Editing Reefer ship (section)

== Description ==
''Types of reefers:'' Reefer ships may be categorised into three types:<ref>{{cite web |url=http://crosstree.info/Documents/reefer%20vessels.pdf |last=Kohli |first=Pawanexh |date=July 2000 |title=Reefer Vessels – An Introduction |publisher=CrossTree Techno-visors |access-date=2009-03-22 |archive-date=2009-03-26 |archive-url=https://wayback.archive-it.org/all/20090326013334/http://crosstree.info/Documents/reefer%20vessels.pdf |url-status=dead }}</ref>
# '''Side-door vessels''' have water-tight ports on the ship's hull, which open into a cargo hold. Elevators or ramps leading from the [[quay]] serve as loading and discharging access for the [[forklift]]s or [[conveyor]]s. Inside these access ports or side doors, pallet lifts or another series of [[conveyor]]s bring the cargo to the respective decks. This special design makes the vessels particularly well suited for inclement weather operations as the tops of the cargo holds are always closed against rain and sun.
# '''Conventional vessels''' have a traditional cargo operation with top opening hatches and [[crane (machine)|crane]]s/[[derrick (lifting device)|derrick]]s. On such ships, when facing wet weather, the hatches need to be closed to prevent heavy rain from flooding the holds. Both above ship types are well suited for the handling of palletized and loose cargo.
# '''Refrigerated [[container ship]]s''' are specifically designed to carry containerised unit loads where each container has its individual refrigerated unit. These containers are nearly always twenty-foot equivalent units (often called TEU) that are the size of "standard" cargo containers that are loaded and unloaded at container terminals and aboard [[container ship]]s. These ships differ from conventional container ships in their design, power generation, and electrical distribution equipment. They need provisions made for powering each container's cooling system. Because of their ease of loading and unloading cargo many container ships are now being built or redesigned to carry [[refrigerated container]]s.

[[File:Unloading frozen meat from 'Clan MacDougall'.jpg|thumb|Unloading frozen pork from the [[Clan Line]] ship ''Clan MacDougall'' in the mid-20th century]]
A major use of refrigerated cargo hold type ships was for the transportation of bananas and frozen meat, but most of these ships have been partly replaced by refrigerated containers that have a refrigeration system attached to the rear end of the container. While on a ship these containers are plugged into an electrical outlet (typically 440 [[Alternating current|VAC]]) that ties into the ship's power generation. Refrigerated container ships are not limited by the number of refrigeration containers they can carry, unlike other container ships which may be limited in their number of refrigeration outlets or have insufficient generator capacity. Each reefer container unit is typically designed with a stand-alone electrical circuit and has its own breaker switch that allows it to be connected and disconnected as required. In principle each individual unit could be repaired while the ship was still underway.

Refrigerated cargo is a key part of the income for some shipping companies. On multi-purpose ships, refrigerated containers are mostly carried above deck, as they have to be checked for proper operation. Also, a major part of the refrigeration system (such as a compressor) may fail, which would have to be replaced or unplugged quickly in the event of a fire. Modern container vessels stow the reefer containers in cellguides with adjacent inspection walkways that enable reefer containers to be carried in the holds as well as on the deck. Modern refrigerated container vessels are designed to incorporate a water-cooling system for containers stowed under deck. This does not replace the refrigeration system but facilitates cooling down of the external machinery. Containers stowed on the exposed upper deck are air-cooled, while those under deck are water-cooled. The water cooling design allows additional refrigerated containers under deck, as water can be used to dissipate the high amount of heat they generate. This system draws fresh water from the ship's water supply, which in turn transfers the heat through heat exchangers to the abundantly available sea water.

[[File:Dole Honduras in San Diego.jpg|thumbnail|The reefer ship ''Dole Honduras'' unloading bananas in the [[Port of San Diego]]]]
There are also refrigeration systems that have two compressors for very precise and low-temperature operations, such as transporting a container of blood to a war zone. Cargoes of shrimp, asparagus, caviar and blood are considered among the most expensive refrigerated items. Bananas, fruit and meat have historically been the main cargo of refrigerated ships.