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Parker Gear Pump analysis: The gear pump is compact, easy to operate and has a limited number of moving parts. They do not match the pressure generated by the reciprocating pump or the flow rate of the centrifugal pump, but provide higher pressure and throughput than the vane pump or cam pump. External gear pumps are particularly suitable for pumping water, polymers, fuels and chemical additives. Small external gear pumps typically operate at speeds up to 3, 500 rpm, and larger models of helical or herringbone gears can operate at speeds up to 700 rpm. The external gear pump has precision tolerances and shaft support on both sides of the gear. This allows them to operate at pressures up to 7250 psi (500 bar), making them ideal for hydraulic power applications.
Since the output is proportional to speed and is a smooth, pulse-free flow, external gear pumps are typically used for metering and mixing operations because metering is continuous and the output is easy to monitor. The low internal volume reliably measures the liquid passing through the pump for precise flow control. They are also widely used in engines and gearboxes to circulate lubricants. External gear pumps can also be used in hydraulic power applications, typically in vehicles, hoisting machinery and mobile plant equipment. The gear pump is reverse driven using oil pumped from elsewhere in the system (usually through a series pump in the engine) to form an electric motor. This is particularly useful for providing power in areas where electrical equipment is bulky, expensive or inconvenient. For example, tractors rely on engine-driven external gear pumps to power their services.
The external gear pump can be designed to handle corrosive liquids. Although they are usually made of cast iron or stainless steel, the new alloys and composites enable the pump to handle corrosive liquids such as sulfuric acid, sodium hypochlorite, ferric chloride and sodium hydroxide.
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