A dye house should not have both continuous and discontinuous machines

WRONG

To most dyers and finishers, continuous and discontinuous processes are mutually exclusive concepts. In cotton finishing, dye houses that start off with exhaust dyeing( for batch / discontinuous dyeing) equipment usually remain with that concept, even if their daily output warrants a closer look at the economic benefits that a combination of the two concepts can offer.

Rather than being mutually exclusive alternatives, continuous and discontinuous wet processing equipment can work perfectly, as highly efficient and economically, compelling complementary solutions. One of the main reasons why such integral solutions have not been widely applied is that they have till date not been available from a single supplier and have thus, been seen as competitive rather than complementary process concepts. Only now the suppliers have created one-stop sales organizations( e. g. FONG’ S) that offer both exhaust and continuous equipment.

When existing piece dyeing capacity is at its limits, always add more dyeing machines

WRONG

Particularly in situations where existing piece dyeing capacity is at its limits, the usual reflex is to add more dyeing machines. However, there are

If the bleaching processes were to be continuous, the daily dye house production would increase by 38 %, i. e. from the current theoretical batch rate of 4.96 to 6.85. In tonnes per day, we would see an output of more than 15 tonnes – without the addition of a single dyeing machine.

alternatives, some with compelling arguments. The main consideration has to be whether more capacity can be added economically by separating pre-treatment from the core dyeing process.

By separating pre-treatment( e. g. scouring and bleaching) from the core dyeing process, the process time in dyeing machines is reduced by typically around 60 to 90 minutes( the time usually taken for bleaching). This means that in reactive cellulose dyeing, the exhaust process is shortened to 2 hours, allowing correspondingly more batches to be dyed per day. The bleaching is carried out on a continuous line instead.

Continuous processing lines may only make sense for extremely large daily outputs

RIGHT

When piece dye houses reach their maximum capacity, the usual opinion is to consider adding more dyeing vessels.

It would surprise most readers to know that a continuous bleaching range already makes a lot of sense with a daily dye house output of around 5 tonnes. That is, by any standards, not a large operation.

As we can see from the above output figures( and quite general), it also makes a lot of sense to first look at which processes that are presently part of the exhaust dyeing process could be handled more economically on a continuous line. This holds particularly true for washing and

bleaching. In addition, where vertical operations are concerned, it also makes sense to approach the issue of surface handle and appearance from the yarn construction and fibre blend angle, rather than devoting up to 30 % of the dye house capacity attempting to increase lustre through enzyme treatment( and suffering substantial fabric weight loss in the process).

Exhaust dyeing is not the only concept for processing small and medium batches

RIGHT

Conversely, the commonly held opinion is that exhaust dyeing is the only concept for processing small and medium batches. As we can see from the simple point made above about a bleaching range, continuous processing is a term that does not only cover complete washing, bleaching and dyeing ranges, but also individual process steps. In this article, our focus is not on bed sheet plants, where thousands of metres of fabric are dyed in the same pastel shade for days on end. Far rather, our attention is on dyers and finishers that have smaller batch sizes in many shades but nevertheless use reasonably similar grey fabrics across their range. Can continuous equipment be of any use to them?

Let us look at a medium-size exhaust dye house with a daily( revenue) capacity of 10 tonnes of cotton knit fabric. To achieve this, an installed capacity of 2,500 kg is required( based on 4 batches a day, easily