Internal protection at the field-weld zone
Pipelines with internal liquid-epoxy lining or internal FBE protection have an obvious weak point: the mainline lining stops 50-100 mm short of the bevel so the welder doesn't damage it. Once two pipes are welded together, that 100-200 mm girth zone is internally bare steel — exposed to whatever the line carries. For sour-service oil & gas, sea-water injection or potable-water service, that's not acceptable.
Insert sleeves bridge that gap. They're pre-fabricated, pre-coated steel sleeves designed to fit inside the bare girth zone after welding, restoring continuous internal protection.
How they work
- The pipeline pipe sections are welded together as normal in the field
- After the weld is QC-approved, an insert sleeve — pre-coated to match the mainline lining — is positioned inside the bare girth zone
- The sleeve seals against the existing internal lining via mechanical compression or bonding adhesive
- Result: a fully internally-protected pipeline with no break in the corrosion barrier
Sleeve types we supply
Sour-service insert sleeves
For oil & gas pipelines carrying H₂S/CO₂. Pre-coated with phenolic FBE or sour-service liquid epoxy. Sealed via mechanical compression with elastomer O-rings or via in-situ bonding adhesive.
Potable-water insert sleeves
For drinking-water pipelines. NSF/ANSI 61-certified internal coating. Stainless or epoxy-coated carbon steel sleeve material.
Welding-pipe insert sleeves
Combined function — provides internal corrosion protection AND acts as a backing ring for high-quality root weld penetration. Common in critical refinery and petrochemical applications.
Sea-water insert sleeves
For sea-water intake/outfall lines and offshore production pipelines. Pre-coated with sea-water-grade epoxy or polyurea internal lining; outer surface pre-treated for compatibility with carrier-pipe welding.
Construction
| Component | Material |
|---|---|
| Sleeve body | Carbon steel, stainless steel, or duplex per project spec |
| Internal coating | Matched to carrier-pipe internal lining (FBE, liquid epoxy, polyurea, etc.) |
| Sealing element | EPDM, NBR, FKM (Viton®) or PTFE per service |
| Standard length | 200-400 mm (project-spec) |
| Diameter range | matched to internal pipe ID |
Where we deploy them
- Sour oil & gas pipelines with internal sour-service epoxy lining
- Sea-water injection lines for water-flood enhanced oil recovery
- Potable-water transmission and distribution networks
- Process piping in refineries, petrochemical plants and chemical plants
- Pre-fabricated pipe spools where multiple welds in one assembly need internal coverage
- In-service rehabilitation projects where existing internal damage needs sleeve insertion
Standards
- ISO 21809-1 — pipeline external/internal coatings (for the sleeve coating itself)
- NACE MR0175 / ISO 15156 — sour-service materials qualification
- AWWA C210 — liquid epoxy lining (potable-water sleeves)
- NSF/ANSI 61 — drinking-water safety
- API 5L — line pipe specifications (for the sleeve substrate)
Common questions
How does an insert sleeve seal against the internal lining without damage? Mechanical sleeves use elastomeric O-rings on the outside, designed to compress against the existing lining without scratching it. Bonded sleeves use a thin adhesive layer that flows during installation to fill any gap.
What about the weld root area itself? The insert sleeve typically extends past the weld root, so the weld root sees the same internal environment as the rest of the line — but with the protection of the sleeve coating just outboard.
Can sleeves be installed remotely on long lines? Yes — for in-service or post-construction rehab, we deploy mandrel-mounted sleeves that travel through the pipe with a pigging or remote-installation system and lock at the target weld location.
