Pulse bag dust collector ten common fault diagnosis and solutions

1. Abnormal increase in filter bag pressure difference: diagnosis and treatment

During the operation of pulse bag dust collector, the filter bag pressure difference exceeding the design value is the most common fault phenomenon, which directly leads to a decrease in system air volume, a surge in energy consumption and even shutdown. According to industrial field data, abnormal pressure difference is usually caused by the following seven reasons:

- Failure of the cleaning system: Pulse valve diaphragm damage (accounting for 45% of the failure rate), insufficient injection pressure (recommended 0.5-0.6MPa) or incorrect timing setting (standard cycle 10-30 seconds) will cause the dust layer to be unable to be effectively removed.

A case of a cement plant shows that when the injection pressure is lower than 0.15MPa, the cleaning efficiency decreases by 60%. Solution: Use a multimeter to detect the solenoid valve coil resistance (normal value 20-50Ω), adjust the PLC pulse width to 0.1-0.2 seconds, and install a pressure sensor to monitor the peak pressure in real time.

- Filter bag blockage: Dust viscosity is too high or the wrong filter material selection (such as not using coated filter material) will cause deep blockage, especially when the filtration speed exceeds the design standard.

Solution: Pre-spray neutral conditioning powder (such as lime powder) to establish a protective layer; the filtration speed of sticky dust needs to be controlled below 1.0m/min; in case of severe blockage, it is necessary to clean the dust offline and rinse the filter bag with hot water.

- Condensation and hardening: When the flue gas temperature is lower than the dew point (common in the shutdown stage), moisture and dust mix to form a hard shell.

A power plant once had a box of filter bags hardened and scrapped due to a sudden drop in intake temperature in winter.

Solution: Preheat the intake air to above the dew point +10℃ before starting; add a 50mm rock wool insulation layer to the shell; install an adsorption dryer for compressed air.

- Structural defects: Uneven flower plates (allowable tolerance ≤2mm), offset of the spray pipe or detachment of the venturi tube will weaken the cleaning kinetic energy.

Correction method: Use a laser alignment instrument to adjust the injection pipe to ensure that the deviation between the center line of the airflow and the axis of the filter bag is less than 2mm; install a venturi fixing clamp. 

- Dust overload: A sudden increase in inlet concentration (such as blockage in the crusher) or insufficient filtration area causes a sharp increase in pressure difference.

Emergency plan: Open the bypass damper; a permanent solution requires the addition of a pre-cyclone dust collector.

- Secondary dust: The dust hopper is too high (the recommended volume is ≤70%), and the back-blowing airflow will raise the dust again.

Operation specification: Set the level meter to link the ash discharge valve; the ash cleaning adopts a random mode instead of a sequential mode.

- Measurement error: The differential pressure gauge pipeline is blocked or leaking, causing false alarms.

Maintenance requirements: Use compressed air to purge the pressure measuring tube every month; calibrate the differential pressure sensor every quarter.

2. Pulse valve failure: a complete process from diagnosis to repair

As the core actuator of the dust cleaning system, pulse valve failure will directly cause the dust collector to paralyze. According to the fault characteristics, it can be divided into three categories:

2.1 Solenoid valve does not move (silent and vibration-free)

- Power supply and signal problems: Measure the output voltage of the controller (normal DC24V±10%). If abnormal, check whether the PLC program is disordered or the relay is damaged.

- Coil circuit breakage: Use a multimeter to detect the coil resistance. If the resistance value is infinite, the coil needs to be replaced (the common model Φ25mm coil resistance is about 42Ω).

- Loose wiring: The terminal is easy to fall off in a vibrating environment. It is recommended to use an IP67 protection grade plug and install an anti-vibration bracket.

2.2 Diaphragm system failure (leakage or weak blowing)

- Diaphragm aging and rupture: The life of the rubber diaphragm is usually 2000 hours, and the high temperature area needs to be replaced with fluorosilicone material.

Diagnostic tips: Disassemble the valve cover to check the diaphragm cracks, and the center should be elastically reset when pressed.

- Impurity blockage: welding slag and rust block the air pressure balance hole (80% of the blockage is caused by unfiltered air source). Processing steps: remove the valve and clean the channel with kerosene; install a 0.01μm precision filter at the front end.

- Spring failure: the elastic force is weakened, resulting in the diaphragm not being pressed tightly.

Preventive measures: replace the spring every year and choose stainless steel to prevent rust.

2.3 Air source problem (insufficient pressure or water)

- Pipeline leakage: Use soapy water to detect the joint at a pressure of 0.6MPa.

- Insufficient gas tank volume: It should meet more than 3 times the gas consumption of a single injection (for example: a 3-inch pulse valve consumes 0.3m³ of gas per time, and the tank is ≥1m³).

- Condensate freezing: Electric heating tape needs to be installed in the north in winter to maintain the pipeline temperature >5℃.

Deep repair case: The DMC-240 dust collector of a steel plant did not spray the entire chamber, the detection control signal was normal but the air bag pressure returned to zero. Finally, it was found that the center hole of the diaphragm was bonded with oil sludge due to the infiltration of air compressor lubricating oil. Solution: ① Replace all diaphragm components; ② Install a three-stage filter (40μm+5μm+0.01μm) at the air source end; ③ Add an oil mist separator. After the repair, the life of the pulse valve was extended from 3 months to 2 years.

3. Abnormal damage of filter bags: root cause analysis and prevention strategies

As the core filter unit of dust removal, abnormal damage of filter bags directly leads to excessive emissions and equipment wear. According to the damage mode, it can be divided into three categories:

3.1 Mechanical wear (accounting for 65% of the damage rate)

- Bag cage burr scratches: The welding points are polished to Ra≤3.2μm, and silicone coating skeletons are preferred.

- Air flow scouring: The windward side of the filter bag is prone to damage when the inlet flow rate is ＞18m/s.

Optimization plan: Add a porous flow plate; use wear-resistant polyester (weight ≥550g/m²) in areas with severe wear.

- Improper installation: The gap between the filter bag and the bag cage should be kept at 10-20mm. Too tight will cause friction, and too loose will cause shaking.

Operation specification: There should be no resistance when manually rotating the bag cage after installation.

3.2 High temperature burnout (instantaneous temperature exceeds the standard)

- Spark penetration: Biomass boiler flue gas needs to be equipped with pre-dust removal + spark arrester.

- Misuse of heat-sensitive materials: For example, PPS fiber oxidizes rapidly when the oxygen content is greater than 10% and the temperature is greater than 160°C.

Selection rules: Select filter materials according to the flue gas composition. PTFE coated filter bags are recommended for high temperature areas.

3.3 Chemical corrosion (acidic and alkaline environment)

- Acid dew point corrosion: When the flue gas temperature is lower than the acid dew point (about 110-130°C for coal-fired boilers), SO₂ is converted into sulfuric acid to corrode the fiber.

Control strategy: The operating temperature is maintained above the acid dew point + 15°C; the shell is insulated to reduce heat dissipation.

- Hydrolysis reaction: The strength of polyester filter bags decreases when the humidity is greater than 30% and the temperature is greater than 60°C.

Alternative solution: Use polyacrylonitrile or PTFE fiber.

Economical maintenance suggestions: Establish a filter bag life prediction model, and formulate a replacement plan based on the pressure difference curve (ΔP＞2500Pa), emission concentration (＞30mg/m³), and broken bag locator (such as fluorescent powder detection method) to avoid blind replacement of the entire batch.

4. Sudden drop in dust removal efficiency: Systematic troubleshooting guide

When the chimney emission concentration continues to exceed the design value (usually >30mg/Nm³), it is necessary to follow the following five-level process for troubleshooting:

- Missing initial dust layer: New filter bags or excessive cleaning lead to dust penetration.

Countermeasures: Pre-spray raw material powder (such as spraying calcium-based powder before cement kiln feeding); reduce the cleaning frequency by 50% until the pressure difference is stable.

- Flower plate leakage: Weld cracking or aging of the sealing gasket forms a short circuit.

Detection technology: After injecting fluorescent powder, UV light is used to locate the leakage point.

- Penetration damage of filter bags: The broken bag position is usually 300mm from the bag mouth or the bottom. After stopping, open the cover and check each bag.

- Bypass valve leakage: Dust accumulation on the sealing strip or the actuator is not in place.

Maintenance points: Clean the sealing groove every month; calibrate the lift valve stroke.

- Uneven air flow distribution: The pressure difference deviation of each room >15% indicates abnormal distribution.

Optimization method: add a guide grille at the inlet; adjust by computational fluid dynamics (CFD) simulation.

5. Failure of air source system: optimization from air compressor to terminal

The quality of compressed air directly determines the cleaning effect. High water content or pressure fluctuation is the main source of problems:

- Insufficient pressure: pressure drop of main pipeline>0.05MPa

Need to check the blockage point; the air storage tank is <10 meters away from the dust collector.

- Oil and water pollution: when the oil content in each cubic meter of air is>1ppm, the filter bag will be hardened within 3 months.

Processing equipment: Refrigeration + adsorption combined dryer; automatic drain valve discharges every shift.

- Abnormal usage: spraying time>0.2 seconds will cause gas waste.

Parameter setting: adjust the pulse width to 0.1 seconds through the oscilloscope.

6. Abnormal operation of the lifting valve: Mechanical adjustment tips

Lifting valve failure will lead to failure of chamber isolation. Focus on two types of problems:

- Valve plate detachment: because the lower limit of the cylinder stroke is set too low (deformation>5mm).

Correction method: adjust the position of the screw nut to make the valve plate deformation ≤3mm.

- Cylinder does not move: the two-position five-way valve is blocked or the piston seal is aged.

Disassembly and cleaning: clean the valve core with kerosene and apply lithium grease; the seal is replaced every 2 years.

7. Fan system failure: vibration and wear treatment

- Impeller dust accumulation: vibration value > 6.3mm/s

Need to stop and clean, and weld the wear-resistant layer to extend the life.

- Bearing damage: temperature > 85℃ or obvious abnormal noise

Replace immediately.

- Insufficient air volume: check the static pressure value and adjust the belt tension (deformation under pressure < 10mm).

8. Equipment air leakage: precise positioning and blocking

Air leakage rate > 3% will cause condensation and increase energy consumption:

- Detection method: thermal imager scans low temperature points; soapy water in positive pressure section to check for leaks.

- Key sealing points: silicone rubber strips for maintenance doors; four-layer graphite winding pads for flanges.

9. Ash hopper blockage: preventive design

Bridging of materials leads to interruption of ash discharge:

- Electric heating and heating: maintain the ash hopper wall temperature > dew point + 10℃.

- Activation device: pneumatic vibrator (0.6MPa) or sonic cleaner.

- Structural optimization: bucket wall inclination angle>65°; inner wall polishing Ra≤1.6μm.

10. Control system failure: modular diagnosis

- PLC program disorder: backup program regular restoration; isolation of strong electrical interference sources.

- Sensor failure: differential pressure gauge monthly purge; temperature sensor annual calibration.

- Communication interruption: switch to optical fiber communication; surge protector grounding.

Ultimate maintenance suggestion: implement a predictive maintenance system, monitor the air bag pressure fluctuation rate (>10% alarm), filter bag cleaning energy consumption trend (15% increase warning), valve action count statistics (replacement recommended if more than 500,000 times) and other parameters in real time through the Internet of Things platform, and predict faults 2 weeks in advance. At the same time, establish a fault code library (such as F01 represents pulse valve response timeout) to shorten the fault diagnosis time by 90%.