The use of belts, gears, pulleys and other mechanical drive components have been used in industrial machines for over 200 years and for a variety of industries ranging from paper mills to food processing facilities to textiles and more. Although many of these components can be and have been replaced with motorized components, there are enough of them still in use today to support a niche market for replacement parts. So what is keeping these older machines from becoming obsolete?
In order to understand the advantages of this niche market, one must first understand functional obsolescence. Basically, functional obsolescence refers to the loss in value or usefulness of a machine caused by the machine itself. In other words, the machine is inefficient or inadequate when compared to a more efficient replacement that incorporates newer technology. Since the industrial revolution, machines are always being improved upon to enable increased production in terms of speed, closer tolerances (precision) and capacity (or size). The introduction of computers has taken some machines to a whole new level of speed and precision. All of this new technology, however, has a price. And sometimes, that price can be significant. Replacement parts can be a competitive option that provides great return on investment. The replacement parts industry helps bridge the gap between old and new technology by removing functional obsolescence from the equation. To better illustrate this point, we will look at one industry in particular – paper manufacturing. If a new, motorized paper manufacturing machine can produce 5,000 feet per minute, then a machine using older mechanical components is functionally obsolete since it generates 3,000 feet per minute. The goal for the replacement parts company is to upgrade the older machine so that it can also generate 5,000 feet per minute.
There are three basic ways in which a machine can increase productivity. One is to maximize running time and bring both planned and unplanned down time to a minimum. PTS helps with this by performing periodic gear inspections on gear drive machines, with the resulting report pointing out ways for the customer to optimize uptime. Another is to increase the width of the paper, thereby enabling more of the finished product to be run at a given speed. In the case of our illustration, the paper manufacturing machine, increasing width is not a feasible option as it is very difficult and cost prohibitive, as every cross-machine component used throughout the manufacturing process would have to be changed and in all probability the structural components that support the cross machine components, and perhaps even the building that houses the machine would need to be added to. A third, more feasible option is to increase the speed of production.
Many factors must be considered when increasing the speed of the machine – can enough paper stock (raw material) be pumped to the machine, can the desired sheet be formed sufficiently in the forming zone, can the rotating machine components operate safely at faster speeds, and can the mechanical drive train components operate safely at faster speeds – are just a few of the main considerations. The increase in sheet speed can be accomplished in two main ways – a major rebuild, where a significant increase in speed is designed and planned for; or incrementally, where speed is simply increased until a bottleneck is discovered. That bottleneck is then addressed and the machine speed is again increased until the next bottleneck is found, and so forth. These bottlenecks are sometimes easily addressed, while others again need significant rebuild work to be designed and performed.
As brand new paper machines are designed to be driven with electric motors, it is often the desire to increase the sheet speed of mechanical drive (“line shaft” drive machine where the machine is driven by a series of pulleys and belts) machines by replacing that system with a series of electric motors, although this can be quite cost prohibitive. Another thought that is used quite often is to gain speed capacity by simply replacing the mechanical drive components that are limiting the speed of the machine with new components designed to safely operate at the projected increased sheet speeds. An engineering study of the mechanical drive train can be performed by someone such as PTS, where the limiting components can be determined and a plan formed to target them. In an example of a line shaft drive machine, PTS can assist in resizing half of the pulleys in such a way (for example, all of the driver pulleys) that a fairly significant increase in machine speed can be achieved by replacing just a portion of the existing mechanical components. According to feedback from customers where PTS has helped with this, the return on the investment in the upgrade using replacement parts can be within six months, whereas converting to electric motors often costs 10 times or more than the previously described upgrade, and the return on the investment takes years.
Another approach often used to increase the speed is a “technology improvement” while still using the mechanical drive system on the paper machine. One example is that some of the very old machines still operating in the U.S. were originally designed to use “friction-style” (sleeve or babbitt) bearings on the dryers and other rolls on the machine. PTS has helped some mills with a re-engineering of the design so that they can convert to “anti-friction style” (ball or roller) bearings, with a redesign of the existing bearing housings. Another involves older machines where the original design of the dryer gearing involved all cast iron gears, which was satisfactory for the original slower operating speeds. As the paper machine is sped up, though, iron to iron contact of the gearing causes a significant amount of noise and vibration. PTS can work with the customer to develop a plan to reduce noise and vibration levels, with a program of changing every other gear in the drive train to nylon style gears. Making this improvement has allowed some paper machines to operate over 3,000 feet per minute, which is in the ballpark of new equipment.
The decision to upgrade a machine with replacement parts or a new machine is a determination that should be made on a machine-by-machine basis. What works for one machine or industry may not be an option for a similar machine or different industry. There are many factors that should be considered.
Increasingly, manufacturers are setting up shop overseas. Many of the older, outdated machines from the U.S. are able to run, profitably, with some functional obsolescence because of favorable labor rates and different government regulations. Using replacement parts to upgrade these machines is possible but usually not a preferred option because it is more profitable and expedient to run the machines for as long as possible and then replace them entirely with a similar or newer version of the machine available on the used equipment market.
In addition to location, companies should also consider the age, maximum speed, maximum capacity and ultimate objectives for the machine. These should be balanced against the cost of the upgrade, the cost of a new machine and the financing or funds available. A replacement parts upgrade is just one way that a manufacturer can stay competitive within their industry without a large capital outlay.
Russell Fox is a Mechanical Drives Engineer and co-owner of Power Train Services, LLC., an engineering and replacement parts company located in De Pere, Wisconsin. For more information, visit www.pts-wi.com or contact Russell at 920 336-4631 or firstname.lastname@example.org. The opinions expressed in this article are those of Power Train Services, LLC., and do not necessarily reflect those of AccuVal Associates, Inc., its owners or affiliates.
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