Dust collector operators typically utilize cleaning systems to help them ensure effective dust control for their process areas while saving compressed air (which is very expensive when you look at your electric bill). And, for as much as some consider that the cleaner the filter is, the better it works, that is not always the case. Although some will suggest cleaning the bags on a regular basis using a timer setting… in this article you will learn why setting up your cleaning system based on the differential pressure is better for you.

In order to understand all the reasons, let’s start with the cleaning basics.

What is Pulse Jet Cleaning?

Graphic showing compressed air dislodging the dust cake from the filters

During pulse jet cleaning, a reverse flow of clean compressed air puffs a row of bags outwards, dislodging the dust cake on each bag’s surface. The bags react to the initial shock of compressed air, followed by a bubble-like expansion that moves along the bag length.

During pulse jet cleaning, a reverse flow of clean compressed air puffs a row of bags outwards, dislodging the dust cake on each bag’s surface. During this cleaning cycle, the bags in the row being pulsed do not inflate all at once, but in a wavelike manner, which enhances cleaning. The bags react to the initial shock of compressed air, followed by a bubble-like expansion that moves along the bag length. During the cleaning procedure, the baghouse remains online, and filtration continues, with no downtime required.

What is Differential Pressure?

Diagram of a pulse jet system

During pulse jet cleaning, the compressed air accumulated in the air header reaches the blowpipe with a frequency and strength determined by the controller, the gauge and the diaphragm

Differential pressure in a dust collector is the difference in air pressure between the dirty side of the collector and the clean side (these two sides divided by the tubesheet). When dust particles are collected by the filter, they build up on the filter surface, making it harder for air to pass through. This creates a pressure difference: the air inside the filter becomes more pressurized compared to the clean air outside the filter.

As the dust builds up, the pressure difference increases, which can affect the efficiency of the dust collector. High differential pressure usually means the filter is getting clogged and needs cleaning. Monitoring differential pressure helps ensure the dust collector is working properly and efficiently.

Why is It Important to Monitor Differential Pressure?

Differential Pressure gauges

Así como la presión arterial indica la salud y eficiencia del sistema circulatorio, la presión diferencial ofrece una medición vital de qué tan bien está funcionando el colector de polvo.

Differential pressure can warn us when the baghouse needs help. It can be as simple as indicating when it’s time to pulse clean filters or more extensive service, like it’s time to replace the filters. Continuously monitoring pressure drop can reveal problems early, when they are faster, easier and cheaper to fix, and helps extend bag life.

Why Set Cleaning Based on Differential Pressure Instead of a Timer?

Setting your cleaning based on differential pressure helps stop wasting compressed air. This is because the filters are cleaned only when the pressure reaches a certain level, which prevents overuse. It’s important to maintain the right amount of dust cake (the layer of dust on the filter) because cleaning too often or not enough can cause problems. Under-cleaning creates high differential pressure, while over-cleaning wears the filters out faster.

DID YOU KNOW? The primary benefit of differential pressure controllers is their ability to program a high set point (when a filter cleaning system turns on) and a low set point (when the cleaning system turns off). Usually the low and high points for the differential pressure are 3” to 5” respectively. By programming the high and low set points effectively, the controller triggers filter cleaning only within the desired range.

During normal use and operation, these controllers monitor the differential pressure across the filters in the collector. The dust collector operator receives a visual indication of the pressure drop across the filters, indicating how clean or dirty the filters may be. Typically, the lower the indicator value for pressure drop, the cleaner the filters, and the higher the value, the dirtier the filters.

Dirty filters tend to provide better filtration efficiency with their cake of accumulated dust, but they require additional energy from the fan in order to maintain airflow volume.

In summary: Your dust collector’s cleaning system does not need to run continuously or clean in fixed periods of time. Using the differential pressure to control the cleaning will save you lots of money and time, since the system will only clean when is necessary, and your filters will last longer.

How Often Should We Monitor the Differential Pressure?

A good preventive maintenance program should include daily (or per shift) checks of the filter differential pressure on each pulse jet unit. This includes visually inspecting and listening to each collector while it’s running to check the pulsing sound and frequency, as well as checking the compressed air pressure in the cleaning manifold before and after pulses. Weekly, monthly, and longer-term checks should also be included. A simple and effective way to do this is to assign one person per shift to monitor the dust collectors and record that information. After a short time, they will become familiar with the normal differential pressure trends and sounds, helping them quickly identify any issues.

 

What Are The Best Settings For Your Pulse Cleaning System?

  1. Pulse Duration

   It’s important to set your pulse time correctly. We recommend a pulse duration between 300 and 500 milliseconds. This is enough time to allow a solid “pop” of air, without an additional “Shhhh” with it. This provides a strong burst of air, without wasting air with additional unnecessary flow. A pulse that lasts too long results in wasted air after the initial “pop,” as the lower pressure doesn’t improve cleaning. If pulses are too short, they might not clean the filters thoroughly, leading to premature wear. You can adjust pulse duration on the timer board or controller.

  1. Pulse Frequency 

   The key to effective pulsing is giving the manifold enough time to recover the compressed air between pulses. Avoid pulsing too frequently, as this can prevent the manifold from refilling to the correct pressure. If the pressure isn’t high enough, cleaning will be inefficient, leading to wasted compressed air. Always ensure there’s enough delay between pulses to allow the manifold to recover properly. This can also be set on the timer board or controller.

  1. Pulse Sequence 

   It might seem logical to pulse the filters in row order, but this actually wastes air. When row 1 is cleaned, its lower static pressure allows air to take the path of least resistance, potentially carrying dust back into row 1 during subsequent pulses. This reduces the effectiveness of the cleaning. Instead, we recommend pulsing in a non-sequential order. For example, pulse rows 1, 4, 7, and 10 first, then rows 2, 5, 8, and 3, 6, 9, repeating. This method ensures better cleaning and minimizes air waste. You can change the sequence by adjusting the wiring on the timer board.

By following these guidelines, you can improve the efficiency of your dust collection system, saving both time and money.

 

Do you have any additional questions? 

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