Fill-rite TS SS F & W Precision Meter Manuel d'utilisateur télécharger pdf (Page 26)

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SCL, continued

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, 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 50 gallon (189.27 liter) prover (can), the can

reads 17.3 cubic inches (284 ml) high. The meter error

is (284/189,270) = 0.0015 or 0.15%. 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 284 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-

x 100

= % correction

SCL is not yet approved for use in the EU.

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Fill-rite TS SS F & W Precision Meter Manuel d'utilisateur Page 26

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