Air lock diving-bell plant

The barge as depicted in a painting by Charles Pears[1][2]

Gibraltar Harbour's air lock diving-bell plant, or caisson diving bell barge, was a purpose-built barge for the laying, examination and repair of moorings for battleships.[1][2][3][4] It was designed by Siebe Gorman & Company of Lambeth and Forrestt & Co. Ltd of Wivenhoe in Essex, who built and supplied it in 1902 for the British Admiralty.[1]

Local conditions at Gibraltar dictated the need for such a craft. The heavy harbour moorings have three chains extending out radially along the seabed from a central ring, each terminating in a large anchor. Most harbours have a soft seabed, and it is usual to lay down moorings by settling anchors in the mud, clay or sand, but this could not be done in Gibraltar harbour where the seabed is hard rock.[5]

For Gibraltar the seabed needed to be dug out sufficiently for an anchor point to hold. The barge would be towed over the work site, moored in place with anchors, and the bell would be lowered to the seabed.[6][3][7] Air pumped into the bell would displace the water, and workers accessed the bell through the airlock in the central access shaft.[3][7] This system allowed continuous work with changes of workmen in four-hour shifts,[3][7] and allowed men to work on the seabed in normal work clothing.[5]

In 1969 the Gibraltar Chronicle reported the plant as still working in the harbour; it was believed to be the only vessel of its type in the world.

  1. ^ a b c Cite error: The named reference ILN 1906 was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference The Times 1917 was invoked but never defined (see the help page).
  3. ^ a b c d Cite error: The named reference Davis 1909 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Gibraltar Chronicle 1969 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Encyclopædia Britannica 1911 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference divinglocker was invoked but never defined (see the help page).