Q1: What are the key steps in pipeline installation?
A1: Steps include surveying, trenching, pipe stringing, welding, coating repairs, lowering-in, backfilling, and hydrotesting. Welds are inspected via NDT (e.g., X-ray). Proper bending avoids stress concentrations. Offshore pipelines may use S-lay or J-lay methods. Compliance with environmental regulations is critical.
Q2: How are line pipes welded in the field?
A2: Field welding uses shielded metal arc welding (SMAW) or automated techniques. Preheat and post-weld heat treatment (PWHT) prevent cracking. Welders must be certified to API 1104 standards. Inspection includes visual, UT, and RT. Poor welds can cause leaks or failures.
Q3: What is pipeline pigging?
A3: Pigging involves sending devices (pigs) through pipelines for cleaning, inspection, or separation. Smart pigs use sensors to detect corrosion or dents. Cleaning pigs remove debris to maintain flow efficiency. Pigging is done during commissioning, maintenance, or decommissioning.
Q4: How are pipeline leaks detected?
A4: Methods include pressure monitoring, acoustic sensors, fiber optics, and SCADA systems. Smart pigs with magnetic flux leakage (MFL) or ultrasonic sensors pinpoint defects. Drones and satellites inspect remote areas. Early detection prevents environmental damage.
Q5: What is stress corrosion cracking (SCC), and how is it prevented?
A5: SCC occurs under tensile stress in corrosive environments. Prevention includes proper material selection (e.g., X65 steel), coatings, CP, and stress-relieving heat treatments. Regular inspections and pH control of transported fluids reduce risks.
