Hydraulics

Question 1

What are hydraulic pumps and where are they used?

Answer 1

Hydraulic pumps convert mechanical power or energy into hydraulic power/energy

They are used at the power input end of the system

Question 2

What are the three main types of pumps?

Answer 2

Gear, vane, piston

Question 3

What are the 6 types of piston pumps?

Answer 3

• Simple piston pump
• Swash plate piston pump
• Bent axis pump
• Wobble plate pistion pump
• Simplex piston pump
• Duplex piston pump (double acting reciprocating steam pump)

Question 4

What are accumulators and where are they used?

Answer 4

They are an isolated energy store obtaining a volume of hydraulic fluid under pressure from a spring, dead weight, or compressed air.

Question 5

What are brake power boosters?

Answer 5

Accumulator (pressure intensifier) to add thrust to brake actuation. Located between the footbrake linkage and the master cylinder.

Question 6

What are the four types of brake boosters?

Answer 6

• Vacuum suspended
• Air suspended
• Hydraulic
• Electro hydraulic

Question 7

What are pressure converters and what do they do?

Answer 7

• Also known as pressure intensifiers or de-intensifiers
• Displacement devices peforming as simple pumps
• Low pressure -> larger piston area, vice versa.

Question 8

What are hydraulic actuators and what to they do?

Answer 8

• Convert hydraulic power or energy back into mechanical power or energy.
• Similar to a power input device (ie pump)
• Rotary actuators - hydraulic motors
• Linear actuators - hydraulic cylinders

Question 9

What are the three types of control valves?

Answer 9

Pressure control
Flow control
Directional control

Question 10

Why is pressure control necessary?

Answer 10

Fluid is essentially trapped, so in the interest of the equipment and safety, we must incorporate a relief valve

Question 11

What are the five types of pressure control valves?

Answer 11

• Direct acting/single stage relief valve
• Pilot controlled or two-stage relief valve
• Pressure-reducing valve
• Differential pressure regulator
• Proportioning pressure regulator

Question 12

When are direct-acting/single-stage relief valves used?

Answer 12

When the power being transmitted is comparatively small

Question 13

When are pilot controlled/two-stage relief valves employed?

Answer 13

When sensitive control of the system is required

Question 14

Why are pressure-reducing valves used?

Answer 14

Different maximum pressures exist in the same system, thus pressure reducing valves must be used

Question 15

What are pressure regulators used for?

Answer 15

Used to control a pressure within a certain fixed amount of another pressure (differential and proportioning)

Question 16

What do differential pressure regulators do?

Answer 16

ensures that there is a fixed difference between inlet and outlet pressure at all times, where the difference in pressure will usually correspond to the spring setting.

Question 17

What does a proportioning pressure regulator do?

Answer 17

It maintains a fixed ratio between inlet and outlet pressures

Question 18

How can flow control be achieved?

Answer 18

• Variable pump delivery or throttling valves

Question 19

What are the three types of directional control valves?

Answer 19

Flow divider
Non-return valve
Multi-way directional control valve

Question 20

What is the purpose of a flow divider?

Answer 20

It is used to divide the hydraulic flow into two or more equal parts

Question 21

What is the purpose of a non-return/check valve?

Answer 21

It is used to restrict flows only in one direction?

Question 22

What is a shuttle valve and what is it used for?

Answer 22

It connects two pressure sources to a common outlet.

Question 23

What are multi-way directional valves used for?

Answer 23

Where a double-acting actuator is used, it is necessary to reverse the direction of flow into the actuator so as to obtain reverse motion.