Scope: The following paragraphs cover the general requirements for proving a master meter by a master tank prover
CALIBRATION OF MASTER METER BY MASTER TANK PROVER
Frequency: As indicated
Procedure The same method and general procedure for calibrating an AFO meter or
a load rack meter should be followed when proving a master meter with
one exception. At each flow rate the master meter is calibrated, the
master meter’s MF should be calculated as the average of at least three
(3) consecutive calibration runs having a repeatability within 0.02 percent
(%). Repeatability is defined as:
% Repeatability = (Maximum MF of runs – Minimum MF of runs) x 100 ) / Minimum MF of runs
Note: Wetting run and pre-run are not included in the calibration
runs.
Master meter used for calibrating Air Fueling Operation (AFO) meters
If the application of a master meter is only for calibrating AFO meters, the master meter shall be calibrated at the following rates:
i. at or near its rated minimum flow rate,
ii. at or near its rated maximum flow rate,
iii. and six flow rates spread within.
iv. The flow rates selected should include at least one that is between 15-20 % of the rated (design) maximum flow rate of the working meter (to allow for “slippage test”.)
Master meter used to calibrate Bulk Plant loading/unloading meters
If the application of a master meter is only for calibrating rack meters, the
master meter shall be calibrated at the following rates:
1. If the rack meters are equipped with mechanical preset – the
master meter should be calibrated at the normal loading rate;
2. If the rack meters are equipped with electronic preset – the
master meter should be calibrated at the low, mid, and high
(normal) flow rates used during rack meter operations. This allows
the master meter’s MFs to be applied without interpolation when
the working meter is proved at the corresponding low, mid, and
high flow rate(s).
Report
The calibration report “package” should include, but not be limited
the following information:
A) Location
B) Calibration report number
C) Tag number of the master meter under test
D) Type, make/model, size and serial number of the master
meter
E) Date of calibration
F) Time start and stop calibration of each “proof” and the
duration of entire calibration
G) Flow rate
H) Type of tank prover used, material of construction, size,
scale resolution, scale correction, if any, and serial number
and the prover capacity.
I) Calibration Certificate for the tank prover (as a separate
document attached to the master meter calibration report).
The certificate should include the certification number of the
prover and the date of calibration and the next due date of
calibration.
J) A chart plotting the meter factor at each flow rate
K) Calculation procedure for average MF of the master meter
L) Name of company performing the calibration
M) Name and signature of the person from the calibration
contractor
N) Name and signature of witnesses
O) Official stamp/seal of the company providing the certificate
P) Master meter seal number before and after calibration
Q) Due date for master meter next calibration
R) Reason for calibration(schedule, maintenance, operation
request)