Compac CNG Installation And Service Manual page 41

Loading Post Calibration
Calibration Test Fill Procedure (Method 1)
Calibration Test Fill Procedure (Method 2)
Compac Industries Ltd.
Method 1 of checking calibration involves loading a gas cylinder and
comparing the read-out scale reading with the loading post display
reading.
Before you start, make sure you have:
 Certified weighing scales with a read-out accuracy of +/- 20 g or
better and a range of 0—120 kg
 A CNG cylinder with a fill and release valve
To carry out the calibration test fill procedure (Method 1):
1. Put an empty CNG cylinder on the scales and take note of its weight.
2. Fill the CNG cylinder via the loading post.
3. Subtract the original weight from the full cylinder weight and compare
with the weight shown on the post display.
If the results are not within 0.5% of each other, you will need to
change the calibration, as per the Calculate and Set the New K-Factor
section.
Method 2 of checking calibration involves filling a tank and comparing a
master meter reading with the loading post display readings.
This method assumes that the master meter is sufficiently accurate and
reliable enough to be considered a good reference.
Before you start, make sure you have:
 A Compac Master Meter or other calibrated CNG meter.
To carry out the calibration test fill procedure (Method 2):
1. Connect the master meter between the loading post and a cylinder.
2. Turn on the master meter valve, if applicable, and reset to zero.
3. Commence a fill. You do not have to do a complete fill, you can stop
the fill at any time.
4. Turn off the post valves and master meter valve, if applicable.
5. Compare the master meter read-out (True Quantity) with the loading
post display (Display Amount).
If the results are not within 0.5% of each other, you will need to change
the calibration, as per the Calculate and Set the New K-Factor section.
Page 41
Meter Calibration
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