Seals

Question 0

What is the function of packing?

Answer 0

It restricts leakage between a moving part and a stationary part.

Question 1

Name two functions of a seal.

Answer 1

Keep lubricant in

Keep contaminants out

Question 2

Name three types of seals.

Answer 2

Lip seals 
Shaft seal 
Double lip seals 
Labyrinth seals 
Mechanical seals

Question 3

Name three types of compression packing.

Answer 3

Braided
Plastic
Metal foil

Question 4

What kind of seal face material would you choose for water? For gasoline? For oil? For acids?

Answer 4

Water – Nickel, ceramic, stellite, bronze
Gasoline – Nickel, ceramic, stellite, cast iron
Oil – Nickle, ceramic, stellite, cast iron
Acid – Ceramic, stellite, Hard faced stainless, Carpenter 20 stainless

Question 5

Name three materials used for packing binders.

Answer 5

Grease
Wax
Elastomers
Teflon 
Other Resins

Question 6

What is the function of a positive drive on a seal?

Answer 6

It allows the seal to rotate along with the shaft.

Question 7

Name five types of positive drive designs in seals.

Answer 7

Dent drive Key drive
Pins Dowels
Snap rings Slot and ear drive
Set screws Roll pins
Drive through the elastomer Press fit or shrink drive
Springs

Question 8

What are some special characteristics of fluids that must be considered when choosing a seal?

Answer 8

See if it is (TRUE FACE)
Toxic/noxious Flammable
Radioactive Abrasive
Unstable Corrosive
Explosive Expensive

Question 9

What special operating environment conditions can affect seal choice?

Answer 9

Very low temperatures
Very high temperatures
High pressure
Vacuum; exclusion of water and particle contamination from ingression

Question 10

What are the ten most important things to find out before specifying a seal?

Answer 10

Dimensions Fluids handled
Temperature range Pressure range
Motion Speed
Material in contact with seal Cycle
Mechanical condition Special requirements

Question 11

Give some performance advantages of different elastomeric packing materials.

Answer 11

Natural rubber – wide temperatures
Chloroprene ( Neoprene ) – oil resistant
BUNA N - Inexpensive and available
BUNA S – oil resistant
Thiokol – resists aromatic hydrocarbons
Polyisobutylene ( Butyl) - resists solvents
Polyacrylate – phosphate ester resistant
Fluorinated ( Viton, Teflon ) - high temperature, resistant to synthetics
Silicones – high temperature

Question 12

What elastomeric seal material is most resistant to degradation by petroleum fluids?

Answer 12

Fluorocarbon such as Viton or Teflon

Question 13

Name three seal materials that can be used with synthetic lubricants.

Answer 13

Teflon
Viton
Buna N

Question 14

What are three types of seals used with journal bearings?

Answer 14

Contact ( felt, cork )
Face (lip, radial, axial)
Mechanical ( the Best )

Question 15

What type of face loading on a seal eliminates the need for springs?

Answer 15

Magnetic

Question 16

What is one of the most important functions of a felt packing seal?

Answer 16

Seal out dust

Question 17

A seal that keeps oil in is called a ____________ seal.

Answer 17

Retention

Question 18

If both retention and exclusion are required, then a _______ seal is required.

Answer 18

Double lip or mechanical

In many applications labyrinth seals are effective at both exclusion and retention

Question 19

Which way should a lip seal face to retain lubricant?

Answer 19

Inward

Question 20

What are the advantages of mechanical seals compared to lip seals?

Answer 20

Suitable for higher speeds

Lower leakage

Question 21

If “zero leakage” were required in an application, what kind of seal would you use?

Answer 21

Double mechanical seal with seal oil between them.

Question 22

Where is the most common area of wear in a pump packing assembly that can allow leakage?

Answer 22

On the pump sleeve between the packing and shaft

Question 23

To slow excessive leaking of a packing seal, it is necessary to tighten the ______.

Answer 23

Packing gland nuts

Question 24

When a packing seal is leaking the right amount, _______ usually results.

Answer 24

Proper sealing & lubrication

Minimum wear & adequate cooling

Question 25

What component in a piston assembly is considered a floating packing?

Answer 25

The rings

Question 26

What are more effective, shields or seals?

Answer 26

Seals

Question 27

What is the most common type of seal?

Answer 27

Lip seal

Question 28

A lip seal forms a tight seal in only __________ ___________.

Answer 28

One direction

Question 29

If both retention and exclusion are required, then a ____________of 2, back to back-double lip seals should be used.

Answer 29

Combination

Question 30

A seal, which keeps contaminants out, is called an ___________ seal.

Answer 30

Exclusion

Question 31

Which way should a lip seal face to seal out dust?

Answer 31

Outward

Question 32

What elastomers are compatible with phosphate ester hydraulic fluids?

Answer 32

Ethylene propylene ( EPM, EPDM, EPR )

Question 33

Labyrinth seals are (contacting/non-contacting) and can be used for (higher/lower) speeds due to their cooler running temperatures.

Answer 33

Non-contacting, higher

Question 34

What is a mechanical seal?

Answer 34

A seal that uses two non-resilient materials arranged so that one is pressed against the other to maintain proper clearance.

Question 35

Maximum pressure that a lip seal can take is _________________ psi.

Answer 35

150

Question 36

What is a static seal?

Answer 36

A seal where there is no movement between mating surfaces (O-rings, gaskets, metal rings)

Question 37

On mechanical seal, where would leakage most likely occur?

Answer 37

Across the face