API Publ 1673-2009: Safe Welding Practices for Aboveground Storage Tanks – Technical Overview

API Publ 1673-2009, titled Safe Welding Practices for Aboveground Storage Tanks, provides recommended practices for ensuring safety during welding, cutting, grinding, and other hot work operations on aboveground storage tanks (ASTs). This publication is a key resource for facility operators, contractors, engineers, and safety personnel, offering practical guidance on hazard identification, personnel training, work procedures, and emergency preparedness. It consolidates industry experience to help prevent fires, explosions, and other incidents during hot work on ASTs.

1. Scope and Application

API Publ 1673-2009 applies to all hot work conducted on aboveground storage tanks, including those in crude oil, refined products, chemical, and water service. It covers tanks constructed of carbon steel, stainless steel, and other alloys, and addresses various tank geometries: fixed-roof, external floating-roof, and internal floating-roof designs. The publication is intended for use during new construction, maintenance, repair, alteration, and demolition activities.

The standard supplements but does not supersede requirements in API Standard 653 (Tank Inspection, Repair, Alteration, and Reconstruction), ASME Boiler and Pressure Vessel Code, or applicable local regulations (e.g., OSHA, NFPA). It should be integrated into a facility’s overall safety management system and hot work permit program.

2. Key Technical Requirements

The publication outlines critical technical requirements to ensure safe hot work operations. These include tank condition assessment, gas-freeing and atmospheric testing, welding procedure specifications (WPS), welder qualification, hot work permit systems, fire watch, ventilation, and post-weld inspection.

2.1 Pre-Welding Condition Assessment

Before any hot work begins, the tank must be thoroughly evaluated. This includes:

• Internal and external inspection for corrosion, cracks, thinned areas, or prior repairs that could affect safe welding.
• Product residue removal – tanks must be drained, cleaned, and gas-freed to eliminate flammable or toxic atmospheres.
• Atmospheric testing – the vapor space must be tested for oxygen content (% O₂), lower explosive limit (LEL), and toxic gases (e.g., H₂S, benzene) in accordance with OSHA 29 CFR 1910.146 (confined space entry) and API 2015.
• Isolation – piping, vents, and other connections must be physically blanked, disconnected, or locked out/tagged out to prevent inadvertent introduction of product or vapors.

2.2 Welding Procedures and Personnel Qualification

Welding must be performed in accordance with written Welding Procedure Specifications (WPS) qualified under ASME Section IX, AWS D1.1, or API 1104 as applicable. All welders must be qualified for the specific process, position, and materials. The publication emphasizes:

• Preheat and interpass temperature control to reduce cracking risk, especially in high-strength steels or when welding on tanks containing residual sulfides.
• Electrode storage and handling – low-hydrogen electrodes must be kept dry and used within specified time limits.
• Post-weld heat treatment (PWHT) when required by code or when welding on pressure-containing components or thick sections.

2.3 Hot Work Permit System

A formal hot work permit is mandatory. The permit must be issued by an authorized person and include:

• Specific location and description of work
• Results of atmospheric testing (time-stamped)
• Fire watch assignments (continuous during work and at least 30 minutes after)
• Fire extinguishing equipment provision
• Expiration time and reauthorization requirements

2.4 Post-Weld Inspection

After welding, visual inspection and non-destructive examination (MT, PT, UT) are required per API 653 and the applicable construction code. The publication recommends a hold-point for inspection before coating or relining.

3. Implementation Highlights and Safety Considerations

Effective implementation of API Publ 1673 requires commitment from management and clear communication at all levels. Key implementation considerations include:

• Training: All personnel involved in hot work must receive initial and annual refresher training on the hazards, permit system, and emergency procedures. The standard recommends that employers develop site-specific training programs.
• Supervision: A designated competent person must oversee the operation and have the authority to stop work if unsafe conditions arise.
• Contractor Management: When using outside contractors, ensure they are aware of and comply with facility hot work procedures. Pre-qualification and orientation are essential.
• Continuous Monitoring: Atmospheric conditions must be monitored continuously while hot work is in progress. Interrupt work if readings approach alarm limits.
• Emergency Preparedness: Fire drills, evacuation routes, and communication protocols must be established and rehearsed. Coordinate with local emergency responders.

4. Compliance and Regulatory Notes

API Publ 1673-2009 is a voluntary recommended practice; however, it is widely referenced in industry contracts, insurance requirements, and regulatory frameworks. Key regulatory interfaces include:

• OSHA 29 CFR 1910.252 – general welding, cutting, and brazing standards, including fire prevention and ventilation.
• NFPA 51B – Standard for Fire Prevention During Welding, Cutting, and Other Hot Work.
• API Standard 653 – tank integrity requirements for repair, alteration, and reconstruction.
• EPA and state air quality rules – may require vapor recovery, emission controls, or notification during tank cleaning and hot work.

Records of hot work permits, training certificates, inspection reports, and monitoring logs should be retained for the life of the tank or as required by applicable regulations.