They’re just three little words, but they comprise a deadly sin in the baking process: “Not my problem.”
Accountability is vital to a bakery operation not only because it leads to a sense of pride in a job well done but also because it prevents problems ranging from inefficiency to food safety.
Quality is everyone’s priority, and it must begin before the ingredients even enter the building.
“At the end of the day, the bakers bake, and the trucker unloads the truck,” said Zach Turner, sales engineer, AZO.
This relies on a trusted relationship between the baker and the flour supplier, but the ingredient handling system manufacturer can also play a pivotal role to help things move along as quickly and efficiently as possible.
Bulk ingredients such as flour arrive via tuck or rail car, and despite the fact that unloading is typically up to the driver, there are many things bakers can do to ensure the process moves smoothly, safely and efficiently.
“Truck operators themselves are responsible for the unloading process,” said Jason Stricker, director, sales and marketing, Shick Esteve. “It can be a challenge for a lot of bakeries because they don’t always get the same driver or operator, and they may not be familiar with that particular facility and the optimum operating levels in the unload process.”
That lack of familiarity means it’s incumbent on the operator to confirm the unloading process is running as it should.
“The best thing a bakery can do is ensure staff understand the truck operation and what it should be set to, so when different drivers deliver the flour, the bakery employees can work with them and get to an optimum level quickly,” Mr. Stricker added.
With a few simple best practices and the right equipment and processes in place, the unload can go off without a hitch.
Lay of the land
Typically, it takes about an hour to unload flour into a silo, and under the best circumstances it can get done in 45 minutes. To hit that optimal timeframe, location is everything.
It doesn’t matter if a silo is inside or outside.
“What does matter is the distance,” said Rudolf Gasser, senior process engineer, bakery and material handling, Bühler, Inc. “The closer it is, the less energy is required for the transport.”
When setting up automated ingredient handling, placement of the silo is key.
“It’s hard to fit a truck through a parking lot and around the building, things like that,” said Darren Adams, vice-president, engineering, Fred D. Pfening Co.
Placing the silo near where the truck enters and exits the property will shave off time just by simplifying the first and last steps.
“It’s ideal to have the silo where you can get to it so there’s a shorter run to load into; the shorter the tubing run, the faster it can go,” he said.
To ensure proper silo placement and installation, KB Systems offers project management services for all projects, including a certified onsite installation supervisor for its outdoor silo setup.
It’s not just about the distance from the truck to the silo; it’s also about the distance from the silo to the process. An automated ingredient handling system is often part of a master plan that accounts for growth, and these space issues should be considered.
“But if you don’t have that, it’s a challenge to find the proper space,” said Stephen Marquardt, director, food processing plants, Zeppelin Systems USA. “You want to be closer to the process when it goes from the silo into the bakery. The truck can be right there with the silo, but if that is far away from the rest of the line, you have a long way to convey, and you need a lot of filter area.”
The same challenges exist when receiving via rail car.
“Sometimes a bakery will run into a situation where the most convenient location for the rail side — or the silos — don’t marry well together,” Mr. Stricker said. “It’s important for bakers to keep this in mind so they don’t start down a design path where they end up having to redesign or, worse, have to live with a less than optimal setup.”
To head off these kinds of risks, Shick Esteve works closely with bakers to look at traffic patterns, return radius and other factors to ensure maximized unloading efficiency.
Achieving the highest efficiency is about not only time but also energy.
“We take everything out of the system layout, and we do a calculation by it,” Mr. Gasser said. “You can achieve the desired capacity however long the run is, but it might need more energy. Longer systems need more energy than shorter, simpler systems. It doesn’t really slow things down if the calculation is done correctly, but it could be running on higher energy.”
Moving right along
In addition to the real-estate rule of location, a basic geometrical rule applies: The shortest route between two points is a straight line. Turns and elbows matter, and they add up.
“Each linear foot of tube is a pressure loss, and each bend or elbow is a loss,” Mr. Adams explained.
In most cases, Pfening limits the line’s overall distance to no more than 60 to 80 feet, and that includes four to six elbows.
“There have been times where we’ve had to design the system with hundreds of feet, which obviously limits the flow rate and efficiency,” he noted. “But sometimes you have to.”
Shick Esteve also uses specific calculations to help bakers understand where the elbows and hose bends begin to affect efficiency.
“Every hose bend is worth about two elbows,” Mr. Stricker cautioned. “And every elbow is worth about 40 ft of transfer line.”
With that in mind, getting the truck closer to the silo does little good if the hose is snaking around in that space.
“If you get the truck really close, but you have 10 elbows in it, you could end up with an equivalent of a 450-foot run,” Mr. Stricker said. “But if you move the truck out 150 feet and only have two or three elbows, you effectively have a shorter distance even though you’re physically further away; you’re actually a shorter distance in terms of the back pressure of the system.”
It’s a more complicated equation than basic math.
“There’s some engineering that goes into the length and size of the line and the number of turns that lead up to the silo and into the top of it,” Mr. Turner noted. “Sizing properly affects the filling efficiency and risks for clogging or wasted time.”
Inside the filling line, efficiency of the transfer often hinges on factors like friction and air pressure.
For example, the friction factor in a flexible hose will be higher than inside a metal pipe where the surface is smooth.
“A rubber hose will have a friction factor and increase back pressure in the system,” Mr. Stricker said.
That’s why keeping the hose straight is so important.
Properly sizing the line in the unloading system is important, and that includes the line size. Typically, it will be around a 4-inch diameter, but some can go as wide as 5 or 6 inches. In any case, consistency is key.
“As long as you’re consistent with the size, you won’t feel the impact of changes in velocity and pressure within the system,” Mr. Stricker said.
When it comes to the unloading pressure, it’s all about getting a proper air-to-material ratio. Anywhere from 8 to 12 psi is common, Mr. Stricker said.
“You’ve got a fixed volume in a pipe, and there’s only so much material you can get in there before you overcome the transfer system’s ability to move the material,” he said.
Mr. Adams suggested that the sweet spot looks more like 10 psi or less.
“At that, the truck operator will make sure each hopper is constantly being discharged out of the truck and that there are no long lag times with the product coming out,” he said.
Don’t forget the filter
Efficiency isn’t only about how the flour comes out of the truck, though. It’s also about what happens when it goes into the silo. It’s blown in via air pressure, so it’s important that the filter in the bin vent is functioning properly.
“The point of the filter is to let the air escape and keep the flour in,” Mr. Turner said. “To optimize the escape of air, it’s important to make sure the filter is sized correctly. If an improperly sized filter can’t evacuate the air fast enough, then the pressure release valve is forced to spew air and flour out of the top of the silo, and that can lead to issues down the road with moisture and mold.”
An automatic filter can play an important role in hitting that optimal timeframe for truck unloading, said Mr. Marquardt, who noted that Zeppelin uses a jet filter on its silos.
“You have to keep the filter clean during the filling process because it’s how you get the proper air flow,” he said. “That means you won’t build up the pressure against the truck unloading.”
Zeppelin’s jet filter comes with a pressure sensor that will alert operators to pressure buildup in the silo.
“You know when the back pressure goes up, and that means the filter is getting clogged,” he added.
Mr. Gasser said he often sees filter sleeves that get clogged.
“We usually have a gauge on the filter, so it will alert maintenance personnel if the filters are not okay,” he said.
Bühler can also electronically send a message through the automated system. The company also designs all its unloading systems with a fan on the silo side to keep the silo at a slightly negative pressure. However, he noted that filter maintenance is something that just can’t be avoided.
“Filters have to be changed sooner or later,” he advised. “Keep an eye on it and do the maintenance — don’t neglect it.”
Mr. Stricker also identified the filter as one of the most overlooked maintenance items in the system. When the filter is too dirty, it creates back pressure, which can cause feeding devices to cycle on and off to keep from plugging. Shick Esteve designed its filters to be changed out in as little as 10 minutes.
“They fit into short windows of time so you can get the job done quicker,” he said, noting that the change can be done outside the unit.
As Mr. Turner noted, the bakers bake, and the truckers unload. But this does not grant bakers permission to wash their hands of the unloading stage of the process. In fact, there are certain opportunities to increase efficiency when bakers put control in their own hands.
KB Systems’ computerized systems are custom-designed for indoor or outdoor bulk handling that fit many different ingredients.
Another way for bakers to maintain control is owning their own blower.
“This way, they can condition their own air without relying on the truck board blower,” Mr. Turner said. “When your own blower is tied into your automated control system, it will cut off when you’ve reached a full level; that way you have control.”
Efficiency isn’t always a result of actions taken but sometimes tools that are available to aid the process.
A silo — with the lines that feed it — is a closed system; operators are working with what they simply cannot see. Mr. Adams noted that there are features that can be added to a system to keep a baker in the know.
“There are features that can monitor pressure; there are things that can tell you about the cleanliness of the filters and dust collector,” he said. “There are indicators that will tell you exactly how much is in the silo so you can know when you hit the maximum.”
These tools can help prevent problems that ultimately slow down the process.
And just being present during the unloading process can make a world of difference.
“The plant operator who receives the flour needs to understand the functionality of the system,” Mr. Marquardt said. “When we talk about the silo itself, it’s not just a long, tall bin; there are a lot of things to consider when filling it with flour.”
To keep the process running smoothly, every operator must maintain a sense of ownership. “Not my problem” never applies, even when the flour is still outside.