Tension Linkage Chains

Special types of roller chain, leaf chain, and block chain can be used as tension linkages. Some of these products are described in the American National Standards, but many are manufacturers specials and can only be found in their catalogs or by contacting them directly. Some of these products will be discussed in greater detail. 

Engineering steel chains in various styles of bar-link or block and bar chain are used for tension linkages. These types of chains will be discussed later. 

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Tension linkage chains generally experience high loads at low speeds. They do not fall within the published horsepower tables given in chapter 5. Do not attempt to use horsepower ratings to select tension linkage chains. There are many types and sizes of chains available for use as tension... 

FIGURE 8-1 Comparison of chains showing sizes of tension linkage chains. 

Some tension linkage chains of the engineering steel bar-link type are among the heaviest, most... 

Most heavy tension linkage chains are simple designs. They usually consist of heavy blocks, bars, and leaves with heat-treated pins. The other components are not always hardened. Bar-link and leaf chains are very similar in concept and function, but manufacturing methods differ greatly. 

FIGURE 8-12 Hnge tension linkage chain for dam gates. 

FIGURE 8-16 Tension linkage chain used in locks on the Mississippi River. 

Engineering steel tension linkage chains are used in the hold-down apparatus of rock drills and the ladle-tilting devices in steel mills and foundries. They are used in hydraulic lifts and counterweight balances on the arms of radial drills. And they are used in transmission systems between doubleacting hydraulic cylinders and their shafts. Two such unusual applications are shown in Figure 8-17 and Figure 8-18. 

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

Inspeeting and maintaining tension linkage chains is too critical to covct hrae. Inspection and maintenance of leaf chains are covered in the ASME B29.8 standard. Inspection and maintraiance of roller load chains for overhead hoists are covered in the ASME B29.24 standard. Gnidance on inspeetion and maintenance of other tension linkage chains shonld be obtained from the chain manufactnrer. 

Finally, thae are three types of roller chain for use in tension linkages ... 

The term chain tension linkage is used when the linear motion of the chain is not continuous in one direction. In other words, the chain must move back and forth. RoUct chain is often specified where the positive action of a chain is required for certain hoists, marine steering equipment, and similar applications. 

Leaf chain, sometimes called cable chain or balance chain, is used for tension linkage applications. It consists of steel link plates, with contours that are usually the same as the roller link plates in roller chain, laced on pins in a way that permits the chain to flex freely at each joint. All of the link plates have the same contour to permit the chain to be properly supported when running over a sheave. A typical section of leaf chain is shown in Figure 2-14, as well as a drawing showing a lacing pattern, as it would be shown in the ASME B29.8 standard. Leaf Chain, Clevises, and Sheaves. 

Bar-link chains are frequently used in tension linkage applications. A design of this type is so commonly used in steel mills for this application that it is known as draw bench chain. Steel bar-link chains arc also used on slow-moving conveyors, such as steel mill coil conveyors (with outboard rollers), and arc made in very large versions to raise and Iowct river and canal lock and dam gates. 

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. ... 

Rollerless chains are also used as tension linkages where a chain with the wear resistance of a hardened bushing is needed. Most of these chains have the same basic dimensions as standard roller chain, but they do not have the free-turning roller over the bushings. Because of this feature, these chains usually do not run on sprockets. RoUerless chains are not desaibed by an American National Standard. However, they may be identified with numbers taken from ASME B29.1. The chain number ends with a 5, indicating the roUerless feature. For example, a k-va. pitch no. 60 chain without a roller becomes a no. 65 chain. 

Leaf chain probably is the chain most commonly used for tension linkages. Leaf chain is designed specifically for use where the chain does not engage a sprocket or travel through a complete chain revolution. Leaf chain was briefly described in chapter 2 and an example is shown in Figure 8. Complete information on leaf chain is contained in the ASME B29.8 standard. 

TENSION LINKAGES USING ENGINEERING STEEL CHAINS... 

The engineering steel chains normally used in tension linkages are relatively heavy chains. They are usually the bar-link or block and bar types of chain, and they are much larger in size and much stronger than the leaf and other chains used for lighter tension linkages. 

Chains are often a better choice for very heavy tension linkages because they can be designed to handle very heavy loads. 

Chains used in tension linkage applications are easy to lubricate, and regular lubrication extends the chain s life. 

There are many variables to be considered when selecting engineering steel chains for tension linkages. The designer should consult with manufacturers for more information. 

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. 

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