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

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2.6.4 Applicable Standard 
Calibration method shall be as outlined in latest American Petroleum Institute Manual of 
Petroleum Measurement Standard (API MPMS) Chapters 2.2E, API Standard 2551 or ASTM 
D-1410 captioned “Standard Method for Measurement and Calibration of Horizontal Tanks. 
2.6.5 Calibration Equipment 
These shall be as enumerated in the reference standards and shall comply in all respects 
with the specifications stipulated in the standard. 
 
2.6.6 Calibration Procedure 
The tank shall be thoroughly cleaned, degassed, and completely filled with water prior to 
calibration to ensure that the shells are stretched to the maximum level that they could 
reach during operational life. Therefore, the procedure outlined in the reference standard 
is followed to obtain the necessary parameters for preparing a calibration chart for the 
tanks. Parameters to be obtained shall be those for critical measurements in the tank such 
as shell plate thickness, circumferential perimeters of each ring along the cylindrical portion, 
geometric dimensions of the deadwood, inclination of the tank to the horizontal plane if it 
is off-level and other parameters applicable to the mode of construction of the tank. 
2.6.6.1: Every tank after calibration and approval of usage shall display conspicuously on the 
surface: ‘’Tank number’’, ‘’Tank Service’’, ‘’Date of Calibration’’ and ‘’Due date for 
next Calibration’’. Frequency of storage tank inspection and calibration shall be 
every 5 years. 
2.6.6.2: For all new and repaired or rehabilitated aboveground floating roof storage tanks, 
there shall be lightning protection for unintended upsurge in static electricity and 
lightening arrestors as safeguard against possible rain storm or thunder installed 
within approved specifications in line with API Recommended Practice 545 or NFPA 
780 (Lightning Protection Code) or any other approved international standards or 
recommended practice. 
2.6.7 Presentation of Results 
The field data shall show a diagrammatic representation of the tank with the geometric 
dimensions of each shell ring and the tank heads indicated. Other necessary data to be 
reflected are the liquid type and its level in the tank during strapping, cylinder shell thickness 
and that of the heads, and the horizontal inclination of the tank. Tank calibration report shall 
also include the calculations of the volumes of the main cylinder and that of the two heads, 
the spread diameter and the partial volumes of the tank. The appropriate K factor of the 
circular segments of the tank and those of the segments of the heads shall be obtained from 
the standard tables of the reference standard to produce the required calibration chart for 
the tank to be presented in the format shown below: 
Location: 
Date: 
Name/Address of Calibrating Company: 
Name of Operator: 
Tank Identification: