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Industrial Mechanic 2nd Block, Harmonized > Static seals > Flashcards

Static seals Flashcards

1
Q

A static seal is a seal between:

A

two stationary parts

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2
Q

Seals which prevent any fluid from leaking from one side of a system to another are called:

A

positive seals

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3
Q

Seals which control the amount of leakage are called:

A

non-positive seals

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4
Q

Static seals seal two surfaces which have little or no movement. All static seals are ____ seals

A

positive

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5
Q

Two ways of sealing two mating surfaces without additional materials is: (2)

A
  • tapered fit

- interference fit

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6
Q

_____ are installed at a joint between stationary surfaces to seal against a pressure load, seal against leakage, and to control position.

A

Gaskets

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7
Q

Gaskets are sealed by:

A

Force of compression exerted by the bolts

Note: Must be greater than internal pressure, hydrostatic end force (which pushes the joints apart)

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8
Q

When using gaskets to seal housings, it’s important that the original gasket thickness is known and the same thickness replaced. This avoids changing:

A

internal clearance

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9
Q

Always consider gasket ___ when replacing gaskets in an axially split pump with wearing rings

A

thickness

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10
Q

What are these styles of? flat (full) face, raised face (ring), tongue and groove, spigot and recess?

A

gasket joints

Surfaces must be parallel and regular in finish

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11
Q

Gasket material is designed to conform to machined surfaces or to ___ slightly to fill small irregularities.

A

flow

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12
Q

The compression of a gasket is greatest at the:

A

bolt locations

Closer the bolts, more even the compression. Thinner the material, the more bolts you need for even compression

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13
Q

Gasket material should: (3)

A
  • Withstand the bolt load
  • Withstand temperature and pressure
  • be compatible with the product
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14
Q

This non metallic gasket material is inexpensive. Often impregnated with fillers such as wax and seals well against water, oil, petroleum fuel. Temperature limit is 120°C

A

Paper

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15
Q

This non metallic gasket material is used in low pressure applications. Can be impregnated with an elastomer. Seals well against water, oil, and solvent. Useable between -30°C and 150°C

A

Cork

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16
Q

This non metallic gasket material has excellent mechanical properties and resists water and air. Temperature limit is 121°C

A

Natural rubber

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17
Q

This non metallic gasket material includes a variety of materials such as buna-s, buna-n, butyl, neoprene, nitrile, viton, silicone.

A

Synthetic rubber

18
Q

This non metallic gasket material is used today only for special applications like high temperatures and steam turbines

A

Asbestos

19
Q

This non metallic, plastic gasket material resists heat, oil and oxidization, but does not perform well at low temperatures. Temperature limit of 232°C

A

Acrylic

20
Q

This non metallic, plastic gasket material is nearly chemically inert, performs well in extremely low temperatures. -190°C to 250°C

A

Teflon

21
Q

Gaskets are often coloured to show:

A

thickness

22
Q

Metallic gaskets are usually used in what applications?

A

high temperature high pressure

23
Q

Metallic gaskets can be solid or a:

A

composite of several materials

24
Q

Flat, V or U, rectangular, triangular, octagonal, round, oval, spiral-wound, corrugated, embossed, jacketed with a filler core, metallic inner ring and non metallic outer ring are all examples of what?

A

Metallic gasket cross sections

25
Q

Metallic gaskets seal by the:

A

flow or malleability of the gasket when compressed by bolts. Smoother the surface finish, the better the seal

26
Q

The circular gasket can have two styles: (2)

A
  • Ring style

- Full face

27
Q

The ring style gasket is preferred because: (2)

A
  • Takes less time to make it

- Easier to install

28
Q

_____ gaskets are normally supplied pre stamped and formed for a particular application

A

metallic gaskets

29
Q

What two methods can be used to draw out a seal? (2)

A
  • Take measurements and draw from those

- hold the gasket material against the face and transfer it with blueing or by drawing

30
Q

Protect the end of a gasket hole punch with a:

A

block of wood

31
Q

What three things should you do before installing a new gasket? (3)

A
  • Remove all of the old gasket
  • Check faces for irregularities, smooth if necessary
  • Smear a light film of lube on the contact surfaces
32
Q

An o ring can be a static or a dynamic seal, and is usually made of:

A

synthetic rubber

33
Q

An O ring usually does not make a difference to the _______ of machine parts

A

relative position

Note: the joint is designed so the correct compression of the o ring happens when the two machined surfaces are in contact

34
Q

The material for a chosen o ring is chosen to: (2)

A
  • resist chemical
  • suit temperature

Note: O rings not made of synthetic rubber are marked by the manufacturer

35
Q

Metallic O rings are used where extreme conditions of:

A

temperature, pressure, corrosion exist

36
Q

Multi lobed, square and rectangular cross section “o rings” are often used as gaskets in:

A

hydraulic equipment

Note: made from the same materials as standard O rings

37
Q

A _____ is a gasket forming or sealing compound used in zero to low pressure applications. Found in tape, paste, or liquid form.

A

sealant

Usually used with a gasket to fill minor depressions in sealing surfaces caused by corrosion

38
Q

______ sealants are mastic (resit) materials which are soft and adhesive. Usually contain plasticizer which allows them to remain soft.

A

non hardening sealants

39
Q

_____ sealants are available in a variety of materials such as butyl, acrylic, silicone and polyurethane. These materials contain curing or setting agents which allow them to remain flexible

A

hardening-flexible sealants

40
Q

_____ sealants are based on epoxies, polyesters, acrylics, polyamides, or polyvinyl acetates (PVA). Cure to a rigid state. Tend to crack and result in joints that are difficult to remove. Sometimes used to join as well as seal.

A

Hardening-rigid sealants

41
Q

____ are a type of sealant. Available in a variety of shapes for different applications, such as edge, sandwich, lap sealing

A

tapes

Industrial Mechanic 2nd Block, Harmonized (28 decks)

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