Cleanability is always a priority for food processing equipment, particularly when food contact surfaces are not open to easy visual inspection.
Quicker, easier cleaning of pumps and other precision components is an argument for clean-in-place (CIP). As food and beverage manufacturers continue their push for continuous processes to replace batch, pump fabricators are responding with more CIPable units. Unfortunately, CIP chemicals, temperature extremes and the foods themselves can pose new problems, notably corrosion and deflection of close-tolerance parts. Overcoming those problems is driving consideration of exotic material solutions.
"Sanitizing chemicals aren't the problem anymore, it's the products," believes John Zirbel, an engineer with A&B Process Systems in Stratford, WI. Taco sauce, tomato paste and sports drinks can pose a greater corrosion challenge than sodium hydroxide and other compounds.
Duplex, Hastelloy, AL6XN, 174 stainless: boutique metal brands to meet specific industrial demands are proliferating, and some are being used in food and beverage, when 300 series stainless isn't quite good enough. A cocktail of manganese, copper, silicon and other elements is mixed with chromium and nickel in stainless steel to add desirable properties, be it greater corrosion resistance or heat treatability for additional strength.
"The status quo is still 316 stainless, but in 20 years, there may be a change," allows Bill Rice, technical products manager for Delevan, WI-based Waukesha Cherry-Burrell (WCB). "We're starting to get inquiries from makers of barbecue sauce and other very acidic products about new metallurgies."
"It's not so much the cleaning chemicals as it is the products themselves" that corrode pumps and other parts, agrees Philip R. Frechette, president of Rochester, NY-based JCS Controls Inc. Isotonic drinks and other sodium-heavy products can wreak havoc, particularly if they are heated to high temperatures. A tomato-paste processor suffered through annual weld failures on 316-stainless hold tubes on a heat exchanger until replacing them with AL6XN. Six years after the switch, the system is running without additional repair.
But a properly engineered continuous system can short-circuit the need for super-alloy pump components, Frechette adds. The key is designing the flow so that product moves through the pump at temperatures below 130°F.
The trend in cleaning temperatures, on the other hand, is moving up. The reason: allergen control is front and center, and breaking down oils requires hotter water and possibly new solvents. And while 300 series stainless easily tolerates current chlorine concentrations, more aggressive CIP could pose a problem.
"Select components in high-stress areas are being made with exotic alloys, such as 600 series stainless," says Mike Dillon, president of seepex Inc., Enon, OH. Titanium and even Kynar, a thermoplastic cousin of polypropylene, have been used in applications where the use of sodium hypochlorite and other corrosive chemicals demanded advanced solutions. Engineered plastics could add to the material options in food, though they would face time-consuming regulatory approvals.
Thermoplastics for pump components came into their own in the semiconductor industry, where trace amounts of metal contaminants were found to ruin products such as printed circuits, according to Nancy Westcott, owner of GoatThroat Pumps (see sidebar on page 85). Winning regulatory approval for thermoplastic pumps in dairy production might be years off, she allows, but there are plenty of chemical- and ingredient-storage applications where polypropylene pumps already are being applied.
Duplex stainless and 174 steel already are allowed by 3A, points out Mike Amburgey, a mechanical engineer with Springfield, OH-based Moyno Inc. Heat treatable for added strength and corrosion resistance, those super-alloys are growing in popularity in Europe. "Customers don't specify 174 or duplex, they just say, ‘Make it 3A or USDA compliant,' and then leave it to us to do the application engineering," says Amburgey.
Hastelloy and AL6XN are among the austenitic alloys used for component fabrication for pharmaceutical pumps, and electro-polishing and other steps can provide additional protection against pitting, corrosion and stress cracks, according to Randy Verges, senior applications engineer at Fristam Pumps, Middleton, WI. But cost isn't the only barrier to advanced alloys' use in the food industry: the standards for a process using purified water are not as strict as a process using milk, Verges points out.
Metallurgic overkill?Whether exotic alloys are a solution in search of a problem is a question end-users must answer. The upgrades from 316 stainless can be six to seven times more expensive, estimates Frank Hinlopen, business development manager at Pleasant Prairie, WI-based Alfa Laval. Sometimes the problem they solve isn't particularly serious: de-ionized water can pull ions out of the metal and cause rouging, a discoloration that may mimic rust but is not a safety issue, he says.
A better capital bang comes from higher grade mechanical seals. A dozen years ago, Alfa Laval's Tri-Clover division introduced a self-centering, hydraulically balanced, front-loading seal that slashed maintenance time and extended seal life. "Sometimes they're lasting up to six years in applications where they used to last a couple of months," says Hinlopen.
Shorter lever arms to reduce shaft deflection and extend time between maintenance routines are another design improvement with high payback, adds Fristam's Verges. Besides keeping the rotor close to the bearings and gearbox to reduce maintenance, Fristam has altered oil-bath bearing design to facilitate oil changes. And incremental efficiency improvements are driving energy savings, particularly on large pumps. "A 5 percent efficiency improvement on a 50 HP pump can mean a huge savings over the life of the pump," he says.
Close-coupled pump drives are sometimes promoted as space savers, and they are becoming the norm in centrifugal pumps. Reduced seal replacement is a bigger benefit, with the elimination of the sanitary problem of an exposed shaft another plus. Through a partnership with Nord Gear Corp., WCB is bringing the benefits of close coupling to positive displacement pumps.
"A flange designed around a gear reducer is the next step in the evolution of PD pump drives," WCB's Rice says. The gear reducer replaces the firm's Integral Speed Reducer to step down rotational speed below 50 RPMs. The need for shaft alignment is eliminated, as is bacterial harborage.
The long, thin profile of progressive cavity pumps is not space efficient, a drawback manufacturers are working to temper. On the other hand, their ability to pump at pressures much higher than conventional PD pumps makes them an attractive alternative in continuous processes. "People are looking at equipment changes like scraped-surface heat exchangers to boost throughput while maintaining product integrity, and that means higher pressures to push product through," notes Moyno's Amburgey. seepex's Dillon seconds that, adding, "there are pumps with 75 HP motors on them feeding fruit into a heat exchanger. Aseptic handling of particulate is becoming increasingly common."
Double-duty pumpingThe line between pumping and mixing is being obscured, with fabricators offering modifications that deliver properties of both types of equipment. For example, a process developed by FiberGel Technologies to separate soluble and insoluble fiber to create a fat replacer begins by imparting shear as a slurry circulates through a Fristam pump (see "From the lab to the line," Food Engineering, November 2005). Similarly, the minimal shear of a progressive cavity pump is trumped with the addition of an open hopper chopper to effect size reduction in plant waste streams.
"The more you chop up something, the more surface area you expose to break it down faster," observes Dillon. "That lets you go from batch to continuous in waste handling, which also means smaller reactors and smaller tanks."
The first waste application for seepex came a few years ago at Snyders of Berlin, a Pennsylvania snack-food maker who used submersible chopper pumps and thousands of gallons of water to meet BOD pretreatment targets for waste streams. By switching to a high-pressure progressive cavity system, capacity expanded significantly and soiled water was taken out of the equation. More advanced applications using potato and poultry waste to generate ethanol have since been developed by other processors, according to Dillon.
Developers of the PDX Sonic mixer tout pumping ability as a benefit, though "it's a fringe benefit of the system," concedes A&B's Zirbel. The first two North American commercial Sonic applications were engineered by A&B, including a system at Mexico City-based Grupo Jumex. Sonic is powered by steam, which is great for heating and mixing but a poor energy choice for pumping.
Nonetheless, the Jumex application allowed engineers to eliminate a centrifugal pump from the design, an efficiency that saved both capital and ongoing maintenance costs for seals and VFDs.
Whether they're doing double duty or a single task, today's pumps have more mass and are more reliable, reflects JCS's Frechette. "The 1980s were a hard time for pumps," he recalls. "Today, there are less stamped housings, more beefy pump heads, better impeller designs and better sealing systems. There is a solution for every application-you just have to pick the right one."
Heavy-duty castings that can be machined to closer tolerances without warping have become the norm in food and beverage premium pumping. It's not as glamorous as advanced metals, but it's a fundamental improvement that has helped advance the technology in the last 20 years.
For more information:Frank Hinlopen, Alfa Laval, 262-947-3742
John Zirbel, A&B ProcessSystems, 715-687-3089, firstname.lastname@example.org
Randy Verges, Fristam, 608-831-5001, email@example.com
Philip R. Frechette, JCS Controls Inc., 585-227-5910, firstname.lastname@example.org
Mike Amburgey, Moyno, 937-327-3351, email@example.com
Mike Dillon, seepex Inc., 937-864-7150, firstname.lastname@example.org
Bill Rice, Waukesha Cherry-Burrell, 800-252-5200, ext. 4670, email@example.com
Nancy Westcott, Westcott Distribution Inc., 646-486-3636, firstname.lastname@example.org
Sidebar: Diverse food market demands diverse technical solutionsWhile major manufacturers measure line production in thousands of gallons per hour, food processing entrepreneurs may only need a few gallons of a given ingredient every 60 minutes. Nonetheless, reliable pumping is a prerequisite, and corrosion- and abrasion-resistant pump components can contribute to product quality as their business builds.
Stancato's restaurant exemplifies the entrepreneurial category. A Cleveland area mainstay since 1938, Stancato's began bottling its spaghetti sauce and Italian salad dressings for diners who wanted to enjoy the toppings at home. Last year, the firm branched out into retail distribution and acquired a former cannery in Canton, OH, to meet growing demand. "We were pouring ingredients into a bucket from a 55-gal. drum weighing about 400 lbs.," recalls Scott Six, the plant's production manager. "It was a two-man job, inconvenient, and hard work. " Like many manufacturers before him, Six concluded a pump was the solution; the only question was, what level of complexity?
An air-pressurized pump powered by a shop-air compressor and equipped with a release valve to maintain drum pressure between 2 and 7 psi was the answer. "There's no pulsing, and at four gallons a minute, it is plenty of volume for our purposes," reports Six. Olive oil and red-wine vinegar are among the ingredients being transferred.
"I describe it as a beer tap for chemicals," says Nancy Westcott, president of New York-based Westcott Distribution Inc.-a description that makes her investors cringe but which quickly explains the spring-actuated pump's concept. Westcott purchased the molds and manufacturing rights to the 2-lb. polypropylene pump from a defunct South African firm, renamed it the GoatThroat and partnered with three comanufacturers to fabricate four food-grade versions. Stancato's is the first US food client, though Australia's Yalumbia Winery and other overseas companies have used the self-priming pumps since their introduction in 1997.
Easy cleanability and a replaceable O-ring make the units a good fit for food plants, though Westcott says any manufacturer dealing with drum transfer can use them. And material construction makes them appropriate in any application where chemical degradation is a concern.