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

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2.5.8.2.3 Both the chart and the field data shall be submitted to the Department of
Petroleum Resources for appropriate review and approval before the tank table
becomes valid for official measurement.

2.5.8.2.4 Representative of the Department of Petroleum Resources shall participate during
the tank charts/table generation.
2.5.9 Optical Reference Line Method (ORLM)
Other methods for calibration of storage tanks include: Optical Reference Line Method
(ORLM): This method employs a mobile magnet trolley or similar device which carries the
measuring rule, up and down the tank height. Applicable standards: API 2.2B, ISO 7507 -2 or
any of its recent revisions.
2.5.10 Optical Triangulation Method:
This type accomplishes calibration through optical methods and the tank profile is
established by triangulation. Applicable standards: API Chapter 2.2C or ISO 7570-3 or its
latest revisions.
2.5.11: General Consideration
2.5.11.1 No false-bottom, capillary, inflatable devices, unapproved deadwoods or similar
design is allowed in storage tanks.
2.5.11.2: For all tank farms, all back-loading lines connected to storage tanks or metering
systems and/or stations shall be flanged off and locked via one-way valve, the key of
the padlock shall be kept in custody of Officer In charge (herein referred to as the
Officer of the Department).
2.5.11.3: Conversely, all petroleum inter-tank transfers, circulation, recirculation,
redistribution, diversion or any similar movement of petroleum or petroleum
products shall be with prior written approval of the Department’s Representative or
Officer In-Charge at the facility. However, for activities that will affect the Non-
resettable totalizer, an approval shall be granted by the Director Petroleum
Resources.
2.6 Calibration of Horizontal Storage Tanks
2.6.1 Accreditation
Any corporate body or institution proposed by an operator to carry out the calibration of
this group of tanks shall be accredited on job by job basis by the Department of Petroleum
Resources. The procedure for securing such accreditation shall be as enumerated in Part III
Section 2.5.1 of this guide.
2.6.2 Principle
The underlining principle for calibrating horizontal tanks is that of computing its incremental
volume from geometric dimensions of the cylindrical main body of the tank and those of
the two heads. Other factor like the deadwood contents of the tank, elasticity of the shells
due to liquid pressure and inclination of the tank to the horizontal are also taken into
consideration.
2.6.3 Frequency of Calibration
The frequency of calibration of Horizontal tanks shall be as outlined in Part III Section 2.5.3
above.