Patent GB-888106-A (GB)
Title: Improvements in shot cleaning systems
Inventor: MCCOLL WILLIAM
IPC: F28G3/16
Filed: 1959-10-09
Abstract: 888,106. Cleaning pipes. BABCOCK & WILCOX Ltd. Sept. 21, 1960 [Oct. 9, 1959], No. 34281/59. Glass 99(2). In a shot cleaning system having recovery hopper means 7 containing the shot and collecting hopper means 5A, 5B, into which the shot falls, from which it is returned to the hoppers 7 by a pneumatic conveying system 37A, 37B, the discharge of shot from the hoppers 5A, 5B and 7 is controlled by valves 29A, 29B, 13 actuated by means 43A, 43B, responsive to pressure conditions in the pneumatic system. The pneumatic conveying device comprises a fan forcing air through Venturis 34A, 34B, into the throats of which the shot from the collectors 5A, 5B, is introduced under the control of the valves 29A, 29B, the shot being blown through pipes 37A, B, to separators 39A, B from which the shot drops into a main recovery hopper 7A, excess shot spilling over into a secondary hopper 7B. The delivery of shot is controlled by valves 13, 15, and the hoppers have installed therein devices 63A, B, 83A, B, which determine selected high levels and low levels of the shot in the hoppers. The system is controlled by the electric circuit of Fig. 3. Closing of a time switch 125 or manual switch 127 closes the circuit of the fan motor 135 and suction builds up in Venturis 34A, 34B, until suction responsive devices 43A, 43B close switches 57AX-AZ, 57BX-BZ, which operate relays 141A, 141B, to energise the operating solenoids 18 33A, B of shot delivery valve 13 and collector valves 29A, B. The-shot falling through the exchanger 1 is collected and sucked into the Venturi and the reduction in suction at the causes opening of switches 57AX, 57AZ, 57BX, 57BZ, but relays 141A, 141B remain energised through switches 57AY, 57BY. If the conveying system becomes over-loaded, switches 57AY, 57BY, open and relays 141A, 141B, become de-energised to close valves 13, 29A, 29B, until the excess shot has been cleared, when the rise in suction causes normal operation to be resumed. When the low level device 83A becomes uncovered, switch 85A closes and relay 147 becomes energised to de-energise solenoids 18, 33A, 33B and close valves 13, 29A, 29B. When all the shot has been returned, the increase in suction in the Venturis re-closes switches 57AX, 57AZ, 57BX, 57BZ, to energise a delay device 145 which after a predetermined interval operates a stop relay 133 which de-energises the fan motor 135 and closes switch 135Y. If the returned shot reaches the high level detector 63A, switch 81A is opened and alarm 137 is not operated so that the system proceeds normally to shut down. If, due to shot being trapped in the exchanger 1, the shot does not reach level 63A, switch 81A remains closed and alarm circuit 137 operates to indicate unsatisfactory conditions. A changeover switch is then operated to bring hopper 7B into operation and a fresh cleaning cycle is initiated automatically or by depression of manual switch 127 to dislodge the retained shot. The operation is the same except that valve 15 is opened and on completion alarm 137 is operated if the shot does not reach the level of detector 63B in hopper 7B.