does anyone know the best mild detergent to use when scrubbing down the plates of plate and frame heat exchanger? the manufacture recommends using nitric acid, and water. I do not want to use any acids if necessary, because we would be scrubbing them down on the roof of the building (rubber roof) thanks to all
can't hurt to try a couple of plates and see how they fare. Sounds like you don't have very hard water there (or have been treating your water diligently.) If you do have lime stains, a lower pH will help -- though Sulfamic, citric, and acetic acids are more commonly used. Nu-Calgon has been recommended here a few times, though I have no personal experience with it.
Since your heat exchanger made of multi material, in order to not hurt your equipment, I would recommend you to use 1st TECH Biodegradable Descaler. It is acid free descaler, and works for cleaning the rubber material parts.
Equipment Maintenance Consultant
Industrial Equipment and Facilities Management Solutions