Waterbased cleaning of mixing vessels
5. Investigation Program
| 5.1 | Preliminary tests |
| 5.2 | Full-scale tests |
Taking as a starting basis the results of the laboratory tests and full-scale tests of 1997, as set out in Appendix B, together with the experience of operators and manufacturers of corresponding plants, the following schedule of trials was drawn up.
5.1 Preliminary tests
The aim of the preliminary tests was to determine which media could be used to attain acceptable cleanliness within a reasonable time.
Preliminary tests had been carried out by the supplier companies Renzmann and Riobeer, using samples of solvent-borne paints supplied by Teknos Technology A/S.
Teknos Technology A/S chose paints that are problematic under the aspect of their adhesion to the vessel material and their drying time.
Ten samples, each of about 1 litre, were sent by Teknos Technology A/S to both supplier companies together with Material Safety Data Sheets and product descriptions.
Products in preliminary tests
Preliminary tests were performed with the following products:
 | air-drying topcoat (two types) |
| air-drying shop primer |
| base for two-component epoxy system |
| base for two-component polyurethane system (two types) |
| base for two-component isocyanate-free system |
| oven-drying topcoat (two types) |
| isocyanate reactor |
Cleaning had to be done:
| when the paint is still wet and |
| after allowing the paint to dry for a maximum period of one week |
The materials of the containers were mild steel and stainless steel.
5.2 Full-scale tests
Questions for full-scale tests
Full-scale testing was performed to answer the following more detailed questions:
| Which process in combination with which cleaning agent has the most effective cleaning action? |
| For what types of paint and coatings is water-based cleaning suitable and what aspects have to be taken into account? |
| Which materials are suitable? |
| When and to what extent is it to be expected that subsequent manual cleaning will be necessary? |
| How must valves and lids of vessels be cleaned? |
| What must be done with the spent concentrated washing media? |
| How high are the operating and capital costs? |
Full-scale testing was performed by Renzmann during December 1999. Including preparations and work subsequent to the actual trials, these required a period of around three months.
The tests were followed and supervised by representatives from Teknos Technology A/S and Fichtner.
It was agreed that full-scale tests would be performed for 17 industrial wet paints (quick air-drying paints) including both water-borne and solvent-borne paints.
Procedures for full-scale tests
The following procedure was adopted for the full-scale tests:
A total of 17 products (12 solvent-borne and 5 waterborne paints) were tested.
Data on the chemical and physical characteristics of the paints and the formulas for the solvent mixtures as well as the materials of valves and vessels actually used, had to be supplied to the supplier company before full-scale testing, so that a suitable chemistry could be chosen.
Testing was performed with mild and stainless steel vessels, and with two types of films: film that was still wet and film that had been allowed to dry out over five days.
An important component of the tests, apart from identifying suitable washing solutions, was to determine the results when alternative cleaning processes are applied, employing brushes or high-pressure jets. Particular attention was to be paid to how well corners, valves and vessel lids could be cleaned.