Reasons for Abnormal Pressure Difference at the Inlet and Outlet of Baghouse Dust Collectors

In the operation of baghouse dust collectors—a critical line of defense in industrial environmental protection—abnormal pressure differences at the inlet and outlet often act like a "mysterious assassin," silently affecting dust removal efficiency and even the stability of the entire production process. 

Today, let's put on our "detective hats" and delve into the root causes of this phenomenon, exploring precise and effective solutions to protect this clean environment.

I. Understanding the "Warning Signals" of Abnormal Pressure Difference

The pressure difference at the inlet and outlet of a baghouse dust collector, simply put, is the pressure difference between the dust-laden gas entering and the purified gas exiting. 

Under normal circumstances, it remains within a relatively stable range, which acts as a "barometer" for the healthy operation of the dust removal system. Once the pressure difference deviates from the "normal value," 

it means the system is sounding an alarm: either there is excessive dust accumulation on the filter bags, obstructing the airflow channel, like a blockage in the body's blood vessels; or there is a malfunction in the internal components of the equipment, disrupting the normal airflow, like a joint stiffness affecting limb movement. 

In either case, if not "treated" promptly, the dust removal effect will inevitably be greatly reduced, and a series of "complications" such as soaring energy consumption and exceeding emission standards will follow.

II. Common "Causes" Uncovered

(I) Filter Bag Problems

Excessive Dust Accumulation

This is the most common "culprit" for increased pressure difference. As production continues, dust continuously adheres to the surface of the filter bags. 

Over time, the pores of the filter bags are gradually filled, the resistance to gas flow increases sharply, and the pressure difference between the inlet and outlet naturally rises. For example, in the limestone crushing workshop of a cement plant, the amount of dust is large and highly viscous. 

If the dust cleaning system is even slightly neglected, the filter bags will be "wrapped" in thick dust within a few days, and the pressure difference will quickly exceed the normal limit.

Filter Bag Damage

When the filter bags are damaged, the situation becomes more complicated. On the one hand, the dust-laden gas bypasses the filter and passes directly through the holes without sufficient filtration, leading to increased dust concentration at the outlet and impaired purification effect; 

on the other hand, to maintain overall dust removal efficiency, the fan often automatically increases its power, causing the inlet pressure to rise, and the pressure difference between the inlet and outlet shows abnormal fluctuations. 

For example, in the baghouse dust collectors at the tail end of sintering machines in steel plants, the filter bags are subjected to high temperatures and high wear for extended periods, resulting in a very high risk of damage. Even a slight oversight can lead to differential pressure anomalies.

(II) Cleaning System Malfunctions

Ineffective Cleaning

Reasons such as pulse valve failure and insufficient compressed air pressure can lead to ineffective cleaning, preventing the dust from being effectively shaken off the filter bags. 

This is like trying to clean a house with a weak broom; the dust naturally won't be cleaned properly. In this case, dust accumulates, and the differential pressure continues to rise. 

In a machining workshop, if the air compressor is poorly maintained and the air supply is insufficient, the baghouse dust collector will quickly become overwhelmed with dust, and the differential pressure alarm light will flash frequently.

Irregular Cleaning Cycle

If the differential pressure transmitter malfunctions and transmits incorrect signals, or if the control system parameters are set incorrectly, the cleaning cycle will become chaotic and irregular. 

Either the cleaning is too frequent, damaging the filter bags and potentially preventing the dust from re-attaching evenly during the short cleaning intervals, affecting subsequent filtration; or the cleaning interval is too long, causing the filter bags to be "overburdened" for extended periods, also leading to abnormal differential pressure.

 A food processing plant once experienced a continuous increase in differential pressure in its baghouse dust collector for a week due to a new employee mistakenly modifying the cleaning parameters, resulting in widespread dust in the production workshop.

(III) Equipment Structure and Airflow Problems

Inlet Blockage

If the air inlet is blocked by foreign objects, large dust particles, or due to improper design leading to localized airflow vortices and accumulation of impurities, the airflow will be obstructed, 

the inlet pressure will instantly increase, and consequently, abnormal differential pressure will occur. For example, in a wood processing plant, wood chips sometimes accumulate at the corners of the air inlet, gradually forming a blockage over time, seriously interfering with the normal air intake of the dust collector.

Internal Air Duct Deformation or Leakage

The air ducts, subjected to long-term airflow impact and vibration, may deform, narrowing the airflow channel or creating sharp turns, increasing airflow resistance.  

Meanwhile, poor equipment sealing can cause air leakage, diluting the concentration of dust-laden gas, affecting the filtration effect, and disrupting the airflow field, causing the differential pressure to become irregular. 

In the baghouse dust collectors at the rear of power plant boilers, due to the harsh operating environment, wear, deformation, and air leakage in the ducts frequently occur, posing a significant challenge to maintaining stable differential pressure.

III. Effective Solutions for Addressing the Problem

(I) Filter Bag Maintenance and Upgrade

Optimizing Dust Removal Strategy

Based on dust characteristics and production load, finely adjust parameters such as the dust removal cycle and pulse width to ensure that the filter bags are relieved of their load in a timely manner without excessive cleaning. For example, for sticky dust, appropriately shorten the cleaning cycle and increase the pulse intensity; for light and thin dust, extend the interval and use gentle cleaning.

Regular Inspection and Replacement of Filter Bags

Establish a strict filter bag inspection system, with at least one visual inspection per week, and replace damaged or aged bags promptly. Simultaneously, develop a batch replacement plan based on the expected lifespan of the filter bag material to ensure that the "main force" of filtration always maintains its effectiveness.

(II) Dust Removal System Repair and Calibration

Pulse Valve Inspection and Air Supply Guarantee

Disassemble the pulse valve, inspect the diaphragm and valve core, and replace any damaged parts immediately; regularly maintain the air compressor and clean the filter to ensure that the compressed air pressure remains stable within the process requirements, providing a "boost" to the dust removal process.

Control System Verification

Calibrate the differential pressure transmitter, compare the actual measured pressure with the displayed value, and correct any errors exceeding the tolerance; re-examine the dust removal control parameters, optimize the settings based on actual working conditions, and get the dust removal rhythm back on track.

(III) Equipment Structure Optimization and Airflow Management

Inlet Cleaning and Protection

Install a coarse filter screen at the inlet and regularly clean the inlet channel to prevent foreign objects from blocking it; optimize the inlet design, using a streamlined structure to reduce airflow impact and turbulence, ensuring smooth airflow.

Air Duct Leak Detection and Reinforcement

Regularly use smoke generators and other tools to detect air leaks in the air ducts, repair and reinforce deformed parts, ensuring that the airflow passes smoothly and orderly, maintaining stable differential pressure.

Although abnormal differential pressure at the inlet and outlet of the bag filter is a tricky problem, as long as we develop a keen eye, identify the root cause, and implement precise measures, we can tame this "pressure turbulence" and allow the bag filter to operate continuously and efficiently, creating a clean and blue sky for industrial production.