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Instrumentation > Final Control Element > Flashcards

Final Control Element Flashcards

1
Q

A direct acting actuator does what with air pressure

A

Extends with increased pressure

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2
Q

A reverse acting actuator does what with increasing air pressure

A

Retracts with increasing air pressure

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3
Q

A direct acting valve

A

Is normally open

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4
Q

A reverse acting valve is

A

Normally closed

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5
Q

Valve F O def

A

Fails open

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6
Q

A piston actuator is used

A

When the stroke or thrust of a diaphragm actuator is too short

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7
Q

A valve positioner

A

Positions the valve stem and plug

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8
Q

2 types of electric actuators

A

Solenoid and motor

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9
Q

Springs convert from a double acting rack n pinion actuator too :

A

A single acting, ie the air opens , springs close

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10
Q

Scotch yoke actuators are for

A

2 position operation. I side energized the other side vented

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11
Q

A current to pressure transducer

A

Changes a 4 to 20 ma signal to 3 to
15/20 to 100 kPag

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12
Q

Trip valves

A

Fail/shutdown the system when supply pressure falls below a certain point . Resets when pressure comes up

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13
Q

4 types of actuators

A
  • manual
  • pneumatic
  • electric
  • electro hydraulic
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14
Q

On rotary actuators how often should PMs be done

A

Every 6 months

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15
Q

Bench set is

A

Applying low and high pressure to a diaphragm actuator to get rated valvebplug travel

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16
Q

Why is a weaker actuator spring better than reductions actuator control pressure when differential pressure causes issues,?

A

Because the 20 to 100 kPg signal is often fixed

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17
Q

Hazards associated with servicing controls

A
  • high pressure instrument air
  • electrical power sources
  • stored spring energy
  • pinch points
  • hydraulic fluids
18
Q

Most volume boosters have a gain of

A

1

19
Q

A reciprocal control valve is aka

A

Sliding stem

20
Q

A segmented ball valve is called

A

A chatacterised

21
Q

If a valve won’t stroke at all the issue could be

A

Excess friction/ packing too tight

22
Q

Flashing is

A

Pressure decrease causes the liquid to explode into vapour

23
Q

Cavitation aka

A
  • increased pressure causes liquid to implode back into the fluid,
  • micro jets
24
Q

Def the point of smallest constriction and fastest velocity / least pressure

A

Vena contracta

25
Q

______ damages the trim with a smooth polished appearance

A

Flashing

26
Q

_____ damages the trim with erosioncausing pitting

A

Cavitation

27
Q

Damage type that causes excessive noise and vibration

A

Cavication

28
Q

Anti cavitation trim works how

A

Many smaller holes separates the pressure drop reducing chances of flashing therefore cavication

29
Q

Using a whisper cage can reduce noise by _____ db

A

30 db

30
Q

Industry standard material for valves

A

Type 316 stainless

31
Q

Cro-moly wc9 good for what kind of valve service

A

Steam n boiler feed water

32
Q

317 stainless used for valves of what service

A

Pulp/ paper
Ie : digester

33
Q

Fail safe mode of an air to open valve

A

Failed closed

34
Q

Fail safe mode of an air to close valve

A

Fails open

35
Q

Valve symbol with arrow pointed at “head”

A

Fail open

36
Q

Valve symbol with arrow pointed away ( down ) from head

A

Fail closed

37
Q

Valve symbol with 2 arrows at/away from head

A

Drift open or drift closed

38
Q

For general safety what fails closed

A

Steam / hot oil

39
Q

For general safety what fails open

A

Cold/ chilled watee

40
Q

Flow direction for an unbalanced valve are almost always _____
Because _____

A

FTO flow to open
Because other way will try to close valve giving poor control

41
Q

Noise and cavitation control flows are

A

Opposite

42
Q

PTFE IS also called

A

Teflon

Instrumentation (6 decks)

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