Background

There are several dish washers in a hotel. Due to the nature of application, no chemical except detergent is put into the dish washer and therefore hard scale could not be eliminated especially high water temperature is used in the past. The thick scaling substance can be seen in picture 1.

As referred by another hotel, management decided to install HydroFLOW for the dish washer application.

Result

After three months of operation without pre-cleaning of the dish washer, the scaling substance coated on the surface of heater and the tank started to dissolve as shown in picture 2.

However the descaling process was slower than that in boiler application. It was decided to collect sample of scaling substance from the surface and sent to Hong Kong Polytechnic University for SEM\EDX analysis. It was found the major ingredient is phosphate. After reviewing the report with the supplier of the detergent, it was confirmed the source of phosphate is from the detergent.

An acid provided by the same supplier was applied to remove the scaling substance and the result is shown in picture 3. Obviously the scaling substance was not reacted with the acid applied at all.

After another three months of operation (six months in total since the installation), the scaling substance was further dissolved and the result is satisfied by the customer.