Washable fan filter ... just disintegrates

[jgreco]

Wow. I just had a creepy experience while doing some maintenance. We've got some nice 4U chassis that are probably near 15 years old now, still great for many uses. They've got a washable fan filter in them that needs to be removed every year or two and rinsed, dried, and reinstalled, or else the airflow becomes reduced. The filter is basically extremely low density foam of the kind that is very soft. We wash them out with plain water, crumple them up to squeeze them out, let them dry, and reinstall.

Now bear in mind these have been undergoing the process for many years without incident. So imagine my surprise when I took one out and my thumb went right through it. It was still flexible but it seemed to tear very easily. I put it under the water and it just totally disintegrated.

I have no idea what would have caused this; the filter in the next server up was just fine.

 

[cyberjock]

Yeah. I've seen that before. What you should look for is sources of acids or bases in the atmosphere. I can't go into much detail on how I figured this out, but even things like rotting vegetation releases very small amounts of ammonia which does interact with the foam.

Normally its a "who cares" approach because most servers don't last 15 years like yours do. But in some locations it does matter, and in just a year or two you can see them falling apart. I've seen some that were falling apart inside the chassis. And you just knew it was going to fall apart before you could even get it out of the chassis. Then, after you've made a mess you want to vacuum out the case, but that's not smart either. :P

 

[jgreco]

That'd make more sense if the servers weren't adjacent to each other in an enclosed rack... and they've certainly been in virtually the same environment for at least two years.

I realize most of the world has moved on to cramming servers into 1U or blades, but virtualization has caused space to become relatively easy to come by, and the relative quiet of running in the 4U space, with some lazily spinning cooling fans and oversized CPU heatsink is very attractive. So I keep recycling these, stripping them down to just the metal and building them to modern standards, like the new 4-pin PWM fans and high eff power supply. This is actually a filter for the pair of 120MM front intake fans. It's an odd design ... there's actually a significant space between the filter and the fans which sit several inches back. With the low revs of the fans and the cavity there, there's not a lot of danger of crap from a disintegrating filter getting sucked in, but it was still ... unpleasant to experience. Heh.

Now I have to figure out what to replace it with. Basically the material is similar in character to something like the foam filter you'd find in a ShopVac, and I've thought about that... hm.

 

[John M. Długosz]

You might try the material from the cheap-cheap fiber home HVAC intake filters. They do coarse dust and hair just fine and don't block much air. You might give the guy at http://www.hepaairdirect.com/ a call. You might be able to get something off-catalog or some raw material from them. In particular, the filter module I just bought includes a layer of pre-filter material which I think is just what you need.

 

[jgreco]

Thanks for the thought, but ... ShopVac filter, $2.50, scissors, and the stuff is rated for use in a wet vac, which is about as awful an environment as I can imagine. Plus enough material for two filters.

The ones I have had over the years for my vacs don't seem to degrade and are washable. So I'm hoping that there is no sudden loss of integrity in a nice server rack with comfortable conditions.

 

[TheSmoker]

You should give Demci Filters a try. They also make custom sized ones. ;)


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[joeschmuck]

A lot of these materials breakdown over time. I have some stuff that looks great until you touch it and then it just falls apart. Maybe you have some stuff that was ahead of it's time, BIO-Degradable ;).

 

[jgreco]

Generally speaking, those are a nice option. Would be messy for this use because the chassis actually has "clips" designed to hold the foam filter. I can picture lots of places that might be useful though. Dust is the natural enemy of heatsinks in particular...

 

[jgreco]

A lot of these materials breakdown over time. I have some stuff that looks great until you touch it and then it just falls apart. Maybe you have some stuff that was ahead of it's time, BIO-Degradable ;).

Well, I've seen all sorts of strange stuff over the years. These two boxes are actually fortunate enough to be undergoing a midlife retrofit soon. They've been recycled several times since they were first deployed in the '90's, and these have been deployed as Xeon E3-1230 ESXi nodes for around two years. I'm expecting another two out of them in this configuration, I think. Normally they probably wouldn't get a retrofit unless something had failed, but the transition from ESXi 4.1 to 5.5 is a bit of a pain and they're gonna be getting some minor upgrades and memory swapouts anyways, I think. So I'm giving some serious thought to maybe putting some steel mesh fan filters over the intake fans. These chassis have an odd design; on the front is the filter access door, which also serves as a poor grade slotted dust catcher. Inside that, about an inch back, is the section that holds the actual filter. Then a cavity, and a two 120MM fan tray which is accessible from the inside of the chassis. It was actually quite well designed compared to a lot of stuff from that era. Haven't really found anything heavy duty that's as easy to work in. And we have a bit of a surplus of them, plus the rails and other stuff to go with them.

 

[joeschmuck]

Metal filters work great providing you oil them properly and clean them regularly with an ultrasonic hot sink or good high pressure steam. I like using a corrugated HVAC air filter, the nice ones with an aluminum backside. Once you have a template of what you need, just cut it out of the air filter. If you choose the one with the aluminum backing you can make it fit very nicely into odd shapes/spaces.

 

[cyberjock]

Metal filters work great providing you oil them properly and clean them regularly with an ultrasonic hot sink or good high pressure steam. I like using a corrugated HVAC air filter, the nice ones with an aluminum backside. Once you have a template of what you need, just cut it out of the air filter. If you choose the one with the aluminum backing you can make it fit very nicely into odd shapes/spaces.

Bacon grease for the win! Yum! I'm kidding of course...

 

[TheSmoker]

Demcifle filter are made from metallic mesh, are medical grade and have magnetic frame for quick installation.
http://www.demcifilter.com

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