What is an Engineering Class Chain?

When drives need to move very heavy equipment and withstand shock loads, designers often choose engineering-grade drive chains to do the job. So what is an engineering-grade drive train?

The basic types of engineering chains are roughly divided into transmission chains and conveyor chains. Most conveyor chains are custom designed for use in material handling operations. The drive chains featured in this article are typically compliant with industry (ANSI) standards and they transmit power between driving and driven machines.

Engineering-grade drive chains often operate 24/7 and are often subject to mud, sand, metal fines, and other abrasives. The workhorses of these power transmissions provide a maximum working load of up to 37,000 lbs. Additionally, they can handle intermittent shock loads 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 disposal.

These chains transmit power to a variety of equipment including mixers, compressors, crushers, dredgers, 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 debarking drums in pulp mills, ball mills in ore processing, or shakeout drums in foundries. They also power large rough terrain cranes and draglines.

By understanding the basics of engineered drive trains, designers can choose the best type for a given application so it can run for long periods of time.

Engineering-grade drive chains consist of a series of links assembled by inserting pins and bushings between pairs of metal plates called sidebars. These connected links form a continuous chain to transmit power, usually from a small drive sprocket to a larger driven sprocket on a parallel shaft.

The two most common types of chains, straight and offset, are identified by the shapes of the sidebars that make up the links. Other types of engineered chains with limited use in drive applications include steel bushed roller-less chains and welded steel mill chains. Steel sleeve chains are mainly used in bucket elevators. Welded steel chains are a variation of offset chains made by welding the bushings between the sidebars rather than press-fitting them. Welded steel chains are primarily used in wood, pulp, and paper applications.

Straight side rod chains consist of alternating connections of pin links and bushing links. Each bushing link includes a pair of sidebars connected by two press-fit bushings, and each pin link is connected by two press-fit pins. The pin and bushing links are connected in an alternating fashion, with the pin of one link being installed in the bushing of the adjacent link, so that each link bends in one plane.

Straight Side Fence Chains accept attachments and are primarily used in conveyor applications. However, some drive applications preclude the use of offset sidebar chains because they require short pitch (distance between pinholes in the sidebars) or thick sidebars that cannot be offset. In this case, straight side rod chains are used for drive applications.

An offset sidebar chain is often the first choice for high-load applications because it is easy to adjust in length. Unlike straight sidebar chains, each link of an offset chain is similar, with a pin and bushing connecting a pair of curved sidebars. The pin of one link is installed in the bushing of the next link. The pins are pressed into the sidebars and held in place with cotter pins.

Most chain drives can be adjusted to separate the axles farther apart to compensate for chain elongation, but eventually, the chain may need to be shortened. Because all links of an offset chain are identical, individual links can be removed to shorten the chain and compensate for elongation due to pin and bushing wear. In contrast, the links of straight side fence chains must be removed in pairs.

Most drive chains have hardened (42 Rockwell C) steel rollers mounted on the bushings so the rollers contact the sprocket teeth and act as bearings to reduce friction and wear. Engineering grade chains with rollers are similar in design to conventional roller chains. However, the two types of chains differ in size, strength, tolerances, and ability to operate under adverse conditions. Engineering-grade chains typically carry higher loads, but lower speeds.

Engineering-grade drive chains are tested while operating under harsh conditions with little lubrication. Chains need to be evaluated before buying. Here are some things to look for:

Use alloy steel side rods and bushings, integrally hardened to 375 BHN for increased strength and wear life, especially for larger size chains. Most designers choose steels such as AISI 4130 or 4140 for harsh environments. Alloy steel pins should be induction hardened to 55 Rockwell C for improved wear resistance. Use hardened teeth (minimum 35 Rockwell C) for sprockets with fewer than 15 teeth, speeds over 600 rpm, reduction ratios over 4:1, high loads, and abrasive environments.

Controlling the chain pitch avoids excessive wear due to mismatched chains and sprockets. The spacing is controlled by the positioning of the side rod holes made by the punch, so the punch tool must be accurate.

The diameter of the side rod hole must be maintained throughout the depth of the hole. Some punches tear the material from the hole, causing one end to splay.

Smooth bearing surfaces ensure low motion resistance and long life. The bushings should be precision machined and the pins finely ground to match the bushings they will be inserted into.

If you want to know more about chain-related questions, you can contact us.

ZMIE is a quality transmission chain supplier, since 2003, ZMIE has exhibited high-quality roller chains, forged chains, conveyor chains, welded steel chains, closed track chains, sprockets, components, etc. ZMIE service not only involves the product itself but also related services before and after the product. Even including website design, which means customers will spend time and effort, product and process design means money cost to customers, not to mention inspection, packaging, shipping arrangements, delivery to customer warehouse, quality feedback. These details are very important, and a little different means better by avoiding any potential mistakes for the customer.