Hydraulics

Question 1

Where are pilot to open check valves used?

Answer 1

To lock cylinder in place without internal leakage until the main DVC shifts.

Question 2

What is an advantage of a right angle check valve compared to a straight check valve?

Answer 2

Can handle flow 3 times as high

No turbulence

Question 3

What are the five DVC centres?

Answer 3

Closed

Open

Tandem

Float

Regenerative

Question 4

What are 3 types of servo valves?

Answer 4

Flapper nozzle

Jet pipe

Staging spool

Question 5

What are the five types of centres?

Answer 5

Closed

Open

Tandem

Float

Regenerative

Question 6

What is a disadvantage of an inline check valve?

Answer 6

Causes a drop in pressure.

Question 7

Explain a counterbalance valve.

Answer 7

Used to control vertical loads

Similar to sequence valve the difference being the internal drain had replace the sequence valves external drain.

Normally closed

Reverse flow bypass

Question 8

What would determine if a pressure control valve required an external pilot drain?

Answer 8

Outlet pressure (back pressure)

Question 9

Which proportional DVC control provides the most accurate flow?

Answer 9

Closed outer loop

Question 10

A pressure reducing valve can either be ______ acting of _____ operated.

Answer 10

Direct acting or pilot operated

Question 11

What are some functions of an unloading valve.

Answer 11

Used in accumulator circuits

Shock protection

Allows pump to dump fluid back to tank with low pressure/effort.

Question 12

What are 2 uses for a brake valve?

Answer 12

Prevent excessive pressure buildup when decelerating or stopping a load. ( pressure intensification)

Prevents run away loads.

Question 13

Explain detent actuation.

Answer 13

Little groves in spool

Holds until forced out of groove ( normally leaver actuated)

Question 14

Explain a closed inner loop and a closed outer loop system.

Answer 14

Closed inner controls the spool only

Closed outer had the greatest accuracy.

Question 15

What is cavitation?

How is it recognizable?

What are some effect?

Answer 15

Is a violent collapse of vapour gas bubbles.

Rattling noise, low pressure at pump inlet.

Rapid erudition of metal suffices, severe pump damage, flow reduction.

Question 16

Explain a regenerative circuit in a hydraulic system.

Answer 16

Is designed to provide equal speed and force when the cylinder extends and retracts.

Question 17

What are 4 causes of cavitation?

Answer 17

Clogged inlet filter

Clogged breather

Inlet pipes to small

Fluid is to think

Oil level is to low

Question 18

What are some advantages of hydraulics?

Answer 18

Infinitely variable speed control

Infinitely variable torque/force control

Highly accurate control of movement

Compact

Very little loss from friction

Question 19

What are some disadvantages of hydraulics?

Answer 19

Expensive

Heavy

High pressure fluid hazard

Messy

Question 20

What does pascals law say about fluid at rest in a container?

Answer 20

Pressure is undiminished

Equal in all directions to right angles in the container.

Question 21

What are 3 measurement of pressure?

Answer 21

Gauge

Absolute

Atmospheric

Question 22

How is pressure produced?

Answer 22

By a pump

Resistance to flow

Question 23

What is the flow triangle used for?

Answer 23

Sizing cylinders

Sizing pumps

Calculating speed

Q = S x A
S = Q / A
A = Q / S

Question 24

What is the maximum pump inlet velocity?

What is the maximum pressure line velocity?

Answer 24

Inlet. 2-4 feet per second

Line. 7-20 feet per second

Question 25

What are the 2 types of cartridge valves?

What GPM would you use each one for?

Answer 25

Screw in, 30-35 GPM

Slip in, over 40 GPM

Note: screw in must be throw out after taken out because it has threads.

Question 26

Explain dead band compensation.

Answer 26

Briefly boosts prowler to make spool jump across the overlap distance.

Question 27

Explain what ramp means.

Answer 27

Controls speed of voltage

Controls acceleration/ deceleration of actuators.

Question 28

No feedback means what?

Answer 28

No signal is returned to control RPM is change is needed. (Open loop)