How to clean the blockage at the metal pipe elbow?

Because of the complex structure of the metal pipe elbow, it is easy to accumulate scale, impurities or corrosion products, causing blockage. When cleaning, it is necessary to select the appropriate method based on the nature of the blockage and the removability of the elbow. The following are specific solutions:

1. Preliminary inspection and judgment

Confirm the type of blockage:

Scale (white/grayish hard deposits, common in hot water or steam pipes);
Grease/viscous substances (more common in chemical or food industry pipes);
Rust/welding slag (metal debris, often accompanied by system aging or construction residues).

Evaluate the removability of the elbow:

Removable: Direct removal for more thorough cleaning;
Non-removable: Circulation cleaning or mechanical dredging is required.

2. Cleaning methods for removable elbows

(1) Mechanical cleaning

Tools: wire brush, pipe dredging spring, high-pressure water gun (pressure ≥50MPa).

Steps:
Remove the elbow and use a wire brush or a scraper to remove large deposits;
Use a high-pressure water gun to alternately rinse the inner wall from both ends;
For stubborn rust, use an angle grinder equipped with a soft-shaft brush to grind (pay attention to protecting the pipe wall).

(2) Chemical immersion
Scale/rust:
Soak the elbow in diluted hydrochloric acid (5%~10%) or citric acid solution (10%~15%) for 1~3 hours, then rinse with clean water. Note: Stainless steel elbows require special cleaning agents (such as nitric acid + corrosion inhibitor) to avoid intergranular corrosion.

Oil stains:
Soak in sodium hydroxide (caustic soda) solution (5%) or special degreasing agent, and clean with a brush.

3. Cleaning method for non-detachable elbows

(1) High-pressure water jet cleaning
Tools: Flexible high-pressure spray gun (with rotating nozzle, pressure 70~150MPa).

Operation:
Insert the nozzle into the upstream of the pipeline and extend it to the elbow;
High-pressure water and rotating nozzle impact the blockage, and the residue is discharged from the downstream.

(2) Chemical circulation cleaning
Steps:
Connect the circulation pump and cleaning agent tank to the system;
Inject acidic or alkaline cleaning liquid (select according to the blockage) and circulate for 2 to 6 hours;
After neutralization, empty the agent and rinse with clean water until the pH is neutral.
Applicable scenarios: multi-elbow or long pipeline system.

(3) Pneumatic/mechanical unblocking
Pneumatic pulse: Use compressed air to release pressure instantly and shake off the blockage (need to be used with a pressure relief valve).
Flexible shaft unblocking machine: Insert a flexible shaft with a drill bit or brush head into the elbow to crush impurities.

4. Special blockage treatment
Welding slag/metal debris:

Use a magnetic dredger (for iron debris) to absorb;
Or use a pipeline endoscope to locate and remove with a hook tool.

Colloidal deposits:
First soften with steam (temperature 120~150℃), then dissolve with a solvent (such as acetone).

5. Post-cleaning treatment
Passivation protection (for carbon steel pipes after pickling):
Use sodium phosphate solution (1%~2%) for circulated passivation to form a protective film.

Drying and rust prevention:
Blow dry with compressed air, or inject rust prevention oil (short-term protection).

Safety precautions:

1. Wear acid-resistant gloves, goggles and gas masks during chemical cleaning, and ventilate the work area.
2. Strong acids such as hydrochloric acid are prohibited from being used on stainless steel pipes to avoid stress corrosion cracking.
3. Keep away from people when operating high-pressure water guns/pneumatic tools to prevent injection injuries.
4. If the pipeline is a pressure vessel or high-temperature system, it must be operated by certified personnel.

Prevention suggestions:

Regular flushing: Backwash the pipeline with clean water every month to reduce sedimentation.
Add filters: Install magnetic filters (to intercept metal debris) or basket filters in front of the pump.
Water quality treatment: Install a water softener in hard water areas to control the Ca²⁺/Mg²⁺ concentration.

If the blockage is serious or the pipeline is a high-risk medium (such as flammable or toxic), it is recommended to entrust a professional cleaning company to handle it.

Read more: Guide to rust treatment of pipe elbows or  Elbow pipe fittings: types, applications and purchase considerations