Cleaning steps for heat exchanger fouling and how to prevent it
1. Cleaning sequence
Flushing. Before acid cleaning, flush the exchanger in open circuit. This improves the effect of the acid and reduces acid consumption. Fill the cleaning rig, then introduce the solution into the exchanger.
Acid cleaning. Fill with acid and soak for 2 hours, then circulate dynamically for 3–4 hours, reversing the flow every 30 minutes. Afterwards dilute and neutralise the acid before draining.
Alkaline cleaning. Prepare a solution of NaOH, Na3PO4 and softened water in the specified ratio and circulate it to neutralise the acid and protect the plates from corrosion.
Final rinse. Rinse repeatedly with clean softened water for 0.5 hour to remove all residue.
2. Preventing fouling in plate exchangers
Water quality must be controlled strictly in operation. Water in the system and in the softening tank must be tested before it is admitted to the network.
When a new system is commissioned, keep the exchanger isolated from the heating system. After a period of circulation, connect it so that debris in the pipework cannot enter the exchanger.
