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Stone Casting Production

Introduction.

Stone casting is among non-numerous group of materials which combine a whole complex of positive operational qualities.

High long life reliability, acid- and alkali-resistance, heat resistance in combination with good dielectric and mechanical properties provides compatibility to such materials as steel, cast iron, heat-resistant materials, steel-concrete units, enlarging life of equipment operation up to 4-15 times depending on operating conditions. Every ton of stone cast units saves 5-8 tons of metal and volume of repair works shortens.

Thermo conductivity less in 50 times and more low coefficient of friction of stone casting in comparison with metals highly improves usage characteristics of equipment, especially in winter time, lows the level of frosting of transportation material on tube line walls, pipes, plates, etc.

Stone casting is produced from melted rocks by casting into iron mould, earth and case forms by central rotating method. Depending on operating and usage conditions stone cast units can be produced with more higher data of wearability and heat resistance. Development of stone casting units is enlarging of their sizes, preparation of separate elements for mechanical way of assembling, for example, 3 or 9 element block multi-cyclones, steel pipes up to 1420mm diameter, 6-12m length, lined cast stone fittings, panels for slag, 2200mm diameter rings for etching wells and so on. Getting of glass-stone casting is an interesting direction of production.

Effective method of more wide usage of stone casting units at plants is using of a new material in construction of developing equipment and in buildings being under abrasive wear, aggressive influence and high temperatures, at works and plants projects.

One ton cast stone production price is lower than one ton of metal. If to take into consideration that weight of one tone of stone is 3 times less than one ton of metal, change to cast stone production from cast iron and metal articles is economically perspective.

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Physical and mechanical properties of cast stone.

Main physical and mechanical properties of cast stone in comparison with gray cast iron, fire clay brick and fire concrete are given in Table 1.

It is clearly seen from Table 1 that cast stone overcomes traditional materials in such characteristics as friction coefficient, acid resistance, and hardness and water absorption. According Moose hardness scale cast stone has 7-8 group, leaving alone just diamond and corundum (diamond spar).

More high brittleness (low percussive toughness) is an indication that reduces operational possibilities of cast stone. It should be taken into consideration while in use.

To increase mechanical properties and operational safety articles of more than 400x400mm are reinforced with metal frames. Depending upon demands such articles are supplied by assembly loops and fitting details.

In Table 2 there is medium chemical composition of wearable, heat resistant cast stone

As it is seen from Tables 1 and 2 every type of casting has definite operational benefits. Wearable cast stone articles have minimum friction coefficient and more high mechanical properties and acid resistance. That is why they are most effectively operated in abrasive wear conditions and aggressive surroundings influence. However, low heat resistance of wearable cast iron articles does not allow using them at operating temperatures more than 200C. Heat resistant cast stone is used for equipment that operates at regular high temperatures (up to 700C) and at temperature breaks and with long operating life.

Cast stone is not ageing; its properties do not change as time passes. This allows using it for containers used for exhausted nuclear power fuel and poisonous chemical waste.

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Usage and operational experience of cast stone.

Analysis of equipment and units operation at plants of extractive industry, metallurgy and other branches of industries, where they are used under abrasive wear, aggressive surroundings influence and high temperatures, shows most equipment surface is not protected or poorly protected from destructive operating surrounding influence; at that time more than 90% of equipment and units space operates at not less than 5 Mpa pressure.

At its durability properties cast stone can highly over stand loads overcoming 5 Mpa and that is why it can be widely used for protection of equipment from abrasive wear, aggressive surroundings and high temperature influence, that is improved by multy annual operating usage of cast stone articles in different braches of industry, enlarging the life time of equipment up to 2-6 times.

The following is lined with cast stone:

- at mining processing plants and coal processing plants- ore and coke charge bunkers,--, gutters, feeders, thickening funnels and vacuum filters receivers for -- , preparation – contact tanks for flotation, resonance riddle baths for coal hydraulic classification, riddle baths for magnetite suspension regeneration, hydro cyclones, pulp pipes, pulp dividers, tail races, -- , at load conveyers of coal concentrate to drying, operating space of flotation machines impellers, machines for processing coals, pipes for hydro extraction,-- , , , industrial buildings floor coverings, etc;

- at agglomerating and burning plants – charge bunkers, -- , cyclones, ventury pipes, gas pipes for dirty gas, collectors, scrubbers, pulp pipes, gutters, industrial buildings floor coverings, etc;

- at blast-furnace and steel melting plants – charge and coke bunkers, hot agglomerate bunkers, --, funnels, cyclones, gas pipes for dirty gas, cleaning works, industrial buildings floor coverings, heat units elements operating at temperatures up to 850C;

- at rolling mills – gutters of scale washing out aggressive liquids tanks, cyclones, gas pipes for dirty gas, industrial buildings floor coverings, cleaning works, heat units elements operating at temperature up too 850C. etc.;

- at coke chemical production – charge bunkers, feeders, --, gutters, coke – (heat resistant casting), , industrial buildings floor coverings,, scrubbers, cyclones, gas pipes for dirty gas, etc.;

- at fire resistant production – charge bunkers, feeders, --, cyclones, , industrial buildings floor coverings, gas pipes for dirty gas, cleaning works, pipes of getting back non conditional fire clay for additional milling to sphere mill, industrial buildings floor coverings, heat units elements operating at temperatures up to 850C, etc.;

- in energetics – gas pipes for dirty gas, venturi pipes, industrial buildings floor coverings, hydro and pneumo ashes removal canals, leak gutters, lining bunkers, milling ventilators fume suckers, lower part of fume removal pipe lining;

- at civil and industrial building construction and municipal economy –buildings details surfaces in decorative purposes, pavements 9in chequered and non-chequered variants), collector, buildings which are under acid and biologic influence;

- in chemical and cellulose industries – acid resistant floors for concrete foundation protection under units at aggressive surroundings touch, in crystal receivers, collectors for mother liquor, tanks for --, etching baths, autoclave liquid collectors, lined pressure tanks for acid, refrigerators for oil of vitriol, collectors for weak sulphuric acid, generators for getting acaldegide, cisterns for nitric acid, tanks for sulphuric acid, boilers for periodic boiling of cellulose, sewerage systems surfaces, acid- and alkali-containing pipe bends, poisonous chemicals storage containers;

- in varnish-paint, enamel, pencil production, in ceramics industry as well – abrasive wearing details and sphere mills surfaces, milling bodies for grinding slacker, glaze, etc.;

- in meat processing industry – floors in slaughter houses, blood flooding out canals;

- in aerospace industry – lining of fire resistant canals of starting lines;

- in nuclear industry – special containers for burying nuclear fuel waste.

Possibilities of cast stone are not studied till the end and new spheres of application are being founded.

Some examples of effective operation of cast stone articles can be given.

Tailraces of concentrating mills in South Mining processing plant, Novokrivooirog mining plant and many other mining enterprises as well which are lined with cast stone reflector bricks operate without capital repairing not less than 10 years, earlier they were repaired every 1,5-2 years. Long life of cast stone hydrocyclooones 360-1400 in diameter is not worse and sometimes even better than long life of hydro cyclones which are protected by wearable rubber, polyurethane and carborudum.

1220mm in diameter slack-gutters lined with cast stone fittings operate without serious repairing at Inguletzk mining plant (Krivoi Rog, Ukraine) since 1972, at Kachkanar mining plant since 1977, at Kostomuksha mining plant since 1981, earlier they were changed every 5 years.

Lined with stone and big size plates up to 1000x1000x100 charge bunkers of hot agglomerate at blast-furnace works of such metallurgical enterprises as “Zaparozhsteel”, Dnepropetrovsk “Dzerzhinski” and Makeev have no traces of weariness after 5 years of operation. Wear life between two capital repairings of bunkers protected by fire clay brick, rail blocks, and concrete plates is 5 years.
Wear life of cast stone brick lining of blast-furnace coke bunkers overcome wear life of metal construction that is more than 10-15 years.

Wear life of air lifts made of steel pipe at blast-furnace ovens is not more 4-6 months. Airlift lined by cast stone maintained at the 9th oven of “Krivorozhsteel” operates many years without changing. A result of changing cast iron elements of battery cyclones of agglomerate machines at Dnepropetrovsk “Dzerzhinsk” and Alachevsk metallurgical plants and Enakievsk enterprise, at Visokogorsk mining plant and Gornoblagodatsk plant as well, for block cast stone mylticyclones was enlarging of wear life of battery cyclones between capital repairings from 4 to 8 years, data of gas cleaning rate from hard pieces improves for 4-10%, labour expenditure for assembly and disassembly of battery cyclones was shortened.
Cast stone gutters are assembled instead of cast iron elements at Krivoirog, Mariupol, Nizhnii Tagil metallurgical plants in rolling works in the system of hydro wash out of scale. Due to that period between repairing is prolonged up to 10-15 years.

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