Routine Online Backflushing of Plate Heat Exchangers

During routine operation, periodic online backflushing is performed on plate heat exchangers to remove loose sediment, sand, and algal contaminants accumulated between plates before they harden into scale. This preventive maintenance practice mitigates flow rate reduction caused by fouling and slows scaling rates. Taking a seawater desalination plant's distilled water plate heat exchanger as an example, the online backflushing procedure is as follows:

1. Close the seawater inlet and outlet valves on the plate heat exchanger side. 

2. Disassemble the inlet strainer housing on the seawater side of the heat exchanger. 

3. Connect the seawater inlet drain pipe to the strainer flange on the fixed pressing plate, and link to an external discharge pipeline. 

4. Open the seawater outlet valve to initiate backflushing of the plates. 

Online backflushing precautions:

Avoid overpressure backflushing to prevent gasket dislodgement from seal grooves. 

Conduct multiple flushing cycles. 

Immediately replace damaged strainers upon inspection. 

Different methods apply to varying conditions:

If no leakage occurs but heat transfer efficiency declines, perform offline cleaning annually as a standard maintenance protocol. 

If leakage occurs or offline cleaning proves ineffective, disassemble the unit for plate cleaning.