Belt bucket elevator: operating principle
Material handling equipment is a connecting link of any industrial production. Enterprise's production capacity depends directly on conveyor transport design. The Samara Strommashina plant designs and manufactures material handling equipment of various types, in particular, belt bucket conveyors, one of the most popular industrial elevator types.
In bucket conveyors bulk materials are transported in buckets fixed on a traction unit – travelling rubber-treated belt or chains.
Bucket conveyors are divided into conveyors handling the material in vertical or close to vertical inclined direction, and conveyors handling the material on space or ring path.
The use of such elevators as an inter-floor handling system allows implementing compact handling circuits occupying small areas.
Elevators are used in construction, glass-ceramic, metallurgical, chemical, mining and other industries.
Only bucket elevators used at concrete batch plant to handle mainly powdered materials (cement, lime, gypsum) and in some cases coarse and fine fillers are applied in construction industry. Their capacity is 400 m3/h, lifting height is 40 m.
Bucket elevators are classified based on the following attributes:
a) in terms of traction unit – into belt and chain types;
b) in terms of bucket speed — into high-speed elevators with centrifugal discharge and low-speed elevators with gravity discharge;
c) in terms of bucket arrangement — into elevators with diverged buckets and elevators with converged (lamellar) buckets.
In bucket elevators with a belt traction unit the belt envelopes over drive and tension drums, and in models with a chain traction unit the belt envelopes sprockets. The chain traction unit is applicable at any applied loads and depending on them it is designed with one or two parallel closed flights.
Bucket speed of low-speed elevators is 0.3—1 m/sec, bucket speed of high-speed conveyors is 1.2—2 m/sec.
High-speed elevators are mainly used for handling powdered and fine materials, low-speed conveyors are used for coarse materials.
Bucket elevator consists of a drive and tension drums (sprockets), traction unit (chain or belt) and buckets. The upper part with driving gear is called "head", the lower part with tension take-up is called "boot".
Some part of the material being handled and poured into the charging boot is fed into buckets directly, and the other part of the material is fed onto the rounded boot bottom from where it is scooped by the buckets.
When passing through upper sprockets material is poured from the buckets and is conveyed through a discharging tray into bins or onto handling devices.
The main assemblies of elevators are buckets, traction units, drive head and boot.
Buckets are selected depending on specified elevator capacity and handled material. The bucket dimensions shall be selected so that material lumps were fed into it unimpededly during charging and were discharged from it during discharging. The bucket shape depends on the bucket discharge type (centrifugal or gravity) and on the material mobility degree. The buckets are made welded or stamped from steel sheets; their front edges are reinforced with an apron made of strip steel, and sometimes they are guided with a hard alloy.
The standard establishes three bucket types for general-purpose stationary vertical bucket elevators: deep, shallow with cylindrical bottom and acute-angled with side guides. Deep buckets are used for dry free-flowing materials (sand, cement, fine coal). Shallow buckets with sharp cut-off of the upper edge are used for handling of moist and caking materials. Capacity of buckets with cylindrical bottom varies within 0.65–15.0 l at 135– 450 mm bucket width; distance between buckets (bucket spacing) is 300, 400, 500 and 600 mm. Acute-angled buckets with converged bucket arrangement are used for handling heavy lump cargoes. The width of such buckets is 160 to 900 mm, capacity is 1.5 to 130 l.
Rubber-impregnated belts or bands and chains – plate, bushing and bushing-roller types are used as traction units in elevators. Buckets are bolted to bands, the recesses being made in buckets in bolt locations. Bolt heads are installed in such recesses, thereby the surface of band facing drums is smooth. Plate chains are also bolted to rear or side walls of the buckets.
In terms traction unit type conveyors are divided into single-, double-chain and belt conveyors; in terms of the material movement path – into vertical and inclined; in terms of installation method – into stationary and mobile.
Bucket conveyors are used as independent material-handling devices, and as a part of mortar, concrete and asphalt concrete assemblies, installations for pipe driving, crushing and screening plants, etc.
The traction unit speed depends on charging method and bucket arrangement. The belt (chain) speed of conveyors with material charging into a boot is 1.2 to 2 m/s; such conveyors are called high-speed ones. The traction unit speed of conveyors with material charging into buckets directly is relatively low (0.4 to 0.8 m/s); such conveyors are called low-speed ones.
The Samara Strommashina plant offers services on design of belt bucket elevators and other material handling equipment. We are also ready to provide services on design of turnkey production lines – our plant manufactures equipment for cement, road-building, construction, petrochemical and other industries. Taking into consideration high quality of our equipment and reasonable price, it may safely be said that purchasing the Strommashina brand production equipment (for example, buying a belt bucket elevator) means making a step towards successful production!