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.
Specification
Diameter: 30 inches
Length: 16.5 miles
Wall Thickness: 0.375 inches
Maximum Allowable Operating Pressure (MAOP): 1,440 psi
Challenges
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.