Auxiliary Equipment

Large p.v.c. aprons, each measuring 120 × 30 ft. and weighing nearly half a ton, have recently been made for the Ministry of Supply for lining test areas where petrol tanks of up to 30,000 gallon capacity are subjected to impact and other tests. In use, the aprons are draped inside and over the sides of a sandbagged dispersal, and their purpose is to prevent the wastage of large quantities of petrol in the event of a tank bursting or splitting. The aprons were welded from Vybak VB.177 sheet of 0020 in. thickness by Plysu Products Ltd., Woburn Sands. This special grade of p.v.c. sheeting makes use of a polymeric plasticizer, and is thus resistant to the solvent action of petrol, which is liable to leach out conventional plasticizers. The aprons were made by welding sheets of Vybak together using an RF welder mounted on a wheeled chassis. Two operators were involved in the fabrication, one guiding the p.v.c. sheet, the other manipulating the RF welder. Vybak VB.177 p.v.c. sheet is supplied by Bakclite Ltd., 12–18 Grosvenor Gardens, S.W.1.