The Food Safety Modernization Act has heightened interest in food safety. Dairy processors have always been keenly aware of the importance of maintaining a clean and hygienic facility. Pumps and valves are at the heart of any processing plant. They control the flow of fluid milk, cheese curds, ice cream mix and other dairy products through a facility. Dairy Foods wanted to know what plant managers should look for in pumps and valves. We invited makers of this equipment to share their knowledge. (See the end of the article for contributors.) Here's what they told us:
For processing fluid milk, consider a single-seat mixproof valve. Cheese processors use a long-stroke single seat valve or PMO-approved long-stroke mixproof valves with a larger valve opening to allow for the gentle processing of cheese particulates and curds. Aseptic and single-seat PMO mixproof valves are suitable for cultured products. (PMO is the Pasteurized Milk Ordinance.)A rotary positive displacement pump with a circumferential piston is well-suited to move fluids and solids with minimal damage. Because the circumferential piston pump can handle very thin liquids, it is used in lines with multiple different products. The ability for the circumferential piston pump to handle low viscosities without losing efficiency also translates into energy-cost savings.Most fluid milk applications can be handled with a centrifugal pump, sometimes using an inducer for tough suction conditions. Other applications can be handled using a positive displacement pump.Economics, function and planned maintenance requirements are important when choosing a valve. The best valve is one that is reliable, easy to maintain and has a low total cost of ownership. An unreliable valve can result in line stoppages, thus requiring cleaning and sterilization, which takes time away from producing salable product.To ensure against cross-contamination, use a mixproof valve. This valve is designed so that CIP fluids in one housing cannot contaminate product in the opposite housing. Mixproof valves are generally used where automation and numerous product changeovers are critical to the system design. Processors of multiple fluid products (such as milk, juice and tea) benefit from using mixproof valves because they allow for the running of many products simultaneously without the fear of any cross contamination of products or product and CIP. Some vessels can be filled, some emptied and some cleaned, all at the same time. Mixproof valves in a multiproduct environment allow for a fully sanitary, flexible and automated process design solution. They protect against the mixing of unlike products, including allergens.EPDM (ethylene propylene diene Monomer) is said to be the most versatile elastomer for pumps and valves because the material is resistant to most fluids used in a dairy processing plant, as well as to ozone. EPDM has a wide temperature range, which makes it very good as a standard. Exceptions to the standard include combinations of high temperatures, fat content over 30-40% and highly abrasive or acidic products. There are several options when choosing elastomers and it's always a good idea to consult an application specialist about a specific process or product parameters. Because of thermal expansion and contraction and pressure changes in a processing system, select pumps and valves that are designed with metal-to-metal contact around seal surfaces for defined compression of elastomers. This will limit expansion and contractions of the elastomer and provide maximum seal life.Look for a valve design that does not allow product to be trapped and become stagnant. Valves should not have any crevices or dead-legs in their housing design. Product specifiers should avoid seat and stem gaskets with an O-ring type design because these are prone to rolling as the valve stem moves, which allows product to get behind the gaskets, making the valve harder to properly clean. As for gaskets, a metal-to-metal V-ring design is the optimum because wear is greatly reduced, even when there are large temperature differences across the valve. This ensures longer life of the gasket.There are many valve options, and they are all process dependent. Aseptic and hygienic process valves are used in applications where the highest of sanitary requirements are needed. These valves allow for the ability to sterilize and run a completely aseptic process. The valves also have the benefit of being easy to maintain and are highly modular so that they adapt to multiple application requirements.Valve feedback units help control the valves through the plant's PLC. This allows a central location to control the valves in a system, further increasing efficiency. Feedback is required for PMO mixproof valves. Control technology is a smart choice for single-seat valves because it allows an operator to confirm valve actuation and that the process is ready to start. New designs provide options such as local visual indication, valve speed controls or maintenance intervals. The ability to communicate with valves from a central location and in a recorded database gives plant managers the advantage of increasing production efficiency and enhancing the safety of the product and operators.After a product run, valves should be cleaned-in-place as quickly as possible to prevent product residue from drying or hardening. During the CIP sequence, the valves seats should be pulsed repeatedly to allow the solution to clean underneath the seats and inside the vent cavity of mixproof valves. Mixproof valves provide complete product protection at all times (including during seat lifting), so operators can receive maximum security when there is product and CIP liquids in opposite lines.The majority of cheese and butter applications require a positive displacement pump. A large inlet port mounted to an auger feed will minimize restrictions of entering the high-viscosity liquids into the pump. Normally, a positive displacement pump also is used to handle ice cream mix. Cultured product requires gentle handling, so a large pump with increased pump inlets is the general rule of thumb.It is important to choose proper seal materials and elastomers. In fluid milk plants that also process juices and other non-dairy beverages, a plant manager needs seals that are compatible with all product ranges. The manager should choose the seal that stands up to the most demanding product. A silicon carbide double seal may be necessary for abrasive or sticky products. For example, a specifier might recommend a silicon carbide/silicon carbide seal for concentrated whey. But for fluid milk transfer, a carbon single seal might be suitable.Any pump or valve considered for a processing system should bear the approval of 3-A Sanitary Standards Inc., McLean, Va., a non-profit organization that develops uniform standards and practices.A well-designed pump or valve allows for complete and efficient cleaning in place, or CIP. That means all surfaces, including wetted elastomers. When evaluating pumps and valves, look for designs that have no dead zones, sharp corners or other places where organic materials can set up unmoved.Accessories for valvesBest practices for cleaningFor basic transfer of product and moving product through a process line, a centrifugal pump is often the best solution when the product is of low viscosity and has a very-low percentage of solids (or solids that are very small in size). With the rise in energy costs and the push for environmentally-friendly products, many processers use high-efficiency centrifugal pumps for these applications. The more efficient the pump, the less energy is consumed. With the Energy Independence and Security Act of 2007 now in effect, dairies have a heightened awareness of pumping efficiency.Sorting out valvesThe different configurations of rising-stem valves (including single seat, mixproof and double seal) are all used in the dairy industry. Regulatory agencies write regulations around this valve design. The flexibility of the different configurations, their cleanability and their serviceability are the main reasons why some call this the best valve for the dairy processor.
After a product run, valves should be cleaned-in-place as quickly as possible to prevent product residue from drying or hardening. During the CIP sequence, the valves seats should be pulsed repeatedly to allow the solution to clean underneath the seats and inside the vent cavity of mixproof valves. Mixproof valves provide complete product protection at all times (including during seat lifting), so operators can receive maximum security when there is product and CIP liquids in opposite lines.
