How to Determine if a Plate Heat Exchanger is Scaled

1. Changes in Operating Parameters (The Most Convenient Method for Daily Monitoring)

Heat Exchange Efficiency/Temperature Changes: Under the same operating conditions, if the temperature difference between the hot and cold fluid outlets gradually deviates from the design value, the cold-side outlet temperature decreases by 3-5℃ or more compared to the initial value, or the actual heat exchanger efficiency decreases by more than 15% compared to the initial value, it can be basically determined that scale has occurred. Scale increases thermal resistance and reduces heat transfer efficiency, making it the most direct signal of scale buildup.

Inlet and Outlet Pressure Drop Changes: Compare the initial pressure drop after the equipment is newly commissioned or has just been cleaned. When the actual pressure drop reaches 1.3 times or more of the initial value, it indicates that scale has caused flow channel blockage, and flow resistance has increased significantly. If it reaches 1.5 times the initial value, it is considered severe scale buildup and must be addressed as soon as possible.

Other Indirect Parameters: A significant increase in system energy consumption (increased electricity and gas costs without increased production capacity), and unstable or gradually decreasing flow rate under the same pressure also indicate the possibility of scale blockage.

2. Visual Inspection and Disassembly (Direct Confirmation of Scale)

Without Disassembly: Observe the outer surface of the heat exchanger. If uneven color changes, scale, or rust are observed, internal scale is highly likely.

Disassembly Inspection: Periodically open the heat exchanger and directly observe the plate surface. If a uniform white/yellow scale layer is visible, or the scale layer thickness exceeds 0.5mm, descaling and cleaning are necessary. If significant scale buildup and blockage of the flow channels are observed, the scale buildup is already severe.

3. Professional Equipment Testing (Accurate Determination of Internal Scale)
For plate heat exchangers that cannot be disassembled, professional equipment can be used for testing:

Use an infrared thermometer to detect the temperature distribution on the plate surface. The temperature in scaled areas will be significantly higher than in clean areas, and the temperature distribution will be uneven.

Using ultrasonic measuring instruments, resistance temperature detectors (RTDs), etc., the heat transfer efficiency of the plates and the extent of internal scale buildup can be accurately measured, precisely determining the presence of scale.

The risk of scaling on the plates can also be indirectly determined by analyzing the water quality of the medium. If the water hardness and suspended solids content are significantly exceeded, it can be determined that the plates are at high risk of scaling.