Bimetal thermometer monitors the temperature of food

Bimetal thermometer monitors the temperature of food

To monitor the pulse of food, beverage or dairy factories, measuring instruments are used. These devices ensure the normal operation of process temperature, level, pressure and flow. If the bimetal thermometer is not selected correctly, the spare parts inventory will expand, the storage tank will overflow, the instrument will be damaged, and the production line may stop.

Figure 1: Susceptibility of diaphragm damage

The flush diaphragm in the measuring instrument is a fragile but vital part. It is an extremely thin component that is easily damaged when used in a challenging production environment.

No. 2: Inferior instrument housing

The outer casing of the measuring instrument must protect its internal components from extremely unfavorable environments. Wide temperature changes, harsh flushing solutions and rough processing methods will seriously affect the measurement performance. Various bimetal thermometers are protected by aluminum housings, which may not be able to withstand the harsh tests of the beverage and food processing environments.

No. 3: Incompatible instrument connection

If you visit a brewery or dairy factory, you will observe various manufacturers' measuring instruments. Many suppliers’ products use different electronic equipment, calibration methods, process connections and programming points.

Changing one instrument brand to another instrument brand may mean cutting the original equipment out of the tank or pipeline and then re-welding the new weld seam, which is an expensive and time-consuming process and will require learning new maintenance And calibration procedures.

Figure 4: Insufficient temperature compensation

As part of daily operations, food and beverage processes usually experience large temperature changes. For example, pipes and storage tanks containing cold milk can be passed through a clean-in-place solution at temperatures up to 194°F.

These rapid temperature changes can deceive measurement bimetal thermometers without good temperature compensation, resulting in erroneous process readings. These erroneous readings may cause the manufacturing cycle to start or stop at the wrong time, overflow of the balance tank, or malfunction of the automatic cleaning cycle.

Figure 5: Full-scale and span measurement

The accuracy levels of manufacturers are different. Some manufacturers measure the accuracy of their equipment on the basis of "full scale" (very large span value). However, if your application uses a smaller span, the instrument will be less accurate.

A bimetal thermometer that measures its accuracy based on the "adjustment range" should be used. This ensures that the accuracy of the device is the same at any point within its calibration span. For example, the instrument is rated for a very small span of 1 psi and a very large span of 10 psi. The bimetal thermometer has been calibrated for 1 psi applications. If the accuracy rating of the instrument is measured on the basis of the adjustment range, the accuracy at 1 psi will be 0.1%