Conveyor belt
The conveyor belt (also assembly line , conveyor belt or fachsprachlich belt conveyors , belt conveyors or belt conveyors ) is a mostly stationary conveyor leading to the technical department of the continuous conveyor belongs. Conveying and transport tasks in mining , in industry and on long distances, above or below ground, have been handled by conveyor belts for decades . Conveyor belts have a very high level of operational reliability and have proven themselves in many areas of application. Belt conveyors are reliable transport systems that are economical , very productive and environmentally friendly due to their low energy requirements.
Like conveyor belts, moving walks were developed for the transport of people . They can be used in a similar way, but they are based on a different function and construction. Conversely , treadmills are constructed in a similar way to conveyor belts, but for use by people; they are usually not used as transport systems but as sports equipment.
Layout and function
It is driven by frictional engagement of one or more drive drums. The conveyor belt is used for both bulk goods (e.g. ore) and piece goods (packages). Along with roller conveyors and roller conveyors, it is the most common mechanical continuous conveyor.
The conveyor belt essentially consists of:
- Supporting structure made of steel construction profiles; it carries the roller bearings of the upper and lower run , the drive and the tensioning devices
- Drive station (drive roller, often rubberized, bearings, gears, motors, with or without coupling)
- Reversing station
- Support rollers , mostly in three parts and with toe-in, which can also be padded at the feed station
- Lower belt pulleys
- Leadership roles
- Conveyor belt
- Tensioning station: The tensioning station can be designed as a spindle tensioning station or as a weight tensioning station with or without a tensioning carriage
- Feeding station
- Drop station with transfer funnel. Since abrasive materials often have to be conveyed, a wear lining is necessary.
- Wipers, sometimes also pre-wipers, inner wipers; in front of the pulleys, mostly on the inside of the lower belt as a wedge-shaped plow scraper
- Safety devices such as rip cords, speed monitors, misalignment monitors
Belt misalignment is one of the most common reasons for failure of a belt conveyor. The belt moves sideways due to various causes. If the maximum permitted misalignment is exceeded, the belt, system or system may be damaged or malfunction. The most common problem is that the belt comes into contact with structural components that are dragged through by the conveyor belt. The use of lateral guide rollers is to be avoided.
Belt conveyors that can convey in two directions are called reversing belts . You will e.g. B. used to feed silo groups.
Belt conveyors include steel belt conveyors (for higher temperatures and abrasive conveyed goods) and wire belt conveyors (for hot to glowing piece goods, as cooling belts), in which an endless steel belt or an endless round or flat wire mesh is used as a pulling and carrying means. Further examples from a large number of variants of the belt conveyor are magnetic belt conveyors for separating magnetic components from the bulk material (sorting belts from scrapping systems) or telescopic belt conveyors where the conveying length can be varied.
The longest conveyor belt in the world today is located in Western Sahara : This transports phosphates over a distance of around 100 km from Bou Craa to the Atlantic coast .
Occupational safety
The greatest danger with belt conveyors is that body parts can be drawn in between the belt and the rollers and torn off. As the belts usually run relatively quickly, people do not have enough reaction time to activate the emergency stop cord in time. Belt conveyors usually have drive energies that do not allow the belt to be stopped by hand (typical for a belt drive in a quarry is a drive power of over 100 kW). Strict safety rules therefore apply to belt conveyors (list is not exhaustive):
- Easily accessible emergency stop device next to the belt conveyor, usually a rip cord
- Entry points on drive and deflection rollers must be covered
- Support rollers over which the belt cannot move by at least 5 cm must be covered, this applies in particular to the support rollers under the feed station and to support rollers where the direction of the belt changes by more than 3 ° (buckling rollers)
- Lower belt pulleys up to a height of 2.5 m above the access level must be secured against interference
- Retraction points on tensioning devices in the lower belt, pressure rollers, belt guide rollers and lower belt turning stations must also be secured.
The basic safety and EMC requirements for the construction and equipment of stationary belt conveyors for bulk goods can be found in EN 620: 2002. This European standard is a type C standard according to EN 1070: 1998.
Properties of belt conveyors compared to other continuous conveyors
Advantages:
- large conveying lengths, conveying quantities and conveying speeds with low drive power
- low wear and tear and low maintenance and investment costs
- best efficiency of all continuous conveyors for bulk material
Disadvantage:
- Sensitivity to hot and strongly abrasive conveyed goods
- only straight conveyor lines (deflections in the horizontal direction are only possible to a limited extent due to the large deflection radii and the great effort required to guide them.)
- The angle of inclination of the conveyance is limited (but can be increased by profiling the belt (e.g. ribs))
- Dust-tight design only possible with permanent maintenance or additional mechanical equipment
Special designs of belt conveyors
- Steel belt conveyor : Steel belts are particularly rigid ⇒ large drum diameters
Application: hot, highly abrasive or sticky conveyed goods
- Tubular belt conveyors are belt conveyors in which the conveyor belt is shaped into a tube after being fed.
- Wire belt conveyor : is particularly suitable for cooling and drying belts (small drum diameter, good curve guidance)
- Magnetic belt conveyor: for separating metallic and non-metallic conveyed goods (sorting in scrapping plants).
The rubber band is passed over plate magnets and metallic objects are deflected.
- Telescopic belt conveyor (conveyor length continuously adjustable)
Application: loading and unloading conveyor
- Plastic link conveyor (good horizontal deflection)
- Toothed belt conveyor (positive drive)
- Mobile belt conveyor (telescopic conveyor belt mounted on a truck)
literature
- Walter Bischoff , Heinz Bramann, Westfälische Berggewerkschaftskasse Bochum: The small mining dictionary. 7th edition, Verlag Glückauf GmbH, Essen, 1988, ISBN 3-7739-0501-7
- Reinald Skiba : Taschenbuch Betriebliche Sicherheitstechnik. 3rd edition, Erich Schmidt Verlag, Regensburg and Münster, 1991, ISBN 3-503-02943-5
