Thick Barrier Linings Flashcards
Some thick barrier lining materials are:
- Reinforced plastic materials (such as fiberglass used in polyesters, final esters, epoxy, novolac epoxy, etc.)
-Polymeric sheet materials, including polyethylene - Rubber linings
What are the polymeric plastic sheet materials available?
- poly vinyl chloride (PVC)
- polyethylene (PE)
- polypropylene (PP)
- fluoropolymer materials
- Kynar PVDF
- Halar ETCFE
- Teflon FEP & PTFE
Rubber linings used for in the storage and transportation of:
Acids
certain alkalis,
food, chemicals, and food, products, selected solvent,
specialty chemicals and
other corrosive products, plastic pallets, clays, etc.
Rubber linings are used most commonly in:
Railroad tank cars
truck tanks
barge tanks
What are the two major classes of rubber linings?
Natural and synthetic
What is natural rubber lining?
Derived from latex obtained from Hevia trees and is coagulated with acetic or formic acid.
Unsaturated hydrocarbon known as polyisoprene
What is synthetic rubber lining?
Anyone of a group of man-made elastomers with one or more of the properties of natural rubber
How is rubber lining cured?
Vulcanization
What is vulcanization?
As psysiochemical change, resulting from the cross leaking of unsaturated, hydrocarbon chain of natural rubber with sulfur in the application of heat
What are the three factors that affect the properties of vulcanized product?
Percentage of sulfur and accelerated used, temperature of the curing process, time of cure
What are the cure methods used to vulcanized sheet rubber lining?
Autoclave, internal steam, atmospheric steam, hot water, chemical
Describe soft rubber lining
Greatest flexibility elongation in accommodation to movement of the three groups of rubber, good resistance to a number of corrosive chemicals, excellent abrasion resistance, good temperature resistance up to 140°F, standard for tanks containing hydrochloric acid
Describe try-ply linings
A try apply lining construction is used to form a sandwich which is semi hard, or hard, rubber between two layers of soft rubber
How are triply linings applied?
The steel substrate is coated with a special adhesive primer and then a tie gum (tacky layer of rubber) is applied over the primer to promote bonding of the two surfaces
Triply linings provide excellent corrosion and abrasion resistance. True or false.
True
Semi hard, rubber is compounded with what?
With about 15% by weight of sulfur
Semi hard, rubber linings can be used:
In strong acid concentrations
At temperatures up to 180°F
In water conditioning equipment
In wet chlorine gas
In plating solutions
What are the disadvantages of semi hard rubber linings?
Semi hard rubber compounds:
Are affected by temperature changes
Become very brittle at freezing temperatures
Are not suitable for wide temperature changes
What is an advantage of hard rubber lining?
Can handle highly corrosive solutions such as concentrated HCI and wet chlorine gas at 200 to 220°F
What are hard rubber linings generally used on?
Generally used used on rigid shapes of well-designed equipment that is not subject to rapid temperature changes
What are some characteristics of hard rubber linings?
Low permeability to moisture
Good ab abrasion resistance
Hardness range from 60 to 80 shore D durometer
What are some various types of synthetic rubber?
Butyl
Neoprene
Nitrile
Chlorobutyl
Hypalon
What does butyl rubber have? Excellent resistance to?
Sulfuric acid
Dilute nitric acid
Dilute Hydrofluoric at temperatures up to 200°F
What are some characteristics of chlorobutyl rubber?
Very low permeability
Excellent chemical resistance
Can be applied as thick as 1/2” over tie gum. It is used in flue gas scrubbers in hypochlorite, super phosphorus acid, and sulfuric acid
Neoprene is a general purpose rubber lining and is resistant to:
Lube oils
Gasoline
50% sulfuric acid at 180°F
50 to 70% NaOH
Acid slurries
Ozone
What is nitrile rubber resistant to?
Aliphatic solvents
Animal, vegetable, and mineral oils
Surface conditions and surface preparation requirements are more strict for rubber linings then those required by many liquid dispersion materials. True or false?
True
What are the typical surface preparation requirements for rubber linings?
- Steel shall be new, full weight, steel, free from structural defects
- Steel plate shall be flat with no appreciable warp or buckle
- Steel plate should have a minimum thickness and weight as specified
- Vessel must be braced to avoid bulging
What are the typical surface preparation requirements on wells for rubber linings?
- All welds to be continuous peened and ground to remove sharp edges and high spots
- edges and corners should be ground to a minimum radius as specified
- all spatter should be removed
What is the surface preparation cleaning standard for rubber linings?
Surface should be cleaned of all contaminants and then blasted cleaned to NACE No. 1/SSPC-SP 5 white metal with a surface profile of 1.5 to 2.5 mils
Describe the rubber lining installation process?
Cut lining to proper shape
Edges must fit precisely unless an overlap is to be done
Primer, tie coat, or adhesive applied
Lining positioned and then rolled
Describe rubber lining curing process
Curing is generally performed in an autoclave with live steam at about 50 psi in the temperature of 252 300°F
An inspection of rubber lining may include checking for:
Hardness
Bubbles wrinkles or loose lap seams
Holidays with spark tester
For rubber linings small repairs may be done with what?
A chemically cured rubber such as chlorobutyl
Failures and rubber lining may be caused by:
Incorrect product selected
Using rubber after shelf life has expired
Using rubber that was not properly stored
Incorrect application process
Inadequate cure
Chlorinated polyethyl resins are available as:
Powders
Dispersion/solutions coating
Sheet materials
What are some considerations when applying chlorinated polyether as a coating?
The surface should be cleaned as specified
Each coat should be fused
What are some considerations when applying chlorinated polyether in sheets?
Bonding surfaces must be clean
Adhesive must be applied
Substrate is often heated and rolled
How should chlorinated polyether sheet be prepared?
Cleaned with MEK
Given a light blast or hand sanded
Vacuum cleaned and primed
What are the two basic forms of polyethylene?
High density and low density
What are the three methods for applying polyethylene?
Melting the resin and extruding it onto the surface of the article
Heating the work piece and then emerging it into a fluidized bed
Flame spraying
Which are the most common curing methods for a field applied natural rubber lining project?
A. Autoclave/gas fired
B. Chemical cure
C. Co-Reaction
D. Atmospheric steam or internal steam
D. Atmospheric steam or internal steam
Which component cross-links with the natural rubber, giving a physicochemical change that makes the rubber harder?
A. Unsaturated hydrocarbon
B. Clay
C. Isocyanates
D. Sulfur
D. Sulfur
Typically polymeric sheet materials are ______.
A. Thermosetting
B. Thermoplastic
C. Heat welded together at seams
D. Primed with a suitable adhesive
B. Thermoplastic
C. Heat welded together at seams
D. Primed with a suitable adhesive
