Flow Chart of Indigo Dyeing in Slasher Dyeing Machine

Normally, jeans are dyed to a blue color using indigo dye. Usually for indigo dyeing slasher dyeing machine is used. In this article, I will give a flowchart of indigo dyeing in slasher dyeing machines.

Flow Chart of Indigo Dyeing in Slasher Dyeing Machine

Pretreatment [ 1 bath]
↓
Washing [ 2 baths]
↓
Dyeing [ 6-10 bath]
↓
Washing[ 2-3 bath ]
↓
Pre-drying
↓
Sizing [1 -2 bath]
↓
Drying 

Concept: The patented Benninger trough is a closed trough with a yarn inlet and outlet. Both inlet and outlet are equipped with an oxygen trap. The trough is split into two compartments. The yarn passes first the dipping and wetting compartment with a passage length of 6.6m, then through the flexible squeeze rollers before entering the penetration chamber with a passage length of 6 m. Both compartments are, during the indigo dying process, flooded with 98% pure nitrogen. The nitrogen flow is regulated by adjusting a flow valve. The nitrogen flow volume per trough is approximately 50 – 70 L/min. The dye liquid volume per trough is 360 I at the level of the overflow weir. Additionally to the 360, L in the trough is approximately 70 L in the overflow compartment, which results in a total dye liquid volume of 430 L per trough.

Indigo Dye Liquid Circulation flow schematic

Each trough is filled by a centrifugal pump. The pumps have a capacity ‘of 80 L /min. In this case, the dye liquid exchange rate per trough is every 4.5 min. This exchange frequency is only possible due to the oxygen free atmosphere in the dye troughs. The dye liquid back flow is achieved by the slightly lower level in the mixing tank in comparison to the theoretical level in the dye troughs. The total indigo volume required for a 6 trough dyeing range is 3600 I (including mixing tank), which is substantially less in comparison to conventional slasher dyeing ranges with 8000 to 12000.