JIM suit
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The JIM Suit is probably the most well-known atmospheric diving suit (ADS), which is designed to maintain an interior pressure of one atmosphere despite exterior pressures, and which eliminates the majority of physiological dangers associated with deep diving; the occupant need not decompress, there is no need for special gas mixtures, and there is no danger of nitrogen narcosis or decompression sickness (the 'bends'). It was invented in 1969 by Mike Humphrey and Mike Borrow, partners in the English firm Underwater Marine Engineering, assisted by Joseph Salim Peress, whose Tritonia atmospheric diving suit acted as their main inspiration. The suit was named after Jim Jarrett, Peress's chief diver.
The petrochemical industry was unwilling to finance their research, but a grant was obtained from the British government, and a new company, DHB Construction (for Dennison, Hibberd and Borrow), was formed to develop the suit. The first JIM suit was completed in November 1971 and underwent initial trials aboard HMS Reclaim in early 1972. Two dives were conducted to depths in excess of 400 feet (121 m), and were limited only by the depth of the ambient divers providing support. Further development and testing continued until March 4, 1974, when Mike Humphrey conducted a chamber dive to the equivalent of 1,000 feet (300 m).
In spite of the successful tests, the offshore petroleum industry still expressed little interest in the suit and it was not until 1975, when Oceaneering acquired DHB Construction and exclusive rights to the application of JIM suits in the oilfields, that the suit achieved success. In 1976 the JIM suit was used for a series of four dives on PanArtic's Hecla M25 well which were made through a hole cut in an ice floe 16 feet (5 m) thick, on which the rig was positioned, the first dive setting a record for the longest working dive below 490 feet (149 m), five hours and 59 minutes at a depth of 905 feet (275 m). In 1979, oceanographer Sylvia Earle made the first open-ocean dive, setting a women's depth record of 1250 feet (381m).
The Arctic dives proved that the JIM was capable of performing oilfield operations in very cold and very deep water; the average water temperature at the wellhead was measured at 29 °F, while the average internal suit temperature was about 50 °F. The operators needed no more than a heavy wool sweater for thermal protection. The following year the JIM suit was used on over 35 jobs with an average duration of over two hours and in depths varying from 300 to 1,130 feet (100 to 394 m), and by 1981 there 19 JIM suits had been produced.
The first JIM suits were constructed from cast magnesium for its high strength-to-weight ratio and weighed approximately 1,100 pounds in air including the diver. Corrosion problems were countered through surface preparation and coating. The suit had a negative buoyancy of 15 to 50 pounds. Ballast was attached to the suit's front and could be jettisoned from within, allowing the operator to ascend to the surface at approximately 100 feet (30 m) per minute. The suit also incorporated a communication link and a jettisonable umbilical connection. The original JIM suit had eight annular oil-supported universal joints, one in each shoulder and lower arm, and one at each hip and knee.
The magnesium construction was later replaced with glass reinforced plastic (GRP) and the single joints with many segmented joints, each allowing seven degrees of motion, and when added together giving the operator a very great range of motion. In addition, the four-port domed top of the suit was replaced by a transparent acrylic one that allowed the operator a much-improved field of vision. The fiberglass suit was known as the JAM suit. A lighter more and anthropomorphic suit was built of aluminum or GRP, and was known as the SAM suit. The aluminum model was rated to 1,000 feet (300 m) and the fiberglass suit was rated to 2,000 feet (610 m).
Special JIM suits have been developed by UMEL for the US Navy with bodyshells constructed of carbon fibre reinforced plastic.
