30-inch, Gas Pipeline Integrity Assessment
Location: Louisiana (US)
A midstream company required a Department of Transportation (DOT) integrity assessment on a 30-inch transmission gas pipeline. In order to meet federal compliance standards for continued gas operations, the operator elected to execute a hydrostatic pressure test between an existing compressor station and a mainline valve location. Several variables in the scope of work registered high in the preliminary risk assessment:
- Heavy populated commercial and residential areas required official notification and time for relocation.
- Heavy traffic railway corridors required official prior notice with no usage during pressure test schedule.
- Diameter: 30 inches
- Length: 16.5 miles
- Wall Thickness: 0.375 inches
- Maximum Allowable Operating Pressure (MAOP): 1,440 psi
- Engineered pig train calculations for chemical cleaning.
- Engineered volumetric calculations for pipeline flooding.
- 8-hour CFR standard hydrostatic pressure test; 30-minute CFR standard hydrostatic spike pressure test.
- Pre-engineered pipeline calculations for de-watering procedure to prevent air lock on elevation profile changes.
- Pipeline fluid water treatment as specified by state guidelines.
- Drying to -40°F with ¼” penetration for product preparation.
Plan of Execution
- Pipeline Cleaning
- Chemical surfactants
- Defoaming agents
- Mechanical pigging systems
- AquaGel® Pig Systems
- Pipeline Flooding
- Utilization of filtered water from an adjacent natural source.
- 1.5 miles of 8-inch above ground piping for source water transportation.
- Hydrostatic Pressure Test
- 12-hour pressure stabilization period.
- 8-hour approved pressure test.
- 30-minute spike test at 139% of MAOP.
- Utilization of real-time electronic data recording instrumentation.
- Pipeline Dewatering
- Relinquish used test medium into natural surrounding per state regulations.
- Mechanical pigging systems.
- Pipeline Air Drying
- Achieved dew point of -40°F and ¼ inch penetration.
Technical Achievements & Benefits
- Successfully executed Management of Change (MOC) orders to accommodate clean pipe specifications.
- Responsive field supervision provided real time solution for unplanned water source failures.
- Executed 24-Hour SIMOPS schedule to overcome severe weather delays as a result of a tropical storm.
- Test medium discharge satisfied state environmental regulations.
- Jobs completed with zero incidents and no environmental impact.