Guidance on hyperbaric evacuation systems

Version history

May 2024 Rev. 0.2 – Page 2, reference links, and bookmarking updated; no change to content

August 2018 Rev. 0.1 – Section 5.6 updated to harmonise industry guidance and practice.

May 2013 – Initial publication

Contents

• Introduction
• Background and Explanation
• Medical Aspects of Hyperbaric Evacuation
• Elements to be Considered in the Development of a Hyperbaric
• Evacuation System
• Equipment and Interfaces
• Development of Documentation for Hyperbaric Evacuation
• System Construction and Operation
• Elements to be Considered for the Execution of a Hyperbaric
• Evacuation and Subsequent Decompression
• Operational Emergency
• Risk Assessment/Hyperbaric Evacuation Plan Guidance
• Personnel and Competence (LSP/HRF)
• Audit and Assurance
• Appendix 1 – Acronyms
• Appendix 2 – Glossary

Summary

When a vessel is severely damaged and likely to sink (or subject to other dangers such as a serious fire) there may come a time when it has to be abandoned. For such a situation vessels are required to have adequate lifeboats (or life rafts) on board for all personnel.
In such an emergency, the evacuation of divers in saturation inside a diving system represents a particular problem as they cannot be readily decompressed in order to be evacuated in the same way as other crew members. The divers need to be transferred to a pressurised compartment which can be detached from the diving system on the vessel and launched or floated into the sea.

Therefore for all saturation diving operations a hyperbaric rescue unit (HRU) needs to be provided that, in the event of a vessel (or structure) evacuation, is capable of evacuating the maximum number of divers that the diving system is capable of accommodating then maintaining the divers at the correct pressure with life support for a minimum of 72 hours. Planning and facilities also need to be in place to ensure that, after the initial evacuation, the HRU and its occupants are taken to a designated location where they can be decompressed back to surface pressure in a safe and controlled manner.

The most practical, and most common, way of meeting these requirements is to provide an HRU made up of a pressure vessel mounted inside a conventional lifeboat body. The lifeboat is self-propelled and often uses the engine to provide elements of the life support. Such a unit is called a self-propelled hyperbaric lifeboat (SPHL). At the time of publication of this document a number of HRUs exist (HRCs) that are not self-propelled and while the long term intent of the industry is that all HRUs are self-propelled, it is recognised that these units do provide a means of escape for divers in an emergency although the subsequent requirements for life support and recovery may be much more difficult to comply with due to limitations of design and configuration.

This document aims to provide guidance on minimum requirements needed to achieve these goals and to identify the various factors that need to be considered during the planning phase before diving commences. It also aims to provide guidance on the risk assessment process required to ensure that the necessary standard of safety is achieved.

A number of these sections can be used for checking/audit purposes of specific parts of the hyperbaric evacuation system (HES) planning and risk assessment process. As a result of this approach there is an inevitable duplication of some items in more than one section and it should be understood that in most cases complying with the requirements in one section will also result in complying with this requirement in another section.

This document also seeks to establish standard terminology for the various parts of a hyperbaric evacuation system. Appendices 1 and 2 give lists of acronyms and the definitions for the terms used.

As this document contains many items of technical advice without giving detailed explanations, it is assumed that the reader has knowledge of saturation diving technology, physiology and equipment.