Rubber Lining

Rubber Lining Material: Your Ultimate Guide to Protection and Durability

Rubber lining points to the process of adding a layer of rubber to the surface of various materials and equipment, such as tanks, pipes, valves $ flanges etc.

Rubber lining or the protective layer of rubber helps to prevent corrosion, chemical damage, and abrasion thereby extending the life span of the material and improving overall performance. This kind of protective coating is mainly used in industries, including wastewater treatment plants, mining, chemical processing plants and immersion pipes.

The process of rubber lining involves several steps, including surface preparation, rubber selection, and application. Surface preparation is a critical step as it ensures that the rubber adheres properly to the surface of the material being lined. This process involves cleaning, sandblasting, and priming the surface to remove any contaminants and provide a rough texture for the rubber to bond with.

Vulcanization

Vulcanisation can be defined as the curing of elastomers. It is a chemical process in which the rubber is heated with sulphur, accelerator and activator at between 140-160deg.C

In other words, the process of treating crude or synthetic rubber or similar plastic material chemically to give it useful properties (such as elasticity, strength, and stability)

What is Vulcanisation?

Vulcanisation is a process of physical and chemical changes during the application of heat by cross-linking unsaturated hydrocarbons of natural rubber with the percentage of addition of sulphur

Vulcanized Rubber – Rubber Lining

Vulcanisation is a chemical process in which the rubber is heated with sulphur, accelerator and activator at 140–160°C. The process involves the formation of cross-links between long rubber molecules so as to achieve improved elasticity, resilience, tensile strength, viscosity, hardness and weather resistance.

After the Application of rubber lining or coating, it is sent to an Autoclave/Chamber for curing/Vulcanization. The applied Elastomer coating is vulcanised in a steam pressure at a temperature of 130-150 deg.C for a period of 3.5 to 4 hours.

After the curing process the rubber is taken out and left for cooling, this rubber (Neoprene) converts to thermosetting

Thickness is applied in 3-4 layers of rubber. Each layer could be ranging from 2-6 mm. Tests such as Hardness, holiday detections, thickness, adhesion tests & hammer tests are carried out.

Differences

– Unvulcanized

– Less elastic

– Softer

– Weaker

– Cannot withstand higher temperature

– Easily oxidized

– Becomes soft and sticky easily

Vulcanized

– More elastic

– Harder

– Stronger

– Can withstand higher temperature

– Less oxidized

– Does not become soft and sticky easily

What Is Polychloroprene?

Polychloroprene is the polymer name for the synthetic rubber known as neoprene it is a corrosion protective coating (Rubber Lining). Neoprene, also known as polychloroprene, is one of the first synthetic rubber products ever made

It is a high-performance multipurpose elastomer product because of its inherent balance of good mechanical and physical properties. Neoprene is a commercial name for polymers comprised of chloroprene.

Rubber Lining Material

The neoprene coating must withstand exposure to oxidation and ozone, continuous immersion in aerated seawater and a wide temperature range.The coating must also have good resistance to mechanical damage, and exhibit strong adhesion to steel and cathodic dis-bondment resistance.

Application Process of Rubber Lining

Climatic Condition

The pipe surface temperature shall be at least 3oC above the dew point and this shall be checked using a hygrometer and a digital thermometer.

The surface may be heated prior to blasting. The ambient temperature must be above 10oC and the humidity shall be less than 85%.

Precleaning & Surface Preparation

Remove grease and oil if any, using approved solvents which do not have residue.

Following degreasing all surfaces shall be detergent washed with 5% Biprox or equivalent, rinse repeatedly with high pressure (3000 psi) potable water with less than 200ppm total dissolved solids and less than 50ppm chlorides and allow to dry.

Check by quantitative chemical analysis (Salt meter) for soluble salt contamination, if present, salt contamination should be removed from the pipe spool surface by rinsing with high-pressure fresh potable water.

The acceptable limit for the salt on the pipe is 1. 8 μg/cm2 max., after blasting.

Approved Garnet shall be used to provide the required anchor profile. Check blasting air for oil and moisture contamination.

Application of Primer and Bonding Agent

Bonding agents and primers shall be thoroughly mixed prior to use and stirred continuously or at frequent intervals to prevent sedimentation. The Vendors recommendation for use and stipulated maximum and minimum drying times must be carefully observed.

Application of Elastomer

The elastomer shall be applied onto the pipes up to and including 10 inches to attain a uniformly cured thickness of 15 mm ± 2 mm pipes. Above 10 inches shall receive uniform cured elastomer at a thickness not less than 20mm ± 2mm unless stated otherwise.

Environmental conditions shall be controlled throughout the elastomer application.

Unless otherwise specified the Neoprene coating shall extend in the atmospheric zone up to the riser flange or +5 meters above the mean sea level whichever is higher.

Coating of Straight Pipe Joints

The coating operation shall take place on an automatic pipe coating machine. The extruder, a cold feed unit with variable pitch screw, shall produce a continuous strip of fresh, warm compound which is spirally wound onto the rotating pipe joint and is then firmly stitched down using a pressure roller. The overlap of each helix should be a minimum of 60% and shall ensure that the pipe surface is completely covered and that there is no air entrapment.

End stoppers shall be placed to prevent extrusion of the neoprene during curing and provide a band (of about ½”) to be torn off to check the bond to the pipe.

The traverse speed of the carriage and the speed of rotation of the joint, the overlapping of the strip, and hence the coating thickness, shall be controlled. The speed of the extruder shall be automatically regulated to maintain the correct tension on the strip.

Nylon Tape Wrapping

On the carriage of the coating machine, nylon tape (75 mm – l00 mm width) shall be wound onto a spool which is mounted on an adjustable disc braking system.

The tape shall be then wrapped, by hand, around the end of the pipe joint and the coating operation is commenced. An overlap of 50% shall be achieved by the synchronised speeds of the rotation of the pipe and the carriage traverse. The carriage shall be adjusted to move approximately 25 mm per revolution of the pipe.

Tape tension and overlap shall be adjusted to ensure good consolidation of the coating. At the end of the pipe, the carriage is reversed to produce a 12″ double-wrapped area in order to maintain tension and the end of the nylon tape is secured by means of fiberglass adhesive tape.

Vulcanisation

Following pipe and fitting coating and tape wrapping, the section shall be placed into a steam-pressure autoclave within 24 hours. Temperature and pressure shall be specified by the Contractor in accordance with Vendor’s recommendation. At the end of the prescribed cure period, the autoclave shall be shut down and the pipe/fitting removed.

Vulcanisation – Continuous monitoring of the temperature is required and records shall be attached to the Contractor quality control documentation.

The tape wrapping shall not be removed until the coating temperature is reduced to ambient.

Where the section to be vulcanized is too large to carry out autoclave curving, vulcanization can be carried out in a nylon tape-wrapped section by means of electrical heating tapes

INSPECTION AND TESTING

Every coated component shall be inspected for surface imperfections, lack of bond at joints and ends, blisters, delaminations, cuts, indentations, excessive tape marking and other apparent irregularities.

Following Tests Required

Sounding (Hammer Test)
Adhesion Test
Hardness Test
Electronic Spark Test
Post Cure Thickness Measurement

EQUIPMENT FOR TESTING PCP PROPERTIES

Rubber Hardness Testing Equipment
Rheometer and Viscometer
Electronic Densimeter
Computerised Universal Testing Machine
Compression Set equipment
Abrasion Resistance equipment

Key Takeaways: Rubber Lining Material Selection According to Your Needs

Analyze your environment and the needs associated with your application.
Understand the different kinds of rubber available and their specific properties.
Experience with a reliable supplier will guide you on who to use.

Conclusion on Rubber Lining

Rubber Linings for Maximum Protection and Long Life
The proper rubber lining material can make a huge difference in the protection of your equipment and increase its lifespan.

Rubber Lining | Rubber Lining Material | Vulcanization