At the dry cleaner's, a water ring after spotting or a small grey mark after pressing often comes from the compressed air: water that has not been drained, or oil that has got through a missing or saturated filter. To prevent it, you need a dryer, a fine filter, an activated carbon filter at the spotting gun and automatic drains that actually work. The diagnosis takes half an hour with a white cloth.
The air needs of the trade are set out on our page compressor for dry cleaners. For industrial laundries, with folders and tunnel washers, our article oil stains on laundry covers the same problem on a larger scale. Here, we stay with the dry cleaner's.
Water or oil: how do you recognise the stain?
| Stain | Appearance | Probable cause on the air side |
|---|---|---|
| Light water ring with a sharp edge | Appears as it dries, on silk, wool, viscose | Drop of water at the spotting gun |
| Small droplets after the first blast of the morning | Disappear as they dry, sometimes leave a ring | Condensate built up overnight in the network |
| Grey or yellowish mark, slightly greasy | Does not go when it dries | Oil carried by the air |
| Repeated mark in the same place after pressing | Always on the same area of the garment | Press padding soaked through, or cylinder exhaust |
Not every stain comes from the air. A poorly flushed spotting agent, wet steam from the generator or worn padding can leave marks too. The test below lets you decide.
The white cloth test, dry cleaning version
Take a clean white cloth. Blow for 30 seconds, a few centimetres from the cloth, at each of these points:
- At the compressor outlet, before the dryer if it is separate.
- After the dryer and the filters.
- At the spotting gun, on the first blast of the morning, then in the middle of the day.
- At the air inlet fitting of the press that is leaving marks.
Reading the results:
- Cloth clean after the filters, marked at the gun: the problem lies between the two. An undrained low point, a dirty hose, or a filter at the station that is saturated or missing.
- Cloth marked straight after the filters: the filtration is missing, undersized or saturated, or the dryer is not working.
- Cloth damp only in the morning: water is condensing in the network overnight. Check the dryer and the drains.
- Cloth clean everywhere: look at the spotting agent, the steam generator or the padding.
Where does the water come from?
The air drawn in contains water vapour. Once it has been compressed and then cooled, it gives that vapour back as liquid. A 5.5 kW compressor running all day in a hot, humid dry cleaner's produces several litres of condensate a day. Our condensate volume calculator gives the quantity for your flow and your room.
Without a dryer, this water reaches the stations. With a dryer but a blocked drain, it builds up in the air receiver or a filter and then comes out all at once. Our article water in compressed air goes through the drain points in detail.
Where does the oil come from?
Our screw compressors are lubricated. At the outlet, the air still contains a few ppm of oil: 3 to 5 ppm according to the S series data sheets. Three situations raise this content at the point of use:
- A fine filter that is missing or saturated.
- Oily condensate that sits and gets carried along when the flow increases.
- A worn air/oil separator, or a compressor overheating in a back room that is too hot. Our article oil in compressed air covers these causes in detail.
The filtration to fit in a dry cleaner's
Example calculation for the typical dry cleaner's on our trade page, with indicative figures:
- Machine needs: 350 l/min.
- With a 25% safety margin: 437.5 l/min.
- With 20% for one more machine: 525 l/min.
- The compressor chosen, an S 55, delivers 600 l/min at 8 bar: the dryer and filters are chosen for at least this flow, not for the machines' needs.
A filter chosen too small quickly saturates and lets oil through. The chain, in order:
- Refrigerated dryer at the compressor outlet, or built in if you choose a 4-in-1 such as the K 75.
- General-purpose filter, then a fine filter.
- Activated carbon filter at the spotting gun, the station that blows onto the fabric.
- Automatic condensate drains on the air receiver, the dryer, each filter and the low points of the network.
The air class to aim for under ISO 8573-1 is defined with our technicians. Our guide to ISO 8573-1 air quality explains these classes.
The dry cleaner's network, a forgotten source of stains
- Low points. A pipe that drops down to a press and then rises again holds water. Take the drops off the top of the main pipe.
- Old hoses. After years of condensate, they are contaminated inside. Change them at the same time as the filtration.
- The fall. A network laid with a slight fall towards a drain point gets rid of water instead of holding it.
The maintenance that stops stains coming back
- Every week: press the test button on the drains, and check that the water is discharged.
- When the manufacturer says: change the filter cartridges, even if they look clean.
- Every 1,500 hours, after a first service at 500 hours: service the compressor, including the separator when it is due. See when to service a screw compressor.
Send us the list of your machines and the result of the cloth test with a quote request, or size your installation first with the configurator.
For your trade: Compressor for dry cleaners and dry cleaning shops.