The scrapping standard for boiler tubes

In daily operations, it is essential to assess whether equipment and components remain suitable for continued use. Scrapping standards provide a clear basis for judgment: when the performance, structure, or safety indicators of equipment decline to a level where safe operation or economic efficiency can no longer be ensured, timely replacement or decommissioning is necessary. In simple terms, these standards establish a set of quantitative or qualitative criteria to prevent safety risks due to aging, wear, or damage.

What is a Boiler Tube?

A boiler tube is a steel material with an open-ended, hollow section, significantly longer in length compared to its diameter. Based on manufacturing methods, boiler tubes are classified into seamless steel pipes and welded steel pipes. As a critical component of industrial boilers, their safety and lifespan directly impact boiler performance.

This article explores the scrapping standards for boiler tubes, key factors influencing their lifespan, and best practices for maintenance.

Boiler Tube Scrapping Standards

Scrapping criteria for boiler tubes are primarily based on wall thickness wear and the residual strength ratio. Generally, boiler tubes should be decommissioned when:

Wall thickness wear exceeds 15% of the original tube thickness.

Residual strength falls below 5% of the original design value.

These criteria are derived from thermodynamics and material mechanics to ensure that boiler tubes can withstand high-temperature and high-pressure conditions, preventing failures such as ruptures due to excessive wear or material fatigue.

1. Wall Thickness Wear Exceeds 15%

Continuous exposure to high temperature, high pressure, and corrosive environments leads to material degradation. If the tube wall thins beyond 15% of its original thickness, the structural integrity of the pipe significantly weakens, increasing the risk of failure.

2. Residual Strength Below 5%

Over prolonged use, the load-bearing capacity of a boiler tube diminishes. If the tube’s residual strength drops below 5% of the original design, it becomes unfit for safe operation and must be replaced.

Factors Affecting Boiler Tube Lifespan

1. Material Selection

The lifespan of a boiler tube depends largely on the material used. High-quality boiler tube materials such as 20G and 12CrMoVG offer superior high-temperature and corrosion resistance, often exceeding a 10-year service life under proper operating conditions.

2. Welding Quality

The quality of welding directly affects a boiler tube’s durability. Poor welding may lead to cracks, leaks, or weak joints, compromising the overall integrity and lifespan of the tube.

3. Manufacturing Process

Strict adherence to national and industry standards ensures high-quality boiler tubes. Factors such as raw material selection, forming techniques, and precision control significantly influence the tube’s mechanical properties and durability. In applications requiring precision tubes, even minor process variations can lead to substantial performance differences.

4. Operating Environment

Boiler tubes function in extreme conditions involving high temperatures, high pressures, and corrosive agents, which accelerate material degradation. Tubes exposed to aggressive environments such as sulfur-containing flue gases or alkali metals experience faster wear and require more frequent inspection and maintenance.

5. Operating Conditions

Maintaining optimal temperature, pressure, and water quality extends boiler tube lifespan. Inconsistent operating conditions, excessive thermal stress, or improper maintenance can cause premature damage.