Ask Slashdot: How Do I Make a High-Spec PC Waterproof?

jimwormold writes: I need to build a system for outdoor use, capable of withstanding a high pressure water jet! "Embedded PC," I hear you cry. Well, ideally yes. However, the system does a fair bit of number crunching on a GPU (GTX970) and there don't appear to be any such embedded systems available. The perfect solution will be as small as possible (ideally about 1.5x the size of a motherboard, and the height will be limited to accommodate the graphics card). I'm U.K.- based, so the ambient temperature will range from -5C to 30C, so I presume some sort of active temperature control would be useful.

I found this helpful discussion, but it's 14 years old. Thus, I thought I'd post my question here. Do any of you enlightened Slashdotters have insights to this problem, or know of any products that will help me achieve my goals?

Comments

The right enclosure

[plover]

NEMA rates enclosures for their ability to withstand harsh environments. Search for NEMA enclosures and pick the one that fits your machine.

Re:The right enclosure

[speederaser]

Search for NEMA enclosures and pick the one that fits your machine.

Here's one you might like but it's not cheap at $325 each.

Start here...

[Anonymous Coward]

http://www.skbspecialtycases.com/

I deal with this kind of thing once in a while when deploying hardware in freezing conditions (down to about -60F), and the truth is there aren't many options that are as small as you want.

Re:This seems the obvious solution

[geoskd]

Another idea which I like even better is to immerse the whole machine in mineral oil.

This is actually not that good of an idea. I ran a mineral oil rig back when I was in school, and the mineral oil dissolves the dielectric used in the "can" style capacitors used on almost all electronics. Over the space of about 3 years, the oil will destroy the exposed caps, and the machine will become flaky and ultimately stop working altogether. Also of note, the oil permeates and partially dissolves most silicone caulk and the plastics used for hot glue. Ultimately, its pretty nasty stuff in spite of appearing to be relatively inert.

NEMA 4X is all you need?

[Anonymous Coward]

I'm used to IP67-IP68+(IE. IP69K) for my work in designing autonomous subs(although I have other experience from GPU mining bitcoins), but NEMA 4X is specifically designed for the high pressure water jet conditions you're describing.

Although I'm curious WTF you're doing in a mobile/stationary weatherized application that requires a GTX970(A Jetson TK1 is easier to cool and good enough for most computer vision problems)? I'll answer your question directly instead of asking you how I can back out of your difficult design requirements:

First off: Lets assume IP55 is good enough:
http://cosmotec.stulz.com/en/products/ventilation/kryos-filter-fans/
These are the most cost effective IP55 ventilation fans I've been able to find.

If that's good enough for you: get on McMaster and order a NEMA 4X enclosure and consider yourself lucky that was all you needed. You have an industrial cooling problem, they have industrial cooling solutions. If you want some a little closer to your side of the pond: request a catalog from Rittal or get on their website and see if they have anything that meets your needs.

If IP55 is not good enough, and nothing as generic as a cosmotec fan or a cooled Rittal enclosure can get the job done: you can start by reading all the other responses and see if anyone has a better suggestion I'm unfamiliar with. If not, your job is either impossible, no one here knows what the solution is(or isn't saying if they do), or you have to go custom. That means in house or out of house design.

First off lets make something clear: you have a thermal management problem, not a water ingress problem. It becomes a water ingress problem when you are unable to adequately manage your thermal output without circulating air from the outside of the enclosure.

Shedding the heat of a 500-1000W PC using nothing but convection cooling with the enclosure skin/fins is difficult in the size you've described so the easiest thing to do would be to cheat and exceed your volume constraints via an external radiator in a location where your volume constraints are less of a problem. Supposing that is not possible: in a stationary application the ground becomes a pretty good heat sink if you dig down far enough. An alluminum water block burried beneath your computer circulating water through a NEMA 4X enclosure on the surface with the CPU and GPU pimped out with watercooling blocks. Excluding that as a possibility(mobile application?): pumping the heat in to a thermally conductive chunk of material large enough to dissipate it is still your preferred solution.

If there is no way around self-contained: you're either going to have to spend a lot of time and energy maximizing the thermally conductive surface area(doing analysis to determine it is adequate to meet your use case a high enough percentage of the time to matter), make the system fail gracefully under the conditions where it exceeds it's thermal management capabilities, optimize system thermal efficiency to the greatest extent possible by doing things like underclocking the CPU and using more CUDA/OpenCL for your code, redesigning your system(using a wireless modem to offload the processing requirements to a datacenter like Amazon AWS or even a closet at a nearby facility), or some crazy combination of all of the above in appropriate proportions to maximize the value to the customer(whoever that is) on the time frame/capital investment scale they are willing to pay for, and/or manage their expectations appropriately to where you can redefine your requirements, and/or claim it's impossible and hope a smarter/more ambitious engineer doesn't prove you wrong.

The correct answer is so situation specific it is difficult to tell you what to do without more information. These are some of the questions I would ask. Good luck with your bizarre requirements definition. I'm sure you've been painted in to a corner for good reasons and not because of an unwillingness to compromise on the "I want everything" mentality that makes programs like the F35 and F22 so fucking expensive.

Re:Server Techniques

[Mashiki]

I used to build cabinets for farm use, while I didn't go the immersion route I went with "the box" solution. Basically it meant that air intakes had double bends, sometimes triple bends with a drain hole at the bottom. Doors used a foam sealer, and exhaust was placed wall side. Farms are dirty places, if you're not dealing with feed dust, you're dealing with hay dust, or chemicals for plants, sprayers or livestock. There's always something that would ruin a machine quick.