An 8 mm sandblasting nozzle uses about 4,000 L/min at 7 bar, as a guide. Add a margin for nozzle wear and you need at least 5,000 L/min, or 5 m³/min. That is more than a single 22 kW compressor can give: the answer is two screw compressors in parallel, or a larger S series machine on quotation.
Where does the 4,000 L/min figure come from?
A nozzle's air use depends on the area of its bore, so on the square of its diameter. Our page on the sandblasting compressor gives the usual trade figures: about 2,400 L/min for a 6 mm nozzle and 4,000 L/min for an 8 mm nozzle, at around 7 bar. The exact value is in your blast pot manufacturer's documentation. Always start from that.
The jump from 6 to 8 mm catches many people out. The diameter grows by a third, but the bore area grows by 78%: (8 ÷ 6)² = 1.78. A compressor that kept up with a 6 mm nozzle will not keep up with an 8 mm one.
The calculation, step by step
- New nozzle: 4,000 L/min at 7 bar.
- Nozzle wear: the abrasive opens up the bore. An 8 mm nozzle worn to 9 mm uses (9 ÷ 8)² = 1.27 times more air, about 5,060 L/min.
- Working margin: a 25% margin on the new nozzle gives 5,000 L/min. Treat that as the minimum. If you change nozzles late, aim higher.
- Units: 5,000 L/min is 5 m³/min. Our flow and pressure converter also gives cfm if your blast pot's data sheet uses it.
A screw compressor's flow is read at working pressure. Set the machine to 8 bar so that 6 to 7 bar still reaches the nozzle after hose losses.
Which set-up?
Two screw compressors in parallel
The S 220 PM delivers 3.6 m³/min at 8 bar. Paired with an S 150, which delivers 2.2 m³/min at 8 bar, you get 5.8 m³/min. Two S 220 PM units give 7.2 m³/min at 8 bar, with room for a second, smaller nozzle. Both machines are variable speed: the one used as top-up slows down while the nozzle is new and speeds up as it wears. If one is being serviced, the other keeps you blasting with a smaller nozzle.
One larger machine
The S series goes up to 132 kW on quotation. A single machine keeps the installation simple, but you lose the backup if it stops. For a blasting shop that runs all day, we study the choice with you as an industrial project.
A one-off stripping job
For a campaign of a few weeks, we also rent screw compressors from 5.5 to 132 kW, with servicing included and no long-term commitment. Give us the nozzle size and how long the job lasts, and we will suggest the machine.
Traps that come with an 8 mm nozzle
The hose. At 5 m³/min, a hose that is too narrow or too long costs several tenths of a bar, sometimes more. Put the compressors close to the blast pot and use large-bore hose and fittings all the way.
The dryer. It has to handle the combined flow of both machines, not just one. An undersized dryer lets water through, and damp abrasive blocks the metering valve. Pick one from our range of air dryers based on total flow, then add fine filters before any painting.
The power supply. An S 220 PM and an S 150 add up to 37 kW on 380 V three-phase. Have an electrician check the supply line and protection. Our article on the three-phase screw compressor covers the connection.
Dust. Install the compressors away from the blasting area, with a clean air intake, and check the air filter often.
What about switching to a 6 mm nozzle?
It is a real option. A 6 mm nozzle uses about 40% less air, and a single S 220 PM handles it with margin to spare. Stripping is slower, but the installation is simpler. Where time matters, the 8 mm nozzle still pays off as long as the air supply keeps up.
To price your blasting station, go through the configurator or send your blast pot's data sheet with a quote request.
For your trade: Compressor for sandblasting.