the submarine. Figure 8 shows one of the sections being lifted by crane around
the submarine.
The lower edges of the tank were bonded to a load-bearing concrete dish,
which had been previously laid beneath the submarine and also incorporated the
steel cradle, which had supported the hull while on display at the museum for
the previous 13 years. In order to strengthen the tank, steel ribs were inserted
within the laminate at regular intervals along its length. Cross braces of 15 mm
steel cables were passed through the hull of the submarine to give further
reinforcement when the tank was full of the electrolyte. The total volume of
liquid contained within the tank was 820,000 dm^3 and this posed a problem in
the choice of electrolyte. Figure 9 shows the completed tank for the aqueous
washing of the submarine. Permission had to be sought to dispose of this
quantity of solution into public sewers. In addition, in the event of a leak
developing in the tank, the solution could flow into Portsmouth Harbour as the
submarine was only approximately 50 m from the harbour wall. Sodium
hydroxide was deemed to be unsafe by the local authority and sodium car-
bonate was the solution chosen to meet both conservation and environmental
requirements. To ensure that the concentration of carbonate and chloride
remain uniform throughout the tank, a re-circulating pumping system was
installed. The electrolyte in the tanks returned to the pump via a stainless steel
mixing pump. The emptying of the tank to remove the dissolved chloride ions
took place via a valve located in the floor of the vessel, which exits directly into
the public drainage system.
148 Chapter 6
Figure 8A fibre glass panel being positioned to form a cell around the submarine