Pulse Jet Cleaning System for Silo Dust Collectors
Questions about air header, pulse valves, compressed air pressure, cleaning controller and pulse jet performance.
The pulse-jet system restores media permeability by releasing short, high-energy bursts of compressed air. Reliable cleaning depends on air volume, pressure stability, valve response, timing and accurate alignment with each filter row.
What air pressure does pulse-jet cleaning need?
Published design guidance places pulse pressure in a broad band of roughly 0.2–0.8 MPa (30–120 psi), and many industrial installations are set toward 0.4–0.6 MPa (about 60–90 psi). Sources differ because the correct value depends on bag length, blow-pipe design and the dust being handled, so the equipment manual for the specific collector always governs.
The number that matters in practice is not the compressor gauge but the dynamic pressure measured at the air header during the pulse. Undersized tubing, a restrictive regulator or a long hose can leave the header well below the set value at the moment the valve fires, which produces weak cleaning even when the compressor reads full pressure.
How long should each pulse last?
Published ranges for pulse-on time vary widely, from about 50–200 milliseconds for short-burst designs up to 100–450 milliseconds in other guidance. The pulse must be long enough to open the diaphragm fully and deliver the shock wave down the bag, but longer pulses simply consume more air without improving release.
Pulse interval has to allow the header to recover to working pressure before the next valve fires. If the interval is too short, each successive pulse starts from a lower header pressure and cleaning becomes progressively weaker along the sequence.
Typical pulse-jet cleaning parameters
| Parameter | Typical published range | Notes |
|---|---|---|
| Pulse pressure | 0.2–0.8 MPa (30–120 psi) | Many plants operate 0.4–0.6 MPa; confirm against the equipment manual |
| Pulse-on time | 50–450 ms depending on design | Long enough to open the diaphragm fully; longer wastes air |
| Normal differential pressure | 0.5–1.5 kPa (2–6 in w.g.) | Steady operating band for a healthy filter |
| Cleaning start / stop setpoints | Start near 1.6 kPa (6.5 in w.g.), stop near 0.75 kPa (3 in w.g.) | Example setpoints; prevents continuous over-cleaning |
| Air per pulse | Approx. 28–85 L (1–3 ft³) per bag | Varies with bag size and pulse length |
| Compressed-air demand | Published figures vary widely | Cited from about 0.75 up to 8 SCFM per 1,000 CFM, depending on cleaning frequency, pulse length and bag count |
These are published industry ranges collected for orientation, not a specification for any particular collector. Final settings should follow the manufacturer’s manual and the values recorded during commissioning.
Should cleaning run on a timer or on differential pressure?
Timer-based cleaning fires the valves on a fixed cycle regardless of how loaded the filters are. It is simple, but it keeps pulsing when the filter does not need it, which wastes compressed air and shortens media life.
Differential-pressure-based cleaning starts when the pressure drop reaches a high setpoint and stops at a low setpoint. Using a start and stop band rather than a single trigger is what prevents the collector from cleaning continuously. A commonly cited example is starting near 1.6 kPa (6.5 in w.g.) and stopping near 0.75 kPa (3 in w.g.).
What does the differential pressure reading tell you?
A healthy pulse-jet collector normally settles in a band of about 0.5–1.5 kPa (2–6 in w.g.). Movement out of that band is a diagnostic signal rather than a nuisance reading:
- Rising and not recovering after cleaning — blinded or caking media, wet air reaching the filter surface, or valves that are not firing.
- Unusually low, close to zero — often a torn bag, a failed seal or a bypass path, not good filtration. Emissions usually appear at the stack at the same time.
- Rising only at high load — the air-to-cloth ratio may be too high for the dust, or the cleaning interval is too long.
Why does cleaning stay weak when the valves click?
An audible valve click only proves the solenoid pilot operated. It does not prove that a full-energy pulse reached the filter. The usual causes are:
- Dynamic header pressure collapsing during the sequence because the supply line cannot refill it.
- Diaphragms hardened, split or seated on a fouled pilot passage.
- Blow-pipe holes blocked, or the pipe rotated so nozzles no longer align with the bag centres.
- Moisture or compressor oil carried into the collector, making the dust cake sticky.
- Solenoid supply voltage sagging, so valves partially open.
Measuring header pressure through a complete cleaning sequence, rather than at rest, is the fastest way to separate an air-supply problem from a valve problem.
Frequently asked questions
What compressed air pressure is used for pulse-jet cleaning?
Published guidance gives a broad range of roughly 0.2–0.8 MPa (30–120 psi) across published sources, with many installations set toward 0.4–0.6 MPa. The manufacturer manual for the specific collector governs, and the pressure should be verified at the air header during the pulse rather than at the compressor.
How much compressed air does a pulse-jet dust collector consume?
Published figures differ considerably. Some sources give roughly 0.1–0.2 percent of the cleaned gas volume (about 0.75 SCFM per 1,000 CFM), while others cite 2–8 SCFM per 1,000 CFM. The spread reflects different cleaning frequencies, pulse lengths and bag counts, so the figure should be taken from the equipment manual rather than a generic ratio. Air per individual pulse is commonly given as about 28–85 litres (1–3 cubic feet) per bag.
What is a normal differential pressure for a bag filter?
A common operating band is about 0.5–1.5 kPa (2–6 inches water gauge). A reading that keeps climbing after cleaning suggests blinded media or valves that are not firing; a reading close to zero often indicates a torn bag or a bypass rather than good filtration.
Is timer cleaning or differential-pressure cleaning better?
Differential-pressure control cleans only when the filter is actually loaded, which saves compressed air and extends media life. Using separate start and stop setpoints, rather than one trigger, is what prevents continuous over-cleaning. Timer cleaning is simpler and can be appropriate where loading is very steady.
Why is cleaning weak even though the pulse valves are operating?
A valve click only confirms the pilot operated. Weak cleaning is usually caused by header pressure collapsing during the sequence, hardened or split diaphragms, blocked blow-pipe holes, misaligned nozzles, or moisture and oil in the compressed air. Measuring dynamic header pressure through a full sequence isolates the cause.
Does higher pulse pressure always clean better?
No. Above the range the equipment was designed for, additional pressure mainly increases air consumption and mechanical stress on the media and cages, shortening filter life without improving dust release.
Engineering note: Do not increase pulse pressure beyond component and equipment limits as a substitute for correcting poor sizing or moisture problems.