PDF notes

Question 1

What is hydraulics

Answer 1

the study of liquids

Question 2

What is Pascal’s law?

Answer 2

Pressure applied on a confined fluid is transmitted undiminished in all directions, and acts with equal force on equal areas, and at right angles to them.

Question 3

What are the advantages of hydraulic power?

Answer 3

1. produces high power output with very small weight and size
2. requires minimum day to day maintenance because the same hydraulic fluid used to drive the system is also used to lubricate the parts inside the hydraulic system.
3. is simple to operate
4. can be operated at varying speeds
5. is reversible
6. can be stalled without damage when overloaded and will start up immediately when the load is reduced
7. Can be hooked up in a variety of configurations wherever they are needed to operate most efficiently.

Question 4

Hydraulic systems are significantly less efficient than direct-drive systems.

Answer 4

True

Question 5

What causes hydraulic system’s inefficiency to be more than that for direct-drive systems?

Answer 5

internal leakage called “slip” which is required to lubricate and cool the internal mechanical components of the hydraulic drive system.

Question 6

Why is hydraulic power parasitic in nature?

Answer 6

it derives power from other sources

Question 7

Horsepower

Answer 7

33,000 pounds lifted one foot in one minute.

Question 8

Horsepower equation

Answer 8

multiply the pressure times the fluid rate.

gpm x psi

Question 9

What are the major components of of the hydraulic system?

Answer 9

1. Fluid
2. Plumbing
3. Pumps
4. Actuators
5. Reservior
6. Heat Exchangers

Question 10

Name a non-positive displacement pump.

Answer 10

C-pumps

Question 11

What are non-positive displacement pumps typically used for?

Answer 11

fluid transfer in systems where the only resistance is created by the weight of the fluid and by friction

Question 12

What force do most non-positive displacement pumps operate by?

Answer 12

centrifugal force

Question 13

What defines a non positive displacement pump?

Answer 13

a pump with no positive seal between the inlet and outlet ports, and pressure capabilities are a function of drive speed.

Question 14

For non positive displacement pumps, is the output reduced as the resistance is increased.

Answer 14

True* in fact, it is possible to completely block off the outlet while the pump is running

Question 15

What is second only to contamination in the hydraulic fluid as a source of damage to hydraulic equipment?

Answer 15

cavitation

Question 16

How is cavitaion is caused?

Answer 16

When you pull suction on the fluid, and the pressure at the pump drops below the vapor pressure of the fluid.

Question 17

True or false, Collapsing cavitation bubbles can cause localized stress that literally explodes out small fragments of metal off the pump.

Answer 17

True

Question 18

What is the localized damage due to cavitation called?

Answer 18

pitting damage

Question 19

What is the best way to avoid cavitation?

Answer 19

by designing the equipment so there is adequate net positive suction head (NPSH). One way of doing this is placing the reservoir significantly higher than the pump and by always keeping the reservoir full.

Question 20

What is the role of actuators?

Answer 20

actuators convert hydraulic energy back into mechanical energy.

Question 21

What are the two types of hydraulic actuators?

Answer 21

cylinders and motors

Question 22

True or False. Almost all actuators are reversible, including those used by Schlumberger

Answer 22

True

Question 23

Motors are defined by their performance on four ratings. What are they?

Answer 23

1. maximum pressure limitations
2. displacement
3. speed
4. torque capacity

Question 24

How can flow rate be determined?

Answer 24

multiplying the displacement by the rotations per minute of the device.

Question 25

What is motor speed measured in?

Answer 25

rpm (revolutions per minute)

Question 26

What is maximum motor speed rating defined as?

Answer 26

the highest number of revolutions per minute that the motor can maintain without sustaining damage at a given inlet pressure over a specified period of time.

Question 27

What is torque defined as?

Answer 27

turning or twisting effort. It is the force component of the output of a motor and is expressed in inch-pounds, foot-pounds or newton-meters.

Question 28

What is the mechanical efficiency of a motor?

Answer 28

the ratio of its actual torque delivered to its theoretical torque

Question 29

True or False. Cylindrical or linear actuators output straight-line motion and force

Answer 29

True

Question 30

True or False. Cylindrical or linear actuators have only one fluid chamber and exert force in only one direction

Answer 30

True

Question 31

What is the role of the reservoir?

Answer 31

1. hold the fluid 2. dissipate heat 3. allow entrained air to escape 4. allow solids to settle

Question 32

What type of reservoirs are typically used by Schlumberger?

Answer 32

atmospheric

Question 33

Why are heat exchangers present on hydraulic circuits?

Answer 33

to provide more efficient temperature control of the hydraulic fluid than can be accomplished by the reservoir alone

Question 34

What are a few sources of contamination in which filtering systems seek to remove?

Answer 34

1. built in, such as debris left from the manufacturing process 2. environmentally introduced, such as particles or moisture 3. entering through a breather 4. internally introduced, such as dirt in the fluid

Question 35

Describe oil breathing in a hydraulic system.

Answer 35

When hot oil returns to the hydraulic reservoir and cools, it contracts

Question 36

True or False, Most Schlumberger systems rely on both suction strainers and return filters

Answer 36

True

Question 37

What are the 3 main types of valves?

Answer 37

1. Directional control valves 2. Pressure control valves 3. Flow control valves

Question 38

A check valve is a one-way directional valve

Answer 38

True

Question 39

Define hydraulics

Answer 39

a means of transmitting power by pushing on a confined fluid. The input of the system is called the pump while the output is called an actuator.