HM 86. Guidelines for measurement of crude oil loaded at offshore installations

Overview:

Note: An updated second edition of this publication was released in May 2026. The latest version is now available on the Energy Institute (EI) website and should be consulted for the most up-to-date guidance.

This document focuses on the loading of ships offshore (i.e. not alongside a berth). This type of operation has become much more common with the development of many floating production storage and offloading (FPSO), floating storage offloading (FSO), and floating storage unit (FSU) facilities.

Although general procedures and guidelines for measurement and sampling are available and should be referred to, there are particular issues which need to be considered concerning offshore loadings:

• vessel motion (where tank measurements are used);
• proving facilities (where meters are used);
• free water measurement;
• effects of sediment build-up in export tanks;
• temperature measurement;
• sampling;
• transfer pipeline/hose clearance;
• vapor breakout from oil which is not fully stabilised and can seriously affect meter
  performance, and
• logistical difficulties in attendance of independent inspectors or other cargo
  supervision/measurement personnel.

Movements considered are:

• offshore crude oil transfers (including FPSO, FSO, FSU) where meters are used, and
• offshore crude oil transfers (including FPSO, FSO, FSU) where meters are not used.

Lightering and ship-to-ship (STS) operations are not covered in this document. However, some of the comments and recommendations noted here may apply to these operations.

This document does not address issues relating to ship handling, mooring arrangements, or the mechanical design aspects of the systems involved.