Double-Walled Cabinet Bulkhead Fitting for FM Certified Electrical Penetration
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Solution Overview
Problem
Installing electrical connections in safety cabinets while maintaining compliance with Factory Mutual (FM) regulations is challenging, especially in double-walled designs, as it is difficult to ensure airtight seals and prevent airflow between internal and external environments.
Innovation Solution
The method involves creating a double-walled cabinet with large holes on the exterior and smaller holes on the interior, allowing bulkhead fittings to be inserted through the larger holes to provide airtight seals and secure electrical connections, while using covers to maintain FM integrity and isolate environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If electrical connections are installed in a double-walled safety cabinet, then electrical functionality is enabled, but maintaining airtight seals and preventing airflow between internal and external environments becomes difficult
Solution Approach 1:
The patent divides the penetration system into multiple components: a bulkhead fitting with separate flange portion (external) and collar portion (internal), connected by a stem. This segmentation allows each part to serve its specific function - the flange provides external sealing, the collar provides internal sealing, and the stem transmits the electrical conductor through the airgap, thereby maintaining airtight seals while enabling electrical functionality.
Solution Approach 2:
The bulkhead fitting acts as an intermediary component that bridges the internal and external environments of the double-walled cabinet. It provides a controlled pathway for electrical conductors through the airgap while maintaining separation and preventing uncontrolled airflow, thus enabling electrical connections without compromising the airtight integrity of the cabinet walls.
2Adaptability or versatility
If bulkhead fittings are inserted through large holes in the outer cabinet wall to reach smaller holes in the inner cabinet wall, then electrical connections are enabled, but the complexity of installation increases
Solution Approach 1:
The bulkhead fitting is pre-assembled with the electrical conductor attached to its stem before installation. The fitting is designed with the flange, stem, and collar as integrated components, allowing it to be inserted as a single unit through the large hole in the outer wall. This preliminary preparation simplifies the installation process by reducing the number of separate assembly steps required on-site.
Solution Approach 2:
The bulkhead fitting structure employs a nested configuration where the collar portion fits within the airgap space between the outer and inner cabinet walls, with the stem extending through the airgap to reach the inner wall opening. This nested arrangement allows the fitting to pass through the double-walled structure efficiently without requiring disassembly of the cabinet or complex routing procedures.
3Reliability
If covers are used to seal the large holes in the outer cabinet wall, then FM regulatory compliance is maintained, but the number of components and assembly steps increases
Solution Approach 1:
The bulkhead fitting is designed to integrate multiple functions into a single component: the flange portion provides external mounting and sealing, the stem provides electrical conductor transmission, and the collar portion provides internal sealing and mounting. By merging these functions into one integrated fitting rather than using separate flange, stem, and collar components, the design reduces the total number of parts while maintaining FM compliance through proper sealing capabilities.
Data Source
AI summary
Methods for installing electronic connections into a Factory Mutual certified cabinet may comprise providing a double walled cabinet. The double walled cabinet ay comprise an outer cabinet wall, and inner cabinet wall, and an airgap between the inner cabinet wall and the outer cabinet wall. The method may comprise the steps of including a first large hole in a surface of the outer cabinet wall and including a first small hole in a surface of the inner cabinet wall. Methods can additionally include the steps of inserting a first bulkhead fitting into the first small hole in the surface of the inner cabinet wall via the first large hole and covering the first large hole in the surface of the outer cabinet wall. Methods may additionally include the first small hole at least partially overlapping the first large hole when viewed from a plane normal to the first large hole.