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(Welding on In-Service Vessels, Post-Test Inspection, Industrial Safety…
- Welding on In-Service Vessels
- Vessel might be pressurized
- Heat from welding could cause cracks or explosions
- Welding near flammable contents could cause fires
- Thermal Degradation and Burn-Through
- Excessive heat can compromise structural integrity
- Risk of molten metal penetrating the containment barrier (burn-through)
- Maximum allowable inner diameter (ID) surface temperature limits:
- Low-hydrogen electrodes (e.g., E7018-H4R): 1800°F (982°C)
- Cellulosic electrodes (e.g., E6010): 1400°F (760°C)
- Importance of flow velocity (minimum 1.3 ft/s for liquids) for convective cooling
- Necessity of supplemental purging (steam or inert gases) in static or low-flow conditions
- Potential for hydrocarbon decomposition at high ID temperatures (≤1800°F shown to prevent in ethylene piping study)
- Formation of carburized layers and eutectic iron at higher temperatures
- Importance of real-time temperature monitoring
- Combustion and Explosion Hazards
- Requires rigorous atmospheric controls
- Even trace hydrocarbons in "empty" tanks can create explosive mixtures
- Critical preconditions for combustion:
- Oxygen concentration ≥10%
- Flammable vapor concentration between LEL and UEL
- Ignition source with sufficient energy (e.g., welding arcs at ~6,500°F)
- Blanchard Refinery protocol prohibits work on equipment containing oxygen, plant air, or hydrogen without waivers
- NFPA 326 mandates a four-step purification process for tanks previously holding volatile liquids:
- Degassing: Steam injection (200–250°F for 8–12 hours)
- Inerting: Flooding with nitrogen (target <8% O2)
- Verification: Continuous monitoring of O2, LEL, CO, H2S
- Ventilation: Forced air to maintain safe atmosphere
- Electrical and Operational Hazards
- Amplified electrical risks in maritime environments
- Wilhelmsen SIRE 2.0 guidelines prohibit AC welding on tankers due to ventricular fibrillation risk
- Use of transformer-rectifier units for DC outputs below 50 V
- Precautions for In-Service Welding
- Check for Flammable Vapors – Test for explosive gases
- Use Low-Heat Welding Techniques – Prevents cracks
- Monitor Vessel Pressure & Temperature – Welding can affect metal strength
- Have Emergency Plans Ready – In case something goes wrong
- Safety Protocols and Mitigation Strategies
- Pre-Welding Hazard Assessments
- Stage 1: Fluid and Material Compatibility
- Gases require more stringent controls than liquids
- Hydrogen-containing processes require hardness testing for HIC
- Stagnant lines need supplemental purge plans validated by CFD
- Stage 2: Welding Procedure Specification (WPS)
- Define heat input limits (formula provided)
- Specify preheat requirements (minimum 50°F for carbon steel)
- Detail pass sequencing (temper bead for CRA)
- Stage 3: Atmospheric Monitoring
- Use multi-gas detectors at four elevations in confined spaces
- PIDs with 10.6 eV lamps for trace aromatics in ethylene service
- Regulatory and Industry Standards
- ASME Boiler and Pressure Vessel Code (BPVC)
- Section IX mandates Procedure Qualification Records (PQRs)
- Specifies inspection for root passes (GTAW) and fill/cap passes (SMAW):
- GTAW root passes: 100% visual + radiography
- SMAW fill/cap passes: Ultrasonic testing (UT) at 2" increments
- SIRE 2.0 Maritime Safety Framework
- Mandates flashback arrestors on torch and regulator
- Requires ISO 3821 compliant hoses with quarterly bend testing
- Demands annual practical welder certification exams under simulated pressure
- Emergency Response Planning
- Arc interruption via magnetic breakers (within 0.1 seconds of ground fault)
- Pre-installed nitrogen ports for rapid inerting
- AED deployment and spinal precautions for electric shock
- Hydrogel dressings with silver sulfadiazine for thermal burns
- Should only be done when absolutely necessary
- Complex and high-risk activity
- Economically necessary to avoid downtime
- Advances in technology and regulations have reduced incident rates since 2020
- Future research should prioritize smart welding systems and AI-driven hazard prediction
- Adherence to standards (API, ASME, SIRE) is crucial for safety and operational continuity
- Checks for Leaks, Deformations, or Material Failures
- Visually inspect all joints, connections, and seals for leaks
- Look for deformations in pipes, vessels, or components
- Examine materials for cracks, bulges, or discoloration
- Ensure All Removed Components Are Reinstalled
- Verify all valves, gauges, and other removed components are properly reinstalled
- Check that components are correctly oriented and securely fastened
- Confirm temporary test fittings/plugs are removed and replaced
- Record maximum test pressure achieved
- Note the duration of the test
- Leaks detected and locations
- Observed deformations or material failures
- Components that required reinstallation
- Any repairs or adjustments made
- Include photographs or diagrams if necessary
- Ensure documentation is dated, signed, and stored according to company procedures
- Ensure the system's safety and readiness for operation
- Maintain a comprehensive record of test results for future reference
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