An automatic powder coating line with 12 guns typically uses 2.3 to 3.5 m³/min of compressed air, margin included, depending on the guns, booth and powder centre. For a typical line around 3 m³/min, a 22 kW screw compressor such as the S 220 PM, delivering 3.6 m³/min at 8 bar, keeps up. The guns account for only about half of the total: the rest comes from stations that are easy to forget.
For manual booths and the general rules of the trade, see our page on the compressor for powder coating. Here we work through the calculation for an automatic line.
What uses air on a line
- Automatic guns on the booth's gun movers: conveying, dosing and electrode rinsing air, roughly 80 to 150 l/min each as a guide.
- Manual touch-up guns, often one or two at the booth entrance.
- Filter cleaning pulses on the booth's cartridges or after-filters. On an automatic booth, this weighs more than on a manual one.
- The powder centre: hopper fluidising, sieve, transfer and recovery pumps.
- Part blow-off before coating, and blow guns at colour change.
All these values are orders of magnitude. Collect the figures from your equipment manuals before ordering.
The calculation, step by step
Example of a line with 12 automatic guns and 2 touch-up guns:
- Automatic guns: 12 × 120 l/min = 1,440 l/min
- Touch-up guns: 2 × 120 l/min = 240 l/min
- Booth filter cleaning, average: 300 l/min
- Powder centre: 200 l/min
- Blow guns: 2 × 200 l/min × 50% use = 200 l/min
- Total: 2,380 l/min
- 25% margin for leaks and future changes: 2,380 × 1.25 = 2,975 l/min, or about 3.0 m³/min
With guns at 80 l/min, the same calculation gives about 2.3 m³/min. At 150 l/min, it rises to around 3.5 m³/min. Almost all the spread comes from the guns: their manual is the most important figure to obtain.
On pressure, powder coating equipment usually needs a supply of around 6 bar. A compressor set to 8 bar keeps a margin for losses across the dryer, the filters and a network that runs the length of the line. To read pressure correctly on your installation, see how to calculate compressor pressure.
Which compressor for your line?
- A line around 3 m³/min: the S 220 PM, 3.6 m³/min at 8 bar, with a dryer, a receiver and fine filters. It runs at variable speed: during a colour change, when the guns stop, it slows down instead of idling.
- A shift-run line that must never run short of air: two machines rather than one. Two K 150 units (2 × 2.2 m³/min at 8 bar), each with built-in dryer and filtration, or an S 220 PM paired with an S 150. If one machine is being serviced, the other keeps the line running at reduced output.
- Two lines or more: the S series goes up to 132 kW on request. These installations are handled as an industrial project.
Variable or fixed speed matters a great deal on a line whose demand changes with the parts: see variable speed or fixed speed.
Traps on an automatic line
- Colour change peaks. Cleaning the booth and guns with blow guns creates a short, sharp peak. A well-sized receiver absorbs it: the air receiver size calculator gives a starting volume.
- Leaks. A long line multiplies fittings and hoses. A few leaks can cost the equivalent of one gun running non-stop. See how to detect and repair leaks and put a figure on them with the leak cost calculator.
- Saturated filters. On a shift-run line, filter elements reach the end of their life quickly. A clogged filter costs pressure at the guns and lets oil through. Our screw compressors are oil-lubricated: fine filtration is not optional in powder coating.
- Compressor servicing. First service at 500 hours, then every 1,500 hours. On two shifts, these come round often: plan them during line stoppages.
To estimate the line's energy bill, use the compressor electricity cost calculator. Then send us your equipment list and number of shifts with a quote request: we will check the calculation with you.
For your trade: Compressor for powder coating.