Belt Conveyor parts:
The desirable properties of an ideal belt material are:
- High Strength,
- Low self weight,
- Small specific elongation,
- High Flexibility,
- High resistivity to ply separation
- Low hygroscopic
- Long service life
In general Reinforced Rubber Belts meet these requirements better than any other material.
In general, a conveyor belt consists of three elements:
- Top cover
- Bottom Cover
The carcass is the reinforcing element and takes up the tensile forces necessary in starting and moving the loaded belt, absorbs the impact energy of material during loading. The carcass may be of either textile reinforcement or steel cords. In case of textile reinforcement the carcass is normally built up of a number of plies of textile fabric. These plies may be made from rough woven cotton fabric and are connected by vulcanization with natural or synthetic rubber.
Sometimes the plies are made of extra strong synthetic fabrics like:
- Nylon etc
The strength of fabric and the number of plies in the carcass of the belt may be varied together to suit the strength requirement. However if the belt is too tough, troughing of the belt and bending it round the terminal pulleys will be very difficult. Therefore the belt with lesser number of plies with stronger fabric is generally preferred because it is more flexible. Steel cord belting is used when good trough ability, small specific elongation and higher operating tensile forces are required. PVC belting is generally selected for underground mining applications where fire hazard exists.
Belts cover grades:
The primary purpose of the covers is to protect the belt carcass against damage and any special deteriorating factors that may be present in the operating environment. Rubber or rubbers like compounds are used for the top and bottom covers of conveying belting. Various chemicals are mixed with these compounds to achieve the desired physical properties necessary for service conditions. The properties needed for the cover of belt include resistance to cutting, gauging, tearing, abrasion, aging, moisture absorptions and in some cases resistance to oil, chemical and heat. Different qualities of cover material are designated by different grades. The cover grade is determined by the characteristics of the material to be handled.
Some cover grades are:
Natural rubber compound offering superior resistance to cutting, gauging and abrasion wear
Compounded rubber with improved flex life for moderately abrasive material, high abrasion resistance, resistance to cutting and gauging is inferior to M24
Suitable for handling Alumina, ash, chemical etc at temperatures over 65 deg Celsius up to 120 deg Celsius.
Recommended for handling materials like foundry sand, cement clinker, coke wharf, sinter ore at temperature range 65 °C to 180° C for coarse and fine materials.
Suitable for underground mining and for equipment and materials requiring fire resistant and antistatic charge properties.
Suitable for best possible resistance to mineral, vegetable and animal oil
Designation of Belts:
Belts are designated to denote the full thickness tensile strength per meter width and the number of reinforcing plies of synthetic textile. Examples: 500/3 belt indicates a belt having a minimum guaranteed full thickness tensile strength of 500 KN/m, incorporating 3 plies of textile reinforcement. For all synthetic fabric reinforced conveyor belting usually a factor of safety of 10 is applied to obtain the maximum working tension with vulcanized splicing.
Steel cord belting is designated by the prefix “ST” followed by the minimum full thickness tensile strength in kN/m.
The two ends of a belt are joined directly on the conveyor either by vulcanizing or hinged metal belt fasteners of different designs. Vulcanization is the most reliable method of splicing. Vulcanization technique is a specialized job and expensive, but yields the best result. Mechanical fasteners are often used for connecting flat belting.