Coextruded Polyethylene Pipe With Low-Solar-Absorptivity Outer Layer

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Solution Overview

Problem

Above-ground piping applications experience significant temperature fluctuations due to solar radiation, leading to reduced pressure capability, increased chemical attack, and thermal expansion/contraction, with existing solutions like painting the pipe surface being ineffective and requiring frequent maintenance.

Innovation Solution

A coextruded polyethylene pipe design featuring an inner layer with a first material and an outer layer coextruded with a second material having a higher hydrostatic design basis (HDB) than the inner layer, where the outer layer is non-black to minimize solar absorptivity, thereby reducing temperature fluctuations and maintaining pressure capability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the pipe surface is painted to reduce solar absorptivity, then temperature fluctuations are reduced, but the solution requires frequent maintenance and is ineffective

Engineering Contradiction:

Improvepipe surface temperatureVSAvoidmaintenance frequency

Core Design Contradiction:

TemperatureVSEase of operation

Solution Approach 1:

The patent applies composite materials by creating a multi-layer pipe structure where the outer layer is made of a material with low solar absorptivity (such as white or light-colored polyethylene) while the inner layer provides pressure containment. This integrated composite structure permanently reduces solar heat absorption without requiring external coatings or paints, thereby eliminating frequent maintenance while effectively controlling pipe surface temperature.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent changes the physical parameter of solar absorptivity by selecting materials with inherently low absorptivity characteristics for the outer pipe layer. By modifying the material composition and color properties during manufacturing, the pipe achieves permanent temperature control without needing repeated surface treatments, thus resolving the maintenance frequency issue while effectively managing temperature fluctuations.

Inventive Principle:

Principle #35Parameter changes

2Strength

If a single-layer pipe design is used, then manufacturing is simpler, but pressure capability is reduced under temperature fluctuations

Engineering Contradiction:

Improvepressure capabilityVSAvoidpipe structure

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent employs composite materials by constructing a multi-layer pipe where each layer serves a specific function: the outer layer resists UV degradation and solar heating, while the inner layer provides pressure containment. This composite structure enhances overall pressure capability under temperature fluctuations compared to single-layer pipes, while the layers are integrated during co-extrusion to maintain manufacturing efficiency.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies segmentation by dividing the pipe into functional layers with distinct roles. The outer layer is optimized for environmental resistance and thermal management, while the inner layer is optimized for pressure containment. This functional segmentation allows each layer to be designed for its specific purpose, improving overall pressure capability under temperature variations while maintaining manufacturing simplicity through co-extrusion processes.

Inventive Principle:

Principle #1Segmentation

3Strength

If the outer layer material has higher HDB than the inner layer, then pressure rating is enhanced, but material selection becomes more constrained

Engineering Contradiction:

Improvepressure ratingVSAvoidmaterial selection

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The patent applies composite materials by selecting specific material combinations where the outer layer has higher HDB than the inner layer. This configuration allows the outer layer to provide both environmental resistance and enhanced pressure rating, while the inner layer focuses on fluid compatibility and pressure containment. The co-extrusion process enables efficient manufacturing of these optimized composite structures, balancing material selection constraints with performance requirements.

Inventive Principle:

Principle #40Composite materials

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The coextruded pipe design effectively reduces pipe surface temperatures, minimizes thermal expansion and contraction, and enhances pressure capability while providing increased longevity and wear resistance, eliminating the need for frequent surface treatments.

Implementation Method 1

the outer layer provides for decreased solar absorptivity relative to a same pipe absent the outer layer

Methodology Applied

Scientific EffectSolar absorptivity: Absorption (EM radiation)

Data Source

PatentUS12359753B2Coextruded polyethylene pipe and methods of making and using same

Publication Date: 2025.07.15 CHEVRON PHILLIPS CHEMICAL COMPANY LP

AI summary

A pipe having an inner layer and an outer layer. The inner layer includes a first material having a first hydrostatic design basis (HDB), and the outer layer is coextruded with the inner layer and includes a second material having a second HDB. The second HDB is greater than or equal to the first HDB, and the first HDB and the second HDB are as specified in ASTM Test Method D2387. Also provided re methods of making and using the pipe.