Anthony Bakewell-Smith

A well implemented inspection and maintenance program on all chain types helps the chains run for longer before replacement while also reducing the chance of unexpected failures. Through regular inspections, issues can be identified early and remedial action taken before the chains either fail unexpectedly or are damaged beyond repair.  Inspection and maintenance often costs much less than a breakdown, especially if the system uses a special engineered conveyor chain where parts are not readily available.

Good lubrication is a critical part of increasing a standard chains working life by reducing the amount of wear and corrosion that occurs during operation. Special chains are available that may operate with little in the form of external lubrication using oil impregnated sintered bushes or special sealing arrangements.  Standard chains with a correct lubrication procedure can often perform very well when compared to the more expensive specialist chains.

Bucket elevators are special type of elevators that convey bulk materials vertically or nearly vertically.  They use single or twin strand chain to which specially designed buckets are attached.  Bucket elevators can convey any bulk material that fits into the buckets and is free flowing enough to be discharged via gravitational or centrifugal forces when passing over the head shaft sprockets.

Engineered steel chains are the main group of chains used for conveying applications and are found in many conveying systems. This range of chains can be manufactured to move heavy loads, absorb shock loadings and work in abrasive or corrosive environments, with minimal protection from the conveyed materials or the environment. 

Engineered steel chain drives are often found in heavy duty applications which are in exposed or undesirable environments and where tight tolerance roller chain drives would not be suitable. They are usually of an offset link or crank link design and can come in a wide variety of sizes, with multiple strand options often available.  A basic range of these chains is covered in the ANSI B29.10M and ISO 3512 standards, although manufacturers offer a much wider range.

The first steps in designing any type of chain system is to gather basic information about the system and the requirements.  This information can then be used to make the relevant calculations, consult the required selection tables, or explain the requirements when contacting a supplier.

Roller chain sprockets and engineered chain sprockets share a wide number of similarities in their designs, including materials, boss options and shaft fixing arrangements.  The area where these sprocket types diverge is in the tooth form, which are designed to fulfill the specific roles of each chain type.

Due to the diverse ranges of chains now available, this article will look at chains which are fabricated from steel, have link plates, bushes and pins and are assembled with an interference fit complete with pin ends that are spun or riveted. This type of chain includes standard roller transmission chains and engineered steel or conveyor chains. Examples of chains that are not covered include cast link, silent running, leaf chain and those that are molded from plastic such as integral slat chains/flat top chains.

BS chains are measured in 16ths of an inch.  For chains 06B and larger, the pitch can be found from dividing the chain number by 16 i.e.

06B Chain Pitch (mm) = 06/16 × 25.4 = 9.525mm

A hyphenated number after the initial chain number indicates the number of chain strands. For example, 24B-1 is a single strand, 24B-2 is two strands and 24B-3 is three strands.

Anti-friction, rolling contact or rolling element are terms used to describe bearings that support axial and/or radial forces, while allowing rotation, using rolling contact elements rather than sliding contact elements. Numerous basic designs of bearings are available and bearing selection generally depends upon the type of supported forces/loads, speed, lubricant, size, life requirements and cost.  It should also be noted that at lower speeds, the frictional forces within a bearing are twice that of the same bearing running at high speed, which can directly affect the life of a bearing.  Bearing failure should generally occur due to fatigue of the races or rolling elements, with other failure methods being investigated and remedial action to the system being implemented.