For one milking robot, a 5.5 kW screw compressor such as the S 55 (0.6 m³/min at 8 bar) is enough, with an air receiver and a dryer. For two robots, the 7.5 kW K 75 4-in-1 (1.1 m³/min) is the usual choice. For three robots, move up to the 11 kW K 110 (1.7 m³/min). These guidelines are based on an indicative consumption of around 300 l/min per robot: your robot's manual gives the real figure.
The role of air across the whole farm, from the robot to the cow shed gates, is covered on our page on the compressor for dairy farms and milking robots. Here we do the calculation.
Where do you find your robot's consumption?
A milking robot's air consumption varies with the model, the year, the options (teat cup rinsing, pneumatic or electric gates, concentrate feeding) and the number of milkings per day. There are three sources, from most to least reliable:
- The robot's manual or installation sheet, which gives a consumption in l/min or m³/h and a minimum pressure.
- The robot installer, who knows the exact configuration of your milking box.
- An on-site measurement, if a compressor is already in place. A compressed air audit gives the real flow, day and night.
As a guide, a robot uses around 200 to 400 l/min on average, with peaks when the arm moves and the gates open. If your data sheet gives m³/h, divide by 60 and multiply by 1,000 to get l/min, or use our flow and pressure converter.
The step-by-step calculation
Our configurator follows four steps.
Step 1, continuous equipment. The robot milks day and night, so it is counted at 100%.
Step 2, equipment used in bursts. Sort gate, automatic gates, workshop blow gun: they only use air for a few seconds at a time. The receiver absorbs these peaks, so they are counted at 50%.
Step 3, the safety margin. Add 25% for leaks, wear and the robot's peaks.
Step 4, expansion. Add 20% for future equipment. On a growing farm, that is often one more robot.
One milking robot
Guide values, to be replaced with those in your manuals:
- robot: 300 l/min, counted at 100%: 300 l/min
- sort gate: 50 l/min, counted at 50%: 25 l/min
- blow gun: 150 l/min, counted at 50%: 75 l/min
- total: 400 l/min
- with 25% safety: 500 l/min
- with 20% expansion: 600 l/min
The S 55 delivers 0.6 m³/min at 8 bar, or 600 l/min. It covers the demand, with nothing to spare. It is a standalone screw compressor, so add an air receiver of about 200 L (one litre for every 3 l/min of demand) and a dryer. If your robot is at the top of the range, or if a second robot is planned, go straight for the K 75.
Two milking robots
- two robots: 2 × 300 = 600 l/min
- sort gate: 25 l/min
- blow gun: 75 l/min
- total: 700 l/min
- with 25% safety: 875 l/min
- with 20% expansion: 1,050 l/min
The K 75 delivers 1,100 l/min at 8 bar. It combines the variable speed screw compressor, a 420 L air receiver, the refrigerated dryer and the filtration. One machine to set down and connect, which makes installation in a farm plant room simpler.
Three milking robots
- three robots: 3 × 300 = 900 l/min
- two sort gates: 2 × 50 × 50% = 50 l/min
- blow gun: 75 l/min
- total: 1,025 l/min
- with 25% safety: 1,281 l/min
- with 20% expansion: 1,538 l/min
The K 110 delivers 1.7 m³/min at 8 bar, or 1,700 l/min, with a 340 L air receiver. Beyond that, or if your robots use more than 400 l/min each, the K 150 delivers 2.2 m³/min.
Summary
| Installation | Demand with margins (indicative) | Recommended model |
|---|---|---|
| 1 robot, 1 sort gate | about 600 l/min | S 55 with receiver and dryer, or K 75 |
| 2 robots, 1 sort gate | about 1,050 l/min | K 75 |
| 3 robots, 2 sort gates | about 1,540 l/min | K 110 |
| 3 high-consumption robots or 4 robots | to be calculated | K 150 or several machines |
One large compressor or one per robot?
Some farms fit a small compressor for each robot. It is simple, but each robot then depends on a single machine, with nothing to take over. A central compressor sized for all the robots, backed by a second compressor that can take over, gives better security: if one stops, the other supplies everyone. Our article backup compressor and keeping the robot milking compares the set-ups.
The sizing traps
- Forgetting the pressure. A compressor's flow is given at a pressure: 1.1 m³/min at 8 bar for the K 75. If your robot needs more than the pressure you can set, the calculation no longer holds. Also allow for the losses in the dryer, the filters and the pipework.
- Forgetting leaks. A cattle building has lots of fittings, hoses and cylinders exposed to knocks. A leak of a few millimetres uses as much air as a piece of equipment. Our compressed air leak cost calculator gives the order of magnitude.
- Connecting the workshop to the same network. An impact wrench or a grinder used in the workshop can make the pressure drop during milking. Separate the workshop with a valve and a pressure regulator, or give it its own compressor.
- Choosing a piston compressor. It is not built to run day and night. A milking robot needs a screw compressor.
For the final choice, enter your robots and gates in the configurator, then send us your robots' manuals with a quote request.
For your trade: Air compressor for dairy farms and milking robots.