External Slip Wrap for Insulated Piping Thermal Expansion
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Solution Overview
Problem
High temperature bonded foam insulated piping systems face disbondment issues due to thermal expansion, which can lead to stress and damage, especially at angular changes and expansion loops, where the foam insulation may separate from the carrier pipe, causing structural integrity loss and increased corrosion.
Innovation Solution
An external slip wrap made of flexible polyolefin material, such as polyethylene, is applied around the outer protective jacket at selected locations, allowing axial movement of the piping system relative to the slip wrap, thereby preventing disbondment by accommodating thermal expansion without disrupting the insulating layer's integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the piping system is bonded as a monolithic unit, then thermal expansion is controlled and structural integrity is maintained, but stress concentrates at angular changes and expansion loops causing disbondment
Solution Approach 1:
The piping system is divided into segments by introducing slip wraps at selected locations (elbows, expansion loops). These slip wraps create discrete zones where the jacket can move independently relative to the foam insulation, allowing thermal expansion stress to be distributed across multiple segments rather than concentrated at single points.
Solution Approach 2:
The slip wrap introduces dynamic movement capability into the previously static bonded system. The jacket is allowed to slide axially within the slip wrap envelope, transforming the system from a rigid monolithic structure to one with controlled flexibility that can accommodate thermal expansion without excessive stress.
2Adaptability or versatility
If the carrier pipe thermally expands, then the piping system adapts to temperature changes, but the foam insulation may separate from the pipe at angular changes
Solution Approach 1:
The slip wrap acts as an intermediary element between the carrier pipe and the outer jacket. It provides a controlled interface that allows relative movement between these components, mediating the thermal expansion forces and preventing direct stress transmission that would cause foam delamination at angular changes.
3Stability of the object's composition
If the system remains bonded underground, then the jacket is fixed in place, but the carrier pipe expansion destroys the jacket at the first change of direction
Solution Approach 1:
The continuous bonded system is segmented by introducing slip wraps at critical locations. This segmentation allows the jacket to remain bonded over most of its length while creating specific zones where controlled movement is permitted, preventing jacket failure at angular changes while maintaining overall system integrity.
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 external slip wrap ensures the inner carrier pipe and foam insulation move as a unit, maintaining the structural integrity of the piping system, preventing disbondment and corrosion, even at high temperatures, and extending the pipeline's useful life by allowing relative movement and reducing stress on the system.
Implementation Method 1
The hot fluid in the steel carrier pipe causes the carrier pipe to thermally expand. At temperatures of 400° F. this expansion is on the order of 2.8 inches per 100 feet of pipe.
Implementation Method 2
Around the outside of the steel pipe is a layer of insulating foam such as, for example, polyisocyanurate foam. In the case of high temperature piping systems, the insulating foam serves to keep heat loss from the starting location of the pipeline to the ending location at a minimum.
Data Source
AI summary
The present invention relates generally to an apparatus and method for preventing disbondment in an insulated piping system that is used for conveying high temperature fluids. More specifically, an external slip wrap is shown, capable of surrounding the outer protective jacket of the insulated piping system at a location along the piping before an elbow shaped or angular change in direction. The slip wrap comprises a loosely received outer sleeve which surrounds the outer protective jacket of the piping without being bonded thereto, thereby allowing the insulated and jacketed pipe to move axially relative to the slip wrap for a selected distance once the pipe is buried in the ground.