How to Determine if a Plate Heat Exchanger Needs Cleaning

1. Temperature Signals: Decreased Heat Exchange Efficiency is the Primary Indicator

When the following temperature anomalies occur, after ruling out other factors such as flow rate and changes in heat/cold sources, cleaning is generally required:

The cold fluid outlet temperature is more than 5°C lower than normal operating temperature, or the outlet temperature drops by more than 10% of the design value; the hot fluid outlet temperature is higher than normal.

The logarithmic mean temperature difference between the cold and hot fluids gradually decreases, indicating increased fouling on the plates, increased thermal resistance, and a decline in heat exchange capacity.

2. Pressure Signals: Increased Pressure Difference is a Direct Indication of Blockage

If the inlet and outlet pressure difference increases by more than 20% compared to the initial operating data, or exceeds the design allowable range, it indicates that the flow channels have narrowed due to fouling accumulation, increasing flow resistance.

To maintain normal flow, the pump's operating pressure continuously increases, but the flow rate does not increase significantly, also indicating that the heat exchanger is blocked and needs cleaning.

3. Other Auxiliary Judgment Signals

Decreased Flow Rate: With the system pressure remaining constant, the fluid flow rate through the heat exchanger gradually decreases, indicating that the flow channels are blocked by fouling, reducing the effective flow area.

Increased Energy Consumption: Boilers and pumps need to operate continuously at overload to meet production capacity requirements, leading to increased electricity and gas costs without a corresponding increase in production capacity. This indirectly indicates a decrease in heat exchange efficiency due to scaling.

Leakage Occurrence: If leaks or cross-contamination persist after ruling out issues like aging gaskets or insufficient clamping force, it may be due to excessively thick scale damaging the plates. In this case, the system must be shut down for cleaning and repair of the damaged plates.

Meeting Cycle Requirements: Regular cleaning is required for systems that have operated for one year in normal conditions, for systems operating under hard water/high load conditions for six months, and for systems in the pharmaceutical/food/chemical industries that have not been cleaned after quarterly light cleaning.

4. Final Confirmation Method: The most direct and effective method is to disassemble the heat exchanger and directly observe the plates. If obvious scale, rust, oil, or other deposits are present on the plate surface, cleaning is necessary. If direct disassembly is not possible, non-destructive tools such as thermal imaging and flow meters can be used for auxiliary detection and confirmation.