Materials required for fabrication are classified into (i) metals and (ii) non-metals.Metals are further grouped as (i) ferrous and (ii) non-ferrous. Ferrous metals,containing iron as major constituent along with other elements, hence, vary in their strength, machining properties, etc. Wrought Iron is the purest form of iron, having minimum carbon and other contents. It can easily be machined and welded and can be used for high temperature applications such as steam supply lines, heating coils,exhaust lines, etc. Similarly, cast iron is different having carbon-content 2.5 to 4% and can be casted through mould into any shape. However, it is tough towards machining and welding. Furnace bars, jaws of crushing and grinding machine, bases of pillars, etc. are usually made of this type of iron. Let us discus in detail.
i. Steel
Steel is an iron alloy with carbon between 0.5 to 2.0%. In addition small amount of phosphorus, sulphur, silicon and manganese are added to change their uses. Mild steel with 0.05 to 0.3% carbon is most commonly used steel. Vessels, pipes and fitting are generally made of this iron. This type of steel can be most easily fabricated and machined. Medium carbon steel with 0.3 to 0.5% carbons improves the strength. Hence, shafts, springs, bolts, etc. are made from this material. High carbon steel with carbon content above 0.5% to 2% is very hard. Therefore,cutting tools like blades, saw, chisels, etc. are made of this type of iron.
ii. Alloy Steel
Alloy steel is special steel having selected properties. They are made by adding nickel, chromium, silicon, manganese, molybdenum, titanium, etc. They become highly corrosion resistant and are used for heat exchangers, milk pipelines, and all dairy equipment. Special mention may be made of stainless steel with 18% chromium and 8% nickel. This steel is best as corrosion resistant steel. The sheets are furnished in several degrees of polish covering the range from plain finish to a mirror finish. The No. 4 is finish considered good for general daily use. There are over 100 types of stainless steels. Austenitic stainless steel with American Iron and Steel Institute (AISI) 300 series is most common S.S. used for fabrication of Dairy Equipment.
iii. Non-ferrous Metals
Non-ferrous metals such as aluminum and its alloys are used selectively. Milk cans are usually made of aluminum due to its lightweight. Ladders, door and windows and some frames are also made of aluminum. Aluminum is chemically rather stable to milk and milk products. Its greatest fault is its vulnerability to attack by alkaline detergents. The surface gets pitting type corrosion causing small roughness hence cannot be cleaned easily. Copper-zinc alloys are used for tubing, bushes, and heat exchangers. It is not a very common metal for dairy industries.
iv. Non-metal Materials
Certain non-metal materials commonly used in the dairy industry include glass,rubber, plastic, etc. These are used in very small quantity for special applications such as hose pipe for water, gasket material for plates, flanges or bolts. Glass is used for viewing inside any vessel. Most commonly used synthetic rubbers are neoprene, nitrile, butyl, silicone, fluro-elastomer or viton for sealing or gaskets.These materials do not react with milk or milk product and offer leak proof joint packing. Certain plastics used in dairies are crates, conveyors, and packaging material. Wood is normally not recommended due to its porosity and its vulnerability to microbial attack. It is mostly used as building material.
i. Steel
Steel is an iron alloy with carbon between 0.5 to 2.0%. In addition small amount of phosphorus, sulphur, silicon and manganese are added to change their uses. Mild steel with 0.05 to 0.3% carbon is most commonly used steel. Vessels, pipes and fitting are generally made of this iron. This type of steel can be most easily fabricated and machined. Medium carbon steel with 0.3 to 0.5% carbons improves the strength. Hence, shafts, springs, bolts, etc. are made from this material. High carbon steel with carbon content above 0.5% to 2% is very hard. Therefore,cutting tools like blades, saw, chisels, etc. are made of this type of iron.
ii. Alloy Steel
Alloy steel is special steel having selected properties. They are made by adding nickel, chromium, silicon, manganese, molybdenum, titanium, etc. They become highly corrosion resistant and are used for heat exchangers, milk pipelines, and all dairy equipment. Special mention may be made of stainless steel with 18% chromium and 8% nickel. This steel is best as corrosion resistant steel. The sheets are furnished in several degrees of polish covering the range from plain finish to a mirror finish. The No. 4 is finish considered good for general daily use. There are over 100 types of stainless steels. Austenitic stainless steel with American Iron and Steel Institute (AISI) 300 series is most common S.S. used for fabrication of Dairy Equipment.
iii. Non-ferrous Metals
Non-ferrous metals such as aluminum and its alloys are used selectively. Milk cans are usually made of aluminum due to its lightweight. Ladders, door and windows and some frames are also made of aluminum. Aluminum is chemically rather stable to milk and milk products. Its greatest fault is its vulnerability to attack by alkaline detergents. The surface gets pitting type corrosion causing small roughness hence cannot be cleaned easily. Copper-zinc alloys are used for tubing, bushes, and heat exchangers. It is not a very common metal for dairy industries.
iv. Non-metal Materials
Certain non-metal materials commonly used in the dairy industry include glass,rubber, plastic, etc. These are used in very small quantity for special applications such as hose pipe for water, gasket material for plates, flanges or bolts. Glass is used for viewing inside any vessel. Most commonly used synthetic rubbers are neoprene, nitrile, butyl, silicone, fluro-elastomer or viton for sealing or gaskets.These materials do not react with milk or milk product and offer leak proof joint packing. Certain plastics used in dairies are crates, conveyors, and packaging material. Wood is normally not recommended due to its porosity and its vulnerability to microbial attack. It is mostly used as building material.
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