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