MECHENG236 Hydraulics/Pneumatics Flashcards

Question

Uses of accumulators

Answer 1

Emergency pressure supply Smoothing peak loads

Answer 2

Motor (continuous rotational motion) Rotary and Semi-rotary (limited rotational motion) Linear (hydraulic cylinder)

Answer 3

Simpler Cannot over-extend

Answer 4

Produce limited rotational motion from internal linear motion

Answer 5

Easier to stop and hold

Answer 6

Adv: Large angle range, can use as pump (some) Disadv: More complicated, expensive

Answer 7

Adv: Simpler, cannot over-extend Disadv: Best for end- to-end or oscillatory applications

Answer 8

Adv: Simpler, cannot over-extend, “stop-and- hold” Disadv: More complicated than rotary

Answer 9

Single-acting: Hydraulic pressure acts on one side only Double-acting: Hydraulic pressure acts on both sides of the piston

Answer 10

Piston rod out both ends of casing -equal surface area for extension and retraction

Answer 11

Flow restricted on piston head Increases back pressure near end of stroke Reduces flow rate, slows piston Prevents abrupt end to motion, less damage risk

Answer 12

Provide pressure change between input and output - change proportional to area

Answer 13

Meeting high pressure when low pressure available Can use dissimilar fluids Limited by length of stroke Increase pressure - reduce flow volume

Answer 14

More complicated, safer circuits Control: Pressure, flow, direction

Answer 15

Enable excess pressure to be bled Provide different pressures to different components

Answer 16

Springs Pilot Pressure

Answer 17

Single-stage relief valves (also known as direct acting or check valves) -Max pressure set by spring compression Variant - pilot (sample) pressure line pushes spool. Spring does not resist bulk flow (can be weaker, cheaper) Multi-stage

Answer 18

Direct: Simple, compact, low cost. Suffer hysteresis, losses: If weak spring starts to open at low pressures = hysteresis, losses. If strong spring: starts to open nearer target pressure, does not open far enough (hazard) Two stage valves: Combine two valves, one sampling pilot, one on main line. More complex but less hysteresis. Important for narrow-band pressure response on sensitive components.

Answer 19

Reduce pressure to a set value

Answer 20

Reduce pressure by a set value

Answer 21

Reduce pressure by a fixed ratio

Answer 22

Maintains constant output pressure. Pilot on outflow. If pilot pressure exceeds spring-set target, spool shifts, blocking flow.

Answer 23

Maintain constant pressure difference. Pilot pressure on inflow and outflow. Use a spring to ensure constant pressure difference

Answer 24

Maintain constant pressure ratio Pilot pressure on inflow and outflow Uses area ratio on pilot pressures

Answer 25

Ideally would vary flow rate at pump. If cannot, or have branches, need flow control valve. Introduce flow restriction, slow flow. Combine with non-return valve, reduce flow only one way, free the other.

Answer 26

Flow dividers - split flow into two or more parts, flow constrictors control proportions Non-return (check) valves - prevent flow in one direction

Answer 27

Downstream of pumps (along with relief valves)

Answer 28

Combines non-return valves and pressure control valve -free flow in one direction, set back pressure the other

Answer 29

4/2 4 connections (ports) 2 positions (ways)

Answer 30

-Mechanical -Pneumatic -Hydraulic -Electrical

Answer 31

Cylindrical, maximise filter area, minimise pressure drop Replace regularly Debris enters through open vents, can damage components, clog pipes

Answer 32

- Before reservoirs - Before pump - Before vent

Answer 33

- Provide human monitoring (gauges) - Provide human control (switches)

Answer 34

Pipes (rigid) Hoses (flexible) Fittings (binds hoses and pipes together) Connectors (adapters, connect pipes and fittings to specific components)