Scope
This procedure provides guidelines to determine the volume of uni-directional
and bi-directional pipe provers at base conditions of temperature and pressure
using the master meter method with:
1. Crude oil as the calibration liquid
2. Diesel as the calibration liquid
3. Water as the calibration liquid
PIPE PROVER CALIBRATION Procedure BY MASTER METER
Frequency As indicated in Procedure No. 049
PROVER CLEANING
The prover will not be cleaned prior to commencement of the calibration if
calibration liquid is Crude oil or Diesel. If calibration liquid is Water, Prover
cleaning shall be performed in accordance with Procedure No. 51
Test Set-Up
The test set-up and piping installation for the calibration of the prover is shown
in Attachment I. The distances between the calibration equipment and the
prover under test should be as short as possible, to assist temperature
stability.
Procedure
In the case of royalty transfer provers, an in-house test shall be conducted
to confirm acceptable repeatability of the prover volume. The test procedure
shall be the same as the official test. Once the preliminary test is successful,
the official test will be conducted in the presence of MINPET
representative(s). Saudi Aramco safety procedures and work permit
requirements must be observed at all times.
1. Drain the prover, open the closure and remove the sphere from
the interchange valve.
2. Wipe clean and inspect the entire surface of the sphere for signs
of damage e.g. miss-shape, cuts, wear, blistering, score marks
etc. Replace if damaged.
3. Measure the prover sphere around the equator and pole planes using a diameter tape or sizing ring. Record the smaller of the two
dimensions. The correct inflation size is taken from the previous
calibration certificate. Inflate or deflate as necessary.
4. Return the sphere to the prover and secure the closure.
5. Remove and service or replace detector switches. This depends
on prover performance records. If undecided, always replace
detector switches with new ones.
6. Liaise with operations department to safely establish the flowing
conditions required to perform the calibration. One of the
operational streams will be used to divert the flow of liquid to the
prover under test and the master meter / master prover. The liquid
returns to the pipeline downstream of the operational meters.
7. Check the meter strainer and clean if necessary.
8. Connect hoses and fittings etc. as shown in Attachment I.
9. Carefully flood the system with crude oil, by opening valves in
sequence V1 to V7 and venting at high points for each step in the
sequence. Check for leaks at hoses, fittings and critical valves –
they must be bubble tight.
10. Connect pulse counter power supply. Connect master prover and
prover under test detector switch signal cables to the pulse
counter.
11. Establish a flow of liquid in the system and confirm functionality of
master meter, signal cables and pulse counter.
12. Perform function test of the pressure instruments by substitution
method to confirm agreement within 1 psig. i.e. Observe the
indication of each pressure instrument at a single location where
the pressure remains constant. Compare temperature instrument
readings to confirm agreement within 0.1ºF. Fill each thermowell to
be used with a temperature transmission liquid such as Glycol.
13. Once the above preparations have been made refer to Attachment
I. Valve V1 is the meter stream prover valve. Valves V2, V3, V6
and V7 are isolation valves and are open for the test.
14. Prover and the sphere interchange valve of the prover under test,
to move the spheres through the provers enough times to flush
and eliminate air that may have been caught in parts of the prover
systems. Vent the air at the prover high point vent valves.
Continue to move the spheres to allow the liquid and metal of the
prover systems to reach a common and steady temperature.
15. The flow rate should be monitored, by observing the master meter
flow rate indicator. Flow rate must be maintained within ± 2.5% or
better throughout the entire procedure and shall fall within the
linear range of the meter. Flow rate is set by minor adjustment to
valves V4 and V5.
Proving the Master Meter with the master prover (‘Initial meter factors’)
16. Zero the master meter pulse counter, vent at the master prover
high point vent valves and rotate the master prover 4-way valve.
Record the flow rate.
17. When the sphere of the master prover hits the first and second
detector switches the pulse counter will start and stop respectively.
18. Rotate the master prover 4-way valve again. Record the master
meter and master prover average temperature readings to one
decimal point (F) and the master meter and master prover
average pressure readings to one psig, for the round trip of the
master prover, when the sphere is between the detector switches.
19. When the master prover sphere hits the second detector switch
after completing the round trip the pulse counter will stop. Record
the master meter pulse counter reading for the round trip.
20. Calculate the correction factors needed to determine the meter
factor of the master meter. Record the data on the Master Meter
Proving Report and calculate the meter factor.
21. Repeat step 16 to 20 until at least 2 consecutive meter factors are
achieved which agree within 0.020%.
22. Determine the average initial meter factor, which will be used in
the calculation to determine the volume of the uni-directional pipe
prover to be calibrated.
Calibrating the pipe prover:
23. Vent at the prover high point vent valves and operate the sphere
interchange valve to drive the sphere forward. The pulse counter
starts and stops as the sphere hits the first and second detector
switches respectively.
24. When the sphere is between the detector switches record the
master meter and prover average temperature readings to one
decimal point (°F) and the master meter and prover average
pressure readings to one psig.
25. Repeat steps 23 and 24 until at least three consecutive run
volumes agree within 0.020%.
Re-proving the Master Meter (‘Final meter factors’):
26. Produce ‘final meter factors’ by repeating steps 16 to 22. Verify
that the average final meter factor is within 0.020% of the average
initial meter factor.
27. Repeat steps 16 through 26 at a 25% (minimum) changed flow
rate until two consecutive volumes agree within 0.020% for UniDirectional
pipe provers.
Note: for Bi-Directional Pipe Prover, volumes must agree as follows:
a) First and second forward half trip volumes within
0.020%.
b) First and second reverse half trip volumes within
0.020%.
c) Total of the first round trip volume versus total of
the second round trip volume, within 0.020%.
28. When conditions of 27, above, are achieved calculate the prover
volumes for the initial and the final flow rate calibrations. The
volumes should agree within 0.020%.
29. The new base volume of the prover will be the average of three
initial plus two final calibration run volumes.
30. Disconnect all the calibration equipment following confirmation that
the calibration has been successful.
31. Drain, de-isolate and return the prover to service.
