Euroelettra Sistemi, a leader in the automation of ceramics production from Italy, has designed a skid-mounted blending system for its ceramic slip and colouring materials.

The company’s customers are now enjoying up to a 30percent improvement in their production quality by using the new system as it allows blending of batches of the ceramic raw materials to take place immediately at the time of use, compared to the traditional approach of mixing and maintaining mass quantities for use over extended periods (Fig.1).

Using the technology and measurement accuracy of the Micro Motion Coriolis flowmeter from Emerson, Euroelettra Sistemi can now consistently monitor and control both the density and flow rate of the components being blended. The technique is likely to revolutionise the production of coloured ceramics, which previously had been based on craft rather than science.

In one of the first production installations at a manufacturer of floor and wall tiles, the benefits included:

• Major savings in production space required, since mixing tanks are not required when the blending is done only at the time of use.

• Electricity and water consumption is reduced due to elimination of the requirement for continuous agitation and significantly reduced cleaning.

• Production repeatability and consistency have reached an unheard of level of 90percent, compared to a maximum of 70percent previously, this owing to the close control over the colour mixing.

Conventional production of coloured ceramics involved preparation and blending of the base suspension or slip, and the colour, in quantities of tens of tonnes at a time. Repeated colour analysis and colour addition ensured that once the colour had reached the desired level, enough material was available for a reasonable production quantity to be modelled and fired, achieving a consistent result.

Typically the blending occurred in ball mills, and then in underground agitation tanks, which required significant amounts of energy to maintain the agitation over the days while the material was being used in the modelling process. Inevitably the large tanks and mills required a lot of cleaning, thereby wasting the material that was deposited on the tank walls and associated pipework. High quality products required dedicated tanks to avoid impurity carry-over from previous batches.

Euroelettra Sistemi realised that the most efficient mixing process would be a skid-based unit, and that this would require accurate monitoring and control of the separate materials being delivered. The barrier to achieving this was overcome once Euroelettra investigated the accuracy and measurement capabilities of the Micro Motion

T-Series flowmeter from Emerson, which provides both mass flow and density measurements. This introduced the possibility of blending the colour and the slip in exact mass proportions, achieving consistent colour hue even though the actual blended volume is small (Fig.2).

The diagnostics available within the multi-variable digital (MVD) core processor of the flowmeter, accessible via a Modbus connection, enables the blending system to identify any build-up of material within the straight measuring tube of the Micro Motion Coriolis flowmeter.

This ability to signal when cleaning is required has increased equipment availability by around 50percent, and improves efficiency. Cleaning is relatively straightforward, when needed, because of the straight tube design of the flowmeter. The resulting homogeneity of the material supplied has led to a reduction of typical production rejects by over 90percent compared to previous skid blending system trials.

Future benefits will follow. Traceability of the process parameters used to achieve each blend enables further production batches to be scheduled as needed, with good colour consistency between batches – which both improves productivity and increases customer satisfaction.

Several manual production operations have been eliminated, releasing the people for other work. The production efficiency has been increased by 50percent, impacting the whole company, enabling an overall increase of 10percent in production efficiency.