Seals

Question 1

What is a Static seal?

Answer 1

A seal used between two stationary parts.

Question 2

What is a Dynamic seal?

Answer 2

A seal used between a moving and a stationary part.

Question 3

What is the purpose of a seal?

Answer 3

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

Question 4

Are all Static seals a positive seal?

Answer 4

Yes.

Question 5

What is a Positive seal?

Answer 5

A seal that prevents leakage between stationary and moving parts.

Question 6

What is a Non-Positive seal?

Answer 6

A seal that controls leakage between stationary and moving parts.

Question 7

What are the three functions of Gaskets?

Answer 7

• seal against a pressure load
• seal against leakage
• control position

Question 8

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

Answer 8

Internal pressure and hydrostatic end force.

Question 9

What are the four gasket and flange arrangements?

Answer 9

• flat face
• raised face
• tongue and groove
• spigot and recess

Question 10

When are non-metallic gaskets used?

Answer 10

Low pressure applications.

Question 11

When are metallic gaskets used?

Answer 11

High pressure and high temperature.

Question 12

How does a metallic gasket seal?

Answer 12

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

Question 13

What are the two types of sealants?

Answer 13

Hardening and non-hardening.

Question 14

What are the two types of hardening sealants?

Answer 14

Flexible and Rigid.

Question 15

What are the two types of Dynamic seals?

Answer 15

Contact and Clearance.

Question 16

What is a Contact seal?

Answer 16

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

Question 17

What is a Clearance seal?

Answer 17

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

Question 18

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

Answer 18

Yes.

Question 19

What is Inside packed?

Answer 19

Packing installed in the moving unit.

Question 20

What is Outside packed?

Answer 20

Packing installed in the stationary unit?

Question 21

What are the four things Packing must withstand?

Answer 21

• temperature
• pressure
• various fluids
• shaft misalignment

Question 22

What does a Lantern Ring (Seal Cage) do?

Answer 22

It distributes fluid under pressure to the packing.

Question 23

What is used to remove old packing?

Answer 23

Packing Puller.

Question 24

Name two types of Balanced packing?

Answer 24

U-Ring and V-Ring.

Question 25

Is Cup packing considered to be balanced?

Answer 25

No.

Question 26

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

Answer 26

135% - 150%.

Question 27

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

Answer 27

10% of the ring diameter.

Question 28

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

Answer 28

Anti-Extrusion Rings or Backup Washers.

Question 29

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

Answer 29

Floating Packing.

Question 30

Are piston rings considered a Positive Seal?

Answer 30

No because they leak slightly.

Question 31

What are the two facings of a Lip Seal called?

Answer 31

Inclusion (inward) and Exclusion (outward).

Question 32

What are Ring Seals?

Answer 32

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

Question 33

What is a Wiper Seal?

Answer 33

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

Question 34

What are Boots and Bellows?

Answer 34

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.

Question 35

What is a Diaphragm seals?

Answer 35

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.

Question 36

What are the two types of Diaphragm seals?

Answer 36

Flat and Rolling.

Question 37

What is a Mechanical seal?

Answer 37

An extremely efficient axial seal.

Question 38

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

Answer 38

Yes.

Question 39

What are the four types of Clearance seals?

Answer 39

- bushings - annulus - slinger - labyrinth