How to clean up lab after big capacitor blew?

[jtu]

Hi,

I'm not sure yet what was the reason, my mistake or just defective capacitor. In the afterthought, the view was gorgeous. It spew out some and then there was this cloud of electrolyte mist settling down. It was big cap: 10000uF 50V... Fortunately I'm alive and not injured.

But now the adrenaline is out and I'm left with my lab desk covered with splashes and electrolyte "snow". Unfortunately it is not just desk, it is everything: tools, equipment including scope, cables, screwdrivers, multimeters, etc, some got on to the computer display, keyboard and mouse... Couple pics attached.

In theory it is alkaline, but I'm a bit afraid to apply anything acidic without any peer confirmation. I tried contact cleaner a bit, it kind of helps, but is it good for computer accessories and scope? Display cleaner also kind of helps, but some mechanical force have to be applied to splashes, I'm afraid of scratching it.

Any experiences out here?

Veiksmi,
Janis

[drussell]

Only 10,000 uF, you say?

You haven't really lived until you've seen (and hopefully survived) a 330,000+ or a 1F or something blasting apart!   

Mild soapy water like nice, dilute dish detergent is probably enough for general cleaning up most things like that since it's not super corrosive or anything, but you do want to clean most of it up as much as possible, mostly just like general dirt and grime on equipment over the years. 

You probably don't really need to worry about completely neutralizing it like you would if you had a lead acid battery that exploded or something...  Even though a typical battery acid concentration might only be about 30% rather than 98% H2SO4 it will damage things much worse than any capacitor electrolyte ever could...

[Monkeh]

A nice can of foaming window cleaner and a soft cloth. It's soothing as well as effective.

[Brumby]

I feel like such an innocent.

I haven't had any caps detonate whilst exposed ... in fact, I'm hard pressed to remember if I've been around when any have.  I've had a couple of MOVs fail short across 240V, but even those were encased at the time.

Nice, even distribution though - I must say.

[Jwillis]

I had experience in an exploding capacitor....It was harder cleaning up the blood that leaked from my face than all the shrapnel.... Any way a good house hold cleaner on a soft rag works fine .Just don't spray it directly on the equipment.

[tpowell1830]

Well, you start by removing your pants and underwear, then you go outside and get a water hose outside and spray away all the brown places and wring out all excess water, then throw them into washing machine and get fresh pants and underwear.

Don't know how to clean all of the white junk that came from capacitor...

[james_s]

That's impressive, personally I would use a towel and whatever equivalent to Windex is available, or a mild detergent in warm water.

I had a mosfet half bridge blow up once across a 400V bus, a piece of shrapnel whizzed by my eye and bounced off the ceiling, my ears were ringing for a bit. Since then I've been more careful, a lexan blast shield over power electronics is not a bad idea.

[jordanp123]

Ahhh, an electrical "rite of passage". Worse one I'v had in some time is a music amplifier, had a blown cap, replaced it, and checked for other shorts everything seemed fine. Turned the unit on and I heard a very loud bang, had the new capacitor pop and saw nice blue electric arcing on top of the capacitor....turned out the rectifier bridge had a voltage dependent failure......Get some foaming window cleaner and just clean up, use some IPA on any circuits that were exposed.

[Ian.M]

*DON'T* use Windex.  It had its place for cleaning really dirty CRT screens that had been exposed to heavy smokers, but you had to be really careful with it.   It contains enough Ammonia to cause serious corrosion of copper traces if any leaks between the display and its bezel so could destroy the front panel controls below the scope screen.  Also, its only really suitable for glass, ceramics and highly polished non-cuprous metal surfaces, so its use on a modern LCD screen and other plastics is extremely dubious. 

First RTFM to see what products are permitted for cleaning the screens.   If it doesn't mention any or says no solvents, try ordinary lens cleaner that's suitable for plastic glasses.

For general cleanup, try any reputable brand of foam cleaner, applied sparingly to a soft cloth except on large flat surfaces with no openings where you can spray it on direct.  Frequently fold or replace the cloth to expose a clean piece.  If foam cleaner doesn't shift it, try IPA.

[T3sl4co1l]

My worst story is a blown TO264 IGBT. The explosion was so loud that it attracted the building guard.

Those things sure can crack, but it's the fireworks you get from industrial devices that really sets things apart.

I had a couple SOT-227's go off in front of me; there was lots of black residue and arc tracking on the PCB.  The expanding plasma ball of the former die and bondwires became an arc flash event, interrupted within probably a millisecond, thanks to the "semiconductor" fuses upstream.

On another occasion, someone blew up a larger module (1200V 600A).  Fortunately, that was inside a floor-standing system, with the door closed.  The shrapnel launched from one of those babies can cause real damage!

Tim

[T3sl4co1l]

Regarding cleaning, mind that that vapor / mist will land on every surface in sight.  You may want to wash out some of your more intricate and unsealed electronics, just to make sure it's not gumming up the works.  Electrolyte isn't so much corrosive in and of itself, but because it allows electrolysis, anything energized can eat itself to pieces!

Tim

[medical-nerd]

Hiya

I must have had a misspent childhood. I fondly remember connecting those large metal cased electrolytic capacitors from old radios across the mains when I was about 10 to see how big a hole I could make in my bedroom wall with the resulting projectile. (over 40 years ago!). The only requirement was a supply of replacement fuses!! 

Cheers

[tautech]

The scope display is toughened non-reflective glass so most cleaners should be fine but for the ABS of the case I'd just sponge it with warm soapy water and a good wipe dry afterwards. A little time on a window sill in the sun wouldn't hurt either.

[paulca]

The only time I have blown a cap I put the mains through the low voltage side of a voltage/amp monitor.  It wasn't just electrolyte it was copper dust perfectly plating the inside of the box, along with a burn mark on the carpet that perfectly matched the vent pattern in the side of the box.

[tron9000]

wow that's quite a mess!

First off try soap and warm water, then progress to more hazardous chemicals. Anti-static foam cleaner is pretty good. Isopranol-alcohol is good at shifting oily/greasy stuff. Acetone - be careful on clear plastics with this, it WILL cloud/frost them up.

I would try in that order.

If you want cap explosion stories! I first started my career in a factory that repaired and built welding machines. We had a test area where units were tested as a technician would pop a few beads of weld down, units tended to be test with their lids off. The DC welders had a massive cap bank consisting of several 20,000uF, 200V electrolytic caps (about the size of a coke can) all screwed to a bus bar.

one day there was an almighty 'POP!' as one of the welders was plugged in and the clanking of tin cans on the ground at the other end of this 15m long building! Caps and been screwed wrong way into bus bar and about 60V DC dumped across them!

[EEVblog]

 

[Ampera]

Well, you start by removing your pants and underwear, then you go outside and get a water hose outside and spray away all the brown places and wring out all excess water, then throw them into washing machine and get fresh pants and underwear.

Don't know how to clean all of the white junk that came from capacitor...

It's been around or below freezing over here for ages. That would probably be lethal for me... 

[Yanis]

Reminds me of a story my brother related. We worked in an Instrument Repair Centre for Telstra and he was repairing a vector scope. I was not there when this happened.

There was a fault in the EHT cage which was situated at the very back of the case and he had to pretty much completely dis-assemble the unit to get to it. It turned out the be an electro. So with the electro replaced and the unit back together he powered it on only to be startled by a huge bang.

So he re-dis-assembled it and discovered a splatting of electrolyte and Al foil all over the inside of the unit. He told me that it took the best part of a day to clean up. He then checked the layout to make sure that the electro was in the correct way round. So he checked the silk screen on the board against the circuit diagram only to discover that the silk screen had the cap the wrong way round with reversed polarity.

After he cleaned it up and replaced the cap and re-assembled he rather tentatively turned the power on. All good.

Lesson, never believe the layout diagram or silk screen. Always verify.

[Barny]

Some years ago, I put in a capacitor in reverse.
My workbench looked similar.

I collected all mecanical tools, screws and other parts which are not prone against wather and took them to work.
There they put them in the industrial washingmachine for parts which get spraycoated and soaked all in conservation oil afterwards.

All other parts I cleaned with soap wather.
It was a damn work, but it had to be done.


The loudest electric bang I heared was the switch from the secondary trafo taps of a 15KV / 2400VA transformator.
Thats this type of switch which has ca. 50mm^2 switch contact surface area (2 switches in series) and uses compressed air to blow out the switching spark.
Some idiot decidet its fun to switch on the trafo and change taps while I was fixing the auxiliary compressor in a few meters distance.

[Barny]

Jepp. Sorry.
I missed the K.
It was 2400KVA.

This transformator supplied 4x brushed universal motors.

[ramin110]

Can I try one myself? like 1F 

[jtu]

Thanks everybody for your advice! And encouraging stories to continue

Well, it was ~8 hours of cleaning...

Few notes, maybe those will help coming generations of electronics enthusiasts blowing up electrolytics
* Identify what is contaminated. Not just area, all the space, because the electrolyte mist made snow cloud going everywhere including up and then settled. Mine is marked in the picture, see gallery. Red cross is approximate epicentre where caps were. Yellow - cloud of mist. Orange - splash zone. Blue - whole space cleaned (it extends to the left almost to the other end of the display). Not just that but before, cleaning process and after pics.
* First thought is to save everything, but cleaning is really tedious. Consider what is below the value of your time spent.
* There are two types of damage: splashes and snow.
* Splashes are evil, those need mechanical cleaning first. I used old credit card. Be careful. An experience of mine as an example. I was afraid to mechanically clean the splashes off my beautiful Apple display. Using soapy water or screen cleaner took forever, so I did some mechanical cleaning at the end. Soapy water and  screen cleaner for the finish.
* Snow is more or less easy except if in the places like open electronics PCB's, heatsinks and BNC, USB etc connectors. Sponge or cloth, soapy water, paper towels, PCB/contact cleaner.
* Compressed air and compressor are good tools. Especially for blowing out moisture left from water or any other liquids. It can not blow away the snow.
* I'm pretty sure I did not get all of it off.

It seem ok now. I still have to clean the open electronic load. Need to disassemble it. And the transformer. For the transformer I'm thinking that replacing outer layer of isolation might be easier and safer.

Two sub-stories of my adventure.

I was trying to test transformer 2x30V + rectifier bridge + 2 capacitors 10000uF 50V in a dual rail config. It did seem fine without load. It did seem fine with big resistor as a load over both(~0.5A). For short periods of time, less than a minute. I did not check temperature of the capacitors, just the load. Then I connected step down voltage regulator to the positive rail. I have been using that regulator for couple years as a power supply, you can see it in the shelf. I was going to attach electronic load and apply minimal load, but the capacitor of the negative rail popped. I think it was before I managed to connect the load, maybe in the process, but I'm not sure, adrenaline. I have read the theory of linear power supplies and did calculations several times before I did this. But I'm in not 100% sure about what I did. One of my guesses is to blame cheap caps I use for experiments. The other is that voltage rating must be calculated with more redundancy. Third is misbalance, even with minimal unbalanced load (it was ~50mA with step down regulator attached) on just one of the rails of the dual rail.

In parallel I was setting up mini-ITX Windows computer for use with scope and other instruments. I was trying to do it in the virtual machine on my Mac, but that does not seem to work well, some features at all. The computer enclosure was still open and it was running. Fortunately it sat behind the scope, no splashes. But it got some of the alkaline snow. I inspected it very carefully, there was not much snow in it. I removed "snowflakes" with tweezers, cleaned with PCB cleaner, used compressor on it for several times. Working condition, but let's see.

I'm going to continue after more reading. And build the box of plexiglass or something.

[jtu]

I must have had a misspent childhood. I fondly remember connecting those large metal cased electrolytic capacitors from old radios across the mains when I was about 10 to see how big a hole I could make in my bedroom wall with the resulting projectile. (over 40 years ago!). The only requirement was a supply of replacement fuses!! 

Same here I did big one just once, but small on occasion.

[paulca]

The only requirement was a supply of replacement fuses!! 

Just wrap an old one in oven-foil

[Ian.M]

.... or, as a friend of mine did to get a peace-keeping patrol back on the road in a hostile area, replace the fuse with a chunk cut from a 1/4" UNF bolt.  I believe the vehicle commander was told "If you see smoke, bail out and leg it to your patrol partner's vehicle."