1. Gaskets & Seals
Nizwa College of Technology

2. Gaskets& Seals
Sealing is the process of preventing gases, liquids and solids escaping from containers or mechanisms.
Seals can be broadly divided into two categories:
Static seals - where there is no movement at the contact points.
Dynamic or Mechanical seal - where there is movement between the contact points.

3. Selection of seal
The choice of seal to be used on a particular application is determined by the following factors:
Property of the material being contained
Amount and speed of any movement
Operating pressure
Life expectancy
Operating temperature

4. Seal Materials Non-metallic materials:
Felt, rubber, asbestos, cork, plastics, P.V.C, paper, cloth etc.,
Metallic materials:
Copper, lead, tin, plated steel, beryllium, and often a combination of several materials is used to make a particular seal or gasket.

5. Gaskets
Gaskets are static seals used to prevent fluids or gases passing across mating surfaces, where there is no movement, on a mechanical assembly
Gasket materials- cork, rubber, asbestos, plastic and metallic materials.

6. Fitting gaskets Important rules to follow when fitting a gasket
Conformation
The sealing pressure should be sufficiently high to make the gasket conform to the joint surfaces.
Too little pressure can result in voids in the joint where leakage could occur.
Too much pressure can result in distortion of both gasket and joint surfaces.
Condition of joint surface
The mating surfaces of the joint should be:-
Free from burrs and indentations. '
Reasonably flat and mate together.
Clean and free from oil, grease and other materials.

7. Reasons for leakage in the joint
Wrong gasket material
Incorrect fitting gasket
Poor Joint surfaces
No conformation
Distortion of surfaces
Inaccurate tensioning

8. Dynamic or Mechanical Seals
Mechanical seals are used where there is movement between the parts being sealed
Types
Radial lip seal
Exclusion seal
Clearance seal
Ring seal
Face seal
Diaphragm seal
Packing

9. Radial lip seals Parts of Lip Seal
Frame stainless steel, Monel metal, titanium, bronze ,hastalloy. Lip - rubber, nitrile, chloroprene, ethylene, propylene.
Spring stainless steel, monel, titanium hastallloy.
Features
Take up Little space
Easy to install
Low cost
Accommodate slight misalignment.
One of the most widely used.

10. Fitting mechanical seals
Guide lines to fitting seals
Make sure that the correct type of seal is used, particularly when replacing a seal
Ensure that the housing shaft and seal is in good condition and free from dirt and other foreign matter
Lubricate the surfaces of seal, shaft and housing if necessary
Use a suitable assembly tool if needed
Use a cone or sleeve over any sharp corners of the shaft
Check seal for correct operation before applying power to drive
After a short period of use inspect seal for leaks or other failures

11. Seals &Gaskets-Examples