In-Depth Analysis of Ball Valve Internal Structure

Preface

As critical components in modern fluid control systems, the internal precision of ball valves directly impacts system reliability. This guide demonstrates ASME B16.34 compliant disassembly procedures using a DN50 stainless steel floating ball valve as example.

Safety Protocol

1. System depressurization (≤0.2MPa residual pressure)

2. Lockout-Tagout (LOTO) implementation

3. PPE requirements: Cut-resistant gloves (EN388:2016) + safety goggles (ANSI Z87.1)

Professional Tool Kit

• Precision torque wrench (50-300N·m range)

• 316 stainless hex key set (ISO 2936)

• Seal face protector (PTFE material)

• Ultrasonic cleaner (40kHz frequency)

7-Step Disassembly Process

Step 1: Actuator Detachment
Remove stem nut using T40 Torx bit, document initial torque value. Protect stuffing box area from scratching Ralstonit® coating.

Step 2: Body Separation
Loosen ASTM A193 B8M bolts in crisscross sequence, retain one bolt as safety anchor. Use copper wedge for flange separation.

Step 3: Ball Assembly Extraction
Extract ball with magnetic handler, inspect Ra0.8μm surface finish. Note V-spring preload condition in seat retainer.

Step 4: Seat System Breakdown
Remove PTFE seats using expansion tool, measure original compression (1.2-1.5mm spec). Observe orientation marks on graphite seals.

Step 5: Stem Mechanism Analysis
Disassemble blowout-proof stem assembly, check ISO 5211 mounting surface flatness (≤0.02mm tolerance). Record thrust bearing clearance.

Step 6: Seal Integrity Testing
Perform helium mass spectrometer leak test (Class VI standard). Analyze ball/seat contact pattern with profilometer.

Step 7: Cleaning & Preservation
Clean components per ASTM G131 protocol, store in nitrogen-purged cabinet (≤-40℃ dew point).

Engineering Diagnostics

• Ball eccentric wear >0.15mm requires replacement

• Seat plastic deformation >30% nominal compression needs scrapping

• Stem torsion >3° demands metallurgical analysis

Technical Summary
Proper disassembly extends service life by 80%. Recommend full inspection every 8000 operating hours or 3 maintenance cycles. Complies with API 6D/ISO 17292 standards for demanding applications like petrochemical and LNG systems.