GB730459A - High pressure pumping unit for fire-fighting purposes - Google Patents

Abstract

730,459. Centrifugal pumps; stuffing-box substitutes. HATHAWAY, Ltd., L. Oct. 16, 1953, No. 28579/53. Classes 110 (1) and 122 (5). A single-stage centrifugal pump has annular seals, of substantially equal diameters, between the opposite faces of the impeller and the adjacent casing walls, each seal comprising a carbon ring supported from the pump casing and engaged by a steel ring driven from the impeller by at least one pin extending from the impeller and passing through a slot in the steel ring, the latter being biased towards the carbon ring. A steel ring 25 is driven by the pump impeller 14 through three pins 28 which engage slots in the periphery of the ring, and is pressed by three springs 30 into sealing contact with a stationary carbon ring 21. Rubber seal rings 20, 34 are provided. The springs are assisted by water pressure acting upon the rear surface of the steel ring 25, the external diameter of the cylindrical portion 32 being made less than the external diameter of the carbon ring so that the area of the rear surface subjected to the pressure of the pumped water is greater than that of the front surface. To facilitate assembly, the steel ring 25 is prevented by the engagement of lugs 36 behind projections 38 from being displaced from the impeller by the springs 30 during assembly. A similar sealing means is provided at the back of the impeller 14, and its carbon ring 23 is of the same external diameter as the carbon ring 21 so that the thrusts on the radial faces of the impeller exerted by the pumped water are identical, thus providing axial balance of the impeller. The pump is driven by the engine of a fire-fighting vehicle. To prevent overspeeding, a governor associated with the driving shaft is arranged to open electric contacts in series with the low tension supply to the ignition means of the engine in the event of the pump speed exceeding a predetermined value.