Boiler Accidents: Comprehensive Causes Analysis and Prevention Measures (Part II)

Continuing our analysis of boiler safety, Part II focuses on steam-water priming, heat exchanger failures, and operational errors that compromise boiler integrity. These incidents often stem from poor water quality, design flaws, or inadequate maintenance.

1. Steam-Water Priming Accidents

Phenomenon: Excessive foam and turbulent water surface in the drum, leading to steam contamination with high-salt water. This causes water hammer in pipelines, superheater scaling, and turbine damage.

Causes:

High boiler water alkalinity or impurities, forming stable foam layers.

Sudden load increases or rapid steam valve opening, disrupting vapor-liquid separation.

Overfilled water levels reducing steam space.

Handling:

Reduce combustion and load; close main steam valves.

Activate continuous blowdown to lower salt concentration; inspect steam traps and pipelines.

Resume operation only after water quality improves and 水位 stabilizes.

Prevention:

Strict water quality control (e.g., limit total dissolved solids).

Regular blowdown practices; avoid abrupt load changes or overfilling.

2. Furnace Tube Rupture Accidents

Impact: Common in water-cooled walls and boiling tubes, causing steam/water leaks, furnace pressure surges, and potential fires. Severe cases lead to shutdowns and heat exchanger damage.

Causes:

Scale buildup from poor water treatment, causing overheating and tube thinning.

Blockages by debris (e.g., 脱落水垢，tools) in bends or small-diameter tubes.

Corrosion/erosion from oxygen pitting or fly ash abrasion.

Water circulation failures due to design flaws or operational errors (e.g., insufficient flow).

Handling:

Minor leaks: Reduce load, monitor water level, and prepare for shutdown.

Severe ruptures: Immediate emergency shutdown to prevent secondary damage (e.g., furnace collapse).

Prevention:

Rigorous water treatment and descaling; inspect for debris during maintenance.

Material upgrades for high-heat zones; regular thickness checks for corrosion.

3. Economizer and Superheater Failures

3.1 Economizer Leaks

Symptoms: Reduced feedwater pressure, increased water consumption, smoke temperature drops, and visible leaks near the economizer.

Causes:

Oxygen corrosion from untreated feedwater.

Fly ash erosion in flue gas pathways.

Water hammer from steam condensation or faulty check valves.

Handling:

Boiling economizers: Increase feedwater, reduce load, and avoid recirculation valves.

Non-boiling economizers: Bypass flue gases, isolate the economizer, and inspect for repairs.

Prevention:

Mandatory feedwater deoxygenation; anti-erosion coatings for economizer tubes.

Regular soot blowing to prevent ash accumulation.

3.2 Superheater Ruptures

Symptoms: Unusual noises, positive furnace pressure, reduced steam flow, and lower exhaust temperatures.

Causes:

Scale deposition from poor steam quality, leading to overheating.

Inadequate cooling due to design flaws or low steam flow during low-load operation.

Corrosion from water ingress during shutdowns.

Prevention:

Efficient steam-water separation devices; strict control of drum water levels.

Use of heat-resistant alloys and proper welding techniques for superheater tubes.

4. Water Level Gauge and Water Hammer Accidents

4.1 Gauge Failures

Risks: Glass tube explosions or false readings due to thermal shock, poor installation, or low-quality materials.

Prevention:

Preheat gauges before startup; gentle cleaning to avoid temperature shocks.

Quality glass tubes with thermal stress testing; secure but not over-tightened installations.

4.2 Water Hammer

Causes:

Steam condensation in pipelines (e.g., poor warm-up or priming).

Sudden closure of feedwater valves, creating pressure surges.

Handling:

Reduce steam flow, drain condensate, and inspect pipe supports for damage.

For economizer water hammer: Adjust feedwater flow or replace faulty check valves.

Prevention:

Proper pipeline warm-up and condensate drainage; slow valve operations.

5. Key Takeaways for Part II

This section addresses steam-water dynamics, heat exchanger vulnerabilities, and operational hazards. Key solutions include water quality management, material selection, and rigorous maintenance. In Part III, we will explore furnace explosions, flue gas re-ignition, structural damages, and human-factor errors, providing a holistic safety framework.