Built to withstand the most rugged operating conditions, engineering class chains offer high load capacities along with the fatigue strength needed to stay in operation for long periods of time.

The basic types of engineering class chain are broadly classified as drive chain and conveyor chain. Most conveyor chains are custom designed for use in material handling operations. Drive chains, the focus of this article, generally meet industry (ANSI) standards, and they transmit power between driving and driven machines.

Engineering class drive chains frequently operate around-the-clock, and are often subjected to mud, sand, metal fines, and other abrasives. These workhorses of power transmission offer maximum working loads up to 37,000 lb. Plus, they handle intermittent shock loading, and operate with minimal maintenance and lubrication.

Applications exist in many heavy industries including food processing, earthmoving, lumber, mining, petroleum, pulp and paper, shipbuilding, steel, rubber and plastics, and waste treatment.

These chains transmit power to a variety of equipment including agitators, compressors, crushers, dredges, elevators, fans, hoists, rotary kilns, machine tools, rotary mills, mixers, oil wells, pumps, and screens. They are often used to turn heavy rotating drums, such as barking drums in pulp mills, ball mills in ore processing, or shakeout drums in foundries. They also power large off-road cranes and draglines, Figure 1.

By understanding the basics of engineering drive chain, designers can select the best type for a given application so it will operate for long periods with minimum downtime.

Chain configurations

Engineering class drive chain consists of a series of links that are assembled by inserting pins and bushings between pairs of metal plates called sidebars. These connected links form a continuous chain that transmits power, generally from a small driving sprocket to a larger driven one on parallel shafts.

The two most common chain types, straight and offset, are identified by the shape of the sidebars that form the links, Figure 2. Other types of engineering chain having limited use in drive applications include steel bushed rollerless chain and welded steel mill chain. Steel bushed chain is used primarily for bucket elevators. Welded steel chain is a variation of offset chain made by welding bushings between the sidebars rather than press-fitting them. Welded steel chain is used mainly in wood, pulp, and paper applications.

Straight sidebar chain consists of alternate connections of pin links and bushing links, Figure 2. Each bushing link contains a pair of sidebars connected by two press-fit bushings, whereas each pin link is connected by two pressfit pins. The pin and bushing links join in alternating fashion, with the pin from one link fitting inside the bushing of the adjacent link so that each link flexes in one plane.

Straight sidebar chains accept attachments and are used primarily in conveyor applications. However, some drive applications preclude the use of offset sidebar chain because they require a short pitch (distance between pin holes in sidebars) or thick sidebars that cannot be offset. Where this is the case, straight sidebar chains are used for drive applications.

Offset sidebar chain is generally preferred for high-load applications because of its ease in adjusting length. Unlike straight sidebar chain, every link of offset chain is alike, with one pin and one bushing connecting a pair of bent sidebars, Figure 2. The pin of one link fits inside the bushing of the next link. Pins are press-fit into the sidebars and held in place with cotter pins.

Most chain drives can be adjusted to spread the shafts farther apart to compensate for chain elongation, though, eventually it may be necessary to shorten the chain. Because all links of an offset chain are the same, a single link can be removed to shorten the chain and compensate for elongation due to pin-andbushing wear. By contrast, links of straight sidebar chain must be removed in pairs.

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