes after the calibration gas is removed. If this occurs, purge and stabilize the sensor as
described above, then recalibrate. Of course, always purge the sensor after sensor replacement or heavy sensor
contamination due to severe conditions.
4. Be sure the humidifier bottle is filled with tap water to the Upper Water Level mark.
5. Remove the compressed air line and insert the calibration adapter (Figure 7).
6. Open the regulator on the top of the calibration gas cylinder. This brings the gas into the sampling assembly.
7. Regulate the flow of calibration gas to between 7 and 12 psi on the pressure regulator dial. Adjust flow using only
the valve on the calibration adapter.
8. Let the calibration gas flow into the system for 5 minutes. This assures a full and balanced response from the
sensor.
9. With the gas still flowing, adjust the Meter Adjust potentiometer (Ref figure 5 RV33; ccw to increase, cw to
decrease meter reading) with a small screwdriver. You want to have the meter pass through the low level alarm
point, verify that the alarm light triggers at the 10 ppm point. If it does not, set the meter to the 10 ppm mark and
adjust RV35 (low level alarm pot) turn the switch to OPERATE for a second to verify the horn is operational.
Then adjust the meter gain pot to pass through the 20 ppm point, verify that the alarm light triggers at the 20 ppm
point. If it does not, set the meter gain to the 20 ppm adjust RV34 to trigger the alarm light. Turn the switch to
OPERATE for a second to verify the horn is operational. This sets the alarm points (Refer to Figure 5). Do Not
adjust for instantaneous alarm when test gas is first released. If you do, the calibration is inaccurate, and the sensor
is overly sensitive.
10. Shut off the calibration gas flow at the valve on the gas cylinder.
11. Allow pressure to equalize - wait until the pressure meter on the humidifier-regulator assembly reads zero, then
remove the calibration adapter from the input of the sample head.
C AUTION : If you disassemble the calibration unit before the pressure is equalized, you may cause a back flow of
water from the humidifier. This damages the regulator valve.
12. Remove the calibration gas, reconnect the unit to the air line, the flow of clean air should clear the unit from its
gas alarm state in less than one minute. After the alarms have cleared, turn the switch to OPERATE
13. Clean compressed air results in a meter reading from 0 - 1/3 full scale, Green power light indicates a clean
condition.