Stainless steel speed reducers paying dividends for companies willing to cast aside cast iron
While walking through any food manufacturing facility, it is difficult to look in any direction without encountering stainless steel. The last several decades have seen the industry transform from having stainless steel as a high-end option on food processing and packaging equipment, to an absolute requirement - no substitutes. Yet you need only look behind conveyors, or under processing equipment, to find painted, cast iron speed reducers driving the machinery. In many cases, these reducers are the only exposed non-stainless metal found.
The fact is, the "stainless steel revolution" has yet to find the world of speed reducers. While these products have been offered by a number of manufacturers in recent years, the adoption of the technology has been slow, at best. To many, this is puzzling, considering the advantages stainless steel can offer food manufacturers:
• No fear of rust or paint chips entering the food supply
•Eliminates the possibility of rust creating a hiding place for bacteria
•Requires no repainting or other aesthetic maintenance
•Does not attract unwanted USDA scrutiny
Compared with cast iron, stainless steel does not dissipate heat as well, causing some engineers to think twice about stainless in high duty-cycle applications. This worry, however, pales in comparison to most food manufacturer's larger concern - cost.
It costs what!?!?
A typical stainless steel speed reducer costs at least twice as much as a comparable cast iron one, often pushing it out of the price range where most facilities are even willing to try it. The two largest factors of this cost difference are the cost of stainless steel housings, and the added cost of machining stainless steel.
As many food manufacturers have built their own conveyors for many years, they feel they understand the cost of stainless steel. The problem is that they are buying sheet stainless steel. The difference in price between the regular steel and sheet stainless steel is $0.50 per pound. If your gearbox weighs 40 lbs., it will cost $20 more. The difference between cast iron and cast stainless steel is huge, and that is even before you try to machine it.
Machining presents another problem, as the hardness of cast stainless steel requires the usage of more expensive tooling. That factor by itself can add an additional 10 percent or more to the cost difference.
For a one horsepower gearbox, the added cost to the manufacturer for the cast stainless steel housing and flange approaches $100. Add overhead, machining, and a very modest profit, and the cost to end users is usually double that of a standard gearbox, at the absolute minimum.
Early adopters realizing benefit of stainless steel
Despite this cost difference, a number of industry leaders have taken the plunge and now utilize stainless steel speed reducers in their equipment and facilities.
Fresh Express, a Salinas, CA-based producer of fresh packaged salads, is one of those leaders. "Painted gearboxes do a great job for about a year," states Gene Rizzo, plant manager at Fresh Express. "Unfortunately, at some point the paint gets chipped, and once that has happened there is no saving the gearbox. The chip grows, the epoxy comes off, and before you know it the box is covered in rust. A typical gearbox in our plant was only lasting 18 months before we'd need to replace it. We looked at repainting the gear boxes ourselves, as well as powder coating them, but neither proved to be a good solution."
With stainless steel, Rizzo believes Fresh Express has solved the problem. "All stainless steel speed reducers offer us three main advantages. First, they reduce costs - we may pay twice as much for them, but they last more than twice as long as our painted boxes did. Secondly, they are more sanitary, providing a safer environment for food production. And finally, they are much more aesthetic. We get lots of people going through this plant - USDA, key customers such as McDonald's, AIB inspectors - and each leaves with a certain perception of our quality. Rust on a gearbox is not the perception we want them to have, because it is associated with a dirty, unclean environment."
A number of equipment makers are also leading the change. "In the beginning, we only offered stainless steel speed reducers when customers spec'd them in," states Stuart Olsen, operations manager of KLEENline Corp., a maker of sanitary washdown equipment in Georgetown, MA. "Versus the price of the equipment, the premium for all stainless steel speed reducers is small. Many customers today place a greater value on the problems avoided by an all stainless steel product, as well as the cleaner look of all stainless in front of visitors to their facility, be it management, customers, or inspectors." Today, KLEENline offers a number of lines of conveyors and material handling equipment that come standard with all stainless steel speed reducers and motors.
This is even more evident at Material Systems Engineering Corporation, a Tampa, FL-based manufacturer of sanitary material handling equipment. "The number one thing we supply our customers is reliable, sanitary material handling solutions," asserts Dar Karpy, president of Material Systems. "If you select painted or aluminum gear boxes for use in a caustic washdown environment, then you can not honestly stand behind the sanitary claim, because the caustics will find a way to eat at the paint or degrade the aluminum. What results is rust or oxidation, and while it may not look nice, the greatest danger is that the surface now has thousands of nooks and crannies for bacteria to grow." Material Systems uses stainless steel gearboxes from Boston Gear as standard on all of their equipment.
Not all stainless steel is alike
While most engineers evaluating stainless steel gearboxes compare them to their washdown-painted counterparts, there are a number of key differences amongst the stainless steel gearboxes on the market. The biggest is the grade of stainless steel chosen, either 316 or 304. While the raw material costs are generally 20 to 30 percent more than grade 304 stainless, grade 316 offers several important advantages for food processors, including significantly increased resistance to pitting when exposed to caustic washdown solutions.
The second big difference is that some "stainless steel" gearboxes actually have parts, such as the flange, that are painted rather than pure stainless. When you are exposing your equipment to caustic washdown, you are only as strong as your weakest link.
Take stock of your operation: stainless steel not for everyone
Despite its advantages, stainless steel is clearly overkill for a number of food manufacturing environments. The anti-corrosive benefits of stainless steel don't offer as much to industries like the bakery industry, where washdown is generally done with air or a mild solution and none of their ingredients challenge the integrity of gearbox paint if spilled onto the gearbox or released into the air.
Additionally, smart gearbox design is essential if stainless steel is going to be beneficial. Excessive recesses in the housing where food and water can collect will harbor just as much bacteria growth on stainless steel as on cast iron. Likewise, if condensation, washdown fluid or other contaminants can easily get into the gearbox, the cooling ability of the lubricant is affected and stainless steel gearboxes can overheat.
Still, for many industries, stainless steel gearboxes offer advantages that far outweigh their costs.
Unfortunately, many companies own internal processes that make it difficult to realize those benefits. Some companies cannot justify the expenditure of stainless steel gearboxes even in heavy washdown areas because their labor budget and the MRO budget are separate. So they continue to buy standard gearboxes, and waste a lot of money repainting them.
The early adopters of the technology, however, find that the benefits of stainless steel have paid off.