MATERIAL SOLUTIONS

Sorting for success

2 October 2009



Ian Harris explains how good classification leads to better quality, lower costs and fewer risks


Managing labour costs is essential to a profitable textile rental business.This strategy should start in the sorting department, as soon as the goods enter the laundry.

Carry out a basic work study to make sure that the sorting-belt speed is aligned with the unloading pattern and the number of operators. Correcting any misalignment will bring a great improvement.

Greying and poor stain removal are often regarded as problems for the detergent supplier to solve but such faults can frequently be avoided by more precise sorting.

A well-trained supervisor can reduce the amount of residual staining on table linen far more cheaply by classifying it correctly than the laundry line can by bleaching the linen to death.

Small thin towels may be more prone to greying through over-drying. A skilled and experienced supervisor should recognise this and instruct staff to separate these items, so helping to double the life of circulating towel stock.

Pilling results in unsightly balls (or pills) of fibre clinging tenaciously to the surface of table linen and many plants blame the textile supplier. While pilling can be the result of low yarn twist, which is a matter for the supplier, the problem can often be cured by classifying pure cottons separately.

Every year least one large laundry burns down as the result of spontaneous combustion of oxidisable oils left on a warm, dry and otherwise clean textile. A sharp-eyed sorter can reduce the risk.

All staff skills are important, but profitability starts with a well-trained sorting team.

Make sorting more productive

A few minutes observation in any sorting department will reveal whether it is using its staff efficiently. The first sign of an efficient department is a sorting conveyor that is moving steadily without stopping. Work is that is loaded and spread fairly evenly along the length of the conveyor is a further indication of good management.

The staff should all be moving and sorting steadily in a forward direction all the time, putting the items into hoppers or bags that are either directly in front of them or very nearly so. A laundry that meets all three conditions has probably designed its sorting operation well.

In a poorly managed and designed department the the sorting conveyor will always be stopping then starting so that the sorters have to work very quickly and then wait around for a few seconds until the next batch appears. If the sorters have to take a step or they have to throw to get certain items to their destinations then the system is inefficient because it is wasting time. If a sorter has to twist to send an item behind them, this is a serious health and safety risk.

On average an efficient department will be sorting 1,000 – 1,300 pieces per operator hour ( including the staff that load the conveyor). A department that is not achieving this rate will probably find that the solution lies in adjusting the system so that it follows the guidelines given here.

Reducing fire risks from the start

Every year puzzled fire officers and laundry owners pore over the remains of large thriving laundries trying to work out how a fire could break out in the finished goods area at two o’clock in the morning for no apparent reason. Most of these fires are caused by the spontaneous combustion of oxidisable oils that have been left on the fabrics at the end of the wash.

Operators should be trained to alert a supervisor if work smells rancid when taken from a washer-extractor or from the dryer in a tunnel washer line. The problem arises when one heavily-contaminated kitchen towel is washed in a medium-soil process that leaves half the oily staining behind. This residual oily staining slowly oxidises and gives off heat that affects the whole of the clean dry pile that contains the contaminated towel.

After several hours, when everyone has left the building, the pile can become so hot that it ignites. A hawk-eyed sorter can eliminate this risk, simply by classifying heavily-soiled kitchen “rubbers” and similar cloths into either a heavy-soil program or by sending them straight to a special re-wash/recovery process. Both of these processes should have enough power to remove the high-risk oils completely.

Small, thin towels turn grey

When towels suffer greying, many laundry managers blame the fault on the age of the article. However, if it is the smallest and thinnest towels that are greying most rapidly and that suffer the most, old age may not be the sole cause. Much greying occurs during the wash when soiling from the wash liquor redeposits on the linen. This is usually caused by inadequate suspending power in the wash chemistry so that soiling washed off the linen succumbs to its natural electrochemical attraction to the fabric surface.

Once the soiling has re-deposited onto the material, forming an even layer a few molecules thick, it is virtually impossible to remove so the linen or towelling gets progressively grey overall.

Most modern detergent systems contain plenty of suspending agent but some launderers are reluctant to add sufficient detergent and this precipitates the problem.

However, greying also occurs in the tumble dryer as the result of local over-drying. The smallest and thinnest towels dry first and if they then continue to be tumbled, the ends of the terry loops will acquire a tiny electrostatic charge. This in turn attracts every particle from the drying air stream and progressive greying follows. It is true that the oldest towels will suffer the most from greying but this is because of poor laundering, not old age! The solution is to classify thin, light towelling as a separate category, keeping this apart from the 600gsm bath sheets that the five star hotel market now demands.

Classify pure cotton separately to avoid pilling

Pilling is a common cause of customer complaints. This is because the tight balls of fibre that sometimes spoil polyester and polycotton table linen cannot be brushed or washed off the fabric. When the pills form (usually in the wash process) the mass of cotton fibres anchors itself to the cloth with a single polyester strand from the fabric structure.

This polyester strand is exceptionally strong and provides a secure leash so the only way to remove the pill is to shave it off with a de-fuzzer and this is uneconomic. If the polyester and polyester blend fabrics are washed in a separate classification to cotton items, there will be very little cotton lint in the wash liquor (if any) so pills do not form. If a laundry is getting several complaints about pilling and close examination of the pills reveals that they are composed entirely of cotton fibres then the cause of the problem is probably mixing classifications.

Electro-chemical forces play a part in the initial attraction of cotton to a stray polyester fibre, protruding from the base fabric and once the pill starts to form it rapidly builds to a visible size that is unacceptable even to an undiscerning customer.

Classifying pure cotton fabrics separately will avoid the problem in most cases. The only exception is where a batch of fabric containing polyester has been woven from yarns with too low a twist to them. This can give a very soft luxurious fabric, but a low twist can allow the fibres to work their way out. With this particular fault pilling is inevitable and the consignment should be returned to the supplier.

Oily stain clings to polyester

Polyester is an oleophilic (or oil-loving) material. This means that the fibre surface will be strongly attracted to oily substances. Unless the wash process can break this attraction, a great many types of oily staining will cling stubbornly to the cloth and progressively ruin the circulating stock simply because of the level of residual staining it displays.

Pumpkin oil is now fashionable and many chefs will use it. However, its green tinge will make the residual staining much more noticeable. The problem is most common in laundries that classify cotton and polyester blends together because the chemical system is usually geared to cotton as it is seen as being more difficult to wash. But the problems can be avoided by separating cottons from polyester and polycotton fabrics.

Cottons will need a cool pre-wash (below 38C) to soften the proteins, followed by a vigorous main wash at 75C to remove them and a cool bleach to de-colour any vegetable stains from tea, coffee and red wine. A polyester or polycotton that has been marked with pumpkin oil or other oily staining needs chemistry in the main wash that will overcome the oil-to-polyester attraction. This means a longer wash time (up to 15 minutes) and higher temperature (up to 85C). It will certainly require a detergent with a much higher level of non-ionic surfactant.


2 Reducing fire risks from the start 2 Reducing fire risks from the start
4 Classify pure cotton 4 Classify pure cotton
5 Oily stain clings to polyester 5 Oily stain clings to polyester
1 Make sorting more productive 1 Make sorting more productive
3 Small, thin towels turn grey 3 Small, thin towels turn grey


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