STRUCTURAL DEFICIENCIES OF NATURAL DRAFT COOLING-TOWERS AT UK POWER-STATIONS .3. STRENGTHENING OF NATURAL DRAFT COOLING-TOWER SHELLS

The repair and strengthening of a number of concrete natural draught cooling towers have been completed by National Power. The schemes followed assessment Central Electricity Generating Board (CEGB) towers instigated after the collapse of towers at Ferrybridge (1965), Ardeer (1973) and Fiddlers Ferry (1984). Strengthening works involve techniques developed by the CEGB, some of which are thought to be unique to this form of construction. The design and construction of external mantles around existing shells are described. Details are given of the use of fly ash concrete in cast in-situ mantles and of sprayed concrete work. Detailed survey and inspection techniques for concrete cooling tower, shells are reported. The methods of assessment are; discussed, and procedures for, and examples of, resin injection of cracked shells and a unique repair using parafil ropes as an external girdle to contain a tower shell against failure are presented.