Pipeline Repair ABC Company ABC Chemical Complex Engineering Specification
Pipeline Repair • PURPOSE • Provides repair guidelines on above ground and buried pipelines. • GENERAL • When a pipeline is determined to be leaking, an immediate temporary repair will be made to insure public safety, minimize damage to property, and avoid damage to the environment.
Pipeline Repairs • REFERENCES • API 1104 • Welding of Pipelines and Related Facilities • API 1107 • Pipeline Maintenance Welding Practices • ASME B31.8 • Gas Transmission and Distribution Piping Systems • ASME B31.4 • Liquid Transportation Systems for Hazardous Chemicals and Hydrocarbons
Pipeline Repair • DEFINITIONS • CGI: Combustible Gas Indicator • HVL: Highly Volatile Liquid • LEL: Lower Explosion Level • MAOP: Maximum Allowable Operating Pressure • MSDS: Material Safety Data Sheet
Pipeline Repair • Consult MSDS for the pipeline product during a pipeline repair. Determine personal protective equipment specific to the chemical and request from person in charge of the repair. • The following table summarizes the minimum required safety equipment for pipeline repairs.
Material or Chemical Ethylene Hydrogen VCM Vapors VCM Liquids Kerosene Ethylene Dichloride Natural Gas Safety Equipment Fire extinguisher Combustible Gas Ind. Fire Retard. Clothing Eye goggles Ear plugs Full or air face mask Slicker suits and boots Non-Sparking Tools
Pipeline Repair • Check for gas presence prior to welding in or around an area containing flammable gas or liquids. • Maintenance craftsman have the final authority for work to be performed. • Post warning signs at the entrances of the right-of-way during repair work.
Pipeline Repair • PROCEDURE • Leak Repairs • Leak Classification • Pinpointing the Leak - Aboveground Gas and HVL • Pinpointing the Leak - Underground Gas and HVL • Excavation • Precautions • Preliminary Failure Analysis • Initial Leak Arrest
Pipeline Repair • Methods of Repair - Corroded Areas • Repair, if possible, by cutting out a cylindrical pipe section and replacing it with a pipe of equal or greater design strength. • Do not weld on hydrogen or ethylene pipelines before shutdown/purging operations are complete. • Acceptable repairs on a pipeline during operation: • Weld a nipple over a small leak and install fitting. • Install a leak clamp over a corrosion pit. • Use a patch with rounded corners for pipe with <40K SMYS. • Repair with full encirclement welded split sleeve.
Pipeline Repair • Leak Repair - Cracks or Tears • Replace a cylindrical section containing the crack or tear with an equivalent pipe section. • Reduce the pressure to 20SMYS equivalent or less if the line cannot be removed from service. • Determine the pipe condition by visual and NDE methods. • Stop welding or heating operations on the pipe. • Drill the ends of the crack and test by NDE • Repair with a full encirclement welded split sleeve. • Request Unit Manager approval to return to service.
Pipeline Repair • Leak Repair - Gouges, Grooves, and Dents • Repair by cutting out a section of the pipeline containing the defect and replace with a new section of equivalent or higher strength and composition. • Reduce pressure to 20%SMYS or less if line cannot be removed from service. Use one of the following methods for repair: • Install a full encirclement welded split sleeve. • Repair with installation of a full encirclement welded hot tap sleeve providing the entire defect can be removed with the hot tap coupon.
Pipeline Repair • RECONDITIONING OF PIPE • Pipelines that cannot be removed from service • Repair with replacement of an equivalent section. • Repair cracks in welds by grinding and rewelding. • Repair small corroded areas by weld metal overlay. • Repair small pitted areas with a welded patch. • Repair large corroded area with a full encirclement welded split sleeve. • Repair all gouges or grooves deeper than 10% wall thickness. Use a full encirclement welded sleeve.
Pipeline Repair • Repair dents deeper than 1/4” on pipe to NPS 12 or more than 2% greater than NPS 12. • Repair dents that affect the curvature of the pipe with removal of a cylindrical section containing the defect and replacement with an equivalent section. • Repair dents not meeting the above restrictions by filling the dent with a hardenable material and installing a full encirclement welded split sleeve.
Pipeline Repair • Initial Inspection • Determine soundness of the pipe adjacent to the defect prior to work • Inspect external surface of the pipe by one of the following methods: • Inspect exterior of pipe visually aided by a pit gage. • Use magnetic particle inspection if cracking is suspected. • Determine pipe wall thickness with ultrasonic testing. • Use radiographic inspection as required for definition.
Pipeline Repair • Welding • Check for hardness on hydrogen lines and maintain a hardness equal to or less than BHN 235. • Welding Procedures • Perform all weld repairs by Company employees using Company Welding Procedure Specification (WPS) 1.2. • Perform all weld repairs by Contract employees using Company-approved welding procedures provided by the Contractor.
Pipeline Repair • Welder Qualifications • Use Company welding procedure for qualification of Company employees to make weld repairs. • Use Contractor welding procedure (Company approved) for qualification of Contract employees to make repairs. • Burn through control • Burn through during welding is not expected when welding parameters do not exceed 20 volts and 100 amperes, if the remaining wall thickness is greater than 0.320 inches (See ASME/ANSI B31.8, paragraph 851.43f). Welding performed outside these limits must be approved by the Plant Engineer.
Pipeline Repair • Coating Repair • Repair pipe coating damaged during pipeline repair activities in accordance with the original coating manufacturer’s recommendations. • Hydrotest pipe replacement sections to 1.5 times MAOP prior to installation. Hold for one hour. • Test all field welds with 100% NDE coverage using the best method for the weld configuration. • Grade and repair weld defects in accordance with API 1104 and API 1107 requirements.
Pipeline Repair • Documentation • Include the location of the leak, location class, grade of the leak, and action taken when writing leak reports. • Add repair reports to the original equipment file, the inspection file, and the DOT coordinators file. • The DOT Coordinator shall determine if the leak is classified as an incident that requires reporting to the regulatory authorities.