Intro to hydraulics part A/B Flashcards Preview

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Flashcards in Intro to hydraulics part A/B Deck (35)
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1
Q

Why is pressure transmitted almost instantly through hydraulic fluid?

A

Because hydraulic fluid is almost incompressible.

Compresses about 1/2% at 1000 psi.

2
Q

How can you increase the force exerted by a cylinder of any given size?

A

By increasing the operating pressure.

3
Q

Does a pump produce pressure, flow or both?

A

It only produces flow

4
Q

Would you use a larger or smaller cylinder if you needed to Increase the load capacity at a given pressure?

A

A larger cylinder because area would increase

5
Q

How fast does a two-to-one cylinder extend compared to how fast it retracts?

A

It extends at half the speed of retraction.

6
Q

Defined the characteristics of velocity and pressure in a large diameter pipe and a small diameter pipe.

A

In a larger diameter pipe the pressure is high while the velocity is low. (Good)

In a smaller diameter pipe the pressure is low while the velocity is high. (Bad)

Velocity + pressure are inversely related.

7
Q

How does flow affect the output of a cylinder?

A

It affects the speed.

8
Q

How does pressure affect the output of a cylinder?

A

It affects the force the cylinder exerts.

9
Q

How does cavitation occur?

A

It’s when gases dissolved in hydraulic fluid enter a low pressure area and boil out. When the gas comes in contact with a high pressure area the gasses implode causing cavitation.

10
Q

How is pressure created?

A

By a restriction to flow.

11
Q

What 2 properties are directly related to force?

A

Area and pressure

12
Q

What 2 properties are directly related to speed?

A

Flow rate and area

13
Q

What are 2 ways flow can be produced?

A

By a pump or a pressure drop across an orifice.

14
Q

Describe volumetric efficiency.

A

Volumetric efficiency measures how much fluid you get out of a pump compared to how much you put in.

15
Q

How big is the reservoir on an open loop circuit typically?

A

3 x the pump output

16
Q

What is the annulus area referring too?

A

The position area minus the rod area

17
Q

What is aeration?

A

Aeration occurs when air becomes mixed with the fluid that has leaked into the system through inadequate sealing or air becoming entrapped during maintenance on the system.

18
Q

How do you distinguish a hydraulic line that connects to another line compared to a line that crosses over and does not connect?

A

A like that connects to another line will be simply attached or will have a black dot at the point of connection. A line that crosses over will have a little bump over the line.

19
Q

What are you setting, when you set the pressure on a pressure relief valve?

A

You are setting the maximum force the cylinder exerts

20
Q

What is a directional control valve?

A

A valve that allows you to direct the flow to either end of the cylinder.

The valve can be operated manually, electrically, hydraulically or pneumatically.

21
Q

What are the 4 ports on a directional control valve?

A

A and B are working ports

P and T are the pressure port and return to tank port

22
Q

What does a flow control valve do?

A

It controls the speed at which the cylinder operates.

23
Q

What does a diagonal arrow on a hydraulic symbol represent?

A

That the component is variable (adjustable) in its output.

24
Q

What is the job of a pressure reducing valve?

A

It’s job is to reduce the pressure below the system pressure and thus the force the cylinder can exert.

25
Q

Is a pressure reducing valve normally open or normally closed?

A

Normally open until something happens to push the valve closed.

26
Q

What is the system pressure when you actuate a cylinder to move a load?

A

It will be just what is required to move the load and when the cylinder bottoms out the system pressure will increase to the maximum pressure which will open the maximum pressure relief valve.

27
Q

What is the small dotted line coming from the spring on a pressure reducing valve for?

A

It is a drain line that goes back to tank that prevents pressure build up on top of the valve element (the build-up would prevent the valve from operating)

28
Q

What is a hydraulic sequence valve used for?

A

A sequence valve stops the flow to the second cylinder, but then releases the flow to the second cylinder as soon as the first cylinder reaches the end of its stroke.

(Clamping a work piece with the first cylinder and then a punch coming down with the first cylinder to punch a hole in said piece.)

29
Q

A cylinder that pushes up on a load is called a?

A

Opposing load

30
Q

A cylinder that pulls up on a load is called a?

A

Tractive load

31
Q

Is a hydraulic sequence load normally open or normally closed?

A

Normally closed

32
Q

Does a meter-in flow control attach to the cap end or rod end?

A

Cap end on an opposing load

33
Q

Does a meter-out flow control attach to the cap end or rod end?

A

Rod end on a tractive load

Pulling up

34
Q

What happens to the flow produced by the pump that is not used by the cylinder?

A

It is wasted through the maximum pressure relief valve.

35
Q

What is bleed-off flow control?

A

The flow control can be connected so it bleeds off a set amount of the flow before the flow is delivered to the cylinder. Bleeding off flow through the flow control from the supply line to the directional control allows you to control the speed of the cylinder when it extends and retracts.