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Millwright Level 3 > Pneumatic Systems > Flashcards

Pneumatic Systems Flashcards

1
Q

What must always be considered before working on pneumatic systems?

A

Trapped air in the system even though gauge reads 0

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2
Q

Breathing oils mist from pneumatic systems can result in?

A

Respiratory problems

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3
Q

Basic pneumatic systems include:

A

Compressors
Receivers
Filters
Regulators
Lubricators
Mufflers
Dryers
Actuators
Control valves
Conductors

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4
Q

Air intake for the compressor system should be located where?

A

Coolest part of the building. Cooler air is more dense which makes compressors more efficient

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5
Q

Air receivers compensate for fluctuations in demand and can also _________ with reciprocating compressors.

A

Dampen pulsations

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6
Q

Safety relief valves must be mounted _________ on receiver tanks?

A

Vertically

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7
Q

What should the pressure relief valve be set to?

A

No higher than the lowest maximum pressure rating of any part of the the system

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8
Q

What problems does moisture cause in the system:

A

Air supply’s can freeze
- rust receivers and piping forming sludge and rust
- some processes such as painting can be harmed by water
- harmful effects to proper lubrication.

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9
Q

Because pressure are under 200 psi moisture is often present in the lines. It is common to use non corrosive materials such as:

A

Plastic
Brass
Copper
Aluminum

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10
Q

What problem increases expenses and reduces performance of tools?

A

Air leaks

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11
Q

FRL stands for ?

A

Filter - cleans air
Regulator - sets system pressure
Lubricator - adds a mist of oil to components

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12
Q

Contaminants left in a air system may be from?

A

Contaminate left from assembly or maintenance

Oil and west particles from the system

Pipe scale and rust from the system piping

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13
Q

What is the purpose of the regulator

A

Most parts of the system require less pressure than what comes from the compressor.

You can regulate pressure to different actuators in you system

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14
Q

Lubricators?

A

Supply clean oil, cool and seal different components

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15
Q

Does compressor oil carry over aid the pneumatic system?

A

No it tends to accumulate in the piping causing addition problems of gumming up the system

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16
Q

What is one test to determine if the valve s are getting the right amount of oil?

A

Hold a piece of paper near the exhaust port on the valve. Pale indication of oil should be present. If oil is dripping off the page it is getting to much oil

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17
Q

Where do you find water traps?

A

Anywhere in a system where water can be a problem.

Whenever see point is reached moisture falls out of the air

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18
Q

Symbols are meant to graphically portray the characteristics of pneumatic parts which are:

A

-function
- method of actuation and return
- number of connections and parts
- number of different switched positions
- simplified representation of the flow path

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19
Q

Symbols are not meant to show?

A
  • size or dimension of part
  • physical relationship between parts
  • orientation of ports
  • manufacturer or method of construction
  • unions or connections other than junctions
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20
Q

Shut off positions symbol

A
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21
Q

Symbol inlet outlet ports

A
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22
Q
A
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23
Q

Mechanically operated symbols

A
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24
Q

Pneumatic control symbols

A
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25
Q
A
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26
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27
Q
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28
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29
Q
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30
Q

What is the main difference between pneumatic and hydraulic valves?

A

Hydraulic valves operate on much higher pressure

Pneumatic systems often only operate at 100 psi

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31
Q
A
32
Q

What is the difference between a vented and non vented regulator?

A

Vented regulator can also act as a relief valve for the downstream section

33
Q

When should full flow relief valves be used?

A

Whenever large flows of air must be released

34
Q

Hydraulic valves use used lapped spool design to seal. Because that system needs constant lubrication pneumatic valves use packed bore, packed spool, or sliding plate design

A
35
Q

Both packed bore and packed spool use ________ to seal the space between the spool and bore?

A

O rings

36
Q

Sliding plate

A

Can provide many millions of trouble free cycles even in less ideal conditions

37
Q

A typical pneumatic DCV configuration is ?

A

Four-way/three-position (4/3), spring centred, solenoid actuated valve

38
Q

What is a solenoid?

A

A wire coil around a metal plunger when the coil is electrically energized it builds a magnetic field which pulls the iron plunger into the coil

39
Q

What restrictions are commonly overlooked?

A

Quick disconnects
Hoses with ID’s that are to small
Sharp bends
Kinks in hoses

40
Q

Pilot operated valves are operated with _______ and can be internally piloted or _________.

A

Air

Externally piloted

41
Q

Externally piloted valve requires air source to the _______ port. This pressure can be from a low pressure source if _______ shifting is adequate but if quick reaction time ________ is used in conjunction with a quick exhaust.

A

Slow

High pressure

42
Q

Internally piloted valves need ________ and _________ pressure to operate properly.

A

Minimum

Maximum

43
Q

Directing control valves are used for?

A

Control flow path
Speed
Sequence events

44
Q

Check valves

A

Allow air flow in one direction

45
Q

What is the 2/2 valve used for?

A

Usually on off it’s only function is to allow air to flow through. A trigger on a air tool

46
Q

3/2 two valves are used when?

A

Air needs to be released when the valve is closed. Typical operation would be a single acting cylinder.

47
Q

Schematics for DCVS are usually drawn showing the ________ Position. The way they would come out of the manufacture packaging.

A

De-activated

48
Q

What is happening in this drawing?

A

3/2 valve being used to send a pilot signal another 3/2 actuating valve.can be remotely activated.

49
Q

What is a common use for a 4/2 valve?

A

4 ports: one pressure 2 actuator and 1 exhaust

Reversible motion of a cylinder or motor

50
Q

4/2 valves are always extending or retracting. If there is no movement needed what type of valve would you use?

A

4/3

51
Q

4/3 valve with a closed centre allows for what?

A

Piston rod to be stopped in any position but because air is compressible it’s not an accurate way of controlling location

52
Q

5/2

A

Same as 4/2 but two exhaust ports

53
Q

Which special 5/3 valve is like the 4/3 closed centre valve?

A

5/3 blocked centre
Allows load to be held in position

54
Q

What does a 5/3 pressure centre do?

A

Extends two single acting cylinders at once in the centre position. And when shifted to either side controls the cylinders on their own.

55
Q

5/3 exhaust centre

A

In the centre position both cylinder ports are open to exhaust. Rod can be moved in either direction by hand.

56
Q

What does a shuttle valve do?

A

Automatically selects the higher of two pressure sources to supply a pneumatic signal

57
Q

What is the purpose of a flow control?

A

To vary the speed of the actuators in a specific part of the circuit

58
Q

Needle valve is the most popular style of flow control. What other styles are there?

A

Ball and globe flow controls are used in larger systems.

Needle gives the finest control

59
Q

Usually built in _______ valves are included in the flow control. What is the purpose?

A

Check valve

To offer little resistance to flow in the opposite direction

60
Q

What factors affect the accurate control of flow?

A

Uniformity of the applied load

Friction forces (piston seals, rod seals)

Acceleration forces (rate speed is gained)

61
Q

Where is a quick exhaust located and purpose?

A

Used with 3 or 4 ways valves to increase exhaust flow(speed of cylinder)

Normally mounted on the end caps of the cylinder

62
Q

What are excess flow valves

A

Minimize hose whipping the a line breaks

63
Q

What motors are used in impact guns, grinders and drills?

A

Vane motors

64
Q

High speed grinders and dentist drills use what motor

A

Turbine

65
Q

Gear motors are used when high torque is needed. Up to how much HP

A

60

66
Q

When trouble shooting pneumatic systems it is important to use a systematic approach?

A

Either start at the actuator and work you way to the compressor or vice versa

67
Q

Common causes making a cylinder inoperable would be

A

Corrosion

Dried out lubricant

Gumming

Deterioration of rubber parts

Bad piston seals

68
Q

Sluggish or slow moving control valve can be caused by:

A

Lack of lubrication

Swollen seals

Deteriorating packing

Binding caused by excessive pressure

69
Q

Actuator cylinder is drifting

A
  • piston seal is leaking
  • operating valve is leaking
  • connecting lines are leaking
70
Q

Cylinder is sticking or binding

A

The packing on the cylinder rod was overtightened
- cylinder is misaligned
- seals are defective
- pilot pressure is low

71
Q

Cylinder body is leaking

A

Tie rods are loose
- pressure at the cylinder is excessive
- cylinder body seal is pinched or extruded
- tie rods are loose

72
Q

Rod gland seal is leaking

A

Seal is deteriorating

73
Q

Pneumatic valve is blowing to exhaust when not actuated

A

The inlet poppet is not seating

74
Q

Pneumatic valve is blowing exhaust when actuated

A

Valve seals are faulty

  • the valve-to-base gasket is faulty
  • spool is damaged
75
Q

Pilot section is blowing to exhaust

A

Pilot cover is loose

Poppet is not sealing

76
Q

Poppet is chattering

A

Air supply pressure is to low

Pilot pressure or signal pressure is to low

Millwright Level 3 (15 decks)

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