A compressor that draws in flour-laden air clogs its intake filter far faster than one in a clean room: it runs hot, loses flow and loads its oil with dust. The rule is simple. Install it outside the bakehouse, in a clean, ventilated room whose air comes from a flour-free area, and never blow flour around with a blow gun, because once airborne it forms a cloud of combustible dust. A K 75 draws in around 1,100 litres of air per minute at full load, and that is the air you have to keep clean.
The air demand of the whole bakery is covered on our page on the compressor for bakeries and patisseries. Here we focus on flour and the air intake.
Why does flour damage a compressor?
A screw compressor draws in room air, filters it, then compresses it with oil that cools and lubricates the screws. Flour causes three problems:
- The intake filter clogs. Flour is a very fine powder that packs into the filter media. The compressor draws in less air, so it delivers less and works harder.
- The machine runs hot. Flour also settles on the cooler. Add the heat of the bakehouse and the compressor trips on high temperature, often in summer, in the middle of production. Our article on the compressor that overheats covers this fault in detail.
- The oil gets contaminated. Dust that gets past the filter ends up in the oil and in the air/oil separator, which then wears faster.
Dusting tables with flour, mixing and sifting are the times when there is most flour in the air. In patisserie, icing sugar and ground almonds cause the same problems.
Why should you never blow flour away?
Blowing flour off a machine or a worktop puts it back into suspension in the air. There are three consequences:
- the risk of a dust explosion: flour is a combustible dust. As a cloud, in contact with an ignition source such as an oven or an electrical spark, it can ignite suddenly;
- contamination: the flour settles on finished products, packaging and other machines;
- health: breathing in flour dust irritates bakers' airways.
Clean flour up with a vacuum cleaner suitable for dust, and with a brush or a scraper. Keep the blow gun for parts with no dust on them, outside production. Areas where flour regularly forms a cloud, around a silo, a sifter or a hopper, fall under a risk assessment carried out by your safety manager, sometimes under the ATEX regulations. Our article on ATEX zones in silos sets out the principle: the compressor always stays outside these zones.
Where should the compressor go in a bakery?
| Location | Verdict | Why |
|---|---|---|
| In the bakehouse, next to the mixer | avoid | airborne flour, heat from the oven |
| In the prover or near the oven | avoid | heat and humidity |
| Flour store | avoid | dust at every delivery |
| Cellar or separate ventilated plant room | recommended | clean air, stable temperature |
| Outbuilding against the main building | recommended | clean air, if the room is frost-free |
If you have no room at all, a ventilated enclosure outside the bakehouse or a light outdoor shelter are still possible, and our technicians help you choose.
How much air does it take to ventilate the room?
The compressor needs air for two reasons: the air it compresses and the air that cools it. The second is far larger. The step-by-step calculation for a 7.5 kW K 75 (order of magnitude; the installation manual is the reference):
- Almost all the electrical energy consumed turns into heat, so allow around 7.5 kW to remove.
- A temperature rise of 10 °C between the air entering the room and the air leaving it is generally accepted.
- To carry away 1 kW with a 10 °C rise, you need about 300 m³ of air per hour.
- Ventilation flow: 7.5 × 300 = 2,250 m³/h, or about 37,500 l/min.
- Compare that with the compressed air itself: 1,100 l/min, thirty times less.
So it is the ventilation air, far more than the air drawn in by the screw element, that carries flour into the compressor. Put the room's air inlet on the side opposite the bakehouse, ideally on an outside wall, protected by a grille. Send the hot air outside, away from the inlet. Our article on the compressor room gives the rules for ventilation and grille sizing.
Do you need a special filter on the air intake?
If the room is well placed, the original air filter is enough. You simply have to check it more often than elsewhere:
- look at it every time you go into the room, once a week for the first few months, to learn how quickly your installation fouls it;
- replace it as soon as it looks grey or packed, without waiting for the service interval;
- never clean it with a blow gun: you drive the dust into the media and spread it around the room.
A pre-filter on the room's inlet grille catches most of the dust when the surroundings are heavily loaded. It has to be cleaned or replaced regularly, otherwise it chokes the ventilation and the compressor overheats.
Other good habits
- The cooler. Have it dusted at every service, at 500 hours and then every 1,500 hours. The service kits group the air filter, oil filter and separator.
- Doors. Keep the door between the bakehouse and the compressor room closed.
- Flour deliveries. Unloading sacks or filling a silo pneumatically releases a lot of dust, so keep the room's air inlet away from that area.
- Checking air at the station. A compressor that draws in flour also loads the network filters. For stations in contact with the product, see our article compressed air in contact with dough, which filtration.
For an industrial line with a flour silo, our article on the compressor for an industrial bakery completes these rules. If you are unsure about the location, our technicians can come and carry out a compressed air audit. To choose the model, enter your machines in the configurator or send us a plan of your bakery with a quote request.
For your trade: Air compressor for bakeries, patisseries and viennoiserie.