Millwright Mechanics- 3rd Year Exams - Introduction to
Hydraulics
1. 1. What is the main hazard to always be aware of when you are working on
hydraulic systems?: 1. high pressure
2. 2. What hazard can exist after a hydraulic system has been locked out?: 1.
The system can still be charged with high-pressure fluid.
3. 3. What is the safety reason for taking time to completely understand a
hydraulic system before you begin work on it?: 1. so you can isolate and
depressurize the part of the system on which you will be working
4. 4. Does a hydraulic system develop power?
a) yes
b) no: 1. b) no
5. 5. List the five main parts of a hydraulic system.: 1. reservoir, conductors,
pump, control valves, actuators
6. 6. What is the first main valve after the pump in a hydraulic system?: 1. the
maximum pressure relief valve
7. 7. What are the three functions of a maximum pressure relief valve?: 1. to
protect the system from overload; to divert excess fluid not required by the actuator
back to the tank; and to set the maximum operating pressure in the system
8. 1. Is a pressure-reducing valve normally open or closed?: 1. normally open
9. 1. What is the purpose of a sequence valve?: 1. to allow an actuator to operate
only after another actuator has completed its cycle
10. 1. What valve would you use to prevent the uncontrolled fall of a load due
to gravity?: 1. a counterbalance valve
11. 1. Why is it important to attach an external drain to a sequence valve or to
a pressure-reducing valve?: 1. to prevent the valve from locking up under load
12. What is the purpose of a flow control?: 1. to control the speed of the actuator
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, Millwright Mechanics- 3rd Year Exams - Introduction to
Hydraulics
13. 1. Name three types of flow controls.: 1. meter in, meter out and bleed-off
14. 1. Which type of flow control is the most energy efficient?: 1. the bleed-off
control
15. 1. What is the purpose of cross port relief valves on a hydraulic motor?: 1.
to protect the motor against shock loads, especially when suddenly shifting from
forward to reverse
16. 1. What is pressure?: 1. Pressure is force on a unit of area.
17. 1. When pressure is applied to a fluid that is at rest and confined in a
system, is this pressure distributed equally throughout all parts of the system
or is it concentrated in some parts of the system?: 1. It is distributed equally to
all parts of the system.
18. 1. If a pump delivers flow through an open-ended pipe that has no restric-
tion to the flow, is the pressure at any point in the pipe high, low or zero?: 1.
zero at all points.
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, Millwright Mechanics- 3rd Year Exams - Introduction to
Hydraulics
19. 1. Why is pressure transmitted almost instantly through hydraulic fluid?: 1.
It is almost incompressible.
20. 1. What is meant by gauge pressure?: 1. Gauge pressure is the pressure
indicated on a pressure gauge without including atmospheric pressure.
21. 1. Why does a cylinder have a lower load capacity when it retracts than
when it extends?: 1. The fluid pressure has less area to push on at the rod end of
the piston because the rod occupies part of the piston area.
22. How can you increase the force exerted by a cylinder of any given size?: 1.
by increasing the setting of the operating pressure
23. Would you use a larger or a smaller cylinder if you needed to increase the
load capacity at a given pressure?: 1. a larger cylinder
24. 1. At a given pressure setting, what is the load capacity of a 2-to-1 cylinder
when it extends compared to when it retracts?: 1. twice the capacity for extend-
ing than retracting
25. 1. Does a pump produce pressure, flow, or both pressure and flow?: 1. flow
only
26. 1. Will there be high flow, low flow, or no flow if the pressure is 10 000 psi
on the upstream side of an orifice and 10 000 psi on the downstream side?: 1.
no flow
27. 1. For a given flow rate, which moves faster: a large diameter cylinder or a
small diameter cylinder?: 1. a small diameter cylinder
28. 1. How fast does a two-to-one cylinder extend compared to how fast it
retracts?: 1. It extends at half the speed of retraction.
29. 1. What is the purpose of a regenerative circuit?: 1. to provide equal speed
and equal force in both directions
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16
Hydraulics
1. 1. What is the main hazard to always be aware of when you are working on
hydraulic systems?: 1. high pressure
2. 2. What hazard can exist after a hydraulic system has been locked out?: 1.
The system can still be charged with high-pressure fluid.
3. 3. What is the safety reason for taking time to completely understand a
hydraulic system before you begin work on it?: 1. so you can isolate and
depressurize the part of the system on which you will be working
4. 4. Does a hydraulic system develop power?
a) yes
b) no: 1. b) no
5. 5. List the five main parts of a hydraulic system.: 1. reservoir, conductors,
pump, control valves, actuators
6. 6. What is the first main valve after the pump in a hydraulic system?: 1. the
maximum pressure relief valve
7. 7. What are the three functions of a maximum pressure relief valve?: 1. to
protect the system from overload; to divert excess fluid not required by the actuator
back to the tank; and to set the maximum operating pressure in the system
8. 1. Is a pressure-reducing valve normally open or closed?: 1. normally open
9. 1. What is the purpose of a sequence valve?: 1. to allow an actuator to operate
only after another actuator has completed its cycle
10. 1. What valve would you use to prevent the uncontrolled fall of a load due
to gravity?: 1. a counterbalance valve
11. 1. Why is it important to attach an external drain to a sequence valve or to
a pressure-reducing valve?: 1. to prevent the valve from locking up under load
12. What is the purpose of a flow control?: 1. to control the speed of the actuator
1/
16
, Millwright Mechanics- 3rd Year Exams - Introduction to
Hydraulics
13. 1. Name three types of flow controls.: 1. meter in, meter out and bleed-off
14. 1. Which type of flow control is the most energy efficient?: 1. the bleed-off
control
15. 1. What is the purpose of cross port relief valves on a hydraulic motor?: 1.
to protect the motor against shock loads, especially when suddenly shifting from
forward to reverse
16. 1. What is pressure?: 1. Pressure is force on a unit of area.
17. 1. When pressure is applied to a fluid that is at rest and confined in a
system, is this pressure distributed equally throughout all parts of the system
or is it concentrated in some parts of the system?: 1. It is distributed equally to
all parts of the system.
18. 1. If a pump delivers flow through an open-ended pipe that has no restric-
tion to the flow, is the pressure at any point in the pipe high, low or zero?: 1.
zero at all points.
2/
16
, Millwright Mechanics- 3rd Year Exams - Introduction to
Hydraulics
19. 1. Why is pressure transmitted almost instantly through hydraulic fluid?: 1.
It is almost incompressible.
20. 1. What is meant by gauge pressure?: 1. Gauge pressure is the pressure
indicated on a pressure gauge without including atmospheric pressure.
21. 1. Why does a cylinder have a lower load capacity when it retracts than
when it extends?: 1. The fluid pressure has less area to push on at the rod end of
the piston because the rod occupies part of the piston area.
22. How can you increase the force exerted by a cylinder of any given size?: 1.
by increasing the setting of the operating pressure
23. Would you use a larger or a smaller cylinder if you needed to increase the
load capacity at a given pressure?: 1. a larger cylinder
24. 1. At a given pressure setting, what is the load capacity of a 2-to-1 cylinder
when it extends compared to when it retracts?: 1. twice the capacity for extend-
ing than retracting
25. 1. Does a pump produce pressure, flow, or both pressure and flow?: 1. flow
only
26. 1. Will there be high flow, low flow, or no flow if the pressure is 10 000 psi
on the upstream side of an orifice and 10 000 psi on the downstream side?: 1.
no flow
27. 1. For a given flow rate, which moves faster: a large diameter cylinder or a
small diameter cylinder?: 1. a small diameter cylinder
28. 1. How fast does a two-to-one cylinder extend compared to how fast it
retracts?: 1. It extends at half the speed of retraction.
29. 1. What is the purpose of a regenerative circuit?: 1. to provide equal speed
and equal force in both directions
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16
