Getting the best from the ironer line

29 January 2015



Richard Neale of the Laundry Technology Centre gives some tips that should help supervisors to ensure the ironer line produces both high volumes and a good standard of finish


Organising a modern high volume ironer line so that it runs at its maximum capacity and still produces the high quality that customers expect can be a challenge. However, paying attention to a few important details will ensure superb results and good productivity, even with relatively old equipment

Extraction and conditioning
To obtain the best results, linen should go straight from the membrane press or washer-extractor, before it has a chance to dry out unevenly in the atmosphere. To ensure high productivity cost effectively, it is necessary to e to minimise the fabric's moisture level by optimising the press program or the washer's final extract.
The membrane press should be tuned to give the maximum time at full pressure: at least 30 seconds with a 40bar press or at least 60 seconds with an old 24bar press. Always remember, the longer the time, the better the result. This may mean tuning down the wait times in the press computer program but the effort is well worthwhile.
Washer-extractors need to be run for nine minutes at full speed to minimise moisture levels.
Prompt ironing will then ensure a consistent level of moisture as the pieces in a load enter the ironer line. This means careful planning of the processing so as to avoid a queue at the ironer.
Conditioning time should be kept to a minimum, any longer is a false economy as removing moisture in the tumbler rather than the ironer is very expensive. A cheese of bedlinen from the membrane press should need only 30 seconds in the tumbler to break it up so that it can be separated and fed to the ironer manually. Table linen might need slightly longer to open out the edges but conditioning sheets or pillowcases for three to four minutes will cost too much and use tumbler minutes that could more profitably be used for terry towels. Making an efficient ironer do the drying eases pressure on the tumblers and improves quality.

Maximising ironer productivity
The ironer's drying power is governed by the size of the heated bed and to realise the full potential, the bed should be covered with drying flatwork for as much time as possible. Each piece should be fed so that its leading edge is as near as possible to the trailing edge of the previous piece and all available lanes should be used.
Maximising bed coverage is far more effective than running the ironer faster. If there are only two operators to feed pillowcases it is usually better to run the ironer slowly and let each operator feed two lanes than to use only one lane at high speed. The quality is better and there is no need to condition the pillowcases, even though they are double thickness.

The laundry engineer's role
Tuning the ironer correctly will significantly improve its performance and the most successful ironer supervisors are those that work well with the laundry engineer.
Roll-to-roll stretch: This should be set to 0.2% (equivalent to a stretch of 50mm in 10 turns of an 800mm diameter roll) to maximise heat transfer and crease removal over the gaps and minimise distortion.
Roll vacuum: This should be in the range 30 - 60Pa, with the first roll near the maximum and the last roll nearer to the minimum. This will improve drying performance and give a better leading edge (because there will be less stuttering as the leading edge enters the in-running nip).
Bed temperatures: The temperature should be uniform without any cold spots as these will cause drag, distortion and wrinkles. Cold spots at the lowest point of the bed are usually caused by blocked or under-sized steam traps. Steam-heated ironers will only work properly if they receive dry steam at constant pressure and most engineers know how to achieve this.
Roll size: Rolls must be the correct diameter to fit the bed to ensure maximum roll-to-bed contact and maximum crease removal. This is particularly important when processing new textiles that might contain durable sizing.

Ironing difficult fabrics
Most laundries can handle cotton, polycotton or cotton-rich fabrics but switching from one type to another may bring problems. Trying to mix two or three different types in one run is also problematic and not to be recommended as it can lead to polyester blends becoming grey.
100% cotton: This can usually be ironed at a maximum of around 200C and the best results are obtained from fabric with around 50% moisture. It is usually difficult to remove creases properly if the fabric has less than 40% moisture.
Polycotton: The maximum ironing temperature is around 165C, which is equivalent to 7bar steam. Fabric manufacturers will not usually take responsibility for any problems encountered if the ironing temperature is above the recommended level of 150C. Where problems do arise, this is usually because the fabric has become distorted from the combined effects of roll-to-roll-stretch and bed drag. These can be minimised by dropping the bed temperature to aroudn 165C and by running the waxing cloth more frequently. It should be run with wax at the start of an eight-hour shift and then every hour without any additional wax.
If it is not possible to drop the bed temperature, then ironing from a higher moisture content or at slightly higher speed will usually solve the problem. This will also cure static problems with polyester and polycotton.

Concertina creasing and leading edge rolling: These are examples of problems caused by an over-heated polyester blend trying to enter an in-running nip successfully. The problems are worst when the roll is undersized relative to the bed, or when the bed has become distorted, which is more likely to occur with older cast-steel beds. Modern beds ones are now stress relieved to avoid this happening. Both faults can be minimised by operating at the correct bed temperature (around165C maximum) and by running the waxing cloth more frequently, but these steps will not solve the problem permanently. Rolling, in particular, may get significantly worse if a rolled leading edge flattens the ironer springs. Then re-springing is the only answer.

Cotton-rich: This fabric varies in its performance in the ironer, according to the way the polyester fibres have been incorporated into the yarns. An intimate blend of cotton and polyester in the staple, warp and weft has the greatest tenacity and will have the longest life. The fabric will have the thermal characteristics of polycotton so typically the polyester content will start to soften at 167C. At this point, a cotton-rich fabric loses its strength and the roll-to-roll stretch and bed drag then stretch the fabric in the machine direction.
Unlike a100% cotton, when cotton-rich is distorted in this way it does not revert to its original dimensions in the next wash. The sheet will continue to stretch progressively in one direction and "neck in" in the other, becoming longer and narrower, until it no longer fits the bed.
The ideal solution to this is to reduce the bed temperature down to the correct level. If this is not possible, then change the direction of feeding until the stock returns to the original dimensions, which may take several processes.

Elasticity in the fabric
Some fabric becomes elastic after the first one or two wash and iron processes. It is not yet clear why this happens to some fabrics and not others, but the problem is more common with cotton-rich than with 100% cotton. The fault is probably connected with the conditions in cloth finishing the but it is not well understood.
When it does occur, it is best countered by using the correct ironer temperature and then, if possible, adjusting the roll-to-roll stretch to near 0.1%, but some early ironers cannot be adjusted in this way.
If the elasticity is in the length there will be furrow of stretching fabric, which form lengthways pleats running down the fabric when the piece enters the in-running nip. A sheet that has been severely affected will usually have scallop- shaped pleats at the trailing corners and down the edges.
Elasticity leads to shrinkage wrinkling, the wrinkled areas looking like corrugated cardboard and these cannot be pressed out. This effect can be minimised by improving the roll-to-bed fit but this might mean re-clothing the rolls.

Quality of the folding
The folder must be regularly maintained if the fold quality is to meet the customer's expectations. It should be lubricated regularly paying constant attention to the belts, belt joints and general alignment. Meticulous attention to detail is essential.

The ironer supervisor is a key figure in a modern laundry results on the ironer line depend heavily to procedures in the wash-house and at the tumble dryers.
Good teamwork will lead to success and supervisors need to work at building the team by leading from the top. Supervisors must also recognise the key role played by the laundry engineer.



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