Driver and motor horsepower

Most pumps using fixed speed motor as driver. Many times, steun turbine is chosen as pump driver for their reliability and excess steam in plant. Other possible pump drivers are engines, air or hydraulic motors. 

For radial or mixed flow pumps, required horaepower of a pumping service can be calculated using Eq, (2). However, motor horsepower i s usually selected based on the pumping rate at end of the pump curve (runout) to make sure motor is able to handle the Largest pumping rate or using Eq, (3). 

For axial flow pumps, required horsepower decreases with inaeasing flow rate wifo the maximum horsepower required at shutoff condition. Motors foe axial flow pumps are not selected to handle low Bows. During startup, discharge block valve at axial pump discihaige line should be opened to prevent high horsepower requirement at low flow startup condition. 

ANSI pump is designed per ANSI standard B73.1 and B73.2 for chemical process or light duty users. The standard configuration of an ANSI pump is end suction, frame mounted, with discharge in line with the centerline of pump casing. For each pump size, key envelope dimensions ate the same. Most ANSI pumps use open impeller. They are often used in corrosive service and many dilTerent material of construction are available. 

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