A pneumatic sort gate or automatic gate uses little air: around 50 l/min while it moves, as a guide, for a few seconds each time a cow passes. The milking robot's compressor supplies it without difficulty. The real issue lies elsewhere: these gates are far from the compressor, in a cold and dirty cow shed, and a pipe that freezes or a cylinder that leaks is enough to block the herd's traffic.
Choosing the compressor for the whole farm is covered on our page on the compressor for dairy farms and milking robots. Here we talk about everything around the robot that uses air.
Which pneumatic equipment is found on a dairy farm?
- The sort gate. After milking or at the exit of the feeding area, it sends a cow to the cubicles, the treatment pen, the insemination area or the dry cow pen, as instructed by the robot's software.
- One-way or controlled cow traffic gates, which organise guided traffic between the cubicles, the feed fence and the robot.
- Collecting yard barriers and the entry and exit gates of the milking parlour.
- Feed barriers with pneumatic locking, on some installations.
- Scrapers and some slurry channel flaps, when they are pneumatically operated.
- Cylinders in a conventional milking parlour: automatic cluster removal, breast rails, rapid exit.
Each manufacturer gives the consumption and pressure of its equipment in the manual. The values in this article are orders of magnitude.
How much air do the gates need?
On each stroke, a cylinder uses the volume of its bore multiplied by the pressure. The detailed calculation is in our article on pneumatic cylinder air consumption. Since a gate only moves for a few seconds each time a cow passes, its average consumption is low. Our configurator counts this equipment at 50% of its peak consumption, because the air receiver absorbs the bursts.
Example of a farm with two robots, two sort gates and two automatic gates (guide values):
- Two robots, continuous: 2 × 300 = 600 l/min.
- Four gates, in bursts: 4 × 50 × 50% = 100 l/min.
- One workshop blow gun, in bursts: 150 × 50% = 75 l/min.
- Total: 775 l/min.
- With a 25% safety margin: 969 l/min.
- With 20% expansion: 1,163 l/min.
The K 75 delivers 1,100 l/min at 8 bar. It covers the real demand with its safety margin (969 l/min), but not the whole expansion reserve. If a third robot is planned, the K 110 (1.7 m³/min) is the more sensible choice. Above all, you can see that the gates count for little next to the robots: it is the robots that size the compressor.
Do the gates need a separate compressor?
Generally, no. A central compressor supplying both robots and gates is simpler to maintain. There are two exceptions:
- A very distant gate, in another building, where a long pipe exposed to the cold would be costly. A small local compressor, such as the S 55 with its receiver, may then be justified. But it also has to be serviced and protected.
- A conventional milking parlour and a robot on the same site, with very different hours. The parlour compressor can act as a backup for the robot, and vice versa, if the two networks are linked by a valve.
How do you lay the network in the cow shed?
- Adequate diameter. A pipe that is too narrow makes the pressure drop at the end of the network when several gates move at once. Our pressure drop tool checks the diameter for the length and the flow.
- High, protected pipework. Out of reach of the animals, the loader bucket and the scraper. Cows scratch themselves on anything that sticks out.
- Corrosion-resistant material. Ammonia and humidity attack bare steel. Choose pipes designed for compressed air and resistant to corrosion.
- An isolating valve for each piece of equipment, so you can work on a gate without cutting the air to the robot.
- A filter-regulator before each gate, set to the pressure in the manual. A gate that slams too hard wears its hinges and frightens the animals.
Our article on the leak-free compressed air network gives the installation rules.
Typical faults and their causes
| Symptom | Likely cause | Solution |
|---|---|---|
| Sort gate stuck on winter mornings | Frozen water in the pipe or the cylinder | Dry air with a sub-zero dew point on the cold branch, drains at the low points |
| Slow gate that does not close fully | Pressure too low at the end of the network | Check the pipe diameter and the regulator setting |
| Hissing near a gate | Leak at a fitting or a damaged hose | Replace the part, check the fixings |
| Sticking or rusty cylinder | Water and sludge in the air | Dryer, drain, filter before the gate |
| Compressor running a lot at night | Leaks in the cow shed network | Leak detection, valves closed on unused equipment |
Freezing gates are covered in detail in our article dry air and freezing in the cow shed.
Leaks, the hidden enemy on a livestock farm
A cow shed network has many fittings, hoses and cylinders exposed to knocks, muck and cold. Leaks are common, and they cost money day and night since the compressor never stops. A single leak can use as much air as a gate. Walk round the network when the shed is quiet, with the compressor running, and listen. Our article on detecting leaks gives the method, and our compressed air leak cost calculator puts a figure on their weight over a year.
What air quality for the gates?
The gate cylinders touch neither the milk nor the animals. Dried and filtered air, like that from the K series, suits them. Our compressors are oil-lubricated, and the outlet filtration captures carried-over oil. The key point remains water: on a branch that runs through the cold, the dew point must be clearly lower than the lowest winter temperature.
To size your installation with your robots and your gates, use the configurator, then send us the list of your equipment with a quote request.
For your trade: Air compressor for dairy farms and milking robots.