Chapter 5

Question 1

cogging

Answer 1

movement occurring in short, jerky increments

Question 2

atmospheric pressure

Answer 2

29.92” Hg at sealevel

Question 3

atmospheric pressure is used to:

Answer 3

• bring fluid into the pump

- accelerate fluid inside rotating mechanism

Question 4

cavitation

Answer 4

if there’s not enough pressure to accelerate a fluid, air bubbles form in pump and implosions occur (ruins the pump)

Question 5

implosions

Answer 5

occur because of high pressure as well as low pressure = changes of pressure

Question 6

causes and remedies of real cavitation

Answer 6

• dirty suction strainer (filter)
• undersized or too long of hose on inlet side
• high altitude applications = less atmospheric pressure = move pump inside reservoir (“Flooded Suction”)
• increase rpm of electric motor to increase gpm will cause cavitation
• fluid viscosity is too high = pump starvation = oil is too thick

Question 7

pseudo cavitation

Answer 7

• same effect as real cavitation

- no vacuum, outside air is sucked into the pump

Question 8

causes of pseudo cavitation

Answer 8

• leaking pump shaft seal

- suction hose is not inside of fluid (fill up reservoir) = just sucking up air

Question 9

motor

Answer 9

driven by fluid while a pump delivers flow

Question 10

braking method

Answer 10

want to stop motor but this will create shock = insert braking valve that will sense this pressure and send fluid to tank

Question 11

prevent cavitation

Answer 11

• one way to prevent cavitation is the motor centered spool DCV = if flow suddenly stops, motor can suck fluid from tank
• another way = make up check valves

Question 12

cross over relief valve circuit

Answer 12

prevents shock and cavitation

Question 13

over center pump

Answer 13

has a swashplate that can change the direction of the flow

Question 14

two devices that convert linear motion to rotary motion

Answer 14

skotch yokes and the rack and pinion actuator (what we use in lab)

Question 15

oscillating actuators

Answer 15

vane rotary actuators (single and double vane)