Acrated rctting tanks erectcd by the Ministry of Supply* at H.M. Norfolk Flax Estiibfshmcnt and at othcr flax mills and their method of operation are described. Practical difficulties of aeration and tcmpcrature control are discusscd.
The aerated retting process described by Brandon and Taylor' was introduced at H.M. Norfolk Flax Establishment and at seven standard flax mills. The aerated retting tanks built at the standard mills are much smaller than at H.M. Norfolk Flax Establishment and are of the open type, that is, the hot water storage tank is not superimposed over the retting tanks, but is built separately at such a level that the liquor from any of the retting tanks can be discharged into it by gravity. Both open and closed aerated retting tanks are similar in their essential details and a description of the Norfolk tanks illustrates suffi- ciently the large scale method found to be practicable.
Retting tanks constructed at H.M. Norfolk Flax Estab-
The concrete tanks at H.M. Norfolk Flax Establishment are arranged on the three-tier (Belgian) principle. The lowest tier consists of retting tanks with sliding steel doors, the middle tier comprises the hot water storage tanks, and the top tier consists ofopen cold waterstorage tanks. There are five retting tanks divided into a group of three and another of two. One of the hot water storage tanks and one of the cold water storage tanks cover the whole area occupied by the group of three retring tanks and the other hot and cold water storage tanks cover the area occupied by the group of two retting tanks.
Di,Ne,isions and capacities of rettiiig tanks and storage tanks Retting ranks.-z~ by 18: by 10 ft. (from floor to ceiling), 25 by 18f by 94 ft. (from floor to overflow). Actual volume = 4453 cu. ft. = 27,740 gallons capacity. Hof sforuge futi&s.-(u) Three unit : 25 by 58i by 6 ft. (from floor to ceiling), 25 by 58i by 5& ft. (from floor to overflow) = 8009 cu. ft. Recesses (6 off) = 404 cu. ft. \701 cU. ft. Actual volume = 7308 cu. ft. = 45,520 gallons. (6) Two unit: 25 by 38i by 6 ft. (from floor to ceiling), 25 by 38& by 5i ft. (from floor to overflow) = 5294 cu. ft. Recesses (4 off) = 270 CU. ft. .Actual volume = 4838 cu. ft. = 30,140 gallons. Cold storage tanbs.-Three unit : 26 by 594 by 6 ft. = 9243 cu. ft. Recesses (2 off) = 300 cu. ft. Actual volume = 8943 cu. ft. = 55,700 gallons. Two unit : 26 by 391 by 6 ft. = 6162 cu. ft. Recesses (2 off) = 300 cu. ft. Actual volume = 5862 cu. ft. = 36,520 gallons. IVurcr sirppt'y.-A 12-in. common fill and draw pipe line runs the whole length of the retting tanks with 8411. branch connexions which pass under the floor of each tank to a grate inlet in the middle of the floor, filling the tanks by upward flow. The retting tanks are filled from two verlical Y-piece pipes (two 6-in. bore conuexions welded to an 8411. bore filling header) * At thc time of dcvelopmcnt all flax mills werc administcred by the Ministry of Supply. As from April I, 1946, responsibility for thc Raw Materials Department and Controls other than in the field of enginwring was transfcrrcd from the Ministry of Supply to the Board of Tradc. lishment CO~UIIIIIS (24 off) = 297 CU. ft. J COlUtlltlS (I5 Off) = I86 CU. ft.