page_title: Standard diving dress
section_title: Air supply
hierarchical_section_title: Standard diving dress / General description / Air supply
caption_attribution_description: English: Pressure gauge on Siebe Gorman manual diver's pump
context_page_description: Standard diving dress is a type of diving suit that was formerly used for all relatively deep underwater work that required more than breath-hold duration, which included marine salvage, civil engineering, pearl shell diving and other commercial diving work, and similar naval diving applications. Standard diving dress has largely been superseded by lighter and more comfortable equipment.
  Standard diving dress consists of a diving helmet made from copper and brass or bronze, an air hose from a surface-supplied manually operated pump or low pressure breathing air compressor, a waterproofed canvas suit, a diving knife, and weights to counteract buoyancy, generally on the chest, back and shoes. Later models were equipped with a diver's telephone for voice communications with the surface.
  Some variants used rebreather systems to extend the use of gas supplies carried by the diver, and were effectively self-contained underwater breathing apparatus, and others were suitable for use with helium based breathing gases for deeper work. Divers could be deployed directly by lowering or raising them using the lifeline, or could be transported on a diving stage.
context_section_description: Originally supplied with air by a manually operated diver's air pump. Later also supplied by mechanised compressors, but the manual pump remained an option well into the 20th century. Air was supplied through a hose, and a rope strength member added to support the weight of the diver. Later a telephone cable was added and the diver's umbilical was the result of combining these items. Air supply passes through a non-return valve at the connection to the helmet, which prevents back flow if the hose is cut.
  Flow of air through the helmet could be controlled by manually adjusting the back-pressure on the helmet exhaust valve, usually on the lower right side of the bonnet, and by manually adjusting the inlet supply valve on the airline, usually fastened to the front lower left of the corselet. Flow rate would also be affected by the surface delivery system and depth. Manual pumps would be operated at the speed necessary for sufficient air supply, which could be judged by delivery pressure and feedback from the diver. Many manual pumps had delivery pressure gauges calibrated in units of water depth - feet or metres of water column - which would provide the supervisor with a reasonable indication of diver depth.
caption: Pressure gauge on Siebe Gorman manual diver's pump, indicating delivered pressure in pounds per square inch (black) and feet sea water (red)
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