Common Failures and Solutions for Alloy Steel Seamless Pipes in Power Plants.
Q1: Why does pitting corrosion and internal wall corrosion occur in my high-pressure steam pipes?
A1: Causes and Solutions
Causes: Presence of oxygen, chlorides, or sulfides in the steam pipes; water quality corrosion due to improper water treatment; scouring wear caused by excessive flow velocity.
Solutions:
Select corrosion-resistant alloy steels such as 15CrMoG, 12Cr1MoVG, or 304/316 stainless steel.
Improve water treatment processes to control dissolved oxygen and chloride ion concentrations.
Conduct regular cleaning of steam and water pipes to remove deposits and oxides.
Promptly grind, apply anti-corrosion coatings, or replace pipe sections where localized corrosion is detected.
Q2: Why do pipelines develop cracks or creep under high temperatures?
A2: Causes and Solutions
Causes: Long-term operation under high temperature and pressure induces creep; improper welding or heat treatment causes stress concentration; presence of corrosive substances (e.g., hydrogen or sulfides) in the medium.
Solutions:
Select alloy steel materials suitable for operating temperatures to ensure creep resistance.
Perform stress-relief annealing on welded pipe sections to reduce internal stresses.
Install temperature monitoring systems to prevent localized overheating.
Conduct regular non-destructive testing (UT or eddy current testing) to detect and address microcracks promptly.
For pipelines carrying corrosive media, add protective linings or surface coatings.
Q3: What causes steam or water leakage at pipe joints?
A3: Causes and Solutions
Causes: Substandard welding quality; inadequate sealing of flanges or joints; insufficient stress allowance for thermal expansion in piping.
Solutions:
Strictly inspect welding procedures before welding to ensure weld quality.
Use qualified gaskets during joint installation and tighten flange bolts to standard torque.
Install expansion joints in high-temperature pipelines to alleviate thermal expansion/contraction stresses.
Regularly inspect welds and joints; promptly repair leaks or replace gaskets when detected.
Q4: Why do pipes sag, bend, or vibrate?
A4: Causes and Solutions
Causes: Insufficient support or improper installation; fluid pulsation or mechanical vibration; inadequate consideration of thermal expansion.
Solutions:
Set support spacing according to design specifications to ensure reliable pipe fixation.
Install expansion joints on high-temperature pipelines to accommodate thermal expansion.
Add vibration dampers or reinforce pipe clamps for severely vibrating pipelines.
Conduct regular inspections of supports and bolts to prevent loosening.
Q5: How to determine if pipelines need replacement after long-term use?
A5: Causes and Solutions
Cause: Prolonged high-temperature and high-pressure operation leads to wall thinning, crack propagation, or severe corrosion, compromising safety.
Solutions:
Establish a pipeline periodic inspection system: Use ultrasonic testing, eddy current testing, or radiographic testing to monitor wall thickness and cracks.
Calculate remaining service life based on inspection data; immediately replace pipe sections exceeding safety thresholds.
For severely corroded but repairable sections, apply localized anti-corrosion coatings or replace linings.
Periodically review process conditions (e.g., flow velocity, pressure, temperature) to ensure pipelines operate within design parameters.
