User:Pbsouthwood/Hyperbaric evacuation and rescue: Difference between revisions
== Design and Construction ==
== Design and Construction ==
[[File:Hyperbaric escape module 20151203 133659.jpg|thumb| Small hyperbaric escape module]]
A set of design specifications for various aspects of the hyperbaric evacuation unit are provided by IMCA D 051. These cover towing and lifting points and connections, location aids, transfer under pressure connection flange and clamp details and positions, and service connections, to ensure mutual compatibility of units from different sources.
A set of design specifications for various aspects of the hyperbaric evacuation unit are provided by IMCA D 051. These cover towing and lifting points and connections, location aids, transfer under pressure connection flange and clamp details and positions, and service connections, to ensure mutual compatibility of units from different sources.
Emergency transport of divers under a decompression obligation to a place of safety
Hyperbaric evacuation and rescue are the emergency transportation of divers under a major decompression obligation to a place of safety where decompression can be completed at acceptable risk and in reasonable comfort.[1]
Divers in saturation inside a diving system cannot be quickly decompressed to be evacuated in the same way as other installation personnel. The divers must be transferred to a pressurised chamber which can be detached from the installation’s saturation diving system and moved to a safe location. A hyperbaric rescue unit (HRU) is required that has the capacity to evacuate the maximum number of divers that the diving system can accommodate, with life support to maintain the hyperbaric environment for at least 72 hours. After the initial evacuation, the HRU and its occupants are taken to a designated location
where they can be safely decompressed to surface pressure.[2]
The preferred way is to provide an self-propelled hyperbaric lifeboat (SPHL). Hyperbaric rescue chambers without propulsion (HRCs) are also accepted, but requirements for life support and recovery are complicated by limitations of design and configuration, and the unit must be towed clear of the installation by another vessel. Detailed guidance on hyperbaric evacuation is provided in IMCA D 052 – Guidance on hyperbaric evacuation systems.[2]
Purpose[edit]
Saturation diving is normally done from a saturation system on a diving support vessel or an offshore platform. While under saturation, the divers cannot be decompressed quickly in response to an emergency as that would be rapidly fatal, and though unusual, emergencies requiring personnel evacuation have occurred on such platforms due to extreme weather or accidents. Any attempt to evacuate saturated divers must be done at or very near their saturation storage pressure, in a hyperbaric chamber provided with life support systems which maintain the pressure and temperature, and keep the breathing gas correctly oxygenated and free of excessive carbon dioxide. A hyperbaric evacuation and rescue plan is necessary, and the equipment is normally required to be on standby during all saturation diving operations.[2]
The International Maritime Organization’s Code of Safety for Diving Systems, 1995, provides guidance and recommendations on saturation diving systems including the provision of hyperbaric evacuation facilities. The owners of the ships and installations involved in the diving operations are responsible for providing these contingency plans and equipment, which must cover irreparable damage to life support systems, explosion, fire and other damage or circumstances making it untenable for divers to remain in the saturation habitat.[3]: Sec. 1
The risk to personnel in a hyperbaric evacuation unit is greater than in a full saturation installation, particularly when it is floating independently in the sea, and it should be possible to delay launch until it is clear that no further delay is acceptable, and this implies that the platform or vessel should be designed and constructed to provide a high level of protection to the diving system against fire, loss of stability and critical loss of buoyancy. Hyperbaric evacuation is the last resort, but when it is no longer avoidable it must be possible to launch quickly and safely.[3]: Sec. 1
If the contingency plans include possible decompression in another saturation system, it will be necessary to ensure that the locking on connections are compatible, or an adapter is available. Evacuation by hyperbaric lifeboat or floating capsule may cause severe dehydration of the occupants from motion sickness. Appropriate countermeasures should be available. Premature evacuation could expose the divers to unnecessary risk.[3]: Sec. 1
Requirements[edit]
International Maritime Organization Resolution A.536(13) as amended by resolution A.831(19) provides guidance to minimize…
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