How to unclog a boiler tube?

Boiler tube blockage is a common but thorny problem that may lead to reduced boiler efficiency or even equipment damage. The method of unclogging a boiler tube blockage needs to be selected according to the cause of the blockage (such as scale, impurities, corrosion products, etc.) and the type of pipe (water pipe or smoke pipe). The following are several effective unclogging methods that combine physical and chemical means and are suitable for different types of blockages:

1. Preliminary inspection and judgment
Confirm the location of the blockage: Locate the blockage area by observing abnormal pressure, uneven temperature or local hot spots.

Determine the blocking material:
Scale (common in water pipes, prone to occur when the water is hard);
Impurities (such as welding slag, mud and sand);

Soot/carbon deposits (smoke pipe blockage).

2. Methods for unclogging water pipe blockage

(1) Mechanical unclogging (physical unclogging)
High-pressure water gun flushing: Use professional equipment (such as a high-pressure cleaner) to flush the inner wall of the pipe, which is suitable for loose impurities.
Pipeline unclogging device: For harder blockages, flexible unclogging springs or hard brushes can be used for physical cleaning.

Pulse cleaning: Use a mixture of water and air to generate pulse waves to flush out dirt and scale in the pipe. During operation, connect the pulse cleaning machine to the pipe and adjust the pressure and frequency until the discharged water becomes clear. ‌

Shot cleaning: Use special projectiles (such as sponge bullets) to be sent into the pipe through compressed air to scrape the dirt on the pipe wall. After the projectile travels in the pipe, check the dirt on its surface and repeat the operation if necessary. ‌
Flexible shaft unblocking: Use the flexible shaft and alloy steel drill bit of the pipe cleaning machine to remove dirt on the inner wall of the pipe by rapid rotation. This method is suitable for blockages with coking materials with high viscosity. ‌

Disassembly and cleaning: If the blockage is serious, it is necessary to disassemble the local pipe and remove it manually (such as using a wire hook to remove debris).

(2) Chemical cleaning

a. Special cleaning agent ‌
Select an acidic or alkaline cleaning agent suitable for the pipe material, inject it into the pipe system and circulate it for several hours to a day to dissolve or decompose scale and rust. After cleaning, rinse repeatedly with clean water until the pH of the discharged water returns to normal.

Acidic cleaning agent (for scale):
Use diluted hydrochloric acid, citric acid or special descaling agent for cyclic cleaning, and completely neutralize the residual acid after completion. Note: Acid cleaning may corrode the pipe, so the concentration and time need to be controlled. Use with caution on stainless steel pipes.

Alkaline cleaning agent (for oil stains): It can be cleaned with sodium hydroxide solution.

b. Descaling agent ‌
Add the descaling agent to the boiler water, steam it and mix it for 30 minutes, then flush the pipe with clean water to remove residual dirt.

(3) Reverse flushing
Switch the direction of water flow and use reverse pressure to disperse the blockage (the system needs to support reverse circulation).

3. Methods for unblocking smoke pipe blockage
Mechanical cleaning: Use a long-pole brush or compressed air to blow away soot and carbon deposits.
Chemical cleaning: Spray soot cleaning agent to dissolve carbon deposits, and then rinse with water.
Preventive measures: Improve combustion efficiency and reduce soot generation; clean the flue regularly.

4. Other professional methods
Ultrasonic cleaning: suitable for precision pipes, using high-frequency vibration to peel off sediments.
Air pulse technology: high-pressure gas pulses are used to shake off blockages (effective for stubborn blockages).

5. Treatment after unblocking
System flushing: remove residual impurities or chemicals.
Check the tightness: test for leaks after restoring the pipeline.

Water quality/combustion optimization:
Water pipes: install filters or softening water treatment equipment.
Smoke pipes: adjust combustion parameters and clean ash regularly.

Safety precautions:
Turn off the boiler power/fuel before operation, release pressure and cool the system.
Wear protective equipment (gloves, goggles) during chemical cleaning to avoid contact with skin.
After pickling, it must be neutralized and rinsed to prevent corrosion.
If the blockage is serious or cannot be located, it is recommended to contact professional boiler maintenance personnel.

Prevention suggestions:
Regular maintenance: Clean the pipeline at least once a year, and shorten the cycle in areas with poor water quality.
Install filters: Install Y-type filters in the water system to intercept impurities and clean them regularly to prevent mud and rust from entering the pipeline.
Monitor water quality: control hardness and pH value to prevent scaling.

Special treatment for biomass boilers:
‌ Fuel management ‌: select fuel with low ash content and few impurities, and perform pretreatment (such as screening and crushing) to reduce the generation of ash residue. ‌
Pipeline design improvement ‌: optimize pipeline layout, reduce bends and diameter changes, use insulation measures to prevent water vapor condensation, and install ash hoppers and ash removal devices.

Choose the appropriate method according to the degree of blockage and pipeline material. If self-treatment is ineffective or involves high-pressure/high-temperature components, be sure to seek help from professionals.

Read more: Boiler tube size chart or Carbon steel ERW boiler tube & air heater tube specification