Closed-Type (Tubular) Heat Shrink Casing
Field Joint Encapsulation and Sealing for Pre-Insulated Pipelines
Product Overview
Our Closed-Type (Tubular) Heat Shrink Casing is a pre-formed, seamless heat-shrinkable sleeve designed for the encapsulation and sealing of field joints on pre-insulated (jacketed) pipelines. Unlike wraparound sleeves, this casing is supplied as a fully closed tubular structure that is slid over the pipe end before welding and then positioned over the joint after welding is completed.
This product is specifically engineered for pre-insulated pipeline field joints, providing a continuous outer jacket reconstruction that seals the insulation cavity against moisture ingress while delivering mechanical protection equivalent to the parent pipe insulation jacket.
Configuration for 10-Inch Application
| Parameter |
Specification |
| Nominal Pipe Size |
4'',6'',8'',10 inch |
| Suitable Pipe OD |
114,168,273,355 mm |
| Casing Configuration |
Closed tubular (seamless) |
| Casing Thickness |
2–4 mm |
| Width per Part |
Minimum 600 mm |
| Parent Pipe Insulation Gap |
600 mm |
| Extension Past Inner Sleeve Edges |
60 mm beyond each outer edge of the 1000 mm wide inner sleeve |
| Overlap Between Casing Parts |
80 mm |
The two-part configuration allows the casing to span the full insulation gap while providing controlled overlap at the center, ensuring a continuous sealed enclosure over the joint area.
System Function
In a pre-insulated pipeline system, the carrier steel pipe is wrapped with polyurethane foam insulation and protected by an outer jacket (typically HDPE). At field joints, this jacket must be reconstructed after welding to:
Seal the insulation cavity against groundwater and moisture ingress
Provide mechanical protection to the joint insulation equivalent to the parent jacket
Accommodate thermal movement of the carrier pipe without compromising the seal
The Closed-Type Heat Shrink Casing accomplishes this by shrinking down at both ends onto the parent jacket pipe, with a pre-applied or field-applied mastic sealant forming a watertight bond. The central portion remains at full diameter, creating a cavity that is subsequently filled with pour-in-place foam through a fill hole
Construction
| Layer |
Material |
Function |
| Backing |
Radiation cross-linked high-density polyethylene (HDPE) |
Mechanical protection, UV resistance, shrink memory |
| Sealant (at ends) |
Elastomeric mastic / hot-melt adhesive |
Watertight sealing to parent jacket pipe |
| Central section |
Non-shrinking or reduced-shrink tubular section |
Maintains cavity for subsequent foaming |
The cross-linked HDPE backing provides the necessary shrink force and thermal stability to withstand torch application without melting or degrading
Key Features & Benefits
| Feature |
Benefit |
| Closed Tubular Design |
No seam or closure patch—inherently more reliable seal than wraparound alternatives |
| Two-Part Configuration |
Accommodates the full 850 mm insulation gap with controlled 80 mm center overlap |
| Extended Coverage |
60 mm extension past the inner sleeve edges ensures complete encapsulation of the joint zone |
| Thick-Wall Construction |
Provides mechanical protection comparable to the parent HDPE jacket |
| Heat-Shrink End Sealing |
Ends shrink down onto the jacket pipe with mastic, forming a permanent watertight bond |
| Foam Fill Compatible |
Central section remains at full diameter, allowing post-installation foam injection through a drilled fill hole |
| Pressure Testable |
Joint can be pressure-tested after casing installation and before foaming 1 |
Application Sequence
Pre-installation: Slide the closed casing sections over one pipe end before welding (or position on the carrier pipe prior to joint assembly).
Pipe Welding: Complete the girth weld and apply any required corrosion protection to the steel joint.
Surface Preparation: Clean and abrade the parent jacket pipe surfaces where the casing ends will seal.
Position Casing: Center the casing over the insulation gap, ensuring the two parts overlap by 80 mm and extend 60 mm past each inner sleeve edge.
Shrink Ends: Apply heat uniformly around each casing end with a propane torch until the backing shrinks down and the mastic sealant flows to form a watertight bond.
Pressure Test: Test the seal at the designated test port.
Foam Injection: Drill a fill hole in the central casing section and inject polyurethane foam to fill the joint cavity.
-
Seal Fill Hole: Close the foam hole with a plug or welded patch
Typical Properties (Reference)
| Property |
Typical Value |
| Backing Material |
Cross-linked HDPE |
| Backing Thickness |
2–4 mm (project-specific) |
| Tensile Strength (HDPE) |
≥ 23 MPa |
| Elongation at Break |
≥ 600% |
| Hardness |
60–67 Shore D |
| Max Operating Temperature |
50–60°C (standard pre-insulated pipe service) |
| Shrink Ratio (ends) |
≥ 25% radial recovery |
| Sealant Type |
Elastomeric mastic / hot-melt adhesive |
Values are indicative and shall be confirmed against the specific product data sheet and project specification.
Standards & Compliance
Heat-shrinkable materials for pipeline field joint coatings are addressed under ISO 21809-3 (Petroleum and natural gas industries — External coatings for buried or submerged pipelines — Part 3: Field joint coatings), which classifies heat-shrinkable materials and specifies test requirements for peel strength, cathodic disbondment, impact resistance, indentation resistance, and thermal ageing
For pre-insulated district heating and jacketed pipeline systems, relevant product standards and industry practices apply in addition to ISO 21809-3, particularly regarding foam compatibility and pressure testing.
Primary Applications
Pre-insulated district heating pipelines — Field joint jacket reconstruction and sealing
Oil and gas pre-insulated flowlines — Joint encapsulation for temperature-maintained pipelines
Pre-insulated pipeline systems — Specifically configured for 355 mm OD carrier pipe with 850 mm insulation gap
Any jacketed pipeline requiring field joint sealing — Where a closed tubular casing is preferred over wraparound sleeves
CNpetro — Protecting pipelines. Advancing performance.
For project-specific configurations, data sheets, or technical consultation, please contact our sales team.
Keywords: closed type heat shrink casing, tubular heat shrink casing, pre-insulated pipe joint, field joint sealing, 10 inch heat shrink casing, ISO 21809-3, HDPE casing, foam injection joint
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