Overhead drive chains: The hidden heroes

In my 38 years of working with beef plants, not once did I wonder about the origin of overhead drive chains — the moving force behind the entire process. For those unfamiliar with modern beef processing plants, overhead drive chains reside in a plant’s ceiling.

A brief history

I decided to investigate the history of overhead rivetless drive chains in beef processing, going back to the origins of this chain type. A young engineer, Jervis Bennett Webb, was working in Pennsylvania’s coal fields when he studied a chain design that was commonly used in this industry. Webb decided to modify this heavy, forged chain and quickly realized that his innovation may have other uses in many industries.

Webb’s design simplified the chain and reduced its weight by 30 pounds per foot. The result was referred to as “Keystone” chain in honor of its Pennsylvania origins. Webb’s product was on the brink of reshaping America’s assembly lines in the mining industry and beyond.

Then Henry Ford visited a meat plant in the early 1920s and saw the gravity-operated overhead rails, which were not yet mechanically powered. He was inspired to change his lines to overhead, and the new automobile assembly line was in the making — rendering cumbersome floor-based chains obsolete. This update freed up valuable floor space and started the overhead chain revolution in 1921.

The innovation

This new chain was a game-changer that made the assembly line adaptable. The simple design of a center link, two side plates and two pins allowed the chain to make the turns and elevation changes required in different process lines and applications.

The new design was the Swiss Army knife of the chain world. Like the iconic knife — one product, many uses — this chain made a real difference with its adaptability. We are focused on beef processing in this article, but virtually any manufacturing using overhead chain in the assembly line can be adapted to use several off-the-shelf components. Plus, with a good machine shop crew, you can make custom attachments for your application. The applications and industries are undoubtedly too numerous to mention, and I have seen this chain class as a manufacturing mainstay for years in many industries, both large and small.

Beef plant applications

In its infancy, as far back as 1870, the beef industry used steam power, monorails and trolleys. Into the 1920s, stationary workers still had an individual process in the animal disassembly lines using the old-style gravity flow, but changes were starting. By the mid-20th century, industrial technology took giant leaps forward as beef plants became automated with mechanically driven overhead chain systems, leaving gravity dependence behind. This was the beginning of today’s plants that can process up to 6,000 head in a two-shift day. The gear-reducer-powered chain allows for high-speed, consistent, efficient processing of large numbers of cattle per shift.

The chains that most plants use today have 3-, 4- and 6-inch pitches that most refer to as X348, X458 and X678. These chains have remained pretty much unchanged for years and, along with a cat drive chain, were the processing workhorse of any beef plant. But now, the cat drive system is rarely used, and the new preferred method to power the chain is a friction/traction drive system. The friction drive is a large-diameter sprocket, and the chain is wrapped around the driver sprocket at 180 degrees. The traction wheel or take-up can be one or two smooth-face traction wheels used to tension the system. These traction wheels can be adjusted manually with a fixed take (no self-adjustment). But most prefer the chain to self-adjust either by air- or nitrogen-filled cylinders or by a gravity-weighted take-up.

More innovations allowed for rail switches and transitions to move the beef along the rails from station to station, creating the need for rails, trolleys, switches, hangers and hooks. These attachments that are still commonplace in beef processing have been around for over 50 years. This system allows product to move — without removal from the hooks — and switch like a train track from the harvest station to the cooler, then the freezer, and finally the fabrication floor where the modified product is removed. This expanded model allowed the beef processing plants to increase the capacity of cattle slaughtered daily.

Extending chain life

We must remember that beef processing has to be performed in a sanitary environment. For government-inspected sanitary applications, a huge concern is applying a food-grade lubricant to the chain while eliminating drips or spills. Many plants use white oil or mineral oil as chain lube.

In my experience, there is no common practice for lubrication. Although many plants still lubricate manually, automated lubrication systems have been introduced. These systems spray a small burst of oil toward the pin. There have been several attempts to develop improved coatings or finishes and introduce new materials to provide more resistance to the harsh washdown environment for longer life. Rivetless chain is only as strong as the weakest pin — which can be the chain’s Achilles’ heel. The quality of the pin and its finish are paramount to the chain’s life. If you have pin wear, the chain elongates and can throw off the synchronized process and disrupt the timing. If several are worn, it can cause the transfer of too many cattle (known as “throwing doubles” — moving more than one carcass). Looking for worn pins can be very time-consuming: In many plants, these chains operate on slider or trolley rails and can be hundreds of feet long, making replacement a several-day maintenance project.

If the pin has an unpolished finish and shows casting overpour, it will easily burnish, wear and quickly elongate. Using a polished pin is a best practice to avoid those issues. All pins are not manufactured in the same process, so review your chain supplier closely. You could also try an electronic chain measurement monitor that uses magnetic pickups to detect pin wear and reveal the exact location of a worn pin or pins. If you value your budget dollars, the polished pin will return the best value over time.

The last 15 years have seen improvements in developing chains with a new pin design. One domestic manufacturer is producing a chain series referred to as "smooth link" that has a polished pin and shows minimal wear after prolonged usage. A dramatic change from the old design is a chain with a pin that can be rotated to three different positions, 120 degrees at a time, to double the normal wear life. Today's coatings are plain, polished, zinc, yellow zinc and now different alloys with better wear properties. Stainless steel construction has also markedly improved, and the newest chain is the X248 in stainless that replaces long-outdated cable conveyors. This new 2-inch pitch chain will handle elevation changes and turns much better than a cable chain that historically wore at each lug, or roughly every 12 inches.

The workhorse chain that brought automation to the assembly line over 100 years ago is still key to beef processing and will continue as the hidden hero in the overhead of modern processing plants. Hopefully, you have learned something new about the overhead chain’s interesting history, and this information will inspire you to review your systems to help extend chain life and realize significant cost savings.

A Food & Beverage Specialist at Motion, Brandon Brownlee has served the food and beverage industry for 38 years. His experience includes 25 years of helping customers in all industries optimize efficiency and maximize asset life via reliability-centered maintenance and best warehousing practices. Brownlee has worked for Motion for over 25 years.

For more information, visit Motion.com/processing