GAS SHIP MEASUREMENT GUIDELINES

These guidelines were developed in 1998/99 for Exxon Chemical Europe Inc., Basic Chemicals Europe by Captain C. Allport of Standard Marine Services Limited and replace earlier guidance. They are based upon the report and advice from an LPG Measurement Survey conducted by Srini Sivaraman of ER&E in May/June 1997 and incorporate the earlier guidelines for Liquefied Gas Cargo Measurement and Calculation, produced in 1987 for Exxon Chemicals International by the Centre for Advanced Maritime Studies, Edinburgh.

The earlier guidelines were adopted by Exxon Chemical International Inc. and approved by Regional Audit in 1988. The key to accurate cargo measurement based upon ship's figures depends on the precision of the tank calibration and calibration of associated level, temperature and pressure measuring devices in addition to the use of consistent methodology. Conformance to the recommendations made in these guidelines will result in transfer custody quality that is within the expectation of Exxon Corporation controls. The practices and procedures described in this document provide guidance for improving or maintaining liquefied gas measurement level of uncertainty within the accuracy requirements of Exxon's Hydrocarbon Measurement Practices (HMP) .

Contrary to the general recommendations contained in the HMP, these practices and procedures will demonstrate that quantity determination can be based upon ship or barge measurement. Custody transfer integrity is comparable to and in some cases can be better than shore systems and match HMP requirements.