The cleaning of large buffer tanks is notably difficult due to the inability to achieve rapid water velocities across metal surfaces. Physical cleaning, filling, and emptying vessels provides marginal cleaning at best and consumes signficiant amounts of water. Mill scales created during metal fabrication are not removed. Chemical cleaning is more effective but typically requires the consumption and pollution of ten times the volume of the buffer vessel. Buffer vessel cleaning tends to be time consuming with cleaning times of two to five weeks not uncommon.

A New Way Forward

A 90,000 litre steel buffer vessel was installed at County Hall, Leicester as part of a district heating system. Prior to being put into use, the Strengite System was used to clean the vessel without any discharge. This saved and avoiding polluting 900,000 litres of water. Approximately 17 kg of rusts were removed by the cleaning. Cleaning times were equal to or shorter than alternative methods. All flash rusting issues were avoided. Over 1 ton of CO2 emmissions were avoided.

The Strengite Cleaning

Initally 200 litres of Strengite C1 cleaner was added and circulated for three days. The water was unheated (March temperatures). After three days, the pH had risen to 5.4 indicating that approximately 95% of the cleaner had reacted with 17 kg of iron oxides (equivalent to a dissolved iron level of 500 ppm).
The Strengite equipment was then set up and the precipitation phase of the cleaning begun where the dissolved contaminants are forced out of solution and separated by filtration. The Strengite equipment is designed to enable rapid and easy changing of filter bags and avoid water loss.