Gear pumps
Page 57
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Four separate circuits from one multiple gear pump unit is one of a number of system options made possible by the introduction of the new Webster YDS series of hydraulic gear pumps.
The YDS pump element-available in five flow capabilities from 4 igpm to 24 igpm—has been widely incorporated in mobile machinery of various kinds for about 10 years. It is a pressure-balanced unit, with high volumetric efficiency. Now, with the aid of a newly developed double-bearing linking section, two or three gear pump elements can be bolted together to form a single unit driven from the one shaft—thereby saving space and cost.
The design also allows a flow divider to be bolted direct onto one of the pumps, enabling the flow from that element to be split between two circuits, one of which has priority—so a triple pump with built-in flow divider can serve four circuits. There are a number of porting options, including common inlets to reduce pipe-work. A further refinement is that the bearing sections can incorporate seals if isolation of different fluids is required.
Maximum operating pressure of YDS6 pumps is 2500 psi and maximum speed is 3500 rpm. The five pump elements (graded by displacement) can be combined in any way into a double or triple unit.
Materials used in YDS pumps have been selected to give.
strength and durability combined with lightness. Shafts are of high alloy steel, hardened and precision ground, and the hardened steel gears are either shrunk onto the shaft or machined integral--eliminating problems of fatigue failure associated with keyed construction. All castings are die cast of special aluminium alloy.
Each gear/shaft assembly is carried in two heavy-duty full-complement needle bearings. These are much more tolerant of contaminants than journal bearings, and their minimal lubrication requirements add to the volumetric efficiency of the units.
YDS pumps are manufactured for the British and Continental European markets.
Made by: T. Webster Ltd, Industrial Estate, Somersham Road, St Ives, Hunts.