I. Material Selection Optimization: Enhance Environmental Resistance at the Source

1. Targeted Base Material Selection
   • Conventional Media (Water/Steam): Use 304 stainless steel (06Cr19Ni10), tensile strength ≥520MPa, oxidation resistance ≤800℃;
   • Corrosive Media (Acids/Alkalis/Salt Solutions): Upgrade to 316L (022Cr17Ni12Mo2) with ≥2% molybdenum, 3x improvement in chloride resistance;
   • High-Temperature Conditions (>450℃): Adopt Inconel 625 alloy (Ni-Cr-Mo alloy), maintaining 70% yield strength at 650℃.
2. Surface Protection Enhancement
   • Corrosion-Resistant Coatings: Spray PTFE (thickness ≥0.3mm) on inner walls, resistant to strong acids/alkalis (pH 1-14);
   • Wear-Resistant Treatment: Surfacing Stellite alloy in severe erosion areas (e.g., downstream of elbows), hardness HRC 55-62, 5x improvement in particle wear resistance.

II. Structural Design Optimization: Balance Compensation and Fatigue Life

III. Installation Process Control: Avoid 人为 Damage and Stress Concentration

1. Positioning & Installation Key Points
   • Coaxiality Requirement: Axial deviation ≤1mm/m, flange parallelism ≤0.5mm (calibrated with dial indicator);
   • Pre-Stretching/Compression: Execute within ±5% of design value (e.g., DN200 compensator pre-stretched 10mm±0.5mm), fix with positioning bolts before welding.
2. Support System Configuration
   • Fixed Support: Install within 10D, load-bearing capacity ≥1.2×medium thrust (e.g., PN16 DN200 thrust 50kN, support withstands 60kN);
   • Guide Support: Install at 3D, gap ≤2mm (prevents excessive lateral displacement).

IV. Operation Condition Management: Control Media & Environmental Loads

1. Media Pretreatment
   • Impurity Filtration: Install Y-type filter (precision ≤40 mesh) upstream to prevent welding slag/sediment from abrasion;
   • pH Regulation: Maintain media pH 6-8, add neutralizers (NaOH or citric acid) when out of range.
2. Operation Monitoring Thresholds
   • Temperature Control: Avoid over-temperature operation (304 stainless steel upper limit 350℃, short-term over-temperature ≤400℃ for ≤10h/month);
   • Pressure Fluctuation: Limit transient pressure surges ≤1.3×design pressure (install surge tanks or pressure relief valves).

V. Periodic Maintenance Strategies: Proactive Failure Prevention

1. Routine Inspection Items
   • Visual Inspection: Check bellows surface quarterly; replace if cracks ≥1mm or wall thickness reduction ≥15%;
   • Bolt Torque Retest: Check flange bolts annually with torque wrench, maintain M20 bolt torque at 180-220N·m.
2. Advanced Testing Techniques
   • NDT: Perform ultrasonic thickness measurement (replace if wall deviation >20%) and magnetic particle inspection (0.5mm crack sensitivity) every 2 years;
   • Pressure Testing: Conduct 1.5×design pressure hydrostatic test every 5 years (hold for 30min without leakage).

VI. Special Condition Countermeasures

VII. Failure Mode Prediction & Improvement

1. Common Failure Causes and Countermeasures
   • Corrosion Perforation: Switch to 317L stainless steel (Mo 3-4%) when media Cl⁻＞50ppm;
   • Fatigue Fracture: Calculate fatigue life (e.g., DN150 compensator designed for 5000 cycles), shorten inspection cycles after 3000 cycles;
   • Buckling Deformation: Add internal support rings (spacing ≤200mm) when pitch/height ratio >2.5.