Patent GB-571167-A (GB)
Title: Improvements in means for the operation and control of steam generators
IPC: F22B35/00
Filed: 1943-10-14
Abstract: 571,167. Boiler control systems. HINDLE,T. Oct. 14, 1943, No. 16871. [Class 135] [Also in Group XXXV] In a control system for a flash boiler, particularly for use on a steam-driven vehicle, a feed-water pump 4, a fan 5 for supplying combustion air, and an oil pump 3, which delivers oil under pressure to servomotors controlling the supplies of feed-water and air, are mechanically connected together to operate at fixed relative speeds and are driven by an engine receiving steam from the boiler, the feed-water and air being delivered concurrently, the latter at a variable rate regulated by a damper 40 controlled by a thermostat 17 subject to steam temperature at the boiler outlet, when the boiler outlet pressure is below normal and being simultaneously cut off when the normal pressure is attained. Fig. 1 shows the system applied to a solid-fuel fired boiler having a grate 37 and comprising economizer, evaporator and superheater sections 11, 14, 16, the latter delivering the superheated steam through pipe 18 to a reversible main engine 21 connected through reduction gearing to the road wheels of a vehicle. Part of the steam which has been partially expanded in the high-pressure cylinders 22, and subsequently reheated in a section 24 of the boiler for delivery to the low-pressure cylinders 26, passes a check valve 28 and is led through pipes 29, 30 and valve 31 to a donkey engine 1 which drives the pumps 3, 4 and fan 5 through a free-wheel clutch 2. An electric motor 6 is provided for operating these auxiliaries during the starting-up period. When the main engine is temporarily stopped by closure of the throttle valve 20, steam is supplied direct from the boiler through pipe 34 and reducing valve 35 to maintain the donkey engine 1 running at a relatively low speed. The output of the feed-water pump is controlled by a valve 8 which, when free to open, allows the water to return to the tank 7 without passing to the boiler and when held in the closed position by oil pressure applied from the pump 3 through pipe 61, valve 53, controlled by an electromagnet 54, and diaphragm 52 prevents the water returning to the tank, thus causing it to pass through pipe 9 to the boiler. Oil is also supplied from the pump 3 through pipe 60 to a servomotor 42 interposed between the thermostat 17 and the damper 40, the arrangement being such that the damper is fully opened or fully closed at temperatures respectively 100‹ F. below and above the normal steam outlet temperature. The air supply duct 39 is fitted with a second damper 41 which is operated by an electromagnet 51 so as to be either fully open or fully closed. Current for actuating the electromagnets 51, 54, the motor 6 and an electromagnet 32 controlling the valve 31 is supplied from a storage battery 57, there being provided in the circuit a manually-operated main switch 58, contacts 56, 59 both actuated by a diaphragm device 55 responsive to the steam pressure in the pipe 18, and air and water contacts 48, 49 which control the energization of the magnets 51, 54. The contacts 48, 49 are normally respectively closed and open and are connected to the thermostat 17 in such a manner that the former is opened when the steam temperature is about 50‹ F. above normal and the latter closed when this temperature reaches or exceeds about 50‹ F. below normal. In normal operation, the pressure contact 56 opens and closes at intervals as the steam pressure fluctuates, the supplies of air and feed-water being, in consequence, suspended and restored concurrently by the actuation of the magnets 51, 54 ; during the supply periods the whole of the water delivered by the pump 4 passes to the boiler, while the quantity of air supplied below the grate 37 is continuously regulated by the damper 40 in accordance with the steam temperature at the boiler outlet. Should the fuel or water supply become exhausted or interrupted, the thermostat 17 acts as a safety device by reason of its actuation of the contact 49 or 48 to cut off the supply of water or air as the case may be. A modification is described in which the donkey engine 1 is omitted, the oil pump 3, feed-water pump 4 and fan 5 being driven by the main engine 21 which is of the uni-directional type and drives the road wheels through a clutch and gear-box. Specifications 565,655 and 566,955 are referred to.