The laundry engineer is usually responsible for maintaining not only the laundry equipment but also the drycleaning machine which many laundries have tucked away in the corner. This is very much the Cinderella when it comes to maintenance because, although the laundry probably makes a good margin on drycleaned work, the machine does not have to cope with the high volume demanded of washing and ironing machines. As a result, the maintenance is neglected and the relative complexity of the machine means that essential principles of maintenance are often poorly understood.

Recently, there have been problems of repeat failures, which need a sound understanding of chemical breakdown in the drycleaning machine if they are to be cured permanently. This understanding is made much more urgent by the requirement now being enforced by factory inspectors.

Competent person

Under the Provision and Use of Work Equipment Regulations a drycleaning machine needs to be maintained in accordance with the manufacturer’s instructions by a competent person. A “competent person” is not clearly defined, but it is generally taken to mean someone qualified by knowledge, training and experience to execute all of the tasks correctly. This means not only carrying out all the procedures and renewing faulty parts, but making sure that any parts fitted are compatible with the machine and solvents.

One of the reasons for the explosion of the drycleaning machine at Cheadle (which occurred some years ago and was fully reported by LCN at the time) was the fitting of a still chimney connection made from plastic which progressively deteriorated in the presence of perchloroethylene vapour.

There are regular reports of failing stills and failing still condensers. When many of these are investigated it is frequently found that failures are avoidable and occur because of faulty settings or poor operation. One of the prime causes is the setting of the thermostat that controls the still jacket temperature on a steam or pressurised hot water system. This is a pressure thermostat – for an electrically heated oil bath, it is a straightforward electrical thermostat with a back-up in case the main one fails.

These stats need to be set to the lowest level consistent with maintaining distillation at a rate that keeps up with production requirements. Too high a setting encourages chemical breakdown in the still with reactions between the perchloroethylene (or hydrocarbon) solvent and the contaminants removed from the work. Sometimes these reactions produce alkaline compounds and amines which corrode anything containing copper, particularly a copper-coated cooling coil. This type of attack can be recognised by the deep ultramarine blue discoloration that can be seen over the copper surface being attacked.

Acid attack

Other reactions actually crack the solvent to produce acids which start to pit the still heating surfaces and eventually create a pinhole. The same acids can be carried over with the hot vapours and attack both copper and iron to cause pinholes in the condenser coil. This type of attack is characterised by a greeny blue discoloration of the copper surface, usually indicating the presence of chlorides of iron. Although the worst examples of component corrosion result in component lifecycles of only a few weeks, there are a great many machines operating for which component lifecycles are reduced from four or five years to less than two years.

There is a limit to what good maintenance alone can achieve and this limit is being tested in many organisations by habitual dosing of the drycleaning machine with other chemicals to improve performance. Potentially the worst offenders are those laundries with contracts for cleaning paint sprayers’ garments. Perchloroethylene will remove fresh paint quite well but dried on staining can be very obstinate. The miraculous improvement obtained using the appropriate spotting chemical in large quantities within the machine itself is a temptation that must be resisted.

In the Cheadle explosion, dosing the machine with a flammable chemical was a major contributory factor. Modern spotting chemicals are designed to be used sparingly so that they can be removed with the still residue. Where they do contain volatiles, these are safe provided the spotting instructions are followed. However, it is vital when using hydrocarbon solvent that only spotting chemicals designed for hydrocarbon machines are employed because these alone are guaranteed not to lower the flash point within the system below 56°C, the limit at which these machines are designed to operate safely.

It is often possible to recognise a poorly maintained drycleaning machine as soon as you walk through the door of the laundry. Sometimes this is because of the escape of solvent odour through leaking seals and joints, but often it is another smelly consequence of chemical reaction within the system.

Dank and dirty

Chemical amines formed by reaction at high temperature between drycleaning fluid and fatty acids from body fluids washed off the garments have a particularly unpleasant sewer-like smell, producing a dank and dirty odour that one would not want associated with recently cleaned garments. When corrosive acids are produced the odours tend to be more pungent but can be equally unpleasant.

However, the worst smells occur when butyric acid and other organic acids are produced, causing the whole area to stink of vomit and worse. This is a slight problem with perchloroethylene machines and used to be a problem with fluorocarbon machines. The worst instances are starting to occur in older hydrocarbon machines. In his paper to the TSA Retail Sector Conference, Kaspar Hasenclever from Kreussler described the German experience.

If tanks and stills are not properly cleaned then contaminated hydrocarbon on the base of the tank can be covered with a layer of water creating ideal conditions for bacterial breakdown to produce a “stinking” machine. These problems are now being prevented by incorporation of biocides in the detergent system and by proper use of a combination of adsorption filters and distillation. Both purification systems are needed because many hydrocarbon distillation systems allow fatty acids to be carried over with the solvent and these must be removed by adsorption.

So when a laundry engineer takes on drycleaning machine maintenance the various tasks have to be executed precisely and any of the symptoms mentioned here have to be investigated, the cause identified and the correct solution implemented. Unsafe systems, accelerated corrosion and unpleasant odours are all avoidable faults that a well-trained engineer has to deal with in the course of the working day.