Rockwood Pigments switches to peristaltic pumps
2 Sep 2009
Stoke-on-Trent, UK - Rockwood Pigments UK Ltd has reported significant gains following a move to peristaltic pumps at its Stoke-on-Trent operation which manufactures liquid, powder and granulated colour pigments. The company's products are used in coatings, plastics, rubber, paper, vinyl, concrete, cosmetics, ink and many other industrial products.
Until recently, Rockwood had used progressive cavity pumps for transferring cadmium sulphide slurry to its filter presses for dewatering. In slurry form cadmium is mildly abrasive, a factor that caused the repeated failure of seals and glands within the progressive cavity pumps.
“The leaks caused by the cadmium pigment slurry were a constant source of disruption and cost to our manufacturing process,” explains Phil Tansley, operations manager at Rockwood. “Of course, the leaks also meant we were losing product, adding to our costs further, while cadmium is also toxic and is subject to strict health, safety and environmental controls in the workplace.”
Initially, Rockwood tried switching to progressive cavity pumps featuring water flush to remove cadmium residues after each process. However, this failed to reduce the level of leaks significantly and also introduced the need to drain water from the system.
Tansley initially encountered Watson-Marlow technology at the company’s headquarters in the US, where peristaltic pumps are used very effectively for iron oxide transfer duties.
“In the US the pumps run maintenance-free, with the hoses replaced only once every 4-5 years,” he says. “This fact sold me on peristaltic technology and so I decided it might be worthwhile applying the pumps to cadmium-based duties here in the UK.”
Rockwood purchased a single Bredel SPX65 high pressure peristaltic hose pump from Watson-Marlow, a model that can displace up to 6.7 litres per rev, with an operating speed of up to 50 rpm continuous or 90 rpm intermittent. These pumps have no seals, glands or valves, and the fluid only contacts the bore of the hose or tube.
“Obviously the most important factor for us is that peristaltic pumps are liquid-tight and have no seals,” said Tansley. “The success of the initial Bredel SPX65 led to the acquisition of a further four identical models that have replaced our original progressive cavity pumps for transferring cadmium pigment slurry to the filter presses.
Since installation we have eliminated leaks and witnessed a 10% yield gain by product volume. Furthermore, where we previously required an operator in almost constant attendance, we can now walk away and leave the pumps to run unmonitored.”
Other benefits described by Tansley include reduced maintenance and far less burden on the company’s effluent plant as there are no residue slurries to wash away. This is because the new system installed at Rockwood Pigments features an automated wash-water flush applied by the peristaltic pumps.
“Press cake washing is a crucial step in our process as it removes all of the soluble or free cadmium left in the press cakes,” he says. “Overall the switch to peristaltic pumps has been a great success and while we are looking forward to a rapid return on our investment; ultimately we have created a safer, cleaner working environment for our employees.”
