Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

HET3 Hydraulics > 190301fA Pressure Control Valves > Flashcards

190301fA Pressure Control Valves Flashcards

1
Q

What is this type of valve?
Fixed or variable?
Series or parallel to the system?

A

Pressure relief valve
Variable
Parallel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What do system and circuit relief valve protect?

A

System relief valves protect the complete system from excessive pressure.

Circuit relief valves protects the components in the circuit from shock loads and pressure spikes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What characteristics do all Relief Valves have in common

A

• A relief valve is always Normally Closed.
• Pilot pressure to open the valve is connected in parallel directly upstream of the valve.
• The inlet port is connected parallel with the system or circuit it protects.
• The outlet port is connected to the reservoir.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are some general steps required to adjust system relief valve pressure?

A
  1. Install a pressure gauge in parallel with pump outlet line.
  2. Warm up the hydraulic oil to normal operating temp. (65.5C - 82.2C)
  3. Maximum system pressure can be read on the gauge by stalling an actuator while running the engine at full throttle
  4. Compare the readings with specs
  5. If out of spec, adjust system relief valve by adjusting the screw. Or replace if non-adjustable.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Factors to consider when adjusting circuit relief valve procedure:

A

• they are usually tested and adjusted at their cracking pressure
• they are set at a higher pressure than the maximum system pressure
• follow service manual

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the 3 types of Hydraulic accumulators?

A

• weighted
• spring loaded
• gas charged

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the 3 styles of gas accumulators?

A

• piston
• bladder
• diaphragm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why are accumulators installed in a hydraulic system?

A

• energy storage
• shock absorption
• gradual pressure buildup
• constant pressure maintenance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What type of valve is this?

A

Unloader Valve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why do unloader valves differ from relief valves?

A

• always used in conjunction with a check valve
• pilot pressure to open the valve is sensed downstream of check or high pressure side of the check valve

Bonus: they are typically used in closed center system!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does an unloader valve do?

A

Allows full pump flow to return to the tank while maintaining a minimum pressure at the pump outlet

Bonus also reduces chatter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are pressure reducing valves?

A

They are a pressure control valve that allow one circuit of a hydraulic system to have maximum operating pressure that is less than the maximum operating pressure of the rest of the system.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are some pressure reducing valve characteristics?

A

• normally open (the only one)
• pilot pressure to close valve is sensed downstream of the valve
• inlet is connected to system pressure
• outlet connected to circuit to be operated at reduced pressure
• drain line is required to allow internal leakage to return to tank

Bonus: uses a check valve in parallel to reverse flow from actuator!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the 7 types of pressure control valves?

A

• pressure relief
• unloader
• pressure reducing
• sequence

Back pressure valves:
• counter balance
• brake
• line lock (double pilot operated check valves)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are Pilot operated pressure control valve?

A

They are often called a compound pressure control because of two direct operating relief valves that operate together as one unit. Providing much more accurate pressure control
Normally closed

The pilot valve is designed to deal with hight pressure and low flow rates

the other is intended to handle low pressure and high flow rates.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

In a pilot operated relief valve, which spring will be overcome first?

A

The pilot valve will crack first (cracking pressure), then the bigger stage opens.

Pilot will also close first then bigger stage.

17
Q

Why do we use pilot operated pressure controls?

A

Much more accurate pressure control with significantly reduced pressure override

18
Q

What is Pressure override?

A

The difference between cracking pressure and full flow pressure

19
Q

What is this valve?

A

Pressure reducing valve

20
Q

What valve cause actions in a hydraulic system to occur in a certain order?

A

Sequence valve

21
Q

What are some characteristics of a sequence valve?

A
  • Normally closed
  • Pilot pressure to open valve is sensed upstream of valve
  • Inlet port is connected in parallel to the function that must operate first
  • Outlet port is connected to the circuit to be operate second (in series)
  • Must have a drain line to allow leakage to return to tank
  • Check valve is required for rapid return of reversible actuators.
22
Q

What valve is in this circuit?

A

Sequence valve

23
Q

What are the 3 Back Pressure valves?

A
  • Counterbalance valve
  • Brake valve
  • Lock valve
24
Q

What is a Counterbalance valve?

A

its a safety device used to control the lowering of a vertical load so it does not fall freely.

25
Q

What characteristics do Counterbalance valves have?

A
  • Normally closed
  • Installed on return line from base of cylinder
  • Internal pilot line sensing directly upstream of the valve, pilot pressure then opens the valve
26
Q

What valve is used in this circuit?

A

Counterbalance valve

27
Q

What does a Brake valve do?

A
  • Prevents the load from overspeeding the motor
  • Provides a controlled deceleration of the load
28
Q

What is the main difference between a Counterbalance valve and a Brake valve?

A

The Brake valve has pilot pressure that is sensed from both the motor inlet and outlet port

29
Q

What type of valve is this?

A

Brake valve

30
Q

What do Lock valves do?

Also known as Line Lock and Double pilot operated checks

A
  • Hold a suspended load in the event of a hydraulic line rupture
  • Prevent the load from drifting due to leakage in the directional control valve
  • Prevent the load from overspeeding the actuator
31
Q
A
32
Q

What valve is shown in this circuit?

A

Lock Valve
Or
Line lock
Or
Double pilot operated check valves

33
Q

What are two classifications that apply to pressure control valves?

A

Normally Open
And
Normally Closed

HET3 Hydraulics (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions