Henry Valence "Val" Hempleman (25 March 1922 - 14 July 2006) was a researcher in the field ofdiving decompression.[1][2]
Val Hempleman was the son of Harry Hempleman, a sea captain on the UK-New Zealand route. He was born in at Neasham, Darlington and moved to Hull as a boy. He won a scholarship toHymers College, Hull,[2] followed bySt Catharine's College, Cambridge, where he studied inorganic chemistry and physics. This was interrupted by the Second World War, and he was called up to the Royal Navy and became a research assistant at the physiological laboratoryVernon II atHMSDolphin in Gosport, where he was involved in experimental work assessing the effects of explosions on immersed personnel. After the war he continued his studies, and received an honours degree in chemistry. In 1946 he was employed at the Wellcome Physiological Research Laboratory in Beckham, Kent, where he worked on chemotherapeutic agents for the treatment ofpertussis infections.[1]
In 1949 he rejoinedVernon II, which had become theRoyal Naval Physiological Laboratory, as a scientific officer, and was soon involved in the development ofdecompression tables. In 1952 he published a paper ondecompression procedures and the calculation ofdecompression schedules. Further work involved decompression from greater depths to develop the Royal Navy's capacity for rescue from disabled submarines.[1]
In 1960 he started work on decompression forcompressed air workers, applicable tocaisson and tunneling operations, and in 1966 published theBlackpool Decompression Tables, which became an internationally accepted industry standard. He was appointed superintendent of the RNPL in 1968 and soon thereafter was awarded his PhD for research into prevention ofdecompression sickness. Experimental work in the use of helium basedbreathing gases resulted in a record breakingchamber dive in 1970 by associated researchers to 1,535 feet (468 m), followed in 1980 by a simulated depth of 2,165 feet (660 m) at the same facility.[1]
In 1972 the RNPL published decompression tables based on Hempleman'stissue slab diffusion model.[3]
Thecritical volume concept was developed byT. R. Hennessy and Hempleman who formulated a simple mathematical condition linking the dissolved gas and the safe ascent pressure:
Where Ptissue represents the dissolved gas tension, Pambient, the ambient pressure and two coefficients, a and b. This linear relationship between dissolved gas and ambient pressure has the same mathematical form as anM-value, which suggests that all the dissolved state models using M-values (including the US Navy tables previous to those based on theExponential–Linear model, theBühlmann tables and all the French Navy tables), may be considered expressions of the critical volume criterion, though their authors may have argued for other interpretations.[4] He retired in 1982.[1]
Between 1974 and 1976 Hempleman was involved in the tests of the "Jim",atmospheric diving suit to depths of up to 1,500 ft.[2]
In 1951, Val Hempleman married Barbara Smith, a co-worker at RNPL, who survived him with their two sons.[2]
Cowan, Mark; Robson, Martin (22 July 2021).Between the Devil and the Deep: One Man's Battle to Beat the Bends. Unbound.ISBN 9781800180291.
