page_title: Standard diving dress
section_title: Twelve bolt equipment
hierarchical_section_title: Standard diving dress / Variations / Twelve bolt equipment
caption_attribution_description: English: cropped three quarter right view of 12 bolt 4 light diving helmet
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 Standard diving dress has largely been superseded by lighter and more comfortable equipment.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: In twelve bolt equipment the rim of the corselet is clamped to the gasket of the suit, using brass brails to spread the load evenly.
  Twelve bolt equipment was manufactured in the UK by Siebe-Gorman and Heinke, in France by Rouquayrol-Denayrouze, and in the US by several manufacturers for the US Navy.
caption: Twelve bolt helmet, showing the spit-cock
exif: {}