Abnormal reasons for the inlet and outlet pressure difference of bag filter

During the operation of bag dust collector, the pressure difference between the inlet and outlet is often like a "mysterious assassin", silently affecting the dust removal efficiency and even the stability of the entire production process. Today, let us become detectives, deeply analyze the root cause behind this phenomenon, explore accurate and effective solutions, and protect this clean world.

1. Understand the "alarm signal" of abnormal pressure difference

The inlet and outlet pressure difference of the bag filter is simply the pressure difference between the dust-containing gas before entering and the gas discharged after purification.

Under normal circumstances, it is maintained in a relatively stable range, which is like a "barometer" for the healthy operation of the dust removal system.

Once the pressure difference deviates from the "normal value", the system is sounding the alarm: either there is too much dust accumulation on the filter bag, the airflow channel is blocked, just like the blockage of blood vessels in the human body;

Or there is a malfunction in the internal parts of the equipment, disrupting the normal airflow direction, just like the joint jamming affecting the movement of the limbs.

In either case, if it is not "diagnosed and treated" in time, the dust removal effect will inevitably be greatly reduced, and a series of "complications" such as soaring energy consumption and excessive emissions will follow.

2. Common "Causes" Revealed

(I) Filter Bag Problems

Excessive Dust Accumulation

This is the most common "culprit" for increased differential pressure. As production continues, dust continuously adheres to the surface of the filter bag. Over time, the pores of the filter bag are gradually filled, and the resistance to gas passing through increases dramatically, so the differential pressure at the inlet and outlet naturally increases.

For example, in the limestone crushing workshop of a cement plant, the amount of dust is large and the viscosity is high. If the dust cleaning system is slightly slack, the filter bag will be "wrapped" by thick dust in just a few days, and the differential pressure will quickly exceed the normal upper limit.

Damaged filter bag

When the filter bag is damaged, the situation becomes complicated. On the one hand, the dust-containing gas directly "takes a shortcut" through the hole without being fully filtered, resulting in an increase in the dust concentration at the outlet and a loss of purification effect; on the other hand, in order to maintain the overall dust removal efficiency, the fan often automatically increases the power, causing the inlet pressure to increase and the differential pressure at the inlet and outlet to fluctuate abnormally.

For example, the bag dust collector at the tail of the sintering machine in a steel plant has a very high risk of breakage because the filter bags are subjected to high temperature and high wear for a long time, and the slightest carelessness will cause pressure difference chaos.

(II) Failure of the cleaning system

Ineffective cleaning

Pulse valve failure, insufficient compressed air pressure and other reasons lead to ineffective cleaning, which cannot effectively shake off the dust on the filter bag. It is like cleaning a house. If the broom is weak, the dust will not be swept clean. At this time, the dust accumulates more and more, and the pressure difference continues to rise.

In a machining workshop, if the air compressor is not maintained and the air supply is insufficient, the bag filter will soon be trapped in the "dust siege", and the pressure difference alarm light will flash frequently.

Disordered cleaning cycle

If the pressure difference transmitter fails to transmit the wrong signal, or the control system parameters are set incorrectly, the cleaning cycle will become chaotic and disordered. Either the cleaning is too frequent, which will damage the life of the filter bag, and it may also cause the dust to not have time to re-attach evenly within the short cleaning interval, affecting the subsequent filtering effect; or the cleaning interval is too long, so that the filter bag is "loaded" for a long time, which also causes abnormal pressure difference.

A food processing factory once had a new employee mistakenly modify the cleaning parameters, causing the pressure difference of the bag dust collector to continue to rise within a week and filling the production workshop with dust.

(III) Equipment structure and airflow problems

Air inlet blockage

If the air inlet is blocked by foreign matter, large pieces of dust, or due to improper design, the local air vortex entrained with impurities will accumulate, the air intake will be blocked, the inlet pressure will increase instantly, and the pressure difference will be abnormal.

For example, in a wood processing plant, wood chips sometimes gather at the corner of the air inlet, forming a blockage over time, which seriously interferes with the normal air intake of the dust collector.

Internal air duct deformation or air leakage

The air duct may be deformed due to long-term impact and vibration of the air flow, making the air flow channel narrower or making sharp turns, increasing air flow resistance; and the equipment is not tightly sealed and leaks, which will dilute the dust-containing gas concentration, affect the filtering effect, and disrupt the air flow field, making the pressure difference lose its regularity.

In the bag dust collector at the tail of the power plant boiler, due to the harsh operating environment, the air duct wear and deformation and air leakage occur from time to time, which brings great challenges to the stability of the pressure difference.

III. “Prescription for the right disease” collection of magic formulas

(I) Filter bag maintenance and upgrade

Optimize cleaning strategy

According to dust characteristics and production load, finely adjust parameters such as cleaning cycle and pulse width to ensure that the filter bag can be “loaded” in time without excessive cleaning. For example, for sticky dust, appropriately shorten the cleaning cycle and increase the pulse intensity; for light dust, extend the interval and clean gently.

Regularly check and replace filter bags

Establish a strict filter bag inspection system, conduct an appearance inspection at least once a week, and replace them in time if they are damaged or aged. At the same time, formulate a batch replacement plan based on the expected life of the filter bag material to ensure that the “main force” of filtration always maintains its combat effectiveness.

(II) Cleaning system repair and calibration

Pulse valve inspection and air supply guarantee

Disassemble the pulse valve, check the diaphragm and valve core, and replace them immediately if they are damaged; regularly maintain the air compressor, clean the filter, ensure that the compressed air pressure is stable within the process requirements, and inject a “heart shot” for cleaning.

Control system verification

Calibrate the differential pressure transmitter, compare the measured pressure on site with the displayed value, and immediately correct any errors that exceed the standard; review the cleaning control parameters, optimize the settings based on actual working conditions, and get the cleaning rhythm back on track.

(III) Equipment structure optimization and airflow management

Air inlet cleaning and protection

Set a coarse filter at the air inlet and clean the air inlet channel regularly to prevent foreign matter from blocking; optimize the air inlet design and adopt a streamlined structure to reduce airflow impact and vortex to ensure smooth air intake.

Air duct leak detection and reinforcement

Regularly use tools such as smoke generators to detect air duct leaks, repair and reinforce deformed parts, ensure smooth and orderly airflow, and maintain stable pressure difference.

Although the pressure difference between the inlet and outlet of bag dust collector is often tricky, as long as we develop a pair of "fire eyes and golden eyes", find the cause, and take precise measures, we can tame this "pressure turbulence" and let the bag dust collector continue to operate efficiently, supporting a clean blue sky for industrial production.