External-gear hydraulic pump 1P series

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This chapter describes Marzocchi external single gear 1P pumps, their operating features and how to select the right pump for the required application. 1P pumps are small hydraulic machines converting mechanical power into hydraulic power. This section deals with rotary positive- displacement pumps. In this type of pump, a given volume of fluid flows from inlet to outlet at each shaft r otation (theoretical displacement). Pressure depends on delivery line resistance to fluid flow. As gear pumps only transfer fluid, they are subject to pressure generated by the circuit. Therefore, if system flow rate and motor rotation speed are known, it is easy to select the right pump displacement and its model. The diagram indicating flow rate variations according to speed and pressure, shows that not all the theoretically available fluid is transferred from inlet to outlet because of pump internal dripping. Dripping can be remarkably reduced through pressure axial compensating systems (as described at the beginning of this catalogue) but never eliminated. Dripping increases as circuit pressure increases. A pump requires power, even if a limited quantity, just like any other hydraulic machine. Part of this power is given to the fluid to increase pressure required by the circuit, the remaining part is used to win pump inter nal friction. Therefore, for proper pump operation, supplied torque shall be higher than theoretical torque.