Oil stains on linen coming out of a folder or a press often come from the compressed air that blows on or touches the textile. The most common causes are missing or saturated filtration, oily condensate that is not drained, and a worn air/oil separator in the compressor. The fix is a dryer, cascade fine filters, automatic drains and regular maintenance. The air needs of the whole plant are covered on our page on compressors for textiles and laundries.
Where does the oil in the air come from?
Our screw compressors are oil-lubricated. The oil cools and seals the screw element, then the air/oil separator recovers it. At the outlet, the air still carries a few ppm of oil: 3 to 5 ppm according to the S Series data sheets. On a white sheet, even a small amount shows if it builds up in one spot.
Four situations raise the oil content at the point of use:
- No fine filter, or a fine filter with a saturated cartridge.
- Condensate left standing in the receiver, the dryer or low points in the network. This water is laden with oil. When the flow increases, it is carried towards the machines.
- A worn air/oil separator in the compressor. It lets more oil through. Our article on the air/oil separator lists the signs of wear.
- A compressor that runs hot: oil that is too hot separates less well. See compressor overheating, causes and checks.
Not every stain comes from the air. Grease from a cylinder, a lubricator set too high on a machine or a dirty roller can also mark the linen. The test below settles the question.
The white cloth test
Take a clean white cloth and a blow gun. Blow for 30 seconds at each of these points, holding the cloth a few centimetres away:
- At the compressor outlet, before air treatment.
- After the dryer and filters.
- At the farthest point of the network.
- At the connection of the folder or press that leaves stains.
If the cloth stays clean after the filters but gets marked at the machine, the problem is in the network: an undrained low point or dirty pipes. If it gets marked straight after the filters, the filtration is missing, undersized or saturated. If it stays clean everywhere, look at the machine itself.
The treatment chain to install
To prevent stains, the order is:
- Refrigerated dryer: it removes the water that carries the oil.
- General filter: it stops droplets and particles.
- Fine filter: it captures oil aerosols.
- Activated carbon filter at the stations that blow directly on the linen, for oil vapour.
- Automatic condensate drains on the receiver, the dryer, each filter and the low points.
The target air class under ISO 8573-1 is defined with our technicians, based on what your machine makers require. Our ISO 8573-1 air quality guide explains these classes.
Sizing the filters: an example
Filters are chosen on the compressor flow. An undersized filter saturates quickly and lets oil through. A laundry example, with indicative values:
- Valves and cylinders of the tunnel washer: 150 L/min.
- Extraction press: 200 L/min.
- 2 folders at 300 L/min: 600 L/min.
- 2 ironing presses at 200 L/min, which do not close together: 200 L/min.
- Total: 1,150 L/min. With a 20% margin: 1,380 L/min, or 1.4 m³/min.
The K 110 delivers 1.7 m³/min at 8 bar with a 340 L receiver, dryer and filtration built in and sized for its flow. If the laundry already has a dryer, the S 110 delivers the same flow: check that the existing filters can handle 1.7 m³/min. Add the activated carbon filter at the folders that blow the linen.
Maintenance that keeps the stains away
- Replace cartridges on schedule or when the clogging indicator calls for it.
- Check the drains every week: a stuck drain sends condensate back into the network. Our article on water in compressed air lists the drain points.
- Follow the compressor service plan: first service at 500 hours, then every 1,500 hours. The separator is one of the parts to watch. See when to service a screw compressor.
- Keep the compressor cool, away from dryers and ironers, and blow out its cooler: lint blocks it.
Send us the list of your machines and the result of the cloth test in a quote request: we will define the dryer and filtration with you.
For your trade: Compressor for the textile industry and laundries.