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Sweet Success


Alan Walton was aghast when his boss at Hersheys confectionery plant in Memphis, Tenn., handed him a two-pronged order: Use only food grade lubricants throughout the entire facility, and cut the total number of lubricants used from 18 to just four oils plus one lubricating grease.

At the time, food grade lubricants were not as good as conventional ones, and so I told him, We cant do it, recalled Walton, a certified lubrication specialist who is the plants senior lead mechanic. Yet after nearly six years of research and trials, the first part of that challenge – adopt an all-food grade lineup – is complete.

As for the second part of the mandate, were getting there, he conceded. But we have some older equipment that still need some specific lubricants, and so were not quite down to just four lubricants yet.

Why take this journey at all? The Hershey Co. stresses consumer protection, and this is part of that effort, Walton told LubesnGreases. Quality and safety of its food products is a fundamental concern, since any problem with ingredients or packaging could trigger a recall and generate unwelcome publicity – which could damage Hersheys valuable brand and hurt its 14 percent share of the global confectionery market.

The Memphis plant, where Walton has worked for 27 years, originally was the Don Russ Co., maker of Super Bubble bubble gum. It was sold first to General Mills and then in 2000 to Hershey. Although the $5 billion candy company is synonymous with chocolate, this is one of just two non-chocolate factories it owns. It makes breath mints, stick and bubble gum (Bubble Yum brand now), Good & Plenty candies, Twizzlers and Twizzler Bites licorice confections, and more.

The plant has a variety of equipment, some old, some new, some U.S.- made, some European, some of it inherited from other Hershey plants. None of the candies it makes now are the ones it made three decades ago, though, as confectionery fashions change quickly. Processes include cooking, melting, mixing, molding and drying equipment, as well as wrapping and packaging. Choppers, hoppers, drums and conveyors also need lubrication. The gum extruders are a particularly difficult application, Walton added, with their large, high-pressure worm gears.

In May, Walton related how the Memphis facility now lubricates its bubble gum, licorice and mint-making operations. Polyalkylene glycol lubricants solved most of the problems we had, he told the annual meeting of the Society of Tribologists and Lubrication Engineers, in Orlando, Fla. They didnt foam, they had good lubricity, and were able to use them now in about 95 percent of the equipment.

The path to all-food grade lubes was by no means smooth. Memphis first endured a number of conventional H1 lubricant failures, which led to premature equipment damage. Then, early trials with PAGs triggered a flood of compatibility problems with seals, other lubricants and paints – although most of these can be overcome, Walton declared.

Lucas Kerley, a lubrication engineer with ExxonMobil Lubricants & Specialties, picked up the thread from Walton, explaining that food grade lubricants are a very specific niche. Also known as H1 lubricants, they are intended for use in food processing equipment where incidental food contact might occur, such as through leaks or equipment malfunctions. H1 lubricants must be colorless, odorless and tasteless, and contain no toxic levels of ingredients. Many are registered by NSF (, following formulary rules laid down by the U.S. Department of Agriculture and the Food and Drug Administration.

Even with H1 lubricants, food contact is not permitted; in case of an accident, the food product must be recalled. But at least any harmful effects of the lubricant would be minimized.

Polyalkylene glycol lubricants can be made to fit these requirements, Kerley explained. They also offer very high viscosity indices – about twice that of polyalphaolefins – for good performance across a broad range of temperatures. While they have limited compatibility with mineral oil based lubricants, they offer better lubricity than either PAO or esters, he said. They also have good thermal oxidative stability and deposit control, for cleanliness of operations, and help save energy as well. However, you cannot mix PAG with other oils, and so you have to be diligent about where PAG ends up, Kerley cautioned.

Hershey already was using Exxon brand lubricants companywide when it acquired the Tennessee plant, and so Memphis adopted them as well, benefiting from its parents volume-leveraged purchasing. First, it looked at using Group III white mineral oil food grade lubes, but abandoned them after seeing problems with foaming and air entrainment. Next, Walton tried an H1 reciprocating compressor oil from Exxons lineup; it didnt foam, but it didnt stand up to the worm gears that feed the gum extruding equipment either. It began to look like wed need 25 different lubricants if we were going to be 100 percent H1, he said.

Thats when PAGs entered the picture. PAGs let us consolidate the oils. We now have four PAG products in the plant, including H1 gear oils, hydraulic fluid and compressor lubes. We also still are using one H1 mineral oil product, for where our ingredients may have compatibility issues with PAG, Walton continued.

One of the biggest puzzles was how to introduce PAG into equipment that had been running on mineral oil or polyalphaolefin based lubricants, Kerley and Walton agreed.

I dont work for a lube company, but a food company, Walton told the STLE meeting, and if youre thinking of trying this, you need to flush out all the old stuff because PAG is compatible with almost nothing. That means youre going to need downtime, like weekends, when the equipment isnt needed. And you cant just drain out the old oil and refill it with PAG. To begin, we would drain the oil, refill with a diester fluid, and let it run for about four hours. Then finally wed drain that and refill with PAG. Besides being time-consuming, the whole process created a fair amount of waste.

Rethinking these steps, Walton and Kerley found it was possible to use the PAG itself as the flushing fluid. Now we drain, fill with PAG, run the machine, drain and refill with fresh PAG again. The remnants of the old oil are expelled by the process, and in the reservoir float to the top of the heavier PAG in the reservoir, where they can be skimmed off.

PAGs also tend to absorb water rather than reject it, Kerley explained. One fun fact is that unlike mineral oil and polyalphaolefins, water in the reservoir will float to the top of PAG, which is heavier. So you cant drain the water from the bottom of the reservoir as youd normally do.

Walton elaborated: Its a persistent misconception, but PAG is not water soluble – its hydroscopic. By absorbing water, the droplets of oil actually help to keep moisture away from sensitive machinery parts, reducing rust and corrosion.

As Walton and Kerley both noted, compatibility is also an issue with seals and paints exposed to PAG. Nitrile seals are particularly sensitive to the fluids, and PAGs also dont play nice with alkyd and vinyl paints. Epoxy phenolic paints do much better.

I cant stress enough that you have to get all the old oil out, and all PAO too, Walton said. We spent a lot of time training our people to use the new fluids. We also clearly label all machinery, with lubrication tags. In the food industry, we do a lot of obsessive cleaning, with air and water wash-downs. We used to use simple paper tags on wire, but we found these tags were tearing off. Simply using tags with wire grommets helped hold them in place.

Walton said that the biggest initial resistance to PAG lubes came from the plants own staff, who tended to blame every problem on the fluids. We had three gearbox failures due to tooth breakage, and they even wanted to blame that on the lubricant. We had to educate them, and show that gear tooth breakage is not due to any lubricant. Its caused by stress, vibration, overloading and misalignment.

Some workers worried that PAGs hydroscopic tendencies would make it unsuitable in high-humidity areas, since water contamination is a problem with mineral oil lubes. A few objected when they saw how simply PAG cleaned up with water, reasoning (wrongly) that it couldnt lubricate well if it cleaned up easily. Still, Walton told LubesnGreases, they resisted more over the change to food-grade-only than the change to PAGs. Folks just need to be educated, to be shown why it works.

The Memphis plant now uses oil analysis on most of its equipment, and the oil quality reports have helped it extend drain intervals. Were seeing tremendous drain intervals – four to five times over mineral oil lubes, Walton said.

Early in the conversion efforts, Walton noticed one peculiar phenomenon: Some gear boxes on the PAG were operating at 10 percent higher temperatures than before. That scared me to death at first, because previously that was always a sign of poor lubricity. Was there more friction in the gearbox? No, it turns out that the oil is so dense that it just doesnt get rid of heat so easy. After watching it nervously, he concluded that although its warmer, the gear box is fine.

Another problem arose with fluid-lubricated bearings in one process. The plant has some unique airborne contaminants – salt, sugar, flour, talc and sorbitol – which can hinder lubrication. Sorbitol, a dextrose made from corn sweeteners, was peculiarly difficult. At high temperatures it reacted with PAG to make a paste which would not flow or lubricate. To solve the problem, the affected bearings were converted to grease lubrication.

By consolidating oils, the plant also cut the chances for misapplication. And with PAG fluids, backed by oil analysis and full-flow filtration, weve gone three or four years now without changing the oil in some gearboxes, Walton said.

Although the PAG lubes cost roughly double what regular H1 lubricants do, he estimated that the Memphis operation has saved $30,000 per year in lubrication costs since it converted to PAGs. Those gains mostly came in the form of longer drain intervals and less relubrication. The plant also increased the life of the worm gear drives on its candy-making machinery by 300 percent.

We estimate the energy savings were about 2 percent on large systems, too, like the extruder. And weve reduced inventory, eliminating 13 different lubricants, the bubble gum maker concluded.