Set ON, OFF and Pause Time in a Sequential Timer
Ask a few maintenance engineers how they set the timings on their dust collector controller and you’ll hear a range of answers. “We left it at the factory setting.” “We copied what the last plant used.” “Someone changed it years ago and it seemed to work.” Yet these few numbers decide how much compressed air the cleaning system uses, how well the filter bags are cleaned, and how hard the valve diaphragms are worked. A sequential timer with the wrong settings can clean poorly and waste air at the same time.
This guide explains what pulse ON time, OFF time, and pause time mean, how they interact, and a practical method to set them for your own installation. No setting is correct for every filter, so the focus here is on how to find the right values, not on quoting one set of numbers for everyone.
Safety note: isolate and lock out power before working inside the control panel. Adjusting settings on a running system should be done by trained personnel following your plant’s procedures.
The Three Timings Explained
A sequential timer, also called a sequential timer controller, sequential controller, or sequence controller, fires pulse jet valves one after another. Three timings shape that sequence.
| Timing | What It Is | What It Controls |
| ON time (pulse duration) | How long each valve stays energised and open | How much compressed air each pulse delivers |
| OFF time (pulse interval) | The gap between one valve firing and the next | Time for manifold pressure to recover and dust to settle |
| Pause time | A longer rest between complete cleaning cycles, on controllers that have it | How often each row of bags is cleaned again |
Important: manufacturers use these terms differently. On some controllers, “OFF time” means the gap between consecutive valves, and “pause” means the delay after the last valve before the sequence restarts. Others combine or rename them. Check your controller’s manual and note exactly how each timing is defined before you adjust anything.
Why These Settings Matter
ON time too short: the pulse may not flex the bag enough to dislodge the dust cake. Cleaning is weak and differential pressure rises.
ON time too long: extra compressed air is used without much additional cleaning, and the valve diaphragm works harder than necessary.
OFF time too short: the manifold has not recovered pressure when the next valve fires, so later pulses are weaker.
OFF time too long: each cleaning cycle takes longer, and dust may build up between cleanings.
Pause time too short: bags are cleaned more often than needed, using extra air and adding wear.
Pause time too long: bags load up between cycles and differential pressure climbs.
How the Timings Add Up: Cycle Time
To see how often each row of bags is cleaned, work out the full cycle time.
Cycle time ≈ number of valves × (ON time + OFF time) + pause time
This tells you how long a given row waits before it is pulsed again. If your controller defines OFF time as start-to-start instead, adjust the formula accordingly.
Worked example (illustration only)
Suppose a filter has 12 valves, and the controller is set to:
- ON time: 0.1 seconds
- OFF time: 10 seconds
- Pause time: 60 seconds
Step time per valve ≈ 0.1 + 10 = 10.1 seconds Sequence time for 12 valves ≈ 12 × 10.1 = 121.2 seconds Total cycle time ≈ 121.2 + 60 = about 181 seconds
So each row is cleaned roughly once every three minutes. If differential pressure is creeping up, you could shorten the pause time. If you’re using more compressed air than necessary and the filter is clean, you could lengthen it.
These numbers are only to show the arithmetic. They are not recommended settings for your filter.
Before You Adjust: Gather What You Need
Collect this information first:
- Valve data: size and manufacturer’s recommended pulse duration range
- Filter data: number of valves, bag type, filter design differential pressure range
- Compressed air: supply pressure at the manifold, and the capacity of the compressor and receiver
- Instruments: a pressure gauge on the manifold, and a differential pressure gauge or transmitter across the filter
- Current settings: write down what the controller is set to now
- Baseline: note the current differential pressure and how it behaves over a cleaning cycle
If your plant has a commissioning record or filter manual, start there. It may specify recommended settings.
Step 1: Set the ON Time
ON time controls how much air each pulse delivers. The aim is the shortest ON time that still cleans effectively.
Method:
- Start within the valve manufacturer’s recommended range, not at the maximum.
- Run a cleaning cycle and listen to the pulse. It should be a clear, sharp burst.
- Watch differential pressure. After a cleaning cycle, it should fall noticeably.
- If cleaning seems weak, increase ON time in small steps and observe the change.
- If differential pressure responds well, don’t keep lengthening. Extra time beyond the point of effective cleaning mostly wastes air.
Things that influence the right ON time: valve size, manifold pressure, blow pipe and venturi design, bag length and type, and dust characteristics. This is why settings from a different plant rarely transfer exactly.
Step 2: Set the OFF Time
OFF time gives the manifold time to recover pressure and the dislodged dust time to fall into the hopper.
Method:
- With a pressure gauge on the manifold, run a cleaning sequence and watch the needle.
- After each pulse, pressure dips and then recovers. The OFF time should be long enough for pressure to return close to the normal supply level before the next valve fires.
- If pressure hasn’t recovered by the next pulse, increase OFF time.
- If recovery is complete well before the next pulse, you may be able to shorten OFF time slightly, but only if cleaning and air supply allow.
- If recovery is always slow even with long OFF times, the problem may be an undersized supply line, receiver, or compressor rather than the timer.
Choosing a too-short OFF time is one of the most common reasons later valves in the sequence clean poorly.
Step 3: Set the Pause Time
Pause time (where available) controls how long the system rests between complete cleaning cycles. It determines how often each row is cleaned.
Method:
- Monitor differential pressure across the filter during normal production.
- Aim to keep it within the filter’s design range, with some margin below the upper limit.
- If differential pressure trends upward, shorten the pause time (cleaning more often) after first checking that ON time and OFF time are effective.
- If differential pressure is low and stable and air consumption is high, lengthen the pause time gradually.
- Allow enough time between adjustments to see the effect. Dust loading changes over hours, not minutes.
Remember that cleaning more often isn’t automatically better. Excess cleaning uses more air and puts more cycles on valve diaphragms.
Settings Direction by Situation
This table shows which way to adjust, not specific values.
| Situation | Typical Direction |
| Heavy or sticky dust, differential pressure rising | Check ON time is effective; shorten pause time |
| Light dust, very stable differential pressure | Consider longer pause time to save air |
| Later valves in the sequence sound weaker | Lengthen OFF time; check manifold recovery |
| Air consumption high, filter clean | Shorten ON time if cleaning still effective; lengthen pause time |
| Compressor struggling during cleaning | Lengthen OFF time; review supply capacity |
| New filter bags installed | Re-check settings; new bags behave differently from conditioned bags |
| Process throughput increased | Re-evaluate all three timings |
A Practical Step-by-Step Tuning Routine
- Record current settings and baseline readings.
- Check hardware first: valves firing, diaphragms in good condition, compressed air dry and at proper pressure.
- Set ON time within the valve manufacturer’s range, then confirm pulse quality.
- Set OFF time using manifold pressure recovery.
- Calculate cycle time and compare it to how quickly differential pressure rises.
- Adjust pause time to hold differential pressure within the desired band.
- Observe for several hours or shifts, not just a few minutes.
- Record the final settings and keep them with the panel.
- Review periodically, especially after bag changes or process changes.
Symptoms and What to Adjust
| Symptom | Possible Cause | What to Check or Adjust |
| Differential pressure keeps rising | Cleaning too weak or too infrequent | Check ON time effectiveness, then shorten pause time |
| Later valves weak, early valves strong | OFF time too short | Lengthen OFF time, check manifold recovery |
| High compressed air consumption | ON time or cleaning frequency too high | Shorten ON time or lengthen pause time, if cleaning stays effective |
| Valves fire but no cleaning effect | Weak pulses, valve or air supply problem | Check diaphragms, air pressure, and ON time |
| Differential pressure swings widely | Pause time too long, or dust load fluctuating | Shorten pause time, consider differential pressure control |
| Compressor loading constantly | Cleaning demand exceeds supply | Lengthen OFF time, review compressor and receiver capacity |
Common Mistakes When Setting Timings
- Copying settings from another plant without considering differences in valves, bags, and dust
- Using the longest ON time “to be safe,” wasting air and stressing diaphragms
- Setting OFF time without watching manifold pressure
- Changing several settings at once, making it impossible to see what worked
- Adjusting for a few minutes only and not observing real production conditions
- Compensating for hardware faults with timings, such as lengthening ON time to cover for a worn diaphragm
- Not recording the changes
- Ignoring terminology differences between controller brands
When a Fixed Timer Isn’t Enough: Differential Pressure Control
If dust loading varies a lot, fixed timings will always be a compromise. Controllers with differential pressure input can start cleaning when pressure rises and stop it when pressure falls, so the settings above define how the cleaning behaves while it runs. Where this feature is available on your controller, it can reduce cleaning when the filter doesn’t need it.
A Note on “Sequence Controller for Burner”
A sequence controller for burner use is a combustion safety device that manages ignition, purge, and shutdown. Its timings serve an entirely different purpose and are often safety-critical. Don’t confuse it with the sequential timer used for pulse jet cleaning, and never apply dust collector timing advice to burner control.
Sequence Controller Price and Adjustment Range
When comparing sequence controller price, look at the adjustment range for ON time, OFF time, and pause time. A controller with a narrow range may force you to run settings that waste air. Also check the display or markings, whether settings are easy to read and lock, and whether the number of channels matches your valves. Better adjustability and clear indication usually save time and compressed air over the controller’s life.
Frequently Asked Questions
What is pulse ON time in a sequential timer?
Pulse ON time, also called pulse duration, is how long the controller keeps each valve energised so that it stays open. It determines how much compressed air each cleaning pulse delivers. It’s usually a fraction of a second, and the right value depends on valve size, manifold pressure, and filter design.
What is OFF time, and how is it different from pause time?
OFF time is generally the gap between one valve firing and the next, giving the manifold time to recover pressure. Pause time, on controllers that have it, is a longer rest between complete cleaning cycles. Definitions vary between manufacturers, so confirm the meaning in your controller’s manual.
How do I calculate the cleaning cycle time?
Multiply the number of valves by the sum of ON time and OFF time, then add the pause time. This approximate figure tells you how long each row waits before it is pulsed again. Adjust the formula if your controller defines OFF time differently.
What ON time and OFF time should I use for my dust collector?
There isn’t one value for all filters. Start within the valve manufacturer’s recommended range for ON time, then set OFF time by watching manifold pressure recover between pulses. Fine-tune using differential pressure results and record the final settings.
Why do the last valves in the sequence clean worse?
Usually because the OFF time is too short, so the manifold hasn’t recovered pressure when later valves fire. It can also point to an undersized air supply. Check manifold pressure during a cleaning cycle to confirm.
Is a sequence controller for burner the same as a dust collector sequential timer?
No. A burner sequence controller manages ignition and shutdown of combustion equipment. A dust collector sequential timer sequences pulse valves for filter cleaning. They serve different purposes, so don’t interchange them or their settings.
Does sequence controller price depend on adjustment range?
It can. Controllers with wider, finer adjustment, clearer indication, more channels, or additional inputs usually cost more. These features can pay back through better cleaning control and lower compressed air use, so compare features and support along with price.
Conclusion
Setting ON time, OFF time, and pause time in a sequential timer isn’t guesswork when you follow a method. Set ON time to the shortest effective pulse, use manifold pressure to set OFF time, and use differential pressure trends to set pause time. Change one thing at a time, observe under real production conditions, and record the result.
Good settings protect filter bags, reduce unnecessary compressed air use, and reduce wear on valves. They also make future troubleshooting much easier, because you’ll know what the system was meant to be doing.
Need help choosing or configuring a sequential timer for your dust collector?
Maniks has manufactured sequential timer controllers and dust collector components for over 47 years, serving cement, steel, power, pharmaceutical, chemical, and other industries. Share your valve count, valve size, and current settings with our technical team, and we’ll help you find a suitable controller and a sensible starting point for your installation.
Explore the Maniks Solid-State Sequential Controller or contact us for technical assistance and a quotation.