2.6. Practical Bulk Experience

Figures 4 and 5 illustrate the same dark red shade washed off on the same machine using either conventional or Smart Rinsing techniques. The machine was a Thies Roto-stream which was fitted with a controllable hot water feed and a low level overflow weir.

The improved efficiency from Smart Rinsing in the initial dilution phase is clearly illustrated by the time taken to reduce the salt concentration below 2 g/l, approximately 10 minutes, compared with the Drain/fill system that required three discrete rinses to achieve the same end point. This could take over one hour when filling, heating (cold water) and draining times are all taken into account. The benefit of the hot water (70C) in the early rinse is also clearly demonstrated with respect to the rapid removal of unfixed dyestuff leaving little to be diffused out in the re-circulation 'soaping' bath.

The exploitation of such technologies is vital to those companies who wish to reduce their total costs of production and gain competitive advantage. However, the first step in any productivity improvement program should be a complete audit (and possible upgrading) of utilities to ensure that the benefits of the new equipment can be exploited to the full.

Further process optimisation may see these Smart systems, which have already seen the on-line use of conductivity meters to signal the attainment of pre-set salt concentrations and step on the process automatically, develop into truly 'intelligent' systems through the introduction of colorimeters to facilitate rinsing to the optimum end point.

There are several such 'smart rinsing' systems available now from the leading machinery suppliers.

2.7. Concluding Remarks

• Rinsing and soaping processes can be optimised to a limited extent to improve efficiency and maintain high wet fastness levels without capital investment. Careful audits of existing procedures and equipment will identify how.
• Some elements of the newer machinery developments can be retro- fitted to existing machinery, allowing further efficiency gains.
• Any dyehouse considering upgrading dyeing machinery or increasing capacity should seriously consider the benefits offered by machines fitted with the latest rinsing technology.
• It is important that the commissioning and optimising processes for such machinery are done alongside a deep and full understanding of Reactive Dye design, manufacture and application technology.

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