“It’s a poor workman who blames his tools.” This anonymous proverb may hold some truth when applied to today’s food and beverage production machinery and components. Suppliers of these tools have a zillion regulations and specifications to follow regarding clean design, and they have hygienic design down to a T—as long as the “T” doesn’t represent a “dead end” in a pipe carrying a food or beverage product.
- Following the specifications
- Hygienic design is not just using stainless steel
- Stainless … or stainless?
- Design for CIP?
Since the 2008 Listeria outbreak, attributed to an accumulation of bacteria in a hard-to-reach section of a meat slicing machine in a Maple Leaf Foods plant in the Toronto area, machine suppliers have taken a close, hard look at their equipment and components and made redesigns where necessary. With all these engineering efforts to reduce pathogen harborage and make cleaning easier, however, it’s still incumbent on food processors to do their part and keep the equipment and spaces in which it’s located clean.
For example, the FDA shut down a soy manufacturer in Sacramento because it found repeated safety violations, including improperly cleaned equipment and failure to protect against contamination of food and food contact surfaces. With the recent Blue Bell ice cream plant(s) shutdown, the potential cause of Listeria contamination at the Oklahoma plant was attributed to cleaned equipment being stored outside the sanitary production area, which was possibly contaminated because of its proximity to a floor drain. Would this be akin to storing your clean cooking utensils near the basement sump pump and reusing them without rewashing?
A year ago (FE, October 2015), we covered the latest on 3-A and the European EHEDG standards, and two years ago (FE, April 2014), we also looked at PMMI’s OpX Engineering Solutions Group’s “One Voice for Hygienic Equipment Design for Low-Moisture Food,” which brought together OEM machine builders and food processors to work toward producing a document to help processors and suppliers understand each other’s needs for equipment design where there were not a lot of standards to follow. The finished document can be found at PMMI’s OpX website.
Meanwhile, most process equipment providers know what they have to do because the rules are black and white. For SEEPEX, Inc., maker of rotary positive displacement pumps that meet FDA, USDA, 3-A, USP, EHEDG and/or NSF requirements, the rules for materials are spelled out, according to President Mike Dillon.
“Materials requirements are very specific and are set by the standards of the compliance organization favored or demanded by the customer. Some standards require certifications by third-party laboratories or inspectors,” he says.
Some, like NSF, require actual testing of equipment on specific products on an annual basis and have random audits of the equipment or parts inventory to ensure compliance. Designs for the dairy industry have to typically be easy to clean in place (CIP), with specific radii and surface finishes in food contact areas. In the last five years, more intensive audits have been performed, and the use of materials traceability and positive materials identification have become more routine, adds Dillon. The need for thorough cleaning, especially through CIP, has become critical to meet regulatory demands.
“We have experienced customers’ need for greater flexibility in the creation of cleaning programs so they can tailor the programs to effectively clean individual circuits,” says Kevin Nowack, director of engineering at ESE, Inc., a Control System Integrators Association member. “Plants are looking for greater visibility of the wash cycles completed and the circuits cleaned daily.” Process flows are becoming more complex with mix-proof valves and valve clusters, and documenting the pulsing sequences of the circuits to insure the clusters are being washed correctly is critical.
Alfa Laval supplies a large array of sanitary fluid handling components to the food and beverage industry, and most all have CIP functionality. Specific design guidelines incorporated for a product’s wetted parts include meeting EHEDG and 3-A criteria for a hygienic design to ensure cleanability, says Christian Thommen, Alfa Laval USA fluid handling product manager.
“Over the past five years, there has been an increased focus on offering an all-stainless-steel solution to not only the product’s wetted parts, but also the complementary components such as gearboxes and motors,” he says. “Alfa Laval has now standardized on an all-stainless-steel positive displacement pump and gearbox solution for the SRU [product line]. The all-stainless SRU offering reduces potential contamination issues in the process environment by eliminating the possibility of broken epoxy paint flakes and rust, as well as holding up to the harsh cleaning/foaming chemicals used on the plant floor.”
The materials on components must not be susceptible to becoming a part of the food, suggests Bill Sutton, Kollmorgen business development manager. He says the company’s motors are made of 316L stainless steel (SS), so they are corrosion resistant.
“The paint on food-grade servo motors inevitably flakes, and the underlying aluminum corrodes, creating two problems. The paint can become a part of the food product, and the rough surface of the corroded aluminum makes it very difficult to remove product or pathogens,” adds Sutton. “Even in adjacent areas to the food zone, these issues create problems because the paint or pathogens can migrate to the food zone.”
There’s more to the story than chipping paint. Sutton explains that, at first, Kollmorgen assumed it could make a SS motor that looked like its standard motors, but would just be sealed better. After conferring with more than 100 food processors during the development of the AKMH servo motor and observing what happened during sanitation procedures, Kollmorgen’s vision changed.
“We realized that a much higher level of ruggedness was required in the design of the motor,” says Sutton. “So, we designed our motor with seals, cables and cable glands to insure durability that goes well beyond its IP69K rating.”
KHS is an international manufacturer of filling and packaging technology for the food and beverage and non-food industries. Diana Wolf, beverage technologist, sees new technologies, such as the latest servo drives, allowing for totally new equipment designs with moving parts that need no lubrication.
“The best part to clean is the one that doesn’t exist. So the design results in fewer surfaces and individual parts. All materials are certified to come in contact with food,” she says. An important criterion, however, is the selection of suitable components in addition to the use of suitable material specifications (FDA-compliant materials) and EHEDG approval.
Bühler Aeroglide makes conveyor drying and cooling equipment and is the drying center of competence for the Bühler Group. Before the machine builder designs a piece of equipment, two important pieces of information are needed: the hygienic zone where the equipment will live and the cleaning method to be used, specifically wet or dry cleaned.
“Once we understand the cleaning method and hygienic zone of the installation, this will guide us in the design details,” says Steve Blackowiac, Bühler director R&D and food safety. “In either case, wet or dry clean, we give much attention to access for cleaning.” For example, important details include minimizing collection points such as cracks and crevices. Wet wash equipment must be self-draining to avoid water pooling, he adds.
“When it comes to specifying conveyors for the food industry, you really need to start by explaining the difference between a SS conveyor and a sanitary conveyor,” says Stacy Johnson, Dorner Manufacturing Corp. senior marketing manager. “That’s because there’s a common misconception that all SS conveyors are sanitary. A sanitary conveyor removes harboring areas where bacteria and other contaminants can collect and ultimately find their way into the food manufacturing process.” This is important because hidden crevices on the conveyor frame can become catch points and promote the growth of microorganisms. A true sanitary conveyor system has a design that eliminates the development of bacteria and is completely accessible for cleaning, says Johnson.
Stainless steel is certainly the right material to use in applications that call for regular washings with light chemical cleaning agents. A basic SS conveyor can be washed throughout the day as needed, depending on how it is built, but it’s not necessarily sanitized. That’s because sanitizing or cleaning a conveyor involves an entirely different process than simply washing it down, and much of achieving a sanitized conveyor depends on the way it was initially designed.
Johnson says a sanitary design for a conveyor eliminates flat level surfaces within the frame structure, replacing them with rounded cross members that prevent food and water from accumulating. Also, the overall openness of the frame should be designed such that if any product falls off the belt, it will land in a catch pan below or on the floor—preventing food from getting trapped within the frame. Additionally important, hygienic designs remove the bolted-on, plate-on-plate construction where crevices collect bacteria and replace them with smooth, polished welds, creating a continuous, smooth surface where bacteria won’t cling.
“Over the last five years, there have been many changes to the design of our equipment, driven by hygienic design,” says Blackowiak. These include:
- The use of materials appropriate for wet wash, for example, with a surface roughness of 32 Ra (roughness average in microinches) or better (a 3-A certified dairy finish has an Ra range of 18-31 microinches).
- Use of open structural members over traditional hollow shapes, such as tubing, to prevent harboring places where moisture can collect and bacteria grow.
- Locating bearings and drives to the exterior of the equipment is not only a hygiene improvement, but by keeping lubricant outside of the dryer, makes maintenance much easier.
- Improved welding and finishing techniques have also improved in meeting today’s sanitary requirements.
- Clean-in-place (CIP) options and automated belt cleaning systems are available.
Meeting today’s specifications can be tough for some OEMs, and machine builders fill in the gaps when OEM components aren’t quite up to spec.
“Some of our OEM component suppliers are doing a great job of providing components that meet our food safety specification,” says Blackowiak. “Others have struggled, and in some of those cases, we have had to design and fabricate our own solutions. We are determined to have a complete food-safe [component] supply and continue to work with our suppliers to improve where needed.”
In Europe, there are CE-directives and EHEDG guidelines, but even so, OEMs aren’t always on track. GEA, being an international supplier of food processing equipment (e.g., CookStar and Flowcook), designs and builds equipment to not only European standards, but also to any country’s legislation where it sells equipment, according to Vlemmings.
“We notice that OEM suppliers are not always up to speed on providing food-safe parts,” says Alex Vlemmings, head of product development—food processing, GEA. “They should comply to legislation required on CE and EHEDG directives.”
In this case, we’re talking about 304/304L SS versus 316/316L SS. What’s the difference between the two alloys? In a nutshell, 316 SS resists corrosive and caustic washdowns and ingredients better than 304 SS, but there is a cost penalty. An important differentiator between 304 and 316 SS is that 316 SS has typically 2-3 percent molybdenum content, whereas 304 SS has none. The molybdenum content is the reason 316 SS has greater resistance to various forms of deterioration. While 304 SS may be acceptable for some architectural elements that don’t get washed down with harsh chemicals, it won’t satisfy the needs of applications where components come into direct contact with harsh chemicals, such as CIP fluids. For these applications, using the more expensive 316 is an absolute must, for example, in pumps.
“All of our equipment is AISI [American Iron and Steel Institute] 316 or better,” says SEEPEX’s Dillon. “AISI 304 is rarely used because it may not stand up to CIP fluids or can be easily stained. We have standardized on AISI 316L because of the frequent need for fabrication or special modifications to even normally machined parts.”
Also, there are some grades of stainless steel that offer additional properties that are used in SEEPEX equipment. Metal-to-metal contact areas where there may be rubbing must have different metallurgies to minimize galvanic erosion or “galling.” In many cases, the main wear component is made of a “duplex” material. The most common is AISI 630, a precipitation-hardened material that is harder than AISI 316. It is also commonly referred to as 17-4 ph (precipitation hardened with 17 percent chrome and 4 percent nickel).
“Other materials are used on a special basis if there are high chlorides [due to pickling or salt curing, for example],” says Dillon. “These duplex materials may have 22 percent chrome and 5 percent nickel. Occasionally, exotic metals like AISI 900 series, Hastelloy® or titanium parts are needed for corrosion resistance.”
SPX FLOW Inc. manufactures a wide range of process technology that is used in the food and beverage industry such as valves, pumps, homogenizers, mixers, separators, heat exchangers, dryers, evaporators and full process systems. SPX FLOW tends to use 316L SS for wetted parts and 304 SS for the non-contact parts of equipment such as pumps and valves for use in food processing, according to Christopher Sinutko, global product manager - food & beverage valves.
“High chlorine content is found in processes such as those that involve certain cleaning chemicals, some sauces and tomato-based products, and this can corrode stainless steel,” he adds. “In such applications, SPX Flow provides alternative materials that hold up much better to this chemical—such as AL6XN, Hastelloy® alloys and duplex 2205 SS. However, these come at a cost, and food processors need to weigh the corrosion risk against the additional investment required. The use of these materials, therefore, very much depends on the application. Whichever material is selected, it must of course be approved for use in food and beverage processing.”
“We offer both 304 and 316 SS for our equipment, supplying 316 SS for those projects where caustics or other harsh chemicals are used for cleaning,” says Blackowiak. “Because there is a cost impact to the use of 316 material, exclusive use across the board doesn’t make sense to us.”
For smaller components, using 316 SS is less costly than using it for extensive machine housings that are either infrequently washed or dry cleaned. “We chose 316L for use in our motors,” says Kollmorgen’s Sutton. “We consulted with food processors and with cleaning solution providers. The increased resistance to corrosion [with 316 SS] was worth the extra cost.”
“A lot of machine parts, especially for process technology, are built with 316,” says KHS’s Wolf. “It is always a question of concentrations and temperatures of the liquids that come into contact with the machine parts. The execution of product contact parts in 316 is a selectable option for KHS machines. The higher price for [316 SS] makes up about 8 percent of the machine price.” Since all of KHS machines are able to be cleaned in place, and for large tanks, spray nozzles are used, the choice of 316 SS over 304 SS may be appropriate, depending on the concentration and temperature of the cleaning chemicals.
More and more production equipment is being designed for CIP, and even some equipment that would seem an unlikely candidate—such as GEA’s CookStar Turbo oven series, which has an “inside-out-spray” system using a rotating drum. The oven’s belt features a continuous wash and lecithin dip and, when combined with the internal CIP system, allows the unit to operate for up to 72 continuous hours.
Of course, it’s not always possible to run CIP on every part of the process, and in some cases, there will be a mix of CIP and clean out of place (COP). So, what about CIP?
“This really depends on the customers’ requirements,” says SEEPEX’s Dillon. “Dairy products producers must design for CIP. That is not true for confections. Many users in sugar refineries are using cast iron and carbon steel. Most chocolate processors still use cast iron pumps, carbon steel pipe and copper tanks. Cookie icing is commonly handled with SS industrial pumps that never get CIPed.
“CIP must be defined by the plant and their food scientists,” adds Dillon. “Equipment used are just pieces of an entire system. The chemicals and velocities used to clean equipment used for soft drinks is entirely different than, say, yogurt. In general, standards set by 3-A are applicable for the dairy industry, but each user has to design the system for their products.” The real challenge, adds Dillon, is doing a swab test and counting the bacteria that can grow in a Petri dish after a defined time. That’s a job for the food processor to do before the appropriate government inspector arrives.
“There is an increasing trend towards equipment designed for CIP,” says Sinutko. “Some areas, such as meat processing, still use COP with daily disassembly, cleaning and inspection. Any COP equipment needs to be designed for easy disassembly and maintenance.”
The SPX Flow Universal 1 pump, for example, is a COP device designed for easy disassembly, cleaning and maintenance. But not all pumps are COP.
“Pumps and valves that can be used within a CIP system can be cleaned without disassembly—reducing cleaning time, manual labor and potential errors in reassembly,” adds Sinutko. “When installing a pump, the CIP system design should consider if a pump bypass valve is required to allow the proper flow rate to clean the piping while keeping the correct delta pressure across the pump.”
CIP equipment must be designed, certified and tested to 3-A and/or EHEDG standards. This shows that it is cleanable—but this will only happen with a correctly designed CIP process, adds Sinutko.
New, creative CIP designs are underway, such as Bühler’s newly developed high-hygiene wet-wash solution with CIP and belt cleaning solutions. The system includes a water management system that is integral to the floor design. It also has new direct drive hygienic recirculation fans, hygienic dampers, hygienic doors and latch designs along with new TIG (tungsten inert gas) welding techniques.
“We are currently working on a high-hygiene, dry-clean piece of equipment that will be available by year’s end,” adds Blackowiak.
Finally, clean design is an investment in food safety and your brand—and time. It’s the time spent in teams—food and beverage processors and suppliers working together (as with the OpX group) to create safe, clean designs in equipment to produce food-safe products.
For more information:
“Leveraging Stainless Steel Finishes on Sanitary Equipment,” Whitepaper,
Apache Stainless Equipment Corporation, www.apachestainless.com/Leveraging-stainless-finishes.pdf
“Hygienic Design Enhances Food Safety, Brand Protection, Regulatory Compliance
… and the Bottom Line,” Whitepaper, Kollmorgen, 2016.
“One Voice for Hygienic Equipment Design for Low-Moisture Food,”
OpX, PMMI, 2014, PMMI website.