Quality cost productivity

The standard of finishing provides a convenient measure of the quality of a rental laundry's service, but the right quality must be achieved without sending costs soaring or reducing productivity. In the average rental plant, it is the finishing area which generates the majority of revenue costs because quality finishing requires the highest level of training and staff skills.

Leadership

The secret of success lies in the leadership given to staff on the finishing line so they can achieve results which exceed the customer's expectation without eroding the profit margin or lowering production speeds. Managers need to examine the basic techniques which will help them to achieve this balance and to be aware of errors to be avoided

Traditionally, the five star hotel has taken pride in well-starched pure cotton table linen that is crisp and square and that has a good sheen to the face.

This requires a starching stage which is long enough for the starch to build into the cotton fibres, so you need to follow the supplier's recommendations for concentration, time, temperature and dip. If this is done correctly you can extract down to 54% moisture retention and, with very little conditioning in the tumble dryer, iron from this state .

Then, the leading edge going into the ironer should be flat. It may be advantageous to adjust the position of the front guide tape roller to help to flatten out minor undulations, rather than allowing these to be folded back to form a long leading edge crease.

Maintaining as high a leading edge tension as possible will also help. A modern ironer is designed to dry cotton from 54% moisture retention but it will only achieve this if you have a good roll to bed fit, the correct roll to bed pressure and a slight roll to roll speed differential.

However, the linen will come out slightly damp and limp if you do not maintain edge to edge feeding and cover as much of the bed as possible so that you can afford to run at a linear speed low enough to ensure complete drying. Only then, will the product have the crispness and sheen that the customer demands.

In attempting to maximise ironer productivity, laundries often make the mistake of turning the ironer speed up. They then find that the linen comes out damp and attempt to correct this by conditioning for six or seven or even ten minutes in a tumble dryer. Running the ironer at a higher speed also makes it difficult for operators to maintain edge to edge feeding in every lane and so much of the drying capacity of the ironer is wasted.

Over dry

Conditioning in a tumble dryer frequently results in some items being over dry. As a result they run through the folder quickly, generating static and producing snarl-ups and a generally unsatisfactory result.

The only reason for conditioning should be to relax some of the creases which have been put in at hydro-extraction, especially along the leading edge.

Polyester-cotton table linen is usually best processed in an open-pocket washer- extractor with a short spin and a medium temperature tumble to open out.

Good results can be achieved in a tunnel washer, provided the hydro-extraction time and pressure are carefully controlled using a modern programmable press.

In every case, table linen should be left in the barrow for as short a time as possible to avoid pressure creasing.

Terry towelling

When processing terry towelling, launderers are always faced with the problem of preventing hardness and harshness, as the customer looks for the softness of a brand new towel.

Minimising drying costs demands maximum hydro-extraction and this also ensures that most of the total dissolved solids are pressed out with the rinse water.

It is these fine particles that contribute to the harshness of a towel surface, so in this respect low cost coincides with high quality. In theory, wet terry towelling should withstand a high tumble dryer air inlet temperature for the first part of the drying cycle, but if the temperature is above 200°C, the terry loops become hard and harsh, even if the the heat is reduced towards the end of the cycle into the cooldown.

At one site I know, work has been carried out with a slightly lower drying temperature (180ºC) at the start of the cycle whilst all of the loops were opening up and fluffing out. It was then possible to go up to the maximum temperature (around 200ºC), only reducing this when the towelling neared dryness, cutting off the heat altogether through the cooldown.

It is important to remember that a dry towel contains 8-10% moisture because this is the natural regain from atmospheric humidity in the room. It is false economy to try to get it any dryer than this.

It will also be found that if the drying endpoint is correctly identified so that towels retain this amount of moisture after the cooldown, greying will be far less of a problem because there will be little or no tendency for the terry loops to develop a static charge when bone dry.

It is this static charge which attracts the greying particles from the drying air stream. Not only will the cooldown of towelling significantly reduce the risk of a laundry fire through spontaneous combustion but it will also help to redistribute any residual moisture from the centre of the base fabric out into the individual loops, again improving the softness and handle.

In a modern textile rental plant accurate detection of the endpoint for tumbling is essential, but so far the laundry sector has not come up with devices which are sufficiently cheap and reliable to be fitted as manufacturer's original equipment on every tumbler.

Work carried out many years ago by the Fabric Care Research Association (supported by a Department of Energy grant) identified one key parameter that would indicate the endpoint more reliably than exit temperature or even exit humidity of the drying air stream.

  A glance at the drying curve for towelling indicates that the bulk of the drying occurs at a constant rate from the cotton surface. Only when the towel is almost dry and the moisture has to migrate from the middle of the towel to the outside does the rate slow down. Eventually, when all the moisture has evaporated, drying ceases and the weight of the towel remains unchanged.

Shape of the curve

This process can be followed very cheaply by monitoring the shape of the outlet temperature curve, noting the point where this starts to flatten out. During the constant drying period the slope of the drying curve is constant, as it is when the towel is fully dry.

At the critical transition point the gradient changes rapidly and with modern electronics it is possible to measure this rate of change quite accurately. If the rate of change gradient is plotted against time, a unique blip appears on the curve, quite sufficient to trigger the dryness endpoint regardless of ambient temperature or humidity from the weather outside.

  So tumble dryer control throughout the entire drying cycle is vital to tunnel washer output and productivity. It is also fundamental to minimising operating cost and achieving the desired quality. It is vital to get this right and tumble dryer suppliers still have a role to play here.

  Modern tunnel finishers will rapidly warm up a damp garment allowing crumple creases to be relaxed out in the conditioning zone.

When the garment enters the drying zone it encounters a high velocity downward stream of hot air at controlled humidity to produce uniform overll drying and further crease removal and smoothing.

It is in the drying zone, however, where most problems start. There are still many puzzled operators wondering why garments come out with speckled sleeves or brown collars or single panels that have yellowed. There may even be over all browning, especially when they went in lily white.

Many high-quality garment operators rely on washer-extractors to achieve excellent soil removal and batch separation. Highly successful plants with increasing volumes place greater and greater demand on the laundry boiler.

Wet steam phenomenon

When four or five large washer-extractors call for steam simultaneously it imposes a load on the boiler sufficient to reduce its pressure and this is often accompanied by a froth of water and steam rising into the steam main, the so called wet steam phenomenon. This does not do too much damage at the washer-extractor stage, because it is injected directly into the wash water. However, when it reaches the steam sprays on a tunnel finisher the sleeves of every garment are treated to a fine mist of boiler water which contains 3,500 parts per million total dissolved solids and is usually very alkaline. So during drying the speckles change to a dull grey brown and ruin the batch.

Despite repeated problems over the past ten years, there are still supplies of incorrectly finished polyester-cotton workwear fabric coming into the UK with a either a chlorine-retentive finish or an alkali-retentive finish. These fabrics process perfectly well until they encounter heat in drying when the faulty finish starts to turn yellow. This is at its most striking when all the garments in a batch have a particular panel that has been cut from a bale of faulty fabric, while the rest of the garment is all right.

The result is that the coat which appeared uniformly white at the start of the line, comes out of the tunnel with a yellow sleeve or left front! One can appreciate why operators scratch their heads when this happens.

Wrong decision

When a general manager makes a wrong decision regarding washer-extractor purchase for a garment wash house the results are far reaching. If business is so good that the laundry decides to buy a 200kg machine, you need an open-pocket design with good lifters and a length to diameter ratio as near to unity as possible. Opting instead for D-pocket or a Y-pocket machine or a unit with a large diameter and tiny lifters is going to create creases which no amount of wash process modification or tunnel finishing can put right.

Nevertheless, a well-designed wash process which carefully avoids pressure creasing at each stage, especially when the liquor is hot, and which achieves the right time and speed for interspins and final spin will always produce a better result than a standard process that has not been fine-tuned. At every stage dips have a vital role to play, as does the loading factor. With care it is possible to present to the tunnel a garment that only has crumple creases, which the finisher is designed to remove successfully.

Roping creases

Long roping creases of arms and legs are caused by work rolling in the washer- extractor cage rather than being cleanly lifted to the 11 o'clock position before the work breaks away from the cage circumference.

Long final spins or hot washing with too low a dip, or attempting an interspin when the work is still warm, will all produce sharp creases that are virtually impossible to remove without hand pressing. So the cynic who assumes that good quality is always accompanied by higher cost or lower machine productivity is not always right.

Those launderers who show a good technical lead to their production teams will succeed in achieving good commercial quality at a cost which still leaves an adequate margin, even at today's cut throat prices.

This can be achieved without heavy machine investment. Most laundry ironers work at only a fraction of their design output, usually because of inadequate tuning by the engineer which is then made worse by the short-sighted approach taken by some production supervisors.

If we could put this shortcoming right and at the same time sort out tumble dryer endpoint detection of fully dry goods, we could have the best of all worlds.