When it comes to processing chocolate, temperature is critical for flavor and appearance of the final product. Like the process used in steel production, chocolate is tempered -- that is, gradually heated and then gradually cooled. If tempered properly, the final chocolate bar will taste great and have a shiny finish.
Cadbury's Toronto facility makes many different brands and types of filled chocolate bars for the Canadian market, including Caramilk, Caramilk Dark, Caramilk Rolls, Cappuccino, Cadbury Yogurt and Cerises. Because the Toronto facility has so many production lines and so many different chocolates, John Kang, the environmental and utilities manager, and Ray Kenny, the chief operating engineer, were kept busy adjusting temperature controls during product changeovers in addition to their other job functions. For example, say a batch of Caramilk bars was made on the Carle 600 production line, and the next job on that manufacturing line was to process yogurt bars. Not only did the ingredients change, but often, the temperature requirements also changed. Downtime between runs is a pure cost. The faster the changeover can be completed, the quicker more chocolate can be produced. Due to manual adjustment and icing problems on evaporator coils, the conversion process could take up to 24 hours to complete.
Cool SolutionCimco Refrigeration, Toronto, has been servicing the plant's refrigeration needs for many years, so the company was aware of the chocolate maker's operational challenges.
It was Ron Matwee, manager of service sales at Cimco, who learned about a new motorized valve from Hansen Technologies Corp., Burr Ridge, Ill., which he thought might help Cadbury. After having several discussions and obtaining additional information, Matwee proposed implementing four sealed motor valves on the Carle 600 production line. Cadbury installed four valves to control temperature -- one in the suction line of each of the four cooling coils on the line.
A 4 to 20 mA signal, which is tied directly into the plant computer that monitors coil outlet temperature, is sent to the microprocessor in the motor of the valve. As a result of the signal, the valve automatically opens or closes slowly (15 to 45 sec depending on valve size). This minimizes the potential for liquid velocity shock or "water hammer." Unlike most pressure regulators and solenoid valves, no pressure drop is required to operate these valves. The motor's nonelectric rotor is enclosed in a stainless steel can that contains the fluid pressure. The motor's electric stator is outside the stainless steel can and is isolated from the fluid in the valve.
The compact and lightweight unit is designed for applications that require precise temperature, level or pressure control. There are no valve stem seal leakage problems, and it can be used in refrigeration systems that use ammonia, R22, R134a, glycol, water and brines.
Smooth ResultsThe four motorized valves have proven successful for the Toronto candy maker. Evaporator coil icing problems have been eliminated, and changeover time has been reduced to a few hours. Changing the temperature settings no longer requires manual labor. Now, it is completed with the touch of a button on the control panel.
According to Cadbury, product quality is better and more consistent, too. The valves control temperature at each stage of the tempering process within +/-0.9oF (+/-0.5oC) of the setpoints. Because these valves worked so well on the Carle 600 line, the Toronto facility plans to expand the technology into additional production lines. Finding the time to shut down the production process long enough for renovation is now the biggest challenge.