A spotting gun uses around 100 to 150 l/min while it is blowing, at 3 to 6 bar depending on the setting. Because it blows straight onto the fabric, the air must arrive dry and free of oil: a refrigerated dryer, a fine filter and an activated carbon filter as close to the table as possible. Without them, the gun leaves water or a greasy mark exactly where you have just removed a stain.
The air needs of the whole shop are worked out on our page compressor for dry cleaners. Here, we look closely at the spotting table.
What is air used for on a spotting table?
A spotting table combines several functions: a vacuum board, a steam supply, sometimes a chemical spray gun, and an air gun. Compressed air is used to:
- drive the spotting agent and the dissolved soiling out of the fibres, towards the vacuum board;
- dry the treated area to avoid the water ring that forms when the edge of the damp area dries slowly;
- spray certain chemicals, on tables fitted with an air-fed chemical gun.
In all three cases, the air touches the garment. Its quality matters as much as the quality of the chemical.
What flow and pressure for a spotting gun?
The figures below are indicative only. Refer to your table's manual.
| Setting | Pressure at the gun | Consumption of around |
|---|---|---|
| Silk, fine fabrics, delicate area | 2 to 3 bar | 80 to 100 l/min |
| Everyday use | 4 to 5 bar | 100 to 130 l/min |
| Heavy fabrics, fast drying | 6 bar | 130 to 150 l/min |
The compressor stays set at around 8 bar. The table has its own regulator: you lower the pressure at the station, not at the compressor, so as not to starve the press working next to it.
The gun blows in bursts: a few seconds, a pause, a few more seconds. In the calculation, it is counted at 50% of its consumption, because the air receiver supplies the peaks.
Example for two spotting tables in a central finishing plant:
- Two guns at 120 l/min, counted at 50%: 2 × 60 = 120 l/min.
- With a 25% safety margin: 150 l/min.
- With 20% for one more table: 180 l/min.
These 180 l/min are added to the needs of the presses and form finishers. On its own, spotting weighs little: the problem is the quality of the air, not its volume. Our flow and pressure converter helps if your manual gives m³/h or CFM.
Why the air must be dry
As it leaves the compressor, the hot air is loaded with water vapour. As it cools in the air receiver and the pipes, it gives that vapour back as droplets. Without a dryer, these droplets reach the gun in spurts, especially in the morning when the network is cold, or after a break.
On a spotting table, a drop of water blown onto silk or wool leaves a water ring. It also carries the dissolved soiling back towards the edge of the treated area. A refrigerated dryer brings the dew point down to a few degrees: water no longer condenses in the shop's network. Our guide to the pressure dew point explains this idea, and our article which air dryer to choose compares the types.
Why the air must be clean
Our screw compressors are lubricated. The air/oil separator holds back most of the oil, but the outlet air still contains a few ppm: 3 to 5 ppm according to the S series data sheets. On a white blouse, a greasy mark in the middle of a spotted area is the worst possible result.
The chain to install for the spotting table:
- Refrigerated dryer, at the compressor outlet or built into a 4-in-1.
- General-purpose filter, for particles and droplets.
- Fine filter, for oil aerosols.
- Activated carbon filter at the station, just before the gun hose, for oil vapours and odours.
- Automatic condensate drain on the air receiver, the dryer and each filter.
The air class to aim for under ISO 8573-1 is defined with our technicians and the table manufacturer. Our guide to ISO 8573-1 air quality explains how to read these classes.
Which compressor to supply the spotting tables?
The gun does not decide the model: it is added to everything else. In a high-street dry cleaner's, the S 55 (0.6 m³/min at 8 bar) covers one press, one topper and one spotting table, provided an air receiver, a dryer and filters are added. The K 75 (1.1 m³/min at 8 bar) has the 420 L air receiver, the refrigerated dryer and the filtration built in: only the activated carbon filter at the station remains to be fitted.
Settings and pitfalls at the station
- The hose. An old or contaminated hose releases dust and oil. Replace it when you install the new filtration, otherwise it pollutes the clean air you have just obtained.
- The first blast. After a night or a weekend, blow for a few seconds into the vacuum board, away from the garment, before starting work.
- A saturated filter at the station. An activated carbon filter gives no warning when it is full. Replace it when the manufacturer says, even if it looks clean.
- Too much pressure. On a fine fabric, 6 bar can distort the fibre or spread the stain. Start low and increase if needed.
- A compressor next to the steam generator. A compressor drawing in hot air from the steam generator produces more water and wears out the dryer.
Enter your tables, presses and form finishers in the configurator, then send your spotting table's manual with a quote request: we will define the point-of-use filtration with you.
For your trade: Compressor for dry cleaners and dry cleaning shops.