Chain conveyors bucket elevators

The major uses of the four types of chain fisted above are in drives (power transmission), conveyors, bucket elevators, and tension hnkages. Each of these applications is discussed in detail in subsequent chapters. Some standard chains are designed for use in only one of these application. However, some chains are designed so that they can be adapted to more than one use. 

Many different types of engineering steel chains are used in a wide variety of apphcations. Most engineering steel chains are used in conveyors, bucket elevators, and tension linkages. Only a few are used in drives. Space does not permit a discussion of all the different types of engineCTing steel chains mentioned in chapter 2. Only straight sidebar chains, with and without rollers, for conveyors and bucket elevators, and offset sidebar chains for drives will be discussed. Welded steel chains and block and bar chains are beyond the scope of this chapt. ... 

LUBRICATION OF CONVEYOR, BUCKET ELEVATOR, AND TENSION LINKAGE CHAINS... 

It is often difQcult to lubricate chains used in conveyors, bucket elevators, and tension linkages. They normally cannot be enclosed in a chain casing or protective housing. They have to work in the open and they are exposed to spillage of the product being carried. 

The weight of material in the buckets on the loaded side of an elevator chain causes the elevator to momentarily mn backwards if, during operation, the power is intermpted or there is a failure in the driving system. Because this could be a ha2ard to operating personnel, as well as damage to the elevator, a backstop, similar to that described for a belt conveyor, should be used. 

The most common chain conveyor is the bucket elevator already discussed, but there are a wide variety of special chain conveyors which are used so infrequently that they shoiild be selected only on the specific recommendation of a quahfied materials-handhng engineer. 

CONVEYORS. Pneumatic conveyors for solids are described in Chap. 7. Other common devices for transportation include belt conveyors and bucket elevators, closed-belt conveyors with zipperlike fasteners, and various kinds of drag and flight conveyors. These all include a return leg that carries the empty belt or chain back from the discharge to the loading point. Vibrating conveyors and screw conveyors have no return leg but only operate over relatively short distances. Pneumatic conveyors also have no return leg and are not so limited as to distance of travel. Conveyors for solids are discussed in Ref. 9a. 

Chain conveyors, which have similar advantages and disadvantages to bucket elevators, except that horizontal translation and a path curved in the vertical plane are possible. 

Depending upon how chain and moving elements are mounted for a specific duty, several types of chain conveyors can be obfained. Scraper conveyors will have the moving element, or flight, fitted perpendicular between two strands of roller chains, while apron conveyors will have fhe moving elements, or pans, overlapped and mounted on the same plane of roller chains forming a continuous "apron." When buckefs are fixed to two strands of roller chains mounted on a steep-sloped or vertical structure, elevation of bulk solids can be possible in the so-called bucket elevators. 

Fig.1 Diagram of clinker handling system at a cement works 1 drag-chain or short-plate apron conveyor 2 bucket conveyor or short-pan apron conveyor 3 drag-plate apron conveyor for material distribution 4 short-plate apron conveyor for extraction from hoppers 5 short-pan apron conveyor for collecting 6 bucket elevator 7 drag-plate apron conveyor 8 weigh belt feeder 9 belt conveyor...

There are many general types of engineering steel chains, and some of those covered in this book are shown in Figure 1-19 to Figure 1-22. Those with steel rollers are perhaps the most widely used on both drives and conveyors. The bushed, rollCTless style meets the needs of many conveyor and bucket elevator applications. Welded steel versions of the basic cast chains are now quite popular, and a simple bar-link type is used for slow-moving conveyors and tension hnkages. Each of these types is illustrated and described in detail in a subsequait chapter. 

There are some applications, mostly with rollerless chains on conveyors or bucket elevators, where offset chains give excellent wear life when operated open end forward. The user should carefully follow the manufacturers recommendations for those applications. 

To serve as a guide or to support a chain and material carried on it on tracks or ways, as is characteristic of conveyors and some bucket elevators. 

Roller chains are usually thought of as being mostly for drives, while rargmeoing steel chains are used for conveyors and bucket elevators, but there are many exceptions. In fact, thrae are aiough exceptions that a chapter in the drives section covers heavy-duty offset sidebar raigineering steel chain drives and another chapter in the conveyors section covers roller chain conveyors. Both are the subject of ASME standards. 

ASME standard B29.15 lists a few of the more popular steel roller conveyor chains and attachments. But manufacturers produce many more models of this type of chain and furnish them with a wide variety of attaehments. These chains are mainly used in conveyors with flights or slats, although they are also sometimes used in bucket elevators and scraper conveyors. 

Large steel roller conveyor chains that are used on bucket elevators or in otho- extrranely abrasive applications may be equipped with pressure-lubricating fittings on the rollCTs or pins (Figure 3-39). 

The advice on the maintenance and lubrication of conveyor chains, as given for conveyor chains in chapter 12, can be applied to chains used in bucket elevators as well, except where it is modified by the following remarks. 

A block and tackle or come-along is usually needed to pull the chain into a bucket elevator, and the final connection is usually made at the tail shaft in a bucket elevator. This is because the chain tension is lowest there. Ask the chain or machine supplier for advice on installing large chain in a conveyor or bucket elevator. 

Adjust the chain tension to give the amount of sag recommended by the chain manufacturer. No sag is generally recommended for vertical conveyors and bucket elevators. Adjust the initial chain tension to the amount, and using the method, recommended by the chain manufacturer. 

Mueh of the inspection and maintraiance of conveyors and bucket elevators is the same as for drives. Lubiieation, sprocket wear, and chain tension are as important for conveyors as they are for drives. However, some items for conveyors are more important than for drives and those items need to be ehecked more closely. 

Look for signs of interference between the chain or sprockets and any othCT parts of the machine. Check for contact between the chain and any outside objects. Most chains for conveyors and bucket elevators have attachments carriers, flights, buckets, or crossbars may be added to the chain. These added items increase the chances for interference with a machine member or outside objects. 

Early extractor designs based on solvent percolation were basket-type extractors in which flaked seeds were placed in baskets with perforated bottoms. These systems looked like an enclosed bucket elevator. The baskets were supported by endless chains in a sealed housing and continuously raised and lowered at a slow rate (1 revolution/h). Each basket was filled with flaked seeds by an automatic feed hopper at the top. As the basket started descending solvent is sprayed over the baskets. The spent flakes in baskets ascended to the top of the housing on the opposite side of the feed hopper. At the top baskets were automatically inverted and spent seeds were discharged into a hopper, from which they were transferred to a meal desolventizer on a conveyor belt. Basket type extractors were bulky and hard to maintain. The newer extractor designs are horizontal and rotary type. The design principle for horizontal extractors is similar to the basket-type extractors but the baskets rotate in a... 

The inspection door on the side of the elevator casing makes the chain accessible for inspection and repair. Check the chain, attachments, and buckets as you would those on a bulk-handling conveyor. If the chain pitch has stretched appreciably, adjust the take-ups. 

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