Method of allowing wires into a hermetically sealed unit

[middlj]

Hi,

Quick question, if anybody has any ideas that would be great.

I am looking to allow a few small wires to pass into a hermetically sealed ECU enclosure on a small racecar. How can I allow wires in without compramising the fact its meant to be hermetically sealed (at least IP66).

Would a cable gland work?

Thanks in advance

 

[berkeman]

Hi,

Quick question, if anybody has any ideas that would be great.

I am looking to allow a few small wires to pass into a hermetically sealed ECU enclosure on a small racecar. How can I allow wires in without compramising the fact its meant to be hermetically sealed (at least IP66).

Would a cable gland work?

Thanks in advance

It's done routinely with metal canned oscillators, but I don't know the technique that they use. You might be able to find how they do it with google though...

I googled metal can oscillator construction, and got some pretty good hits. You might look through these to see if they address how the leads are mounted to the can:

http://www.google.com/search?source...S301US302&q=metal+can+oscillator+construction

.

 

[AlephZero]

You can get multipin electrical connectors that are certified to IP6 both when connected and unconnected. For example http://www.servoconnectors.co.uk/products/circluar-connectors/ip68-69k-trim-trio/

If you don't want to do that, I would think about sealing the wires permanently where they enter the enclosure, with epoxy or potting compound. You then could put a standard (un-sealed) connector inside the enclosure if you want to be able to remove the ECU electronics from the enclosure for whatever reason.

 

[middlj]

Thanks for your reply. Very helpful

 

[middlj]

Thanks berkeman, I'll have a look into that.

 

[Mapes]

You also might try searching for "ceramic feedthroughs." I had an awful time keeping a chamber hermetic until a colleague explained these to me and designed a nice interface that didn't involve sloppy wires and epoxy (just speaking for my own techniques here).

 

[dlgoff]

A little off subject, but I had the bad experience of installing pH sensors in a RO water system where the pair of wires were epoxy hermetically sealed. They were 24AWG with a vinyl insulation. The epoxy kept the sightly pressurized water from leaking between the insulation and the epoxy, but water would drip out the end of the wire between the conductor and insulation.

The sensor were from a well know manufacturer and their replacements still leaked. So I learned to live with letting it drip out and away from the 4-20mA transmitter used by the water systems monitor equipment.

 

[Mapes]

Heh, having given advice, maybe I'll share one of my experiences as an inexperienced engineer. I wanted to experiment with In-Sn solder as a way of sealing an implantable drug delivery device at low temperatures so as not to damage the protein payload (let us not discuss the biotoxicity of In-Sn ). I decided to build a Lexan box and evacuate it with a vacuum pump, while maintaining passthroughs caulked with silicone epoxy to ensure electrical connections to a hot plate inside the box. Well, first, the box creaked and cracked upon pumpdown to extent that drove me and my colleagues behind a pillar to avoid possible injury. I had naively thought that 1" thick Lexan would suitably support a 1' cube. Wrong! Also, I had no idea that silicone (PDMS) outgasses to an unbelievable extent that would preclude any valid vacuum solder experiments. Finally, my feedthroughs of wire caulked with epoxy were totally unsuitable. A more experienced engineer finally designed a better (and much more expensive) aluminum chamber with hermetic passthroughs that enabled the experiments we wanted to perform. My lesson: spent as much money as necessary to do the job properly.

 

[middlj]

Haha,

Thanks for your advice gents.

I've gone with the UTS Hi Seal Series. It's a great forum this. I think I'll stick around ;)

 

[AlephZero]

The epoxy kept the sightly pressurized water from leaking between the insulation and the epoxy, but water would drip out the end of the wire between the conductor and insulation.

Next time, remember that water doesn't flow uphill when you design the geometry of your wiring

(Hmm ... but you said the water was slightly pressurized, so that might not work)

I once had a weird problem with intermittent failures in some car electric wiring. The cause was eventually tracked down to water seeping through the "seal" around the radio antenna, then traveling about 4 feet along a cable till it got to the lowest point, dripped off, and shorted out something else directly underneath. GRRRRR!

 

[AlephZero]

I had naively thought that 1" thick Lexan would suitably support a 1' cube. Wrong!

Yeah, for some reason most people know intellectually that force = pressure x area, but they don't realize 14.7psi = nearly 1 ton per square foot.

 

[dlgoff]

I decided to build a Lexan box and evacuate it with a vacuum pump, while maintaining passthroughs caulked with silicone epoxy to ensure electrical connections to a hot plate inside the box.

I wanted to evaporate aluminum on glass slides, so I got an old vacuum pump and bell jar, drilled & tapped a couple of 1/2" holes threaded with Teflon bushings, and inside those, threading brass rods for electrodes for a tungsten foil for melting the aluminum. Worked good.

Yeah, for some reason most people know intellectually that force = pressure x area, but they don't realize 14.7psi = nearly 1 ton per square foot.

How true.

 

[Mapes]

Yeah, for some reason most people know intellectually that force = pressure x area, but they don't realize 14.7psi = nearly 1 ton per square foot.

Yikes, that brings it home. What was I thinking?!