Expanded Tube Joints in Boiler Drums with Special Reference to the Battersea High-Pressure Boilers:

Particulars are given of the major pressure parts of two high-pressure boilers installed at Battersea Power Station, each comprising four alloy steel drums and their interconnecting mild steel tubing. Their design and working conditions are described, and a historical review is presented of their erection and of problems which arose whilst rendering the expanded tube joints leakproof. The gradual resolution of these problems is then traced through several stages. It was realized that the leakage was fundamentally due to the elastic strain which occurs in the tube holes of highly stressed drums, which, at Battersea, amounts to about twice that pertaining to mild steel drums. The holding power of the joint is thus relaxed to an abnormal extent, sufficient to permit leakage. The elastic deflexions, or total “spring” of the joint, resulting from the expanding operation, must therefore be correspondingly increased to accommodate the increased drum strain.Various suggested methods of achieving this are reviewed...