Ingredient handling dumps bags
Sept. 1, 2012
by Shane Whitaker
Buying in bulk has its advantages. First, the cost savings can be significant. Second, bakeries and snack manufacturers usually benefit by the delivery and storage of bulk ingredients compared with the logistics associated with bags.
Automated bulk dry ingredient handling systems generally include indoor or outdoor silos, sifters and pneumatic conveyors, but behind the scenes, they offer much greater control to the front end of the baking process. “Today’s ingredient systems are much more intelligent with the affordable costs of computer-controlled systems,” said Michael Palmer, general manager, KB Systems, Inc., Bangor, PA. “While basic conveying technology remains relatively unchanged, more bakeries are relying on more accurate scaling, integrated major and minor ingredient systems, lot tracking, more intelligent operator interfaces, better safety systems and much more system information to streamline production control and efficiencies.”
Pneumatic ingredient conveying systems continue to feature more sophisticated and centralized control systems, noted Bill Kearns, vice-president, engineering, The Fred D. Pfening Co., Columbus, OH. These include integral maintenance alerts, trending data and extensive use of sensors to provide better performance and control.
Bakeries purchase automated bulk ingredient systems because of the cost savings in both labor and ingredients they can achieve by eliminating bags, according to Mr. Palmer, who added that return on investment typically ranges from two to three years.
The ingredient handling system features that bakeries most value, according to Mr. Kearns, include low initial and operating costs, especially in regard to maintenance. They also desire systems that have long-term support and ease of operation as well as accuracy and reliability.
Pfening’s pneumatic conveying systems are generally designed to deliver ingredients within a tight weight tolerance such as 0.5% accuracy. Depending on the amount of ingredient being batched, the equipment supplier offers solutions with controls appropriate to the task. “This will likely include variable speeds on the feeding devices, reacts on the valves and control algorithms to keep performance within the tolerance band,” Mr. Kearns said.
For example, a standard bulk system arrangement with a rotary airlock feeding into a conveying line to a diverter valve mounted on a scale hopper will meet the requirements for an ingredient being dosed at 1,200 lb per batch. However, Mr. Kearns noted, this system would not be satisfactory for ingredients batched in much smaller quantities.
An ingredient needed at 70 lb per batch and within a 0.5% weight accuracy could be metered using a small displacement airlock or screw feeder in either a loss-in-weight or appropriately sized scale hopper. “Pfening has a split-rotor airlock that offers a small pocket displacement while retaining the positive airlock feature,” he said.
To make today’s ingredient handling systems more accurate, ShickUSA employs proportional-integral-derivative (PID) loops on its controllers, according to Mark Ungashick, executive vice-president of the Kansas City, MO-based company. PID is a control loop feedback mechanism that calculates the difference between a measured process variable and a desired set point, known as the error value, and the controllers try to minimize the error by adjusting the process control inputs. ShickUSA’s systems use the last three weights as part of the PID loop to get a historical overview of what is happening, Mr. Ungashick said.
With today’s control systems, Mr. Ungashick pointed out that bakers can build in preacts and in suspension compensation to make the ingredient handling systems more accurate.
Ingredient handling equipment must deliver accurate quantities of products fast enough to keep up with a bakery’s production requirements. “Reliability is also a significant concern,” said Kevin Rohwer, vice-president, Contemar Silo Systems, Concord, ON. “[With] bulk ingredients, when the system goes down, it has the potential to shut down the entire bakery.”
Zeppelin Systems USA, Inc., Odessa, FL, developed its own algorithm to ensure accuracy, noted Stephen Marquardt, sales director, food. It takes into account previous weightments and adjusts the speed on the rotary valve accordingly.
With bulk systems, Dominique Kull, manager, bakery supply systems, Buhler, Inc., Plymouth, MN, said, two things need to be considered: the accuracy of the scale itself and of the whole system. “It is crucial to design an ingredient system in such a way that all dosed ingredients get to the point of usage without any losses during transportation,” he added.
Buhler developed a flexible scale controller to get the load cell data to the computer. “There, the elaborated, real-time automation system controls the discharge units and, accordingly, the product feed,” Mr. Kull said. “To ensure a dosing that is not only accurate but also fast, the weighing system has a self-learning function that optimizes the process after every single dosing cycle.”
For precise delivery of ingredients, KB Systems uses a closed-loop configuration that incorporates a bypass valve and load cells on the weigh hoppers. “When we make a call for flour from our hopper, the bypass valve will activate and allow the flour to enter the weigh hopper,” Mr. Palmer explained. “As soon as the weight has been achieved, the valve will then switch and create a pass through, which will send the remaining flour back to the bin or silo.”
The dispensing hopper is another type of system configuration available from KB Systems. “This will incorporate a weigh hopper with a rotary feeder on the discharge that registers a loss in weight, or the customer may use a floor scale to accurately determine the weight of the batch,” he explained.
During the past few years, sustainability programs have prompted bakeries to find ways to reduce the energy used by their bulk handling systems. “Choosing the right blowers and sizing them correctly has become increasingly important to help reduce energy consumption,” Mr. Rohwer said.
To conserve energy, ShickUSA looks to reduce the horsepower of blowers on its pneumatic vacuum and pressure conveyors. In fact, Scott Fischer, director of sales and marketing, said the company sizes the blowers so they are big enough but not too big. “As long as you are sizing just above the pickup velocity, you are using the least amount of horsepower or energy to move from point A to point B,” he added.
To get higher capacity with less electrical energy, bakeries can use PID loops, according to Mr. Kull. Also, a correctly sized and designed pneumatic conveying system can save a lot of energy costs. If planned wrong, Mr. Kull added, it can dry out or heat up flour, which has negative effects on final products.
Mr. Kearns noted that inadequate preventive maintenance will likely result in a loss of performance in terms of capacity and accuracy. “Recognizing that the ingredient system is just as important to final product quality as the ovens and packaging is important,” he added.
Well-maintained systems will perform at high levels for many years. “Regularly scheduled filter changes, lubrication and attention to small issues will keep things running smoothly,” Mr. Kearns added. “Over a longer period of time, seals and valves will wear. Conveying piping may have material buildup inside, particularly in the elbows. Periodic inspection and performance evaluation will generally reveal issues like this.”
Providing easily cleanable systems is a much greater concern today because of the emphasis on Hazard Analysis and Critical Control Points programs and food safety, noted Kevin Pecha, sales manager, food, AZO, Inc., Memphis, TN. “Bakeries want to know they can clean the system as needed while mitigating the disruption of production,” he said.
Also, automated ingredient handling systems allow bakeries to trace raw materials throughout processing. “Ingredient tracking helps bakeries to avoid contamination or assists manufacturers in recalling product, if needed,” Mr. Pecha noted.
Stainless steel components are increasly integrated into thedesigns to eliminate corrosion and painted surfaces, Mr. Kearns added.
Zeppelin’s systems monitor temperature and humidity in lines, and they adjust conditions accordingly by adding dehumidifcation packages or heat exchangers so ingredients flow smoothly.
Pfening offers improved filters, in cartridge form, for use in air venting applications. “These are more compact and easier to handle, have better release characteristics and offer superior filtration compared with products commonly used just a short time ago,” Mr. Kearns said.
Bakeries must ensure that the systems they purchase are not only designed correctly, but also installed properly. “Regulations in regard to safety and eliminating the possibility of a dust explosion are becoming increasingly stringent, as they should be,” Mr. Rohwer said. “Although the potential of this type of catastrophe is quite small, if and when it does happen, the consequences are extremely severe.
“Bakeries must ensure that the system they are considering is designed to meet all of the safety codes and is installed correctly so a dust explosion cannot happen,” he continued.
When unloading bulk ingredients into a silo, the most critical time is when the pipe is being purged after the ingredient has been loaded. During this time warm, moist air often gets into the silo, and Zeppelin offers systems to mitigate humidity in silos, Mr. Marquardt said.
Transporting bulk ingredients through a bakery using pneumatic conveyors helps to reduce costs, and these systems are accurate and reliable — two characteristics bakeries demand when dumping bags in favor of automated ingredient handling systems.