Bakery dough is inherently difficult to pump as it typically contains entrained air. Recently a Bimbo baking facility in central Mexico needed to replace a pump that was discontinued and not meeting required flow rates.
In addition to entrained air, the application presented more challenges. Because the pump had to transfer dough from vessels without bottom discharges, the product needed to be sucked up and pumped 20 feet to a mold filler, then baked. Also, each of the eight different dough types had different viscosities, specific gravities and contents, which included dispersed solids like raspberries, nuts and chocolate chips.
A standard Fristam FKL 50 positive displacement pump was chosen to handle eight different dough types at 15 GPM each. The heavy-duty, stainless steel pump features the balanced rotor, strong shaft, offset rotor bolt, cartridge mechanical seal and CIP design required by Bimbo. After installation, the standard FKL was only able to empty the vessels halfway. Fristam’s Mexico office worked with Bimbo to find the right combination of pump options including a variable frequency drive and high clearance rotors. While the variation of speed allowed the FKL to pump some of the dough mixtures and even allowed some to surpass their desired gallons per minute, it did not work for all.
Further analysis directed attention back to the entrained air element of the application. Entrained air in the dough was building a gas bubble in the pump chamber and allowing dough to coat and eventually seal off the inside of the pump. The solution: a degassing cover which allowed entrained air to escape the pump chamber.
Once installed, the combination of the degassing cover and the high clearance rotors allowed the FKL to meet Bimbo’s needs. The new cover helped the pump transfer the air-entrained dough, and Bimbo arranged for a small piping discharge to ensure the installation was completely sanitary.
The pump’s suction performance was also increased by changing a 90° elbow in the suction piping to a straight pipe with two elbows of 30° and 45°.
“The FKL50 provides us with the necessary flow rate,” said Roberto Cuevas, maintenance manager at Bimbo’s Irapuato, Guanajuato plant. This is extremely important because our product has a high specific gravity value with a temperature range between 16-18° C, he added. “The initial cost of the pump itself was less expensive than what we had before and has the option of purchasing separate parts for the seal, instead of a whole kit.”