HYDRAULICS 2024 EXAM TEST QUESTIONS WITH REVISED AND UPDATED ANSWERS
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Course
HYDRAULICS
Institution
HYDRAULICS
HYDRAULICS 2024 EXAM TEST QUESTIONS WITH REVISED AND UPDATED ANSWERS
Piston Motors - Answer-Bent axis piston motor Radial piston motor
- medium & heavy duty applications
- can handle overrunning loads and provide braking at very low speeds
DCV's - Answer-Direct flow or prevent flow through sel...
HYDRAULICS 2024 EXAM TEST
QUESTIONS WITH REVISED AND
UPDATED ANSWERS
Piston Motors - Answer-Bent axis piston motor
Radial piston motor
- medium & heavy duty applications
- can handle overrunning loads and provide braking at very low speeds
DCV's - Answer-Direct flow or prevent flow through selected lines
Check Valves - Answer-Controls direction of fluid flow.
-Standard: one directional
-Pilot operated: allows reverse flow; pilot line senses high pressure
Check Valves (Application) - Answer--positive lock for holding suspended loads (safety)
-safety bypass; provides alternative flow paths around equipment
-facilitates maintenance
Shuttle Valves - Answer-Allows system operation from two alternate power sources =
ensures backup power
DCV Attributes - Answer--Valve porting = # of ways
-Number of positions (envelopes)
-Methods of actuation
-Neutral position = unactivated position
Two-way Valve - Answer--Serves as shut-off valve
-NO or NC
Three-way Valve - Answer--3rd port provides return flow to reservoir
Four-way Valve - Answer--Allows both working and return flow through same valve
position
Needle Valves - Answer-3 factors affecting flow across an orifice:
1. Orifice size
2. Pressure drop across orifice
3. Fluid viscosity
, Center Positions - Answer-NC:
-holds actuator position
-used in parallel circuits
Tandem Center:
-unloads pump
-avoids energy waste, heat generation
-disadvantage: time delay before pressure available to actuator
Open Center:
-unloads pump and actuators are not held in position
-cylinder may drift
Float Center
-motor can freewheel, and coast to stop
Flow Control Valves - Answer-Meters fluid flow at required rate.
Controls speed of actuators by controlling rate of flow out of device.
Needle Valves - Answer-Used when precise control is not required and when system
pressure is constant.
Pressure Compensated FCV - Answer--purpose is to create a pressure drop that keeps
dP constant across needle valve
-maintain output flow within +/-%5 of setting over wide pressure range
Flow Directing Valves - Answer-Bypass flow diverts part of flow back to reservoir.
Flow Divider Valves - Answer-a) Priority Flow Divider
- ensures essential system functions are performed at expense of non-critical functions
b) Proportional Flow Divider
- allows a constant flow to each circuit
Deceleration Valve - Answer--NO
-provides automatic speed control of cylinder
-must drain spring cavity of any leakage past spool = avoid hydraulic lock
-prevents damage to valve
-cam has free play at each end of range of motion
Meter-out Flow Control Circuit - Answer--controls rate of flow leaving cylinder
-creates back pressure on actuator
Meter-in Flow Control Circuit - Answer--controls rate of flow into actuator
-rod side pressure is very low due to return flow back to reservoir
Pressure Control Valves - Answer--only pressure reducing valve actually controls
pressure
-the rest sense pressure and automatically adjust to respond to the senses pressure
- secondary effects: flow rate (decreased), direction of flow
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