Fill-Rite TS06 LPG Precision Meter - Manual (Page 19)

19
Flow Meter Calibration
METER CALIBRATION:

Flow meter re-calibration should be on a volume
equal to 1 minute of flow at maximum flow rate.

All tests should be performed 3 times under identi-
cal conditions to confirm repeatability.

Maintain a permanent file for each flow meter, and
record % change each time the meter is re-
calibrated.
When the change is significantly higher than that
found in previous re-calibrations, it is time to re-
build the flow meter (replace the two oval gears).
METER CALIBRATION:
The calibrator allows you to adjust the output of the SCL up
or down, like a mechanical calibrator, +/- 3% in increments
of 0.03%.
 After calibrating a known volume (X) into an accurate
prover (or through a master meter with adequate resolu-
tion), compare with register reading (Y) and calculate
correction:
To reduce the volume in a prover vessel (can), place
switch S2 in the plus(+) position.
 Adjust the S3 and S4 to the position required for the
necessary volume reduction in the prover can. Switch
S3 and S4 represent readings of 00 to 99, and each
increment will adjust the output approximately 0.03%.
Example:
Using a 20 gallon (75.7 liter) can, the can reads 113.5
ml high. The meter error is (113.5/75700) = 0.0015
or .15%. To adjust the meter output, place S2 in the
positive position, and set S3 and S4 to read 05. This is
approximately a 0.15% adjustment.
Activate the Reset push button switch to enter the new
program settings. Retest the flow meter.
 To increase the volume in the prover vessel. Place
switch S2 in the negative (-) position, and set switches
S3 and S4 to the proper settings to adjust the output.
Activate the Reset push button switch to enter the new
data.
NOTE: If S2 is in the plus (+) position, and S3 and S4
are at 15 as an example, then moving the posi
tion of S3 and S4 to 00 will provide a (0.03 x 15)
=.45% increase in the prover volume. To obtain
a greater increase in the prover volume, S2
must be placed in the minus (-) position and S3
and S4 rotated to the proper position to obtain
the desired change in pulse resolution. The
opposite is true if S2 is already in the minus (-)
position at the beginning of calibration.
 Finally:
 Re-seal the flow meter.
 Enter date and % correction on the permanent flow
meter record.
As long as degree of change is moderate, the flow meter is
in good condition.
If there is a sudden significant jump in correction required,
the rotors are likely about worn out. Rotor replacement
should be considered now, rather than letting further wear
cause rotors to start rubbing on flow meter housing.
METER CALBRATION: INCREASED PRECISION.
The standard method for calculating the single point adjust-
ment is to obtain the error as a percentage of the desired
test volume. In the previous examples, an excess volume in
the prover vessel of 113.5 ml became 0.15% and the adjust-
ment was 05 on S3 and S4.
However, the 0.15% correctly needs to be applied to the
nominal ECF for the particular meter profile in order to more
precisely calculate the adjustment for S3 and S4. The nomi-
nal ECF is the particular profile base divided by the natural
meter pulse resolution.
As an example, a meter type which is scaled to 100 ppl and
has 410 ppg pulse resolution, has a nominal ECF of
378.5/410 = 0.9232. 0.15% of 9232 is 13.84. When divided
by 3, the switch setting is 04.6. In this example, 4.6 is
rounded up to 05. This is the same result as before be-
cause the ECF is close to unity (1.0000). If the ECF was
0.4200, then the switch setting would be 02.
There are applications where the nominal ECF is not near
unity. In those cases, the nominal ECF needs to be known
and used for the calculation. If the standard calculation is
used, the adjustment would be excessive and the meter
technician would have to estimate the reduction in his set-
tings and perform an additional test run.
X - Y
X
x 100 = % correction