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 Underside of theResearch VesselWestern Flyer, showing its moon pool between the two hulls | |
| Other names | Wet porch, wet room, wet bell |
|---|---|
| Uses | Protected access to the water for divers from a vessel, floating platform or underwater habitat |
Amoon pool is an equipment deployment and retrieval feature used bymarine drilling platforms,drillships,diving support vessels,fishing vessels,marine research andunderwaterexploration orresearch vessels, andunderwater habitats.[1] It is also known as awet porch.[2] It is an opening found in the floor or base of thehull, platform, or chamber giving access to the water below. Because of its stable location, it safely allowstechnicians orresearchers to lowertools andinstruments into the sea.
Moon pools also provide shelter and protection so that even if theship is in high seas or surrounded by ice, researchers can work in comfort rather than on a deck exposed to the elements.[3] A moon pool also allows divers, diving bells, ROVs, or smallsubmersible craft to enter or leave the water easily and in a more protected environment.
Moon pools can be used in chambers below sea level, especially for the use ofscuba divers, and their design requires more complex consideration of air and waterpressure acting on the moon pool surface.
Moon pools were first used in theoil drilling industry given the remote offshore locations of oil fields (e.g. sea or in lakes). It has been used for drilling, production, storage and offloading to smaller vessels for transportation of oil. It is also built to pass drilling equipments into the water from a platform or drillship.[4][5] A moon pool supports the need of drill pipes to run vertically through the structure or hull.
The HughesGlomar Explorer was a 50,500 long tons (51,300 t), 619-foot-long (189 m) ship constructed by the United States in the early 1970s for therecovery of a sunken Soviet submarine from the Pacific seabed. The design of the ship was broadly inspired by oil drilling ships and included a moon pool measuring 199 by 74 by 65 feet (61 m × 23 m × 20 m), into which the submarine was to be recovered, with the bottom of the moon pool then closed off by two gates that would allow the recovered vessel to be examined under cover and in dry conditions. This was a singular use of a moon pool and also possibly the largest dedicated moon pool constructed to date.
Very deep moon pools are used inunderwater habitats—submerged chambers used by divers engaged in underwater research,exploration,marine salvage, andrecreation. In this case, shown in part D of the diagram, there is no dry access between the chamber and the sea surface, and the moon pool is the only entry or exit to the chamber. Submerged chambers provide dry areas for work and rest without the need to ascend to the surface.[6] This kind of submerged chamber uses the same principles as thediving bell, except they are fixed to the seafloor and may be called awet porch,wet room, orwet bell. Sometimes the term moon pool is used to mean the complete chamber, not just the opening in the bottom and the air–water interface.
The alternative to a moon pool in an underwater habitat is thelock-out chamber, which is essentially like a fixedsubmarine, maintaining internal air pressures lower than ambient sea pressure down to oneatmosphere, with anairlock to enable entry and exit underwater. Underwater habitats may have connected chambers with moon pools and lock-out chambers.
Moon pools are becoming increasingly used onlonglinefishing vessels to allow for hauling of the gear in worse weather conditions. They also reduce the exposure of fish to air, improving quality. Along with bird scaring lines, shooting and hauling gear from a moon pool reduces the risk of fish falling off or being predated by birds.[9]
