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

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1.16.3 Determination of Density
There are three ways of determining density:
• Measuring its average value directly in the LNG carrier’s tank by means of
densitometers.
• Calculated based on an average composition of LNG in accordance with ISO
6578 and the revised KLOSEK-McKINLEY method.
• Using gas chromatograph.

1.17 DETERMINATION OF TEMPERATURE AND PRESSURE

1.17.1 PRESSURE
At the time of gauging, the pressure in the cargo tanks shall be arithmetic average of the
absolute pressure indicating device for each tank. One absolute pressure indicating device
shall be fitted to the vapor space of each tanks and shall be accurate to ±5 mbars or a range
800mbars to 1,400mbars absolute for purpose of calculation.

1.17.2 Temperature
At the times of gauging, the liquid temperature of the cargo shall be determined by
calculating the arithmetic average of temperature indicated by the temperature resisting
devices immersed in the LNG in all the tanks. Each tank has a minimum of 5 devices
distributed over the entire height of the tanks and shall be accurate to ±0.2 ◦C above the
range of -145◦C to -165◦C. (±1.5◦C outside the range). The vapour temperature shall be the
arithmetic average of the temperatures indicated by the temperature devices which at the
time of gauging are in the vapor space above the surface of the LNG. These temperatures
shall be printed before and after the loading and unloading operations for calculating
average temperature of LNG liquid and LNG vapor and shall be rounded to one decimal
place in degree Celsius.

1.17.3 Sampling determination of composition of LNG in accordance with ISO 8943.

1.17.3.1 Sampling and vaporization of LNG shall be taken at both loading and unloading
in the presence of DPR representatives.
1.17.3.2 LNG samples shall be taken at different time intervals between the duration of
the loading. Samples can be taken automatically or manually.
1.17.3.4 The calibration of the chromatograph utilized during sampling shall be done in
accordance with ISO 1411.
1.17.3.5 Each set of samples obtained during loading or unloading shall be distributed as
follows:
i.
First cylinder - for use of seller at loading or buyer at unloading establishing
the LNG composition for custody transfer by chromatographic analysis.
ii.
Second cylinder - for retention by seller at loading or buyer unloading for a
period of twenty (20) days after the analysis of the first portion has been
reported to the other party during which period any question as to the
accuracy of any analysis shall be raised. In such case, the portion shall be used
as buyer and seller may mutually agree; and
iii.
Third cylinder - for the use by an independent surveyor.