The advance of automation
As a society, over the years, we have become accustomed to the ever-increasing degree of automation. However, it will be obvious that for the foreseeable future, vehicles of all types will still need some form of human input to monitor their performance, together with fuelling and maintenance, if they are to operate safely and reliably. The same applies to drycleaning machines which today, in terms of their operation, place little demand on the operator compared to the early 1960s when, at the end of the day, the shutdown procedure for machines could take an hour, requiring the operator to redirect solvent flows around the machine, as and when necessary, before reconfiguring the machine for the following day. Today the limited operator training on automated machines often leaves very many operators with little or no fundamental understanding of how the solvent levels and condition, or interaction of the various machine components and steam and filter pressure etc can adversely affect the automated operation of the machine or the quality of the cleaned product.
Solvent levels
It may come as a surprise to many that by far and away the most common and easily resolved problem encountered on drycleaning machines is insufficient solvent in the machine! In our view this is often in the mistaken belief that the less solvent there is in the machine, the less it will use. Excluding leaking tanks, spillages and a small amount of solvent lost during still cleaning, the vast majority of solvent usage is from vapour escaping and therefore the less solvent and the more air there is in a tank, the more vapour there is in the tank to escape. If solvent usage is an issue, the first step is to ensure that the machine is topped up to above the minimum levels recommended by the machine manufacturer. In our experience, depending on machine capacity, it is not uncommon to find that a machine needed up to 50 litres or more of solvent to restore the correct working solvent levels.
The next step should be the inspection of the cage, button trap, air filter and still door seals to ensure they are in good condition – also check that the doors are correctly adjusted and forming a good seal in terms of pressure; at this point it would be a good idea to ask your engineer to carry out a thorough check for vapour leaks while the machine is in operation.
Insufficient solvent in the machine can easily result in a number of serious problems which leads to a build-up of fatty acids, colour and other soluble impurities in the solvent, incomplete removal of soiling and stains, greying and cage marks. Greying caused by redeposition of soiling from dirty solvent or inadequate detergent.
In order to maintain the base tank solvent in good condition, a minimum of 2.5 litres of solvent per kg of work cleaned needs to be distilled.
Routine maintenance
Regular maintenance is absolutely vital, both to the efficient and safe operation of your machine and, just as importantly, to the quality of cleaning that it delivers. Typically, lack of attention to the cleaning of the button trap, lint screens and the still, and failure to respond to prompts for filter cleaning or rises in filter pressure, will inevitably lead to an increasing risk of the following problems:
- Blocked button trap, leading to cage marks, incomplete soil removal, fabric damage, extended drying times and solvent retained in garments. This can result in staff being exposed to high solvent vapour concentrations.
- Damaged or blocked lint screens, leading to linting, incomplete drying, blocked air cooler and air heater, and the build-up of lint and debris on the inner surfaces of the machine.
- Dirty still, causing slow distillation; the still should be cleaned as soon as distillation starts to slow. Slowness can lead to overfilling of the still, foaming and a ‘blackover’, contaminating the water separator and possibly the distilled solvent tank. This problem, if not observed by the operator, can easily lead to catastrophic greying and possibly shrinkage due to the carryover of water, detergent and soiling into the distilled solvent.
- Filter cleaning – while some machines prompt the operator when a filter clean programme is needed, others may require a response by the operator in relation to the manufacturer’s maximum recommended filter pressure and require the operator to do a filter clean. Repeated, excessive filter pressure will reduce solvent flow, and compact soiling onto the discs. This will also damage them, allowing breakthrough of particulates that will progressively impact on soil removal from the cleaned work and the solvent, resulting in greying.
Serious machine faults, some of which require an immediate response from the operator.
It is the operator’s responsibility to constantly monitor the drycleaning machine, to ensure that at all times the machine operates efficiently. We would suggest that in a busy unit, the cleaning cycle on a full ‘normal’ process load is carefully checked on a weekly basis. This should expose serious developing issues such as slipping belts, programme errors/imbalances, incorrect dip levels, poor solvent flow through the pump and filter, and distillation rates. A noisy pump often indicates cavitation (check that the holes in the button trap mesh are not blocked) or debris obstructing the impeller.
Water separator
For the separator to operate efficiently, and to avoid the risk of solvent being carried over with the wastewater, the separator needs to be drained and cleaned as soon as debris starts to collect at the solvent/water interface. While some separators may need to be cleaned on a weekly basis, others may remain in a clean condition for much longer periods. Slightly cloudy solvent in the separator is normal in the next load after still-cleaning, but it should rapidly clear. At any other time, ongoing cloudiness in the separator or distilled tank should be investigated immediately because it indicates the presence of moisture (or even water droplets) in the solvent. This puts garments at high risk of greying and shrinkage. A perforated still steam-heater, still condenser or air-heater are the most likely causes of the problem.
On older machines, a blue or greenish discolouration appearing in the separator water indicates that copper corrosion is starting to occur on the still condenser coil. While this does not normally pose an immediate problem the still condenser needs to be checked out by the engineer.
Filter pressure
On many of today’s machines, both the filter pressure gauge and the filtered solvent sight glass can be found in the back of the machine and not in the front panel (where they really should be located for easy visual access). In our experience, probably due to their location, they are rarely if ever checked by the operator and all too often the operator does not understand the significance of high filter pressure and (even more importantly) low filter pressure, together with poor/ intermittent flow through the filtered solvent sight-glass during filtration.
Very low or fluctuating filter pressure (often seen together with bubbles in the filtered solvent sight-glass) and varying noise levels coming from the pump, are serious problems which demand the operator’s immediate attention. They are frequently associated with a blocked button trap, or solvent flow that is insufficient to allow the automatic programmes to maintain the correct dip levels and distillation ratio. Low and fluctuating pressure can also be the result of items such as safety pins or small coins providing a foundation for lint and debris to accumulate and obstruct the pump. This reduces to a varying degree the volume of solvent delivered by the pump and consequently the filter pressure. The first obvious sign of a developing pump problem is usually a variation in the sound of the pump, which in some cases can become very noisy. A good operator will pick this up immediately and investigate by checking the flowrate during the filling of the cage. It is also important to examine the button trap basket for damage and to ascertain whether or not it is seating correctly in the button trap and preventing debris bypassing the basket or escaping through a damaged area. Filter pressure and pump problems are frequently responsible for:
- Risk of greying to medium, light and particularly white items due to incomplete removal of particulates from the filtered solvent.
- High risk of unpleasant odours in cleaned items due to insufficient distillation.
- Risk of physical damage to lightweight/ delicate items from excessive mechanical action caused by low dip levels.
Finally, while the issues that we have discussed are not exhaustive, we hope they will provide a good basis for investigating and resolving some common machine operating mistakes, helping our readers to understand how a simple fault like not having enough solvent in the machine can seriously impact on the automatic operation of the machine, putting customers’ clothes at risk and leading to legitimate complaints and claims for compensation.
