In these exchangers, the product and cooling agent flow between grooved profiled plates alternately. A solution containing glycol is commonly used as the cooling agent. To optimize heat exchange performance and save energy, the partitions between the plates are very thin and closely spaced. Consequently, there is a risk of leaks triggered by pressure surges, product particles, or soil deposits.
If damage occurs, cooling agent containing glycol can penetrate the product and pollute it, presenting a health risk to consumers. To ensure customer safety, our client introduced a reliable quality control directly after the plate heat exchanger with the help of turbidity measurement.
The application
Our customer, a dairy in India, utilizes plate heat exchangers in several stages of the process to cool the milk. To avoid contamination from the cooling agent, the dairy employs an ITM-51 turbidity meter. This ensures that no milk tainted with glycol can get bottled, maximizing product safety for their customers. The instrumentation for this application is complemented by TS temperature sensors and P41 pressure sensors for additional safety monitoring

The Anderson-Negele solution
The ITM-51 turbidity meter is flush-mounted and uses the backscattered light method to gauge the turbidity in the medium, and thus to monitor potential contamination. The measuring accuracy is 200…300 000 NTU. The ITM-51 has an extremely short response time of 0.75 seconds, enabling it to alert the slightest change in turbidity in the medium almost in real time.
In this application, the ITM-51 was installed directly after the heat exchanger in the tubing of the cooling circuit and monitors the purity of the glycol-containing cooling medium. If a cooler plate is damaged, there is always an exchange of liquids, and milk enters the coolant. Therefore, the ITM-51 can be relied upon to monitor the purity of the milk by supervising the cooling agent.
If there is a malfunction, the process can be stopped within a second to keep product loss to a minimum.
This enables the dairy to guarantee absolute product safety while reducing damage cost in the event of a defect in the heat exchanger.
Further instrumentation in the application
Other crucial parameters for the secure functioning of the heat exchanger are temperature and pressure.
The TS temperature sensor has superior measuring precision, allowing accurate monitoring of the process temperatures at the inlet and outlet of the product and of the cooling circuit.

Keeping an eye on the process pressure assists in supervising the correct operation of the cooler. If particles or contamination disrupt the function, the pressure upstream of the cooler increases. In this case, the cooling system can be checked and, if required, cleaned to prevent damage. The P41/P42 pressure sensor is a compact, efficient and reliable transmitter that can easily be integrated before and after the plate heat exchanger to supervise the correct function of the cooler system
The diverse sensor technologies of Anderson-Negele offer multiple levels of safety monitoring of the plate heat exchanger. This enhances consumer safety and prevents damage to the equipment, production downtime, and product loss.
Advantages of Turbidity Meter ITM-51
Extremely short response time of 0.75 s
• Extended temperature and pressure range (process temperature up to 130 °C / 266 °F, pressure -1…20 bar)
• No influence due to reflections caused by small nominal diameters or electropolished surfaces
• High reproducibility: ≤ 1 % of final value
• Selectable measuring value (%TU, NTU, EBC)
• Measuring range: 200…300 000 NTU equivalent
