Waukesha, WI--Using a nickel-based alloy, engineers may now have a more potent means to deal with the problem of galling in food processing machinery.
The alloy, known as Waukesha 88, is mostly nickel, but also includes tin, iron, bismuth and chromium. It solves the problem of galling of stainless steel materials, which are often used to combat corrosion-caused processing of aggressive foods and pharmaceuticals.
Although it may seem innocuous at first glance, galling of stainless steels can cause enormous problems for food processors. The worst problems occur when stainless steel surfaces rub against one another, potentially releasing tiny steel particles into the food or drug that's being processed. The problem is even more pronounced in food processing, where the use of lubricants is often not permitted, and galling is therefore increased.
Waukesha 88 solves that problem because it offers a combination of properties. Like stainless steel, it is corrosion resistant, making it ideal for use in the processing of aggressive foods and pharmaceuticals. Unlike stainless steels, however, Waukesha 88 also incorporates bismuth, which provides an anti-galling effect. That, in turn, enables its use in dynamic applications where galling can be a problem.
As a result, some engineers now employ Waukesha 88 in rotors for positive displacement pumps, in bushings for pump shafts, and as plungers and formplates for meat patty machines. The alloy was recently used as a piston material in multi-station filling machines, which fill cans and bottles with foods ranging from baby meals to ketchup.
Engineers say that the key is to use the material as one of two mating parts, because cost often prohibits its use in large shafts or housings. In the filling machines, for example, engineers used it as a piston but did not apply it to the mating part--a large cylindrical casting.
"It's more costly than stainless steels," notes Tom Kerwin of Waukesha Foundry. "But it lasts longer and solves the galling problems, so it makes sense in critical applications like food processing."