Frequently the question comes up in drycleaning circles on problems with cleaning, odors, cycle times, color of separator water, and other things that can pop-up from time to time. Hopefully if you are having problems with your drycleaning machine you can find the answer here.
There are several problems that can result in slow drying regardless of the solvent used. Generally the steam pressure is set between 60 and 80 psi going into the heating coil. The heat generated by this amount of steam pressure (Between 308 and 324 degrees F.) and is regulated by the thermostat controlling the maximum air temperature as it is leaving the drying chamber.
The most common problem is that daily, or more often, maintenance has not been done or has been done incorrectly. Lint has been allowed to get past the lint filter and found its way to the cooling coils and can impact on them to make a wall that air has a hard time getting through the coils in order to allow for a sufficient airflow to get back to the clothing. Frequently when this happens the drain to the water separator is partially clogged and will not allow the condensed solvent to drain to the water separator. The result of having lint blocking the steam coils can frequently be noticed by observing the sight glass after the drying cycle has stopped and if there are a few drips this would indicate the drain is plugged and needs to be cleaned out and the coils inspected.
Slow drying can also be caused by improper electrical connections which can actually make the fan run backwards and should always be suspect if machine has been moved or electrical work has recently been done and at the same time the drying has slowed.
Overloading of the wash wheel is another common cause of slow drying. The rated capacity of a dry-to-dry machine should be reduced 20% in order to allow sufficient tumbling action of the garments. A drycleaning machine can wash more garments than it can adequately and efficiently dry in the same wash wheel space.
High NVR, or non-volatile residue can also cause slow drying because the NVR is basically oils and greases which do not evaporate easily. Too much anionic detergent is also a NRV and should be distilled from the solvent then a reduced amount either added by hand or injected.
Solutions to Slow Drying
The entire drying chamber, including the wash cylinder, the air passages, cooling and heating coils and inside of the condensing (cold side) chamber should be inspected and thoroughly cleaned with compressed air, and when coils are removed they can be taken to a car wash and cleaned there. There are usually Freon quick disconnect fittings that allow the refrigerant coils to be removed and re-installed with minimal loss of refrigerant. It is a good idea to also check for metal integrity as corrosion can take place especially if distillation has not been proper and/or generic perchloroethylene has been used that does not have inhibitors and stabilizers added to the new perc. If you notice a green or blue cast to your separator water this is an indication of copper corrosion inside the drycleaning machine.
In order to have the most efficient drying the drycleaning machine has to be clean throughout the inside of the machine. With too much detergent or sizing lint can build up within the shell between the rotating cylinder and the cylinder housing. All coils and air passages must be kept immaculately clean and lint bags or filters should be cleaned after every load on some machines and every other load on others.
Steam pressure should be between 60 and 80 psi or as stated by the manufacturer.
Proper Cleaning of the Still
At the end of the day the still should be boiled down, steam swept, cooled and emptied by draining and raking out all of the muck that is possible. With most all solvents the steam pressure to the still can be as low as 20 psi for hydrocarbon (with sufficient vacuum) or as high as 40 to 45 psi when distilling perc. The outlet water temperature is usually around 90 to 100 degrees F. Frequently the still will not be drained and cleaned at the end of the day. It needs to be cleaned at least twice a week then completely cleaned once a week minimum.
After the still has been cleaned it can still form a residue of baked on detergent, sizing and NVR. This forms an insulation over time and the still will become slower and the natural thing for the operator is to increase the steam pressure. This will do two things. It can break down the solvent and if it is perc it can become corrosive. The second thing it can do is make the residue more baked on which makes the still work more slowly.
If the bottom of the still is ground off with a grinding wheel or wire brush it will wear away the metal which can lead to failure. The easiest and safest way is to start with a cold still and pour in a mixture of three gallons of water and one pound of tri sodium phosphate which can be purchased at a hardware store. Normally this is what is used for cleaning concrete.
When the mixture is in the still then you can add water to the still to just above the lint line or where there is a distinct separation of color of the steel inside the distilling unit.
After the water is in the still then very slowly add steam until the water just begins to move then shut the steam off and let it sit for a couple or three hours. At the end of the time drain the still and check the bottom and sides for a clean look. If there is still a residue then the procedure will need to be done again.
Remember that this water is now hazardous waste and must be handled accordingly. Dry the still out with rags and when completely dry it is ready to use again. This procedure will normally need to be done every three or four months. If there is a green or blue cast to the separator then each time the still is cleaned a cup of TSP can be added to container with a pint of water and thoroughly mixed then added to the still. When starting the still it should be watched and the steam stopped if it appears it will boil over due to the water that was added. After stopping the steam entering the still let it cool for a few minutes then add a small amount of steam and the water will boil off rapidly and when it is gone the full regulated steam may then be started.