A compressor installed inside a stone workshop draws in stone dust with the air it compresses: its intake filter clogs, its cooler fouls and it runs hot. The rule is to place it in a separate, ventilated room, with an air intake on the clean side, and to check the air filter between services. On the workshop side, compressed air must never be used to blow silica dust off clothing or the bench.
This article deals with dust. For choosing the compressor to suit your tools, see our page on the compressor for stonemasons.
Where does silica dust come from in a stone workshop?
Granite, sandstone, slate and above all the engineered quartz used for worktops contain crystalline silica. Carving with a hammer, dry sanding, cutting with an angle grinder and sandblast engraving produce a very fine dust. The finest particles stay airborne for a long time and settle everywhere, including in neighbouring rooms.
Respirable crystalline silica is dangerous to the lungs. Preventing people's exposure relies on wet working, extraction at source, ventilation and protective equipment: follow the prevention rules in force for your trade. Here, we deal with what concerns compressed air: the machine and the way it is used.
What does stone dust do to a compressor?
A 7.5 kW screw compressor draws in about 1 m³ of ambient air per minute, more than ten thousand cubic metres a month for a single shift. In dusty air, that is a lot of dust reaching the machine.
- The intake filter clogs. The compressor draws in less air, the air flow falls and the pressure builds more slowly. A clogged air filter is one of the first causes of lost air flow.
- Fine particles get through. Whatever passes a saturated or badly fitted filter ends up in the screw's oil. The oil becomes loaded, wears faster, and the air/oil separator clogs.
- The cooler fouls. Dust sticks to the fins of the oil and air cooler. The heat can no longer escape, the temperature rises and the compressor trips on a fault. Our article on the overheating compressor lists the other causes.
- The electrical cabinet and the motor collect dust too, which holds in heat and moisture.
Where should the compressor go in a stone workshop?
The best protection is to keep the compressor away from the dust rather than to filter more.
- A separate room, closed off from the workshop, with a door that does not open onto the carving or engraving area.
- An air intake on the clean side, preferably from outside, away from the dust extractor exhaust and the cabinet outlets. Protect it with a grille against rain and leaves.
- A hot air outlet high up, so that the compressor's heat does not stay in the room.
- Enough space around the machine to clean the cooler and change the filters.
Our articles on the compressor room installation and the compressor room guide give the rules for ventilation and clearances.
If the compressor has to stay in the workshop for lack of space, place it as far as possible from the carving, sanding and engraving stations, never in the airflow of a dust extractor, and double the frequency of the checks below.
What servicing in a dusty workshop?
The basic schedule stays the same: first service at 500 hours, then every 1,500 hours, with the matching service kit. Dust adds checks between service intervals.
| Check | Indicative frequency in a stone workshop |
|---|---|
| Condition of the air filter | every week in a dusty workshop |
| Cleaning the cooler, machine stopped | every month, more often if deposits are visible |
| Operating temperature on the display | every day, at a glance |
| Grille on the room's air intake | every month |
| Draining and automatic drain | every week |
The cooler is cleaned with the machine stopped and locked out, blowing from the inside outwards, while wearing respiratory protection since it is stone dust you are stirring back into the air. The screw compressor maintenance guide sets out the procedures.
How much air for the dust extractor?
Many engraving cabinets and sanding stations are connected to a dust extractor whose filters are cleaned by pulses of compressed air. This pulse cleaning uses around 100 to 300 l/min depending on the size of the extractor, as a rough guide: take the value from its manual.
Example of a memorial masonry workshop with an engraving cabinet and a dust extractor:
- Engraving, 3 mm nozzle: 600 l/min.
- Dust extractor pulse cleaning: 200 l/min.
- Wet polisher: 600 l/min.
- Subtotal: 1,400 l/min.
- 25% safety margin: 1,750 l/min.
- 20% expansion margin: 2,100 l/min (around 74 CFM).
The K 150, 2.2 m³/min at 8 bar, covers this need. Without the polisher, the total with margins drops back to 1,200 l/min, within reach of the K 110. Our article on bag filter pulse cleaning sets out the calculation.
How do you use the blow gun without stirring the silica back up?
The blow gun is the most common tool in the workshop, and the most misused when it comes to stone dust. Blowing off a bench, a piece or clothing scatters fine silica into the air, where it will be breathed in.
- Never blow dust off yourself or a colleague, or off work clothing. A jet of compressed air aimed at the body is dangerous in itself too.
- Prefer vacuuming to clean stations and pieces, and washing down with water where possible.
- Keep the blow gun for drying a wet piece or clearing an engraving, with a low-noise nozzle and reduced pressure at the station.
Air from a lubricated compressor is not breathing air. If you use air-fed protective equipment, its supply needs specific treatment: define it with our technicians and the equipment manufacturer, using ISO 8573-1 air quality as a basis.
Do you need an audit of the installation?
If your compressor runs hot, loses air flow or needs its filter changed far more often than expected, a compressed air audit by our technicians pinpoints the cause: a badly placed air intake, a room that is too small, a leaking network.
For a new project, enter your tools in the configurator, then describe your room with a quote request.
For your trade: Compressor for stonemasons, memorial masons and worktop fabricators.