Standby Vessel Rescue of Personnel from Offshore Platforms - Section 2

Study Approach

The study commenced in 1994 and investigated various arrangements for rescuing personnel from the sea. The arrangements had to satisfy the requirements of the then proposed UK legislation, which later came into being as the Offshore Installations (Prevention of Fire and Explosion and Emergency Response) Regulations 1995 (SI 1995/743).

The new regulations (PFEER) required operators of offshore oil and gas installations to foresee emergencies and to put into place sufficient recovery and rescue arrangements. This involved establishing performance standards so that personnel who escaped to the sea would be recovered alive and in reasonable health.

In all, nearly 30 different standby vessel sharing schemes were investigated as part of the study. These schemes fell within the following broad categories:

No standby vessel sharing

Each installation would be provided with a dedicated standby vessel. This was in fact the 1994 method of working, when the Operator deployed up to nine standby vessels per day to support the various work fronts in the field.

Conventional standby vessels shared between installations

Conventional standby vessels are equipped with two open fast rescue craft; typically rigid inflatable boats of around 20 ft in length and operated by a three-man crew. Sharing involves placing the standby vessels in positions such that one vessel can support all installations within a defined radius. The use of open fast rescue craft has the disadvantage that rescued personnel are still exposed to the elements until brought back onto the mother vessel.

Enhanced standby vessels shared between installations

This arrangement has become widely known in the UK as a mother vessel/daughter craft arrangement. A mother vessel is basically a conventional standby vessel. The daughter craft are fully enclosed vessels, 30 to 40 ft in length, each with a 3 to 4 man crew depending on operational requirements. The daughter craft are launched and recovered using constant tension, motion-compensated davit systems that allow safe launch and recovery in higher seastates than do conventional systems. As well as serving as fast rescue craft, the daughter craft can operate as standby vessels in their own right in suitable weather conditions, and subject to Marine Safety Agency (MSA) limitations. Rescued personnel are effectively safe when brought onto the enclosed daughter craft, whereas they are still vulnerable to hypothermia when brought onto a conventional, open rescue craft. The daughter craft length of 30-40 ft is also an optimum for typical North Sea conditions, allowing the maximum possible speed to be maintained in most sea states. The conventional, smaller rescue craft perform just as well in calm seas but suffer a much greater loss of speed in heavier seas.

Platform-based rescue craft

Consideration was given to the possible deployment of daughter craft (craft as described above) from manned platforms rather than from mother vessels.

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