Dyeing Machinery Questions and Answers

Answer: C

Both are true and the reason gives the necessity: carriers were the older alternative and are still used where a pressure machine is not available, at the cost of odour and additional effluent load. Pressure vessels are now standard for polyester.

Answer: D

It swells the fibre so that dye can enter at the boil, which avoids the need for a pressure vessel. Its odour, cost and effluent load are why high temperature dyeing is now the norm. Carrier residues also affect the light fastness.

Answer: A

Correct answer: through the centre and out through the yarn

The liquor is pumped up the perforated centre tube and forced radially outward through the wound yarn, so every layer is contacted rather than only the surface. That is what makes it possible to dye a package weighing over a kilogram evenly, and it is why the winding density must be uniform - a hard spot resists flow and dyes lighter.

Answer: B

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the necessity. The liquor loses dye as it passes through the yarn, so the layer it reaches first takes up more than the layer it reaches last. Reversing the flow periodically - in to out, then out to in - equalises the exposure and prevents a package that is darker on the inside than the outside.

Answer: C

Correct answer: 1 and 2 only

Statements 1 and 2 are correct: uniform winding density is essential because the liquor takes the path of least resistance, and the circulation goes through the yarn rather than around it. Statement 3 is wrong - package dyeing is for yarn. Woven fabric is dyed on a beam, a jigger, a jet or a winch depending on its form and its crease sensitivity.

Answer: D

Package machines dye yarn wound on cones or cheeses, while the other three all handle fabric in one form or another. The distinction decides at what stage of manufacture the colour is applied. Yarn dyed goods allow woven patterns.

Answer: A

Correct answer: padding dye and alkali on, then batching

In pad-batch the fabric is padded with reactive dye and alkali together, then rolled up, wrapped and rotated slowly for a few hours to a day while the fixation proceeds at room temperature. It needs no steam and very little water, which makes it one of the most economical routes for cotton - its costs are the floor space and the batching time.

Answer: B

Fixation happens during the dwell rather than in a machine, which is what makes the process so economical. Washing off is still needed because reactive dyes never fix completely. The dwell replaces the machine entirely.

Answer: C

The machine runs at a steady state and the water and energy per kilogram are low, but changing shade wastes a length of fabric. Batch machines suit short runs and frequent shade changes. The break-even batch size decides the choice.

Answer: D

Correct answer: the loss at every shade change

A continuous range holds a large volume of liquor in its pads, boxes and washers, and all of it must be run out and replaced when the shade changes, along with the fabric passing through during the transition. That loss is fixed regardless of the run length, which is exactly why continuous dyeing suits long runs of one shade and batch dyeing suits short ones.