© 2019 Department of Petroleum Resources. All rights reserved Department of Petroleum Resources (DPR) PROCEDURE GUIDE

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The applicable standards for Design, Installation, Operation and Maintenance of proving
systems shall be American Petroleum Institute Manual of Petroleum Measurement
Standards (API MPMS) Chapters 4, 12 and 13.
2.5 Calibration of the Prover Loop
2.5.1 Accreditation
This shall be on job by job basis and any corporate body wishing to carry out a prover
calibration shall be pre-qualified for the job by the Department of Petroleum Resources.
2.5.2 Frequency
2.5.2.1 All new pipe provers shall be calibrated in the presence of representative(s) of The
Department of Petroleum Resources at the site of manufacturer and thereafter
annually for prover loops used for Custody transfer, and every three (3) years for
prover loops used for production monitoring.
2.5.2.2 All calibration exercises shall be witnessed, and the result countersigned, by
representative(s) of the Department of Petroleum Resources.
2.5.2.3 It is mandatory for in-factory calibration of the loop to be by waterdraw method.
2.5.2.4 All other measuring equipment associated with the Prover such as thermometers,
temperature gauges and transmitters, temperature compensators, pressure gauges
and transmitters, auto samplers, densitometers, etc. shall equally be calibrated
according to the relevant sections of this guide.
2.5.3 Procedure
Although only waterdraw method is acceptable for calibrating new Provers, the master
meter method shall be allowed for subsequent calibration of the Prover while in operation.
The field standard test measure to be used for water draw calibration shall be traceable to
a primary standard established at standard condition. All the steps outlined in the reference
standard shall be followed in carrying out the calibration exercise. The base volume to be
established shall be the sum of the volume displaced between the two detectors for a round
trip of the displacer and this shall fall within 0.020% repeatability.
2.5.3.1 Do five or more out of a maximum of ten consecutive runs which shall agree within a
range of 0.020% or less for pre and post meter factor.
2.5.3.2 Do three or more out of a maximum of six consecutive runs which shall agree within
a range of 0.020% or less for calibrated prover volume.
2.5.3.3 The flow rate during a calibration run shall be maintained within a range of ±2.5%.
2.5.3.5 The delta % of pre and post meter factor shall agree within 0.020%
Delta % = (Pre-meter factor – Post-meter factor) * 100
2.5.3.6 During annual recalibration exercise, the difference between the established Base
Prover Volumes and the previous year’s Base Prover Volume shall not exceed 0.02%.
2.5.3.7 A minimum of three (3) flow rates at minimum of 25% interval shall be used during
prover loop certifications. The volumes so derived from each flow rates shall check
within 0.020% repeatability.