This procedure provides the minimum frequency requirements for prover calibrations and methods by prover type.
PROVER CALIBRATION PROCEDURE / METHODS AND FREQUENCY
PROVER CALIBRATION PREPARATION
This procedure provides guidance for prover preparation before the calibration takes place
Frequency: Prior to prover calibration
Procedure Prior to arrival of the calibration rig:
1. The Oil & Gas Operators shall appoint a member of site personnel to liaise with the Calibrating Authority’s calibration engineer.
2. Site management responsible for production shall when possible plan the prover calibration work so that it fits into a period of stable process conditions. (This does not apply when the calibration takes place using fluids other than the process fluids as the calibration medium).
3. A ‘lay-down’ area for the prover calibration rig shall be prepared prior to its arrival.
4. All necessary Permits-to-Work and/or Isolations shall be in place in order to enable the calibration to proceed as soon as possible after the Calibrating Authority’s personnel arrive on site.
5. Unless an ‘As Found’ calibration is required, the site prover shall be drained, with the prover sphere removed and ready for immediate inspection by the Calibrating Authority.
6. The installation Management shall ensure that all relevant site staff has been briefed in advance of their roles and responsibilities so that disruption during the proving process is minimized.
7. Immediately in advance of the arrival of the calibration rig, the Oil & Gas Operators shall ensure that:
o The prover’s 4-way valve is not leaking.
o All relevant isolation valves are leak free, and a means of testing or proving their integrity established.
o All relevant thermowells have been cleaned out and filled with thermally-conducting oil.
8. As a minimum, the following spares shall be held:
o 4-way valve slips
o Prover door seals
PROVER CALIBRATION PREPARATION
o One complete set of prover detector switches; these shall have been checked for correct operation and for correct insertion depth.
o Prover sphere valves.
9. The Oil & Gas Operators shall check that a spare prover sphere of the correct size, material, and condition is available, as well as all necessary sphere tools and a sphere pump. A readily available supply of glycol shall also be provided.
10. The Oil & Gas Operators shall contact the Calibration Authority to determine which specific site services are necessary, and then ensure that that these are provided. For example, the provision of the following may need to be considered:
o Power supplies (440Vac, 240Vac or 110Vac) with suitable connections.
o Potable water for flushing the master prover at the end of the calibration.
o Dry white spot nitrogen at 1000 psi.
11. The Oil & Gas Operators shall have available a suitable pump for hydro-testing or leak testing the hook-up of the site prover to the calibration rig.
During the Prover Calibration:
1. During prover calibration, the Oil & Gas Operators shall strive to maintain, as far as possible, steady flow through the metering station, and remain attentive to the requirements of the calibration, as determined by the Calibration authority’s engineers.
2. Where volume is the agreed measurement unit, it shall be referred to the standard reference conditions of 15°C temperature and 1.01325 bar absolute pressure (dry).