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Questions & Answers relating to ceramics used for minerals handling and processing plant and machinery
What is a ceramic?
What is sintering?
What is alumina?
What is silicon carbide?
What is silicon?
What is an oxide?
What is a carbide?
What is an advanced ceramic?
Questions & Answers relating to ceramic wear, corrosion and high temperature resistant lining systems and components
Are ceramic lining systems suitable for high impact duty?
Can chutes & hoppers be lined before erection?
If something drops onto, and smashes the tiles, can the damage be easily repaired?
What is the maximum temperature at which ceramic lining systems can be successfully utilised, and do high temperature conditions create any special problems that we need to be aware of?
How cost effective are ceramics for high wear, corrosion, and temperature resistant applications?
Can ceramics be easily cut, shaped and machined?
Can ceramic linings be used in vibrating and rotary equipment?
Can ceramic tiled linings be supplied on steel plates for ease and speed of replacement?
Can fan blades be ceramic lined?
Questions & Answers relating to SuperSeal rotary valve lining systems
What wear life can be expected from a ceramic lined SuperSeal rotary valve?
Are SuperSeal rotary valve ceramic lining systems fragile, and will they survive a valve jam or seizure?
Do we have to supply new valves, or can you fit SuperSeal systems into old, worn out rotary valves?
Does OMEGASLATE design and manufacture complete rotary valves?

Questions & Answers relating to ceramics used for minerals handling and processing plant and machinery

Q: What is a ceramic?

A: Ceramic materials are produced by treating non-metallic, inorganic materials at high temperatures. Modern ceramics include such diverse products as: wear, corrosion, and high temperature resistant lining systems and components; rocket nose cones; nozzles; bulletproof armour; taps, dies and metal cutting tool tips; high temperature self-lube bearings and prostheses.

Q: What is sintering?

A: Sintering is the process of bonding together compacted powder particles at temperatures below their melting point. The driving force is the decrease in surface energy that occurs as the particles merge, and their total surface area lessens. The smaller the powder particles, the faster is the sintering. Sintering is used to consolidate ores in powder metallurgy, and in the making of ceramics.

Q: What is alumina?

A: Alumina, or aluminium oxide, is a colourless or white solid, occuring in several crystalline forms, and is found naturally as corundum, emery and bauxite. Solubility in acid and alkali increases with hydration. The melting point of alumina is 2045 degrees centigrade.

Q: What is silicon carbide?

A: Silicon carbide is extremely hard, with a bluish black insoluble crystalline structure produced by heating carbon with sand at high temperature. Silicon carbides are used as refractories, mechanical and electrical components, cutting tool tips, and as wear, corrosion, and high temperature resistant linings and components.

Q: What is silicon?

A: (Si) is a non-metal in group IVA of the Periodic Table; the second most abundant element (after oxygen), occuring as silica and silicates. It is made by reducing silica with coke at high temperatures. Silicon forms an amorphous brown powder, or grey semiconducting crystals, metallic in appearance. It oxidises on heating, and reacts with the halogens, hydrogen fluoride and alkalis. Silicon is used in alloys, and to make transistors and semiconductors. Silicon melts at 1410 degrees, and boils at 2355 degrees centigrade, and has an sg of 2.42.

Q: What is an oxide?

A: Oxides are binary compounds of oxygen with the other elements. All the elements form oxides except helium, neon, argon and krypton. Metallic oxides are typically ionic crystalline solids (containing the O2- ion), and are generally bases, though the less electropositive metals form amphoteric oxides with acidic and basic properties (e.g. aluminium oxide). Non-metal oxides are covalent and typically volatile, though a few are macro molecular refractory solids (e.g. silicon dioxide).

Q: What is a carbide?

A: Carbides are binary compounds of carbon with a metal, prepared by heating the metal or its oxide with carbon. Ionic carbides are mainly acetylides, which react with water to give acetylene, or methanides, which give methane.

Q: What is an advanced ceramic?

A: An advanced ceramic uses a sophisticated formulation that provides relatively stable mechanical, electrical and thermal properties suitable for advanced engineering applications. An advanced ceramic almost always utilises fine powder technology.


Questions & Answers relating to ceramic wear, corrosion, and high temperature resistant lining systems and components

Q: Are ceramic lining systems suitable for high impact duty?

A: Using the correct size and shape of tile, combined with a high strength, fully flexible or ultra-flexible adhesive, a ceramic tiled lining system can handle runs of mine coal and shale dropping from a height of up to 2 metres, depending upon the angle of impact.

Q: Can chutes and hoppers be lined before erection?

A: If high strength fully or ultra-flexible adhesives are used to bond the lining system in position, it is impossible to remove the tiles without the use of high velocity propane burning equipment. The bonded lining system can be attacked with a sledge hammer, which will smash the tiles, but they will remain securely bonded in position.

We have ceramic lined large prefabricated chutes and hoppers at our works, and transported them throughout the UK and overseas without losing tiles during transportation or erection.

It is extremely important that the correct tile adhesive is selected and used. Omegaslate organic tile adhesives can be used in temperatures of -60 to 350 degrees centigrade, and Omegaslate inorganic adhesives can be used for temperatures up to 1800 degrees centigrade. If a tile adhesive becomes rigid and brittle as a result of low temperature, the bond joint can be fractured by impact energies or structural movements.

Q: If something heavy drops onto, and smashes the tiles, can the damage be easily repaired?

A: Yes. We have experienced instances where ceramic tiles in chute lining systems have been smashed by a freak occurence, and have been subsequently left in the smashed condition for years without any further problems. When a tile smashes into 2 or 3 pieces, the smaller pieces become more difficult to break again.

Q: What is the maximum temperature at which ceramic lining systems can be successfully utilised, and does high temperature create any special problems that we need to be aware of?

A: We have used ceramic lining systems and components in temperatures of up to 1350 degrees centigrade, in hoppers, chutes, cyclone separators and fluidised bed pipe work.

There are a number of special design considerations which must be applied to high temperature ceramic lining systems and components, as follow:

Q: How cost effective are ceramics for high wear, corrosion, and temperature resistant applications?

A: Ceramic lining systems and components are designed to greatly reduce maintenance and replacement costs by dramatically improving the service life of the lining system.

In wet coal chute applications, 95% alumina ceramics can outlast EN8 steel by a factor of 60. In dry chute applications, 95% alumina ceramics can outlast EN8 steel by a factor of 15. In pipe bends, 95% alumina ceramics can outlast EN8 steel by a factor exceeding 150. In rotary valves, 95% alumina ceramics can outlast cast iron by a factor exceeding 40.

Rates of wear depend on the type of material being handled, the handling process used, the hardness, shape and grain size of the material being handled, the velocity and angle of impingement of the material being used, and the material being used to combat wear.

The potential savings achievable by using ceramic lining systems and components can be considerable.

Q: Can ceramics be easily cut, shaped and machined?

A: Fired ceramics can be cut and machined with diamond tooling, which makes the machining of ceramics expensive.

Q: Can ceramic linings be used in vibrating and rotary equipment?

A: Ceramic linings can be used for lining vibrating chutes, screens and feeders, provided a high strength flexible adhesive is used. Weldable tile systems can be used for high temperature applications.

Q: Can ceramic tiled linings be supplied on steel plates for ease and speed of replacement?

A: Ceramic tiled linings can be supplied bonded or welded to steel plates. The plates can then be bolted or welded into position.

Q: Can fan blades be ceramic lined?

A: Fan blades can be ceramic lined using a high strength flexible adhesive. If the tip speed of a fan blade lined with a ceramic having a fracture toughness of around 4 Mpa/m exceeds 70 metres per second when handling materials containing particles of silica, it is likely that the ceramic matrix will disintegrate.


Questions & Answers relating to SuperSeal rotary valve lining systems

Q: What wear life can be expected from a ceramic lined SuperSeal rotary valve lining?

A: If an unlined cast iron RV body wears out in 6 to 8 weeks, we would expect a 95% alumina ceramic lining system to require its first 0.3mm regrind after 5 years operation.

The SuperSeal ceramic lining is usually at least 10mm thick, and can be reground at least 20 times.

Q: Are SuperSeal rotary valve ceramic lining systems fragile, and will they survive a valve jam or seizure?

A: SuperSeal ceramic RV lining systems are not particularly fragile in operation. We have had SuperSeal rotary valves returned to us with the rotor blades bent and the hardened steel blades smashed as a result of a jam-up situation, but their ceramic lining systems have not suffered. All we have had to do to these valves is straighten the vanes and fit new hardened steel sealing blades.

Q: Do we have to supply new valves, or can you fit SuperSeal systems into old, worn out rotary valves?

A: We fit SuperSeal systems into new and old, worn out rotary valves. We have fitted SuperSeal systems to rotary valves so badly worn that the bodies have been perforated. We simply repair the body splits and perforations by welding them, before fitting the SuperSeal systems.

Q: Does OMEGASLATE design and manufacture complete rotary valves?

A: As a rule, we do not manufacture complete rotary valves. However, we will design and manufacture rotary valves for special purpose high wear, corrosion, or high temperature resistant applications that cannot be acquired on the general rotary valve market.


If you have any questions or queries which have not been answered above, or if you would just like further information, please contact Omegaslate.


Omegaslate (UK) Limited, 2 Chirk Close,
Forest Gate, Kidderminster, Worcs. DY10 1YG. United Kingdom.
Tel: +44 (0) 1562 755 824 Fax: +44 (0) 1562 742 979
Email: info@omegaslate.com