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

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19 | P a g e

2.3.4.2 Shall be used according to the equipment manufactures’ specification or as specified
in API MPMS 3.1A and 17.
2.3.5 Precautions to be Taken Prior to Commencement of Manual Gauging
2.3.5.1 The petroleum or petroleum product’s surface in the tank shall be free of foam or
waves due to agitation.
2.3.5.2 The tape shall be rubbed with paste to give a good contrast (cut) between the
portions wetted by petroleum or petroleum product from the remaining dry portion of the
tape on withdrawal.
2.3.5.3 The gauge hatch shall be free of any debris from the roof to the datum plate.
2.3.5.4 To avoid static electricity hazards, it shall be ensured that the bob has contact with
the gauge hatch before the bob touches the liquid level. The gauge shall be properly earthed
before gauging. Also, gauging of a tank during a rain storm shall not be allowed.
2.3.6 Manual Gauging Sequence
2.3.6.1 The approved gauging procedure shall be by the innage method for floating and fixed
roof storage tanks, and ullage method for special purpose vessels. The sequence to follow
in carrying out the exercise shall be as outlined below:
2.3.6.2 Innage Method
2.3.6.2.1 The steel tape shall be gradually lowered through the dip hatch situated on the roof
of the tank.
2.3.6.2.2 The first dip is usually done for confirming reference height of storage tanks. If the
reference height as checked does not agree with that stamped on the tank, then, other
things shall be checked e.g. datum plate for debris/sediments, or if gauge hatch has an
obstruction along the length.
2.3.6.1.3 The tape is then reeled back on the pulley and the last mark where the petroleum
or petroleum product wets the tape is read and taken as the tank dip. It is very essential that
care be taken to avoid either the sagging of the tape or its deviation from the vertical plane
as this could introduce appreciable errors into the gauge reading. The exercise is repeated
until two consecutive identical gauges are obtained. Acceptable readings are illustrated as
follows:
Sequence
Gauges Obtained
Remarks

1st Gauging
1st Reading
6m 400mm

Not Acceptable
2nd Reading
6m 399mm
3rd Reading
6m 400mm

2ndGauging
1st Reading
6m 399mm

Acceptable
2nd Reading
6m 400mm
3rd Reading
6m 400mm

3rd Gauging
1st Reading
6m 400mm

Acceptable
2nd Reading
6m 400mm
3rd Reading
6m 399mm