Media Relations for a Connected World
Honeywell Sensing and Control again featured in ECN Magazine
Frequently OEMs and system integrators specify components to category levels in NEMA 250, DIN 40050-9 and/or IEC 60529 standards (and historically MIL-STD-810) in an attempt to maximize robustness for a given application’s environment. Consistently meeting this performance requires a good understanding of the how to minimize the environmental impacts on a given component.
An ideal component enclosure for robustness is hermetic, but in many cases, this is not feasible due to factors related to cost, materials, interconnects, access requirements, adjustability, etc. Therefore, most enclosures rely on a combination of tight fitting components, epoxies and elastomers to provide protection against solid and liquid contaminates.
Elastomers such as O-rings seal better than flat gaskets when space exists to apply them. Elastomer selection needs to consider any extreme temperature exposure. Unfortunately, elastomers that seal well at high temperatures do not typically seal well at cold (and vice versa). Correct seal compression (not too much or too little) on static and dynamic seals is critical and can only be achieved when the parts in an assembly are correctly toleranced.
Packaging challenges are posed by conductors (both connectors and wire harnesses) carrying signals and power that need to access an outside system. Given their geometry and integral features connectors are much simpler to seal than wire harnesses. However, in situations where harnesses must pass through an enclosure, it is best to use a cord grip or wire header to provide a barrier to ingress. It is difficult to simply utilize epoxy to seal over wide ranges of temperature and moisture.
In environments where condensation is expected, trade-offs must be given to allow an enclosure to breathe with a membrane style vent vs. completely sealing in the ambient humidity. Trapping ambient humidity inside where it can condense can be as bad as letting rain into an enclosure.
Laboratory evaluations of sealing performance should be done after testing temperature performance and vibration/shock on a given enclosure. These environmental conditions stress the seals and are the best way to assess design robustness over installation life.
It is critical for a design engineer to work to closely with a component supplier who has proven history of providing effective solutions for protecting sensitive equipment in a wide range of harsh environments and to leverage that expertise to reduce development time and ensure compliance with various applicable worldwide standards.