Pump

**Types of Pumps:**
– Mechanical pumps may be submerged or external.
– Pumps classified by displacement method into various types.
– Basic types include positive-displacement, centrifugal, and axial-flow pumps.
– Centrifugal pumps change fluid flow direction by 90 degrees over an impeller.
– Axial flow pumps maintain the same flow direction.

**Positive-Displacement Pumps:**
– Make fluid move by trapping and displacing a fixed volume.
– Require relief valves to prevent damage.
– Classified into rotary, reciprocating, and linear types.
– Rotary pumps include gear, screw, and vane pumps.
– Efficient for handling viscous fluids.

**Applications and Varieties of Positive-Displacement Pumps:**
– Includes reciprocating pumps like plunger, diaphragm, piston, radial piston, and vibratory pumps.
– Rotary positive-displacement pumps like gear, screw, progressing cavity, roots-type, and plunger pumps.
– Triplex-style plunger pumps used in car washes, oil and gas drilling, and fracking.
– Compressed-air-powered double-diaphragm pumps for handling viscous and abrasive materials.
– Rope pumps, impulse pumps, velocity pumps, regenerative turbine pumps, side-channel pumps, gravity pumps, steam pumps, and valveless pumps.

**Maintenance and Repair of Pumps:**
– Importance of examining repair records and mean time between failures (MTBF).
– Study by John Crane Inc. analyzing repair records from 15 plants with nearly 15,000 pumps in the U.S.
– Impact of unscheduled maintenance, especially for mechanical seals and bearings, on costs.
– Upgrading pumps to increase MTBF and reduce failures.

**Technical Aspects and Efficiency of Pumps:**
– Specifications like horsepower, volumetric flow rate, outlet pressure, and inlet suction.
– Engineers using specific speed to select suitable pump types.
– Understanding head, pump efficiency, and minimum flow protection.
– Calculating pumping power using Bernoulli’s equation and considering factors like rotational speed, fluid density, and viscosity.
– Pump efficiency ratio, variations with discharge and operating head, and decline over time due to wear.