Internal pipeline liners serve a dual purpose: they protect the pipe wall from chemical attack and erosion by transported fluids, and they reduce surface roughness to improve flow efficiency. In the oil and gas industry, even a modest improvement in flow coefficient translates to millions of dollars in pumping energy savings across a large network.
Types of Internal Liners
The primary categories of internal pipeline lining systems include spray-applied liquid coatings, cured-in-place pipe (CIPP) liners, and mechanical slip liners. Each is suited to different pipe diameters, operating conditions, and rehabilitation scenarios.
Spray-Applied Internal Coatings
For large-diameter pipelines (typically 12 inches and above), robotic spray systems apply polyurea or epoxy liners from the interior, achieving consistent film thickness across complex geometries including bends and T-connections. Modern robotic applicators can line up to 1,500 feet of pipe per day with laser-guided thickness monitoring.
Drag Reduction Liners
Specialized smooth-surface epoxy liners reduce the Manning roughness coefficient of steel pipe from 0.013 to as low as 0.009, delivering flow efficiency improvements of 15–25% compared to unlined corroded pipe. When combined with external polyurea protection, a fully lined pipeline represents the gold standard in long-term asset management.
Quality Control and Inspection
Internal coating quality is verified through CCTV inspection, laser profilometry, and random coupon pull tests. AWWA C210 and API 5L provide the foundational standards for internal lining of steel pipelines. Our resources library includes detailed QC procedure guides for internal application projects.