Painting by numbers at Akzo Nobel

Painting by numbers at Akzo Nobel

Keywords Akzo Nobel, Flowmeters, Krohne, Paints

As a major supplier to the combined professional and DIY paint sectors, Akzo Nobel offers a range of paint"recipes" from its Darwen, Lancs., plant. Darwen is the head office of the Decorative Coatings division, and home of the company's major paint brands,including Crown, Berger, Magicote, Sandtex, Macpherson, Sadolin, Sikkens and Valspar. Akzo Nobel's portfolio of water-based emulsion paints highlights the company's commitment to developing environmentally-friendly products and to reducing solvent emission from decorative coatings.

Whilst the basic ingredients for each paint batch do not vary hugely, like any good "recipe"accurate measurement of the ingredients is critical to the process. This applies particularly with low dosage elements such as biocides, or environmentally-sensitive ingredients such as ammonia or white spirit. Akzo Nobel has installed a number of Krohne's straight-tube Corimass G meters to maintain fine control over the mass flow of these raw materials in the final mixing stages of the paint making process. They have replaced metering pumps and disk-type flow meters, neither of which were considered sufficiently accurate.

The choice of single,straight-tube Corimass flow meters was in-line with Akzo Nobel's overall policy of installing systems and equipment that are "ahead of the game", according to process development engineer Howard Jones. "We are upgrading the automation of our emulsion batch manufacturing process, with the development of a new,PLC-based SCADA system. Krohne's Coriolis flow meters already have the built-in communications protocols which are needed for this system. We looked at a variety of flow meter solutions, but Krohne offered a good combination of performance, cost and delivery."

Eight Krohne G meters are installed in three locations in the production hall, and although flow measurement accuracy was a common requirement, safety and low maintenance aspects of its enclosed, straight tube design were also an important consideration.

Ammonium hydroxide is added to the mixing tanks to adjust the paint to a neutral pH value before it is canned. Ammonia was previously handled by metering pumps, which not only needed regular maintenance, but which also developed leaks. They were replaced by two close coupled centrifugal pumps, feeding two Corimass 100 G meters; a maintenance-free system, which Howard Jones says has also produced "significant improvements in the accuracy of raw materials handling. All the meters are performing to their expected accuracy ­ or beyond."

Although solvents have largely been eliminated from the water-based process, small amounts of white spirit and Texanol are still required because of their ability to soften the paint film and assist the drying process. Accurate dosage of these solvents,together with a wetting agent, is controlled by a further three Corimass 100 G meters They have replaced older, disk-type flow meters which were not only less accurate, but also had to be re-calibrated every two to three weeks.

Three Corimass 100 G meters also control the dosage of the anti-foaming agents, dispersants and biocides, which are added to each paint batch, replacing the previous metering pumps which were no longer sufficiently accurate.

With two 10,000 litre bulk white mixing tanks, and one 5,000 litre for coloured paints, the Decorative Coatings division has an annual capacity of some 30,000,000 litres, and emulsion production is based on a 24-hour working shift. In addition, the seasonal nature of the DIY business means that the plant will occasionally be operated for seven days a week. It is a demanding schedule which does not leave much time for maintenance, and another reason to opt for Krohne's straight-through tube design, as Howard Jones points out. "Self-draining and easy cleaning were important considerations when we looked at the various options. The Corimass G meters are easily rodded and inspected if necessary, and we also find their diagnostic and trouble shooting facilities very useful."

Details are available from Krohne Limited, Tel: +44 01933 408509.