Shaft-Sealing Technology Ends Maintenance Problems at Ribbon Blender

Novel shaft-sealing technology solves a chocolate plant’s maintenance woes.

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Benjamin P. Forbes Co. is a chocolate company with a history dating back more than 100 years. After working with Milton Hershey in the late 1800s, Benjamin Forbes moved to Cleveland, and in 1901 founded the company that bears his name.

Today, the company enjoys a national reputation as a blender of cocoa and flavor powders for dairies. Forbes products are also used by ice cream manufacturers, bakeries and upscale restaurants. Powders include chocolate for chocolate milk and a wide range of flavors including mocha, strawberry, vanilla, orange cream, root beer, banana and mango. Custom blending includes chocolate ice cream powders and cocoa powders, including defatted cocoa. Syrups, organic cocoas, extracts, chips, drops and coatings also are available.

When the company moved to a new facility in 2007, “after 100 years of blending powders, we knew what plant improvements we had to make,” says President Keith Geringer. “One of the improvements we needed was in the maintenance of our ribbon blenders. These blenders, used to mix cocoa powder blends and combine the various ingredients, had been giving us maintenance nightmares for some time.”

The company had been employing a common practice for sealing mixers and mixer shafts, using a stuffing box with packing around the shaft. Rings of packing material are placed within the stuffing box to form a seal that controls leakage along the shaft. The packing rings are held in place by a gland follower that, in turn, is held in place with adjusting nuts.

As the nuts are tightened to make the seal, the packing becomes compressed, which causes the packing to expand. But if overtightened, the packing rope can be damaged. And as the shaft rotates, the packing makes contact with the shaft and heat builds up.

This was the basis for the problem at Benjamin Forbes. The mixers were old technology, sealed with packing glands that needed constant adjusting and maintenance. If adjusted too frequently, the packing rope would wear out. If adjusted too tight, it could burn the rope. It was accepted that sooner or later the packing would have to be replaced.

Compounding the problem, product would leak out, causing housekeeping issues and eventually scoring the shaft to the point that it had to be replaced – an expensive proposition. And because the mixers were older, the original shaft tolerances had changed, making it even trickier to adjust the packing.

The real issue was not how long the packing would last, or even the price: it was downtime, constant maintenance and housekeeping. Geringer knew when he moved into the new facility he needed a way to keep the shafts of his ribbon blenders properly sealed. He did not want a new facility with old problems.

The answer lay with Powell Equipment, a Hayes & Stolz Ribbon Mixer and an Inpro/Seal Air Mizer Shaft Seal.

Powell Equipment represents material handling original equipment manufacturers, especially for the manufacture and transfer of powders. Moreover, owner Jeff Powell and Geringer have a relationship that dates back more than 20 years. Powell recommended Hayes & Stolz. “From working with them over the years, I knew they could engineer exactly what Keith needed,” said Powell. “Plus, I knew they had a sealing option that had proved quite successful in similar applications.”

“Our company specializes in batch and continuous mixing,” says Jerry Ferguson, national sales manager at Hayes & Stolz Industrial Manufacturing Co. “Whether it is low-, medium- or high-intensity or custom, we can meet any blending requirement. And with our Inpro/Seal Air Mizer option, we offer the only truly shaft seal maintenance-free blenders and mixers on the market.”

Inpro/Seal invented the bearing isolator, a product that changed the way bearings are protected and shafts are sealed. About 10 years ago, Inpro/Seal unveiled a shaft seal called the Air Mizer-PS. Based on the bearing isolator, it was significantly redesigned to contain powders, abrasives, liquids and toxic vapors. By 2007, an entire line, the Air Mizer series, had evolved.

As with the original bearing isolator, the key to success is a non-contact design feature that avoids direct ingress of the particulate material and assures the highest levels of sealing performance. A solid wall of air functions as a barrier to “product flow thru.” This air purge retains product where it should be: inside the equipment.

All shaft seals in the Air Mizer series are custom-engineered and are easy to install, as they conform to existing clearances, bolt holes and patterns. Split designs allow for installation directly on the shaft without the need to disassemble the equipment.

Inpro/Seal went on to add an articulating design that can handle extreme shaft misalignment and deflection, and a rotorless design that is virtually immune to shaft endplay or thrust. The latest design is the Water Mizer, a shaft seal with all the feature of their other designs, except that it uses water to attain the seal.

“About two years ago, we installed three Air Mizer-equipped ribbon mixers from Hayes & Stolz,” says Geringer. “In the old days, there was no telling how many times we would have to stop to adjust, replace or perform some kind of maintenance on the packing. Since we went on-line with these ribbon blenders, we have not had a single maintenance issue. It looks like our maintenance nightmare has become a thing of the past.”

“As a bonus, Keith does not have to be concerned with food grade sanitary issues associated with packing gland seals,” adds Ferguson.

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