Thick Barrier Linings

Question 1

Two major classes of rubber?

Answer 1

Natural -Derived from latex obtained from hevea trees and is coagulated with acetic or formic acid
Unsaturated hydrocarbon known as polyisoprene
Synthetic - any one of a group of man made elastomers with one or more of the properties of natural rubber

Question 2

What is vulcanisation?

Answer 2

Vulcanisation is a physicochemical (physical and chemical) change resulting from the cross linking of the unsaturated hydrocarbon chain of natural rubber (polyisoprene) with sulphur and the application of heat.

Question 3

Three factors that affect the properties of the vulcanised product are?

Answer 3

Percentage of sulphur and accelerator used
Temperature of the curing process
Time of cure

Question 4

Methods used to cure (vulcanise) rubber are?

Answer 4

Autoclave cure
Internal steam cure
Atmospheric steam cure (also called exhaust steam cure)
Hot water cure
Chemical cure

Question 5

The three categories of natural rubber are?

Answer 5

Soft
Semi-hard
Hard

Question 6

Describe a ‘tri-ply’ lining

Answer 6

A ‘tri-ply- linng construction is used to form a sandwich which is semi-hard, or hard, rubber between 2 layers of soft rubber

Question 7

Some various types of synthetic rubber are?

Answer 7

Butyl rubber
Neoprene Rubber
Nitrile Rubber
Chlorobutyl rubber
Hypalon types

Question 8

Typical rubber lining surface preparation?

Answer 8

1. Steel shall be new, full-weight steel, free from structural defects.
2. Steel plate shall be flat with no appreciable warp or buckle.
3. Steel plate should have a minimum thickness and weight as specified.
4. Vessel must be braced to avoid bulging
5. All welds to be continuous, peened, and ground to remove sharp edges and high spots.
6. Edges and corners should be ground to a minimum radius as specified,
7. All weld spatter should be removed
8. Blast cleaned to Nace No.1/SSPC-SP5 white metal with a surface profile of 38-64 microns (1.5 to 2.5 mils)

Question 9

Some of the causes of failure with rubber linings?

Answer 9

Incorrect product selected for intended service
Using rubber after the shelf life has expired
Using rubber lining that was stored incorrectly
Incorrect application process
Inadequate cure