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

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2.4 Calibration of Metal Tapes 
2.4.1 Accreditation 
Only companies or Institutions that possesses a current Petroleum Resources registration 
permit as an equipment calibrator shall be eligible to carry out metal tape calibration with 
participation of representative(s) of The Department of Petroleum Resources. 
2.4.2 Principle 
Calibration shall be based on comparison of the horizontal length of tape with that of a valid 
Master Tape calibrated in a recognized laboratory under the same tension at a reference 
temperature of 68oF (20oC). 
2.4.3 Frequency of Calibration 
All new tapes shall be deemed calibrated and an attestation to this effect by the 
manufacturer shall be recognized as evidence of this calibration. Annually thereafter 
throughout the operational life of the tape. 
2.4.4 Applicable Standard 
This shall be the API MPMS 2.2A or its latest ASTM equivalent standard. 
2.4.5 Verification and Calibration 
2.4.5.1 The tape shall be calibrated against the length of a secondary standard tape both 
under a tensile force of 1lb or 0.45kgf with both tapes being supported on a horizontal plane 
along their entire length. 
2.4.5.2 The Master Tape shall be covered by a current certificate issued by a recognized 
bureau of standards as evidence of a recent calibration against a primary standard-length 
measure. 
2.4.5.3 Both tapes (Master Tape and Working Tape) shall be inspected for kink before 
calibration. 
 
2.4.6 Presentation of Results 
A report of calibration exercise shall be submitted to the Department of Petroleum 
Resources office for review and approval. However, the allowable tolerance limit of 
variation in total length of the steel tape shall be 0.005ft (0.0015m) for every 100ft (30.48m) 
of tape length. 
2.5 
Calibration of Vertical Cylindrical Tanks 
2.5.1 Accreditation 
This shall be on job basis. Any corporate body proposed by an operator to carry out a tank 
calibration exercise shall formally apply to the Department of petroleum Resources for 
accreditation. Such application shall be considered in the light of the expertise and previous 
performance of the applying company, the proposed programme of calibration and chart 
computation, and other applicable conditions as specified by The Department of Petroleum 
Resources and shall be with participation of its representative(s). 
2.5.2 Principle 
Calibration of vertical cylindrical tanks is a process of accurately measuring such parameters 
of a vertical storage tank like circumferences at specific locations, vertical height, plate 
thickness, weights and volume of internal and external fixtures and bottom plate with the