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 Vane pumps Gear pumps have a disadvantage of small leakage due to the gap between gear teeth and the pump housing. These limitations are overcome in vane pumps.  The leakage is reduced by using spring or hydraulically loaded vanes placed in the slots of the driven rotor.  Capacity and pressure ratings of a vane pump are generally lower than the gear pumps, but reduced leakage gives an improved volumetric efficiency of around 95%. Types: Vane pumps are available in a number of vane configurations including  sliding vane,  flexible vane, swinging vane,  rotary vane, and  external vane, etc.  Each type of vane pump has its own advantages.  External vane pumps can handle large solids.  Flexible vane pumps can handle only the small solids but create a good vacuum.  Sliding vane pumps can run dry for short periods of time and can handle small amounts of vapor.  The vane pumps are known for their dry priming, ease of maintenance, and good suction characteristics. The operating range of these

 Hydraulic gear pumps: The gear pumps are robust and simple positive displacement pumps.  It has two meshed gears revolving about their respective axes. These gears are the only moving parts in the pump.  They are compact, relatively inexpensive, and have few moving parts.  The rigid design of the gears and houses allow for very high pressures and the ability to pump highly viscous fluids.  They are suitable for a wide range of fluids and offer self-priming performance.  Sometimes gear pumps are designed to function as either a motor or a pump.  This pump includes helical and herringbone gear sets (instead of spur gears), lobe-shaped rotors similar to roots blowers (commonly used as superchargers), and mechanical designs that allow the stacking of pumps.  Based on the design, the gear pumps are classified as: External gear pumps  Internal gear pumps Lobe pumps Gerotor pumps Generally, gear pumps are used to pump: Petrochemicals: Pure or filled bitumen, pitch, diesel oil, crude oil, lub

Hydraulic Pumps The electric driving motor combined with the pumping is known as a hydraulic pump (in most pieces of literature, it is referred to as a  motor-driven pump also). The hydraulic pump takes hydraulic fluid (mostly some oil) from the storage tank and delivers it to the rest of the hydraulic circuit.  In general, the speed of the pump is constant and the pump delivers an equal volume of oil in each revolution.  The amount and direction of fluid flow is controlled by some external mechanisms.  In some cases, the hydraulic pump itself is operated by a servo-controlled motor but it makes the system complex.  The hydraulic pumps are characterized by its  flow rate capacity,  power consumption,  drive speed,  the pressure delivered at the outlet and  the efficiency of the pump.  The pumps are not 100% efficient.  The efficiency of a pump can be specified in two ways.   One is the volumetric efficiency which is the ratio of the actual volume of fluid delivered to the maximum the