# Introduction To Hydraulics - Part A Flashcards

1
Q

What is a Prime Mover?

A

The source of energy. Example a electric motor.

2
Q

Output units are refered to as __________

A

Actuators

3
Q

What principles do hydraulics work on?

A

Pressure and flow

4
Q

Pressure is created by ________

A

Resistance to flow

5
Q

How much does hydraulic oil compress when 1000 psi is applied?

A

1/2%

6
Q

How is flow produced?

A

By pump or a pressure drop across a orifice.

7
Q

How is pressure produced?

A

By a resistance to flow.

8
Q

There is only ______ across an orifice if there is a __________.

A
• Flow
• Pressure Drop
9
Q

How is flow expressed?

A
• Feet/minute
• Feet/second
• gallons/minute
• cubic inches/minutes
10
Q

Give the flow triangle

A

V/t = flow rate = cubic inches/minute
S = Speed = inches/minute
A = Area = square inches

11
Q

What is a regenerative circuit designed to do?

A

Provide equal speed and equal force when the cylinder extends and retracts

12
Q

Is an increase in speed because of pipe size good for the hydraulics or bad?

A

Bad, it wastes a lot of energy, robs pressure and wears out components.

13
Q

What are the recommended maximum velocities for hydraulic pipe lines?

A
• Pump Inlet Velocity = 2 to 4 feet/second
• Pressure Line Velocity = 7 to 20 feet/second
14
Q

Increase in Friction in laminar flow is proportional to its _________ doubled.

A
• Velocity Increase

Ex.
Velocity feet/second x 2 = Laminar Friction x 2

15
Q

Increase in Friction in Turbulent Flow is
proportional to the square of its ____________ .

A
• Velocity Increase

Ex. Velocity feet/second x2 = Turbulent Friction x 4

16
Q

What prevents Turbulent Flow?

A
17
Q

What is this?

A

Cavitation

18
Q

What is Cavitation?

A
• The violent collapse of entrained vapour bubbles:

When gases dissolved in hydraulic oil boils out from the fluid because of low pressure or agitated by turbulence. And then moves from low pressure to high pressure causing the bubbles to emplode.

19
Q

What is the purpose of pressurizing a reservoir?

A

To provide a positive charge to the pump and keep dirt out.

20
Q

Cavitation is immediately recognized by what?

And confirmed by what?

A
• A rattling sound
• Abnormal low pressure at the pump inlet.
21
Q

What are the side effects of Cavitation?

A
22
Q

What are some causes of cavitation?

A
• Clogged inlet filters
• Pump mounted too high above resevoit
• Fluid is too thick
• Clogged breathers
• Too many bends or fittings
• Inlet pipes are too small
23
Q

What is Aeration?

A

When air becomes mixed in the fluid resulting in imploding of air bubbles.

24
Q

What identifies Aeration from cavitation?

A

Abnormal and inconsistent sounds from the pump with inlet pressure being normal and not lower.

25
Q

Is aeration more violent then cavitation?

A

No, aeration is not as violent as cavitation.

26
Q

Which causes more damage, Aeration or Cavitation?

A

Cavitation

27
Q

What are the causes of aeration?

A

-Low fluid levels allows air to enter the inlet to the pump.
- Plugged breathers cause the air in the reservoir to be forced into the fluid.
- Leaky Inlet fittings
- Shaft seal on the pump is leaking
- Connections at the cylinder are leaking
- Air became trapped in a component when disconnected for maintenance.
- Gas-charged accumulators are leaking

28
Q

What is power efficiency?

A

% that tells how much power is obtained from the actuators compared to the power you put into the system through the prime mover.

29
Q

What is the equation for Power Efficiency?

A

(Output Horsepower /Input Horsepower) x 100

30
Q

What is the biggest power waster in a hydraulic system?

A

Relief Valve

31
Q

What are Tandem Cylinders?

A

Cylinders that use two piston surfaces to create higher forces without increasing the fluid pressure.

32
Q

What are these?

A
• Single-acting telescopic cylinders
• Double-acting telescopic cylinders
33
Q

What does this symbol mean?

A

Controlled by a reversing electric motor

34
Q

What is a detent?

A

After activated the spools may be held in position by means of a detent. A spring loaded mechanism which fits into grooves on the periphery of the spool extensions.

35
Q

What is an infinite positioning DCV?

What is another name for them?

What is the opposite?

A
• A DCV spool the switches poistions at any rate.
• Throttling DCV
• Non throttling
36
Q

What does this mean?

A

Throttling directional control

37
Q

What type of centre is this?

What does it do?

What is a benefit?

A
• Tandem Centre
• Flow from the pump is directed right back to the tank.
• The tandem position can hold the actuator in poisiton.
38
Q

What type of centre is this?

What does it do?

A
• Float centre
• Both A line and B line connect to tank allowing actuators to be moved manually.
Pump is closed off.
39
Q

What type of centre is this?

What does it do?

A
• Regenerative Center
• Both A line and B line connect to pump. Maintains constant pressure on both sides of the actuator.
40
Q

What is this?

A

Pressure releif valve

41
Q

What is this?

A

Pilot Operated Relief Valve

42
Q

What is this?

Where do you find these?

What does it do?

A
• Counter Balance Valve
• Exhaust side of an Actuator

Used to maintain a set pressure in part of a circuit. This controlled pressure is required to keep a weight or rotating load from falling/running away.

43
Q

What is this?

What does it do?

Where is it found?

A
• Brake Valve
• Stops rotation of a motor as the DCV shifts to its centre position.
• Exhaust side of a motor.
44
Q

What are the signs of a throttle valve and a shut-off valve?

A
45
Q

What is this?

A

Flow Meter

46
Q

What is this?

A

Integrating Flow Meter

47
Q

What is this?

A

Pressure Electric Switch

48
Q

What is this?

A

Heater

49
Q

What is this?

A

Temperature Controller

50
Q

What is this?

A

Air Dryer

51
Q

What is this?

A

Filter with automatically drained water trap

52
Q

What is this?

A

Automatically drained water trap

53
Q

What is this?

A

Electrical Line

54
Q

What is this?

A

Heat Engine

55
Q

What is this?

A

Heat Engine

56
Q

What is this?

A

Flow Dividing Valve

57
Q

What is this?

A

Manually controlled throttle valve

58
Q

What is this?

A

Three-way rotary connection

59
Q

What is this?

A

One-way rotary connection

60
Q

What is this?

A

Weighted Accumulator

61
Q

What is this?

A

Gas Charged Accumulator

62
Q

Where is a pressure line filter usually installed in a hydraulic system?

A

Before the direction control valve.

63
Q