Just about all children and adults love peanut butter, which is practically an American diet mainstay. Consumers expect a quality product that is uniform from batch to batch, but one peanut butter manufacturer had a problem with its product’s uniform consistency. The company knew the problem was in its large mixing vessels and turned for help to Burns Engineering Inc., Minnetonka, Minn., a maker of high performance temperature measurement products.

Temperature is a critical component in the peanut butter production process. The manufacturer used tank heaters to control the temperature of the mix in the vessels, which used thermowells welded to the bottom side of the tanks for inserting temperature sensors into the mix. Burns determined that this method of temperature measurement takes place at the bottom of the tank, which is not representative of the entire batch being mixed. Burns also noted a significant time lag between when the tank heaters turned on and when the heat effect reached the sensors. Sensors could not be placed in the mixing portion of the tank because they would interfere with the mixing blades.

For accurate temperature measurement of peanut butter, a flush-style temperature sensor was placed on the mixing vessel’s interior wall where it did not interfere with mixing blades.

Burns recommended a flush-bulb assembly mounted so the sensing surface is flush with the vessel’s interior wall. Hardware does not intrude into the tank, so the mixing blades and sweeper paddles have no interference. The sensor can be mounted anywhere on the tank that is suitable for the best measurement. Because the control-loop lag time can be shortened, there is less risk of overheating the product.

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