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

Page 69 of 114

68 | P a g e

2.5.6.2 Presentation of Results
2.5.6.2.1 The calibration chart shall bear the full name and address of the calibration
company, the tank number, name of operator, location of tank farm and other
parameters indicated in the format shown in 2.5.8.2.2 below.
2.5.6.2.2 The tank table/chart shall also contain a column in which the approval of the
Director of Petroleum Resources to the use of the tank table shall be endorsed.
2.5.6.3 General Consideration
Serious attention shall be paid to the following factors which shall be adequately
compensated for in the tank table:
2.5.6.3.1 Expansion and contraction of the tank shell under liquid head and temperature.
2.5.6.3.2 Effect of tilt on cylindrical portion of the tank.
2.5.6.3.3 Alignment of the tank bottom
The actual strapping and measurement shall generally follow the procedure described in
the reference standard to obtain the necessary parameter of circumference, shell plate
thickness, height, temperature and gravity of the oil in the tank during strapping.

2.5.6.3.4 Deadwood
The size and locations of the “Deadwood” in the tank shall be accurately determined and
reflected in the field report.
2.5.6.3.5 Floating Roof Adjustment (Correction) Factor
Tanks fitted with floating roofs shall have proper provisions made in the tank table for
computing float roof effect.
The weight of the roof and all its appurtenances shall be separately determined and
reflected in the tank table.
2.5.6.3.6 Critical Zone
All tanks with floating roofs shall have their “critical zones” calibrated with liquid in
accordance with API 2555 or ASTM –D1406. A separate calibration chart for the critical zone
shall be prepared for each tank of this type.
2.5.7 Electro-Optical Distance-Ranging method
2.5.7.1 Calibration Equipment/instrument
These shall be as stated in the reference standards and instrument to be used shall comply
with appropriate specifications including 5.1 of ISO 7507-4.
The tank bottom shall also be calibrated by the liquid method in accordance with API
Standard 2.2A by use of the electro-optical ranging instrument, a surveyor’s level, or by use
of water-filled tubes.
2.5.7.2 Calibration Procedure
Target points shall be sighted along the horizontal plane at each course location, and
measure the slope distance, horizontal angle and vertical angle to each of the reference
target points. After all measurements on a course are completed, repeat the measurements