Thermowell Expansion Joint for Refractory Movement

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Solution Overview

Problem

Thermocouple-thermowell assemblies in harsh environments face failure due to expansion, contraction, and physical movement caused by temperature changes, leading to unreliable temperature measurements, especially in processes like coal gasification where molten slag can fix the assembly to refractory materials, causing damage from movement.

Innovation Solution

A thermowell-thermocouple assembly with an expansion joint, such as a bellows or slip joint, is designed to accommodate these forces, allowing for longitudinal, lateral, and bending movements, ensuring the assembly remains functional despite temperature-induced expansion and contraction, and physical displacement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a rigid thermowell-thermocouple assembly is used to maintain structural strength, then the assembly can withstand harsh process conditions, but it becomes damaged by expansion, contraction, and physical movement forces

Engineering Contradiction:

Improvestructural strengthVSAvoidassembly reliability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The thermowell assembly is divided into multiple sections including a fixed portion, a movable portion, and an expansion joint section. This segmentation allows different parts to perform different functions - the fixed portion maintains structural strength while the movable portion accommodates thermal expansion and contraction forces.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The expansion joint incorporates movable elements that allow the thermowell assembly to dynamically adjust to thermal expansion and contraction. The joint can move axially and laterally, transforming the rigid structure into a dynamic system that adapts to changing conditions.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If the thermowell assembly is made adjustable to accommodate movement, then it can tolerate thermal expansion, but the positioning precision and pressure seal may be compromised

Engineering Contradiction:

Improvemovement accommodationVSAvoidpositioning precision

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The expansion joint acts as an intermediary element between the fixed mounting structure and the movable thermowell portion. It mediates the movement forces, allowing the assembly to accommodate thermal expansion while maintaining precise positioning through its constrained movement mechanism.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The expansion joint utilizes flexible structural elements that can bend and move to accommodate thermal expansion while maintaining the integrity of the pressure seal. The flexible design allows movement without compromising the sealing capability.

Inventive Principle:

Principle #30Flexible shells and thin films

3Strength

If a strong, rigid thermowell-thermocouple assembly is used to prevent failure, then structural integrity is maintained, but the assembly is damaged by forces from refractory material movement

Engineering Contradiction:

Improvestructural integrityVSAvoidrefractory movement forces

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The expansion joint converts the harmful forces from refractory movement into beneficial controlled movement. Instead of resisting the forces rigidly and failing, the joint allows controlled movement that accommodates the refractory expansion and contraction, transforming the harmful thermal cycles into a manageable design parameter.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 expansion joint effectively extends the service life of thermocouple-thermowell assemblies by allowing them to tolerate thermal expansion and contraction, as well as physical movements, thereby maintaining reliable temperature measurements in extreme conditions.

Implementation Method 1

a process unit or a machine that is subject to a wide range of temperature will cause a thermocouple-thermowell assembly to expand and contract as the temperature changes

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

The bellows are surrounded by a support tube that is fixed to the first portion and has a longitudinal slot for a pin-and-slot engagement with the second portion, thereby allowing the second portion to move with respect to the first portion through flexing of the bellows

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS10996113B2Thermowell with expansion joint

Publication Date: 2021.05.04 FOREMAN INSTRUMENTATION & CONTROLS INC

AI summary

A thermowell-thermocouple assembly for installation in a refractory-lined process vessel has an expansion joint for compensating for expansion, contraction and movement of the refractory. Examples of expansion joints include unsupported bellows, bellows that have a support sleeve around the bellows, a sliding, hexagonal coupling with crimping to hold the sliding tubes together, a pin-and-slot coupling and a spring-loaded, pin-and-slot sliding connection. The thermocouple-thermowell assembly can include a metal, a ceramic material, a refractory brick and/or a conical-shaped tip at a distal end, which can be or which can become fixed to the refractory.