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Pumps
Homework #8
20
Engineering
Professional
08/20/2009

Term
 What are the Two major categories of Pumps?
Definition
 Positive Displacement Pumps and Non-Positive Displacement Pumps
Term
 Name Four general classifications of pumps
Definition
 Rotary, Jet, Centrifugal, Reciprocating
Term
 Explain the operation of a Fee-Water Injector
Definition
 It uses a condensable gas to entrain a liquid and discharge against a higher than either the motive or suction pressures.
Term
 What is the maximum feed-water temperature when using injectors?
Definition
 130° to 150° is considered the maximum temperature.
Term
 What are the operating mediums for duplex pumps?
Definition
 Duplex pumps can operate on steam, compressed air, and water.
Term
 How do you set the valves on a duplex pump?
Definition
 1. Close steam and exhaust valves. Drain pump and Tag Out Lock Out.2. Center the Pistons3. Plumb the Rocker arm4. Square the valve over the ports5. Equalize the lost motion6. Move piston off center
Term
 What is meant by the term "Lost Motion"?
Definition
 Lost Motion is the amount the valve rod moves without moving the valve gear
Term
 What is the effect of too much lost motion? Not enough Lost Motion?
Definition
 Too much Lost Motion will cause the pistons to trike the heads, Not enough Lost Motion will cause the pump to Short stroke.
Term
 What is a Cushioned Valve?
Definition
 They are manual valves located at each end of the steam chest, they act as an added control to prevent the steam piston from striking the cylinder heads when the pump operates at high speeds.
Term
 What is the area of a piston 6" in diameter?
Definition
 Area = d² X .7854.6 X 6 X .7854 = 28.27 in²
Term
 Does a Duplex Pump displace an equal amount of water on the forward and reverse stroke? Why?
Definition
 Yes, because the net effect of the piston rod on the displacement is equal on both sides of a duplex pump.
Term
 What type of pump is a Metering Pump? A Vacuum Pump?
Definition
 A metering pump is a Positive displacement Pump and a Vacuum pump is also a Positive displacement Pump
Term
 What type of service would you expect to see a Rotary Pump? A Gear Pump?
Definition
 Rotary pumps and Gear pumps are typically used to pump heavy fuel oils
Term
 Define Cavitation
Definition
 The sudden formation and collapse of low pressure bubbles in water by mechanical forces. This occurs at the inlet of a centrifugal pump when the temperature of the water is too hot or when the suction is too low.
Term
 Explain what you would do if a pump began to cavitate
Definition
 Increase Feed-Water
Term
 What is the best way to avoid pump Cavitation?
Definition
 Make sure there is enough water at the correct temperature at all times
Term
 Explain the operation of a Centrifugal Pump
Definition
 A Centrifugal pump has an impeller attached to the shaft, as the impeller rotates, water enters the center and is thrown outward by Centrifugal force. The water leaves the impeller at a high velocity which is converted to pressure by a volute.
Term