To clean the bag filters of a grain silo, the compressor mainly has to hold a steady pressure and deliver dry air. The flow is modest: a dust collector typically needs somewhere around 100 to 300 L/min. A 4-in-1 screw compressor such as the K 75 (1.1 m³/min at 8 bar) supplies two or three filters and part of the handling equipment. Beyond that, move up to the K 110 or the S 110.
This article covers filter cleaning only. For every air need on a grain intake site (cylinders, dryer, workshop), see our page on the compressor for grain silos.
How does pulse-jet cleaning work?
Each row of bags has its own solenoid valve and blow pipe. The sequencer opens the valves one after another, for a fraction of a second. The air comes from a small tank mounted on the filter, the header, which refills between two pulses.
In practice, the compressor never sees the peak of each pulse. It sees the average refill of the header. That average flow is what you need to calculate.
The calculation, step by step
- Find the air used per pulse in the dust collector manual, in litres of free air.
- Count the pulses per minute: 60 divided by the interval between two pulses, in seconds.
- Multiply, then add up the filters that run at the same time.
- Add a 25% margin for faster cycles at peak intake, diaphragm wear and leaks.
Example, figures for guidance only. A silo has three dust collectors.
- Intake pit: 25 L per pulse, one pulse every 10 seconds, so 6 per minute. 6 × 25 = 150 L/min.
- Elevator boot: 20 L per pulse, every 12 seconds, so 5 per minute. 5 × 20 = 100 L/min.
- Truck loading: 25 L per pulse, every 10 seconds. 150 L/min.
Total: 400 L/min. With a 25% margin: 500 L/min, or 0.5 m³/min. If the same compressor also drives around twenty gate cylinders, allow roughly 100 L/min more: 600 L/min.
If the manual gives the consumption in Nm³/h, our flow and pressure converter turns it into L/min.
Which compressor for how many filters?
| Case | Need (margin included) | Suggested model |
|---|---|---|
| One dust collector only | 200 to 400 L/min | S 55 with receiver and dryer, or a complete K 75 |
| Two or three filters plus cylinders | 500 to 1,000 L/min | K 75, 1.1 m³/min at 8 bar, 420 L receiver |
| Several filters, grain dryer and workshop | 1,000 to 1,600 L/min | K 110, or S 110 if the site already has a receiver and dryer |
The S 55 gives 0.6 m³/min at 8 bar: enough for one filter, but it comes without a receiver or dryer. The K 75 combines compressor, receiver, refrigerated dryer and filtration. Both run at variable speed, which follows a cyclic demand well.
Steady pressure, not high pressure
The filter manual states the working pressure of the header. An 8 bar version suits most cases. Only go to 10 bar if the manual requires it, because flow drops: the K 75 goes from 1.1 m³/min at 8 bar to 0.95 m³/min at 10 bar.
The real risk is pressure loss at the far end of a long network. A header that does not refill gives weak pulses, and the bags slowly blind. A buffer receiver close to the dust collectors keeps the reserve where it is needed. Our air receiver size calculator gives a first volume.
Pitfalls specific to filter cleaning
- Water. A drop that reaches a bag turns the dust into paste, and pulsing no longer shifts it. Water also sticks the solenoid diaphragms. A refrigerated dryer is the minimum. If a line runs outdoors in winter, read which air dryer to choose.
- Draining. Fit an automatic condensate drain on the buffer receiver and at the low points of the network.
- Diaphragms. A split diaphragm leaks constantly and empties the header. A hissing leak near the filter is quick to find and fix.
- Location. The dust collector often sits in an ATEX classified zone. The compressor stays in a clean plant room outside the zone: see where to install a compressor.
Describe your filters in the configurator or send their manuals with a quote request: we check the flow and receiver with you.
For your trade: Compressor for grain silos and agricultural cooperatives.