The development and submission of installation safety cases is an activity which has and will in the future utilise a significant level of operators' manpower. The Amerada Hess Ivanhoe/Rob Roy fields safety case was prepared and submitted initially to the HSE as an early voluntary submission for a floating production system and then as the formal safety case submission in June 1993.

This paper will detail how the safety case was developed starting from the 'Forthwith Studies' defined by the Cullen Report. It will detail the various development stages of the document and the changes that were carried out before a satisfactory format was reached. A particular strength identified in the voluntary safety case was the hazard identification and mitigation section, which also includes the hazard inventory. This section will be presented in detail with examples in some of the main hazard groups, namely (i) loss of containment, (ii) dropped object, (iii) marine impact and helicopter crash, (iv) marine system faults, (v) loss of structural integrity and (vi) environmental hazards. The methods used to justly identify the hazards associated with the installation, then qualitatively risk rank and finally, perform quantified risk assessment will be presented. Detailed information on the dropped object studies will be specifically highlighted.

This paper will provide an insight into the development of a safety case which has been reviewed by the HSE, as part of the voluntary safety case exercise. The sharing of the Amerada Hess experience will be of great benefit to those involved in the development of installation safety cases, particularly in the area of floating production systems.


The preparation of the AH001 Safety Case commenced in early 1991 with the voluntary case being presented to the HSE in January 1992. After additional work the formal safety case was submitted in June 1993.

The format of the Safety Case was initially based on the UKOOA Guidelines since at that time guidance from the HSE was not available. It was subsequently altered to the current format following review and discussion.

In general we had a good starting point - the AH001.

The Ivanhoe and Rob Roy fields are located in Block 15/21a - 100 miles north-east of Aberdeen in a water depth of 140 metres.

The AH001 is a conversion of a Sedco 700 series semi-submersible vessel which, for the purpose of certification, is now designated a fixed floating production facility (Fig. 1).

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