Composite Material Flexible Hose Lining for In-Situ Pipeline Rehabilitation
1. Definition and Technical Principles
Composite material flexible hose lining for old pipeline rehabilitation is a trenchless repair technology in which a factory-premanufactured flexible hose, constructed from multi-layer composite materials (typically combining thermoplastic polymer films, reinforcing fabric layers, and adhesive bonding interfaces), is inserted into an existing deteriorated pipeline to form a structurally independent or semi-structurally independent inner liner. The composite hose conforms to the internal geometry of the host pipe and, upon installation, creates a new corrosion-resistant, pressure-bearing conduit within the original pipeline envelope.
The fundamental operating principle relies on three mechanisms:
- Mechanical Conformity: The flexible composite hose, due to its inherent radial compressibility and bending flexibility, is pulled or pushed into the host pipe and naturally conforms to the internal bore geometry, including minor eccentricities, bends, and slight deformations.
- Interfacial Bonding: Where structural independence is not required, the composite hose is bonded to the internal surface of the host pipe using adhesives, mechanical interlocks, or thermal fusion, creating a unified pressure-bearing structure.
- Barrier Protection: The innermost layer of the composite hose—typically a dense polymer film (polyethylene, polypropylene, or fluoropolymer)—provides an impermeable barrier against corrosive media, effectively isolating the host pipe from the transported fluid.
2. Category and Business Positioning
This technology occupies a strategic position within the pipeline integrity and rehabilitation segment of the cladding and lining industry. It is distinct from conventional cladding technologies such as weld overlay, hydraulic explosive bonding, and explosion welding, which address new fabrication or in-service repair of metallic components. Composite hose lining addresses a different but complementary market need: the rehabilitation of large-diameter, long-span, in-service pipelines where excavation or shutdown is impractical or prohibitively expensive.
Within the company's technology portfolio, this capability serves as a bridge between traditional metallic cladding solutions and advanced polymer-based lining systems. It extends the company's service scope from manufacturing-stage cladding to in-service asset rehabilitation, creating a full-lifecycle value proposition for pipeline operators.
3. Technical Purpose and Value Proposition
3.1 Core Objectives
- Service Life Extension: Restoring aging pipelines to functional condition for an additional 20–40 years of service without full replacement.
- Corrosion Mitigation: Providing a chemically inert inner surface that resists internal corrosion from aggressive media (acidic fluids, chlorides, sulfides, and high-temperature water).
- Flow Restoration: The smooth inner surface of the composite hose (typical roughness coefficient C = 140–150 per the Hazen-Williams equation) significantly reduces friction losses compared to corroded host pipes, improving hydraulic efficiency.
- Leakage Elimination: Sealing defects, cracks, and joint failures in the host pipe through the continuous barrier provided by the composite liner.
3.2 Quantifiable Value
| Value Dimension | Conventional Replacement | Composite Hose Lining |
|---|---|---|
| Installation Cost | 100% (baseline) | 30–50% of replacement cost |
| Project Duration | 8–16 weeks (typical municipal pipeline) | 1–3 weeks |
| Disruption to Operations | Full shutdown required | Minimal or no shutdown |
| Surface Restoration | Full reconstruction required | Minimal surface work |
| Environmental Impact | High (excavation, waste disposal) | Low (no excavation) |
4. Key Process and Implementation Points
4.1 Composite Hose Construction
The composite hose is manufactured through a multi-layer co-extrusion or lamination process. The typical construction from inner to outer surface is as follows:
| Layer (Inner to Outer) | Material | Typical Thickness | Function |
|---|---|---|---|
| 1. Fluid Contact Layer | HDPE / PP / FEP | 0.2–0.5 mm | Corrosion resistance, smooth flow surface |
| 2. Adhesive Bonding Layer | Adhesive primer / tie layer | 0.05–0.1 mm | Interfacial adhesion between layers |
| 3. Structural Reinforcement Layer | Glass fiber / aramid fabric / steel wire helix | 0.5–2.0 mm | Tensile strength, hoop stress resistance |
| 4. Outer Protective Layer | Polyester film / PE jacket | 0.2–0.5 mm | Mechanical protection during installation |
4.2 Installation Process Sequence
- Pipeline Inspection and Assessment: CCTV (closed-circuit television) survey and acoustic thickness measurement of the host pipe to identify defect locations, severity, and remaining wall thickness. The pipeline must retain sufficient structural integrity to support the composite hose during and after installation.
- Pre-Treatment and Cleaning: Internal cleaning of the host pipe to remove debris, scale, rust, and loose material. For bonded installations, the internal surface must be prepared to achieve a surface roughness suitable for adhesive bonding (typically Ra = 25–50 μm).
- Access Point Creation: Installation of entry and exit manholes or access fittings at each end of the pipeline section. The access openings must accommodate the outer diameter of the composite hose with adequate clearance (minimum 50 mm radial clearance recommended).
- Hose Insertion: The composite hose is pulled or pushed through the host pipe using winch systems (pull-in method) or air/water pressure (push-in method). For pull-in installations, a pull cable is attached to the hose and tensioned from the exit end.
- Radial Expansion and Conformity: If the hose is inserted in a compressed state (common for structurally independent liners), it is inflated using air or water pressure to expand against the host pipe wall. Expansion pressure is typically 1.0–1.5 times the design operating pressure.
- Sealing and Connection: End seals are installed at each access point. For bonded systems, adhesive is applied to the host pipe surface prior to hose insertion, and curing time is allowed per adhesive manufacturer specifications.
- Pressure Testing and Verification: Hydrostatic or pneumatic pressure testing to confirm the integrity of the liner system. Testing per relevant standards (see Section 5).
4.3 Critical Process Parameters
| Parameter | Specification Range | Control Method |
|---|---|---|
| Host Pipe Minimum Residual Wall Thickness | ≥ 2 mm (for metallic pipes) | Ultrasonic thickness survey (UT) |
| Composite Hose Outer Diameter Tolerance | ±1.5% of nominal | Laser diameter measurement at factory |
| Insertion Pull Force | ≤ 2.5 × hose tensile strength | Load cell monitoring during pull-in |
| Expansion Pressure | 1.0–1.5 × design operating pressure | Pressure gauge with data logging |
| Adhesive Cure Time (bonded systems) | 24–72 hours (per adhesive datasheet) | Temperature and humidity monitoring |
| Post-Installation Pressure Test Duration | ≥ 2 hours at 1.5 × operating pressure | Pressure decay measurement |
5. Applicable Standards and Acceptance Criteria
5.1 Design and Material Standards
- GB/T 14993-2017 — Thermoplastics — Polyethylene (PE) pipes, fittings, and accessories for the conveyance of water — Specification (applies to PE inner layers)
- GB/T 17657-1998 — Thermoplastics pipes, fittings and accessories for the conveyance of water and gas — Test methods (applies to hydraulic testing of lined pipelines)
- ASTM F2164 — Standard Specification for Cured-in-Place Pipe (CIPP) Systems (reference standard for flexible liner rehabilitation principles)
- ASTM F2165 — Standard Specification for Cured-in-Place Pipe (CIPP) Systems for Sewers and Other Gravity Flow Lines
- ISO 11469-1 — Thermoplastics pipes, fittings and accessories for the conveyance of water and gas — General requirements
- EN 14453 — Non-exhaustive list of methods for the rehabilitation of pipes, fittings, and pipelines
5.2 Inspection and Acceptance Standards
- GB 50268-2008 — Technical Code for Construction and Acceptance of Water Supply and Drainage Pipeline Engineering (acceptance criteria for water supply pipeline rehabilitation)
- GB 50288-2013 — Code for Construction and Acceptance of Urban Water Supply Engineering
- ASME B31.3 — Process Piping (applicable for process piping rehabilitation in petrochemical facilities)
- API 570 — Piping Inspection Code (in-service inspection and repair assessment)
- ASNT Level III — Qualification and Certification of NDE Personnel (for personnel performing post-installation inspection)
5.3 Acceptance Criteria Summary
| Acceptance Item | Criterion | Verification Method |
|---|---|---|
| Hydrostatic Test | No pressure drop exceeding 0.05 MPa over 2 hours at 1.5 × design pressure | Pressure gauge with 0.1 MPa resolution |
| Visual Inspection | No visible wrinkles, tears, or deformation of composite hose | CCTV survey post-installation |
| Flow Performance | Hazen-Williams C value ≥ 130 | Flow measurement under test conditions |
| Seal Integrity | No leakage at end seals or access connections | Visual and dye test inspection |
| Adhesive Bond Strength (bonded systems) | ≥ 1.0 MPa lap shear strength | ASTM D1002 peel test on coupon samples |
6. Common Risks and Controls
6.1 Technical Risks
| Risk | Consequence | Mitigation Control |
|---|---|---|
| Inadequate host pipe structural assessment | Host pipe collapse during or after installation | Comprehensive UT thickness survey and structural analysis prior to design; minimum residual wall thickness verification |
| Excessive insertion force | Composite hose damage (tearing, delamination) | Real-time pull force monitoring; installation speed control; lubricant application |
| Insufficient adhesive cure time | Bond failure under operating pressure | Strict adherence to adhesive cure schedule; temperature and humidity logging; extended cure for cold conditions |
| Poor surface preparation | Adhesive bond strength below specification | Mandatory pre-installation CCTV and surface roughness verification; rejection of surfaces with loose scale or active corrosion |
| Incorrect hose diameter selection | Excessive clearance (flooding risk) or insufficient clearance (installation failure) | Accurate host pipe diameter measurement; factory tolerance verification of composite hose |
| Chemical incompatibility of liner material | Material degradation, permeation, or swelling | Chemical compatibility database review; immersion testing per ASTM D543 for specific media |
6.2 Quality Assurance Controls
- Factory Acceptance Testing (FAT): Each composite hose batch undergoes hydrostatic burst testing per ASTM F1249, dimensional inspection, and visual examination prior to shipment.
- Installation Supervision: A qualified installation supervisor monitors all critical steps, including pull force, expansion pressure, and curing time, with documented sign-off at each milestone.
- Post-Installation NDT: CCTV survey of the installed liner to verify conformity, absence of defects, and proper end seal installation. For metallic host pipes with composite lining, ultrasonic testing (UT) may be applied to verify interfacial bond integrity at designated locations.
- Pressure Testing: Mandatory hydrostatic pressure test at 1.5 times the design operating pressure for a minimum of 2 hours, with pressure decay not exceeding 0.05 MPa.
7. Integration with the Company's Three Technology Routes
7.1 Complementarity with TIG/MIG Weld Overlay
Composite hose lining and TIG/MIG weld overlay address pipeline integrity from different perspectives. Weld overlay is applied to metallic components during fabrication or repair to provide a corrosion-resistant or wear-resistant surface layer through metallurgical bonding. Composite hose lining, by contrast, provides a full-bore internal rehabilitation solution for pipelines where the entire internal surface requires protection and where the host pipe geometry is too large or complex for practical weld overlay application.
In practice, these technologies are often combined in a staged rehabilitation strategy: weld overlay is applied to localized areas of severe corrosion or erosion (such as elbows, reducers, and tees) to restore wall thickness and provide a metallurgically bonded overlay, while composite hose lining is applied to the full pipeline run to provide continuous internal protection. This hybrid approach leverages the metallurgical bond strength of weld overlay at critical points and the continuous barrier protection of composite lining along the full pipeline length.
7.2 Complementarity with Hydraulic Explosive Bonding
Hydraulic explosive bonding (HEB) is a solid-state metallurgical bonding process used primarily for manufacturing clad plates and pipes with a corrosion-resistant cladding layer. The clad products produced via HEB can serve as the host pipe material for composite hose lining applications. For example, a stainless steel-lined carbon steel pipe manufactured by hydraulic explosive bonding provides a structurally sound, corrosion-resistant host pipe that can be further protected with composite hose lining for extreme corrosion environments or for extending the service life beyond the original design life.
Additionally, the composite hose lining technology can be applied to rehabilitate hydraulic explosively bonded clad pipes that have experienced localized damage, delamination, or wear through the cladding layer, providing a non-destructive repair option that preserves the remaining cladding integrity.
7.3 Complementarity with Explosion Welding
Explosion welding produces clad plates and pipes with a metallurgically sound interface between the base metal and cladding material. In pipeline rehabilitation scenarios, explosion-welded clad pipes can be used as replacement sections in areas of severe host pipe deterioration, while composite hose lining is applied to the remaining sections of the pipeline. This combined approach minimizes excavation by replacing only the most severely damaged sections with new clad pipe and rehabilitating the remainder with composite hose lining.
The company's expertise in explosion welding provides a critical input to the composite hose lining business: the ability to manufacture high-quality clad pipe sections for integration into rehabilitation projects, ensuring that replacement sections match the metallurgical and corrosion resistance requirements of the existing pipeline system.
8. Qualification Building and Customer Value
8.1 Qualification Development
Developing competence in composite material flexible hose lining technology strengthens the company's qualification portfolio in several dimensions:
- Expanded Scope of Work: Qualification in trenchless pipeline rehabilitation opens access to municipal water, gas, and industrial pipeline rehabilitation contracts that are not addressable by metallic cladding alone.
- Integrated Solution Capability: The ability to offer both new clad pipe fabrication (via weld overlay, HEB, and explosion welding) and in-service pipeline rehabilitation (via composite hose lining) positions the company as a full-spectrum pipeline integrity solutions provider.
- Personnel Qualification: Training and certification of installation personnel in CCTV survey, UT thickness measurement, and composite hose installation techniques builds institutional knowledge and supports compliance with GB/T and ASNT qualification requirements.
- WPS and Procedure Qualification: Development and qualification of installation procedures (WPS equivalent for composite hose lining) per relevant standards establishes a documented quality framework that supports customer audits and regulatory inspections.
8.2 Customer Value Delivery
For pipeline operators and asset owners, the composite hose lining technology delivers measurable value through:
- Capital Expenditure Reduction: 50–70% cost savings compared to conventional pipeline replacement, enabling capital budget reallocation to other priority infrastructure projects.
- Operational Continuity: Minimal or no shutdown during installation, preserving production output and service continuity for water utilities, petrochemical plants, and power generation facilities.
- Corrosion Risk Management: Continuous internal barrier protection reduces the risk of catastrophic failure from internal corrosion, supporting compliance with pipeline integrity management programs per API 580/581.
- Environmental Compliance: Elimination of excavation reduces environmental permits, surface restoration costs, and community disruption, supporting ESG (Environmental, Social, and Governance) objectives.
9. Application Scenarios
9.1 Municipal Water and Sewer Systems
Composite hose lining is extensively applied to rehabilitate aging water distribution mains and sewer lines where excavation is impractical due to urban infrastructure constraints. Typical applications include DN100–DN1200 pipelines constructed from cast iron, asbestos cement, concrete, or steel, with service ages of 30–60 years experiencing internal corrosion, joint leakage, or structural deterioration.
9.2 Petrochemical and Oil & Gas Pipelines
In petrochemical facilities, composite hose lining is applied to internal circulation water lines, cooling water systems, and process water pipelines where internal corrosion from chlorides, sulfides, and dissolved oxygen has reduced wall thickness. The composite hose provides a chemically inert barrier that resists the aggressive process media while maintaining structural integrity under operating pressures up to 1.6 MPa.
9.3 Power Generation Facilities
Thermal power plants utilize composite hose lining for rehabilitation of condensate return lines, circulating water pipelines, and desalination water supply lines. These systems experience severe internal corrosion due to dissolved oxygen, chlorides, and high-temperature water, and composite hose lining provides an effective rehabilitation solution that extends asset life without extended plant shutdown.
9.4 Mining and Mineral Processing
In mining operations, composite hose lining is applied to slurry pipelines and tailings transport lines where abrasive and corrosive media have caused rapid internal wear and corrosion. The composite hose, when specified with appropriate abrasion-resistant inner layers, provides both corrosion protection and moderate abrasion resistance, extending pipeline service intervals between full replacements.
10. Conclusion
Composite material flexible hose lining for old pipeline rehabilitation represents a strategically valuable addition to the company's technology portfolio. It extends the company's capability from new fabrication cladding to in-service asset rehabilitation, creating a comprehensive pipeline integrity management offering. The technology delivers significant economic value through capital cost reduction, operational continuity, and service life extension, while the integration with the company's TIG/MIG weld overlay, hydraulic explosive bonding, and explosion welding capabilities enables delivery of hybrid solutions that address the full spectrum of pipeline integrity challenges. Rigorous adherence to applicable standards (GB 50268, GB 50288, ASME B31.3, API 570, ASTM F2164, ISO 11469) and systematic quality assurance controls ensure reliable performance and long-term asset protection.