After safely grounding yourself and the tape, slowly lower the bob and tape into the tank until a small portion of the bob is immersed in the liquid. Record the tape reading at the reference gauge point, which is the amount of tape that has been lowered into the tank. Withdraw the tape from the tank and read the liquid cut on the tape. If you are using an outage tape, add the reading on the bob to the tape reading at the reference gauge hatch. If you are using an innage tape, subtract the reading on the bob from the tape reading at the reference gauge hatch. 3.2.6 Gauging for Free Water Although it is acceptable to use either the innage or the outage method when gauging for free water, the recommended procedure for free water gauging is the innage method . Apply a thin coat of water paste to the tape bob, making sure that the measurement scale remains free of paste. Allow the bob to remain in the gauging position for at least 10 seconds for light products such as gasoline and diesel; and, from 1 to 5 minutes for heavy oils.
A clear line of demarcation will give evidence of the water cut; and this is to be recorded as the water cut. If spotting is observed above the solid cut, it should be noted but not used as the water cut.
Your tape should have an SGS calibration record. This certificate is kept with the inspector or in a calibration logbook in the office. Gauges should not be taken from unslotted standpipes. If this situation occurs, contact your supervisor for instructions. 3.2.5.1 Innage Gauging The following procedures are to be used when taking a liquid level gauge using the innage method. • After safely grounding yourself and the tape, slowly lower the bob and tape into the tank, at the reference gauge point, until the tip of the bob barely touches the tank bottom or datum plate. • Note the observed reference height and compare it to the recorded reference height, which you obtain from the tank capacity table prior to gauging. • Withdraw the tape from the tank until the liquid cut is observed; and note this reading as the innage gauge. 3.2.5.2 Outage Gauging The following procedures are to be used when taking a liquid level gauge using the outage or ullage method.
Innage
Gauge tape
Reference gauge point
Gauge hatch
Liquid level
Tank shell
Bob coated with paste
Water cut
Water innage
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