Exam (elaborations)
Pumps for Omaha Third grade engineer
- Module
- 3rd Grade Engineer.
- Institution
- 3rd Grade Engineer.
Pumps for Omaha Third grade engineer
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Pumps for Omaha Third grade engineer177. What are pumps used for and name five types? - ANS-Pumps are used for heating
water, cooling water, boiler feed, lubrication, condensing water, sumps, and boosters.
Five types are centrifugal, rotary, injector, duplex, simplex, and vacuum pumps.
178. How does an injector work? - ANS-It is a device designed to lift and force water
into a boiler that is operating under pressure. It operates on the principle of steam
expanding through a nozzle imparting it's velocity energy to a mass of water.
179. How does a duplex pump work? What is lost motion? - ANS-A duplex pump is a
steam driven, double acting, reciprocating pump with check valves on both sides of the
pistons, so liquid is pumped no matter which way the piston is moving.
Lost motion is the distance between the lugs and nut on the backside of the "D" slide
valve, enabling the valve to close slowly and quietly before the pump reverses stroke.
180. What is an air chamber and why is it used? - ANS-It is located on the intake or
discharge of a reciprocating pump. It absorbs the shock and surges of the liquid being
pumped, relieving the pump from excessive strains.
181. What is a foot valve and it's purpose? - ANS-It's a type of check valve located at
the bottom end of the suction line to prevent the pump from lowering prime and from
running backwards when shut down.
182. Describe a metering pump (power pump) and list it's three features. What are it's
uses in a power plant? - ANS-Metering pumps are either diaphragm, piston, or plunger
operated positive displacement pumps used for low flow applications. Three features
are accuracy of adjustment, capable of pumping a wide variety of chemicals, and high
head service. Metering pumps are used for injecting cooling tower treatment, internal
boiler treatment, or external boiler treatment.
183. What is the difference between a piston and a plunger? - ANS-A plunger moves
inside stationary rings installed into grooves in the cylinder.
A piston has rings installed into grooves in the piston itself.
184. Describe a rotary pump. Does a rotary pump work on the same principle as a
centrifugal pump? - ANS-A rotary pump is a positive displacement pump with gears,
vanes, screws, lobes, or cams, operating in a close fitting casing. They don't use valves
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