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Millwright Year 2 > Seals > Flashcards

Seals Flashcards

1
Q

What is a Static seal?

A

A seal used between two stationary parts.

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2
Q

What is a Dynamic seal?

A

A seal used between a moving and a stationary part.

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3
Q

What is the purpose of a seal?

A

To prevent leakage of fluid (liquid or gas) and to prevent contaminants from entering.

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4
Q

Are all Static seals a positive seal?

A

Yes.

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5
Q

What is a Positive seal?

A

A seal that prevents leakage between stationary and moving parts.

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6
Q

What is a Non-Positive seal?

A

A seal that controls leakage between stationary and moving parts.

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7
Q

What are the three functions of Gaskets?

A
  • seal against a pressure load
  • seal against leakage
  • control position
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8
Q

The force exerted by the bolts (bolt load) on a gasket must be greater than what?

A

Internal pressure and hydrostatic end force.

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9
Q

What are the four gasket and flange arrangements?

A
  • flat face
  • raised face
  • tongue and groove
  • spigot and recess
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10
Q

When are non-metallic gaskets used?

A

Low pressure applications.

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11
Q

When are metallic gaskets used?

A

High pressure and high temperature.

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12
Q

How does a metallic gasket seal?

A

By the malleability of the gasket when compressed between two surfaces.

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13
Q

What are the two types of sealants?

A

Hardening and non-hardening.

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14
Q

What are the two types of hardening sealants?

A

Flexible and Rigid.

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15
Q

What are the two types of Dynamic seals?

A

Contact and Clearance.

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16
Q

What is a Contact seal?

A

Seals that make contact with the two surfaces to be sealed.

17
Q

What is a Clearance seal?

A

In a Clearance seal the two parts do not touch each other but still maintain a seal.

18
Q

Can a Dynamic seal be both Positive and Non-Positive?

A

Yes.

19
Q

What is Inside packed?

A

Packing installed in the moving unit.

20
Q

What is Outside packed?

A

Packing installed in the stationary unit?

21
Q

What are the four things Packing must withstand?

A
  • temperature
  • pressure
  • various fluids
  • shaft misalignment
22
Q

What does a Lantern Ring (Seal Cage) do?

A

It distributes fluid under pressure to the packing.

23
Q

What is used to remove old packing?

A

Packing Puller.

24
Q

Name two types of Balanced packing?

A

U-Ring and V-Ring.

25
Q

Is Cup packing considered to be balanced?

A

No.

26
Q

What percent of the O-Rings cross section determines the width of the groove it sits in?

A

135% - 150%.

27
Q

Generally what is the “squeeze” placed on an O-Ring?

A

10% of the ring diameter.

28
Q

What should be used with O-Rings if psi is above 1500?

A

Anti-Extrusion Rings or Backup Washers.

29
Q

What type of packing is retained in a groove but not held in a static position?

A

Floating Packing.

30
Q

Are piston rings considered a Positive Seal?

A

No because they leak slightly.

31
Q

What are the two facings of a Lip Seal called?

A

Inclusion (inward) and Exclusion (outward).

32
Q

What are Ring Seals?

A

A non-positive seal which is mounted in a groove in the housing.

33
Q

What is a Wiper Seal?

A

A non-positive seal mounted on the stationary housing to expel foreign material.

34
Q

What are Boots and Bellows?

A

They are a positive seal with one end attached to the housing and one end attached to the moving part. Boots are shorter than Bellows.

35
Q

What is a Diaphragm seals?

A

A positive seal usually used in pumps. It is made from a flexible membrane that does not allow fluid transfer from one chamber to another.

36
Q

What are the two types of Diaphragm seals?

A

Flat and Rolling.

37
Q

What is a Mechanical seal?

A

An extremely efficient axial seal.

38
Q

Does a Mechanical seal need to be constantly run in fluid?

A

Yes.

39
Q

What are the four types of Clearance seals?

A
  • bushings
  • annulus
  • slinger
  • labyrinth

Millwright Year 2 (7 decks)

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