Does any one have experienced that improper cleaning of the scale deposit from the tubeside of an exchanger resulted in a pressure drop higher than it was before cleaning ?
Improper cleaning can effectively increase the pressure drop on the tube side. Excessive brushing or mis use of corrosive chemicals (acids) to remove scale increase the inside roughness of the tubes leading to an increase in the friction factor (and the pressure drop) on the tube side.
I've experienced this issue on one of our exchangers a while ago.