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ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
dairy cbs.jpg

I think these have been in maybe 5 years and they have recently had a rash of failures so the guys performed some autopsies. Recent in that somebody finally called.
We suggested then that a fresh air intake should be installed in this electrical room for a dairy separator. Separates the solids and liquids for waste management.

So far its only been the 120 & 240 volt breakers. The 480 has me concerned.
 
I really like what one of my agriculture customers told me a few years ago.

”we’ve done it cheap, now let’s do it right. In the long run it doesn’t cost any more, and probably less.”
 
We do work for a large manure digester adjacent to a huge dairy.

The HMCP breakers in the AB MCC's fail fairly regularly. When I used to take the breakers apart(I don't anymore now that I've seen the problem over and over), the guts inside would be black and discolored. But what killed the breakers, was the spot welds holding the breaker contacts on would corrode away allowing the contacts to fall off and rattle around in the breaker case.

Now the customer keeps a good stock of spare HMCP's on the shelf. As well as ethernet switches. They go through those like skittles.

I'm told it's the H2S gas in the air, and there is no simple fix, short of moving all the electrical equipment a long distance from the site.

For the pump panels and other equipment near manure separators, pits, etc I've found if I can even get the equipment just 25' away from the manure, it seems to last a little longer. That air gap makes a difference.
 
Ventilation won't help much if you are getting same deteriorating gases in the inlet, keep that in consideration.
 
Cow said:
... I'm told it's the H2S gas in the air, and there is no simple fix, short of moving all the electrical equipment a long distance from the site.
... if I can even get the equipment just 25' away from the manure, it seems to last a little longer. ...
Click to expand...
In an existing installation, it might be possible to install positive-pressure ventilation with the air intake 25 or more feet away.

Severely dehumidifying the electrical room and/or heating the electrical panel to prevent condensation might prolong equipment life. It's probably not the H2S by itself that's so corrosive, but the combination of H2S and water.
 
drcampbell said:
In an existing installation, it might be possible to install positive-pressure ventilation with the air intake 25 or more feet away.

Severely dehumidifying the electrical room and/or heating the electrical panel to prevent condensation might prolong equipment life. It's probably not the H2S by itself that's so corrosive, but the combination of H2S and water.
Click to expand...

Good info, thank you.
 
I'm now trying to find equipment to pressurize this location with fresh air. Can someone point me in the direction to become somewhat educated? Most likely a HVAC person will be involved but I would like to have some idea of sizing etc. Winter temps will have to be tempered but not so in the summer.
 
I am deeply immersed in issues related to this right now.

H2S gas is produced by anything that is "rotting", including animal (and human animal) waste. When H2S gas mixes with water, it forms H2SO4, aka sulfuric acid, one of the most virulent acids when it comes to corrosion. Sulfuric acid then eats into most exposed metal surfaces. One nasty aspect of this that is affecting everyone now and for the foreseeable future is that RoHS rules (Reduction of Hazardous Substances) for electronics assemblies have removed lead from the PC boards now. Lead oxide was one of the few materials not affected much by H2SO4 so when things like the "fingers" on PC board edge connectors were cut, exposing the lead substrate, the lead oxide that formed was protecting the gold plating on those fingers from the H2SO4. Now that the lead is gone, newer electronic assemblies are corroding much faster and failing sooner. Most mfrs now put what's called "conformal coating" on their PC boards, but they can't coat those edge connectors.

In addition (and more related to circuit breakers) H2S, when exposed to silver, causes the growth of "whiskers" of silver nitrate to form on the surfaces and they grow over time. When that happens inside of circuit breakers on silver plated current carrying parts such as contacts, nobody notices so long as the breakers are closed. But when they open, the silver whiskers span the air gap that is supposed to interrupt current flow and you get an internal flashover. Sometimes if it's just a little bit of the whiskers, that just looks like a flash and they vaporize without causing much damage. But every now and then the build-up is significant enough that the flashover is destructive to the breaker.

The answer is that the user must use a positive air pressurization system, making sure that the source of air is far away from the source of H2S, or if not possible, install a "scrubber" system for their location. I have seen an entire MCC in a pump station literally dissolve when a scrubber system failed and had no alarm system to tell anyone. On top of that problem, H2S is a severe health hazard in high concentrations (as it was in that case) so someone could have been seriously harmed.

H2S air scrubber...
http://mvseer.com/technologies/h2s-removal-systems/h2splus-system/
 
The digester we wired from the ground up in '12 is in bad shape. We used all copper bussing in most all of the gear, which is standard for us. I can tell you when we open the 2500 amp switchboard, there are BIG flakes of gray corrosion coming off the bussbars. It's not pretty.

Surprisingly, the metering cabinet for the power co., with their aluminum secondary wiring from their transformer looks PERFECT years later. Looks like the day they installed it.

It's counterintuitive, but the aluminum appears to be holding up FAR better than copper.

Among other things, they go through ethernet switches in the AB MCC's like they're skittles. They keep an entire case of spares on the shelf at all times. Maintenance and downtime expenses due to H2S
are in the hundreds of thousands at this point, I'm sure of it.
 
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