Pressure-Resistant Adapter for Field Device Cable Feedthroughs
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Solution Overview
Problem
Conventional cable feedthroughs for field devices in explosion-endangered regions are complex, expensive, and prone to thermomechanical stress cracks due to material mismatches and high thermal expansion coefficients, compromising pressure resistance and sealing.
Innovation Solution
A pressure-resistant adapter with a shell and insert design, using a metal shell and elastic potting compound to absorb thermomechanical stresses, eliminating the need for a pressure-resistant connection between the potting compound and other components, and incorporating a circuit board for conductor connection to the field device electronics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glass- or ceramic-sealed cable feedthroughs are used for pressure-resistant encapsulation, then pressure resistance and explosion protection are improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The adapter is divided into separate functional components: a shell providing pressure resistance, an insert with base element and projection for conductor support, and a potting compound for sealing. This segmentation allows each component to be optimized independently, simplifying manufacturing while maintaining pressure resistance.
Solution Approach 2:
The patent replaces expensive glass- or ceramic-sealed cable feedthroughs with a more economical adapter construction using common materials like metal shell, plastic insert, and potting compound. This substitution significantly reduces manufacturing cost while achieving the same pressure-resistant encapsulation function.
2Reliability
If glass- or ceramic-fillings are used in cable feedthroughs, then pressure resistance is improved, but thermomechanical stress cracks occur due to thermal expansion mismatch
Solution Approach 1:
The patent changes the material parameters of the sealing compound to match the thermal expansion characteristics of the surrounding metal support. The potting compound is specifically selected or formulated to have a coefficient of thermal expansion compatible with the metal shell, eliminating thermomechanical stress during temperature variations.
Solution Approach 2:
The adapter uses a composite construction combining metal shell, plastic insert, and elastomeric potting compound. Each material is selected for its specific properties: the potting compound provides both sealing and thermal compatibility, while the metal shell provides pressure resistance. This composite approach resolves the thermal expansion mismatch problem.
3Reliability
If material combinations with different thermal expansion coefficients are used, then pressure resistance is achieved, but thermomechanical stresses form compromising sealing
Solution Approach 1:
The patent specifically selects materials whose thermal expansion parameters are matched to each other. The potting compound is chosen to have a coefficient of thermal expansion compatible with the metal shell and insert materials, minimizing thermomechanical stresses. This parameter matching eliminates the harmful thermal stress effect while maintaining pressure resistance.
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 adapter provides enhanced pressure resistance against explosive pressures and thermal stability, preventing stress cracks and allowing operation over a wider temperature range, while being simpler and cost-effective to produce.
Implementation Method 1
the materials usable as filling are, as a rule, hard and/or brittle materials, which have coefficients of thermal expansion, which differ significantly from the coefficient of thermal expansion of the metal support externally surrounding the filling. Due to the different coefficients of expansion, thermomechanical stresses form in these cable feedthroughs as a function of the ambient temperature.
Implementation Method 2
using a metal shell and elastic potting compound to absorb thermomechanical stresses
Implementation Method 3
A protection class entitled 'pressure-resistant encapsulation' (Ex-d) provides that devices must have a pressure-resistant housing, to assure that a spark in the interior of the housing, namely a spark possibly even triggering an explosion in the interior of the field device, cannot ignite an explosive medium located outside of the field device.
Data Source
AI summary
A pressure resistant adapter, for connecting a transmission line to a field device has a shell, insertable into a wall of a housing of the field device. The shell has an interior open to an interior of the housing and closed to the exterior by an end wall of the shell. An insert, installed in the shell, includes a base element and a projection protruding out of the shell through an opening in the end wall of the shell. The base element has a basal area greater than a basal area of the opening. A connection element is provided on an end of the projection protruding out from the shell, to which the transmission line is connectable, and at least one conductor extends through a window that is located in the base element adjoining the bore in the projection and opens to the interior of the housing.