Variable speed drive for Lagoon area

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chaterpilar

chaterpilar

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What special precautions and desig considerations are needed to take care of the copper corrosion that takes place in panels near lagoon area ( because of Hydogen sulphide and Ammonia)

if variable speed drive is installed in a room near this lagoon ( to pump out the slurry), what protection can be added to take care..of the corrosive gases.

Any thoughts..
 
It used to be that you could ask for conformal coating on the VFD PC boards, but that is beginning to become more and more rare. The best I have seen of late is to have them in a room that has a good de-humidifier. Without moisture that is no catalysts to accelerate the corrosion.
 
Tin plated copper bus should prevent the corrosion. Do not use silver plated bus as the ammonia will react with the silver plating. Conformal coating on the VFD boards shouold prevent their corrosion.
 
Plug every conduit, hole, and clamp the cabinet tight! We haven't had too many problems from the corrosion of the VFD/VSD's themselves. We have had a lot of problems with the wire connections. They tend to corrode more. As Jraef said a de-humidifier will help. Personally, I don't think there is any way to keep that nasty stuff out!
 
Hoffman makes a industrial corrosion vapor inhibitor. Its a spray or foam ball/strip that is used for the equipment. I've used it but can't say if it works or not, but it has a good write up. Its bulletin A80 in the current hoffman catalog.
Also I have found a enclosure heater works well to reduce condensation, all of our enclosures have a strip heater, some use a Hoffman enc heater.
Do you have instrument air? You could pressurize the enclosure.
 
gedwards said:
Tin plated copper bus should prevent the corrosion. Do not use silver plated bus as the ammonia will react with the silver plating. Conformal coating on the VFD boards shouold prevent their corrosion.
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Good point, I forgot to mention the issue of NO silver plating. It grows "hair" in the presence of H2S.

Silver whiskers
 
Instrument Air

Instrument Air

I would certainly suggest instrument air as purge for the cabinet.

I have seen too much corroded equipment and wiring to suggest another option.

If you don't have instruement air install a system as this would most likely be cheaper than equipment failure/replacement.
 
Southpaw said:
I would certainly suggest instrument air as purge for the cabinet.

I have seen too much corroded equipment and wiring to suggest another option.

If you don't have instruement air install a system as this would most likely be cheaper than equipment failure/replacement.
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I-air is the way to go, hands down. If you don't have an I-air system you can use bottled air. You only need to maintain a slight overpressure on the cabinet.

ASD's(Adjustable Speed Drives) normally come in a NEMA 1 enclosure, so you may want to procure a chassie ASD and mounted it in a NEMA 12 enclosure that you will seal up well and connect air to it through a pressure regulator and a draft gauge pressure indicator. Take into consideration the heat generated that needs to be removed, so even though FRG and SS are attractive choices in a corrosive environment they both are poor heat conductors/dissipators.

Here is a link to a purge kit:
http://www.am.pepperl-fuchs.com/products/productsubfamily.jsp?division=PA&productsubfamily_id=1795
 
The problem with using I-air on a sealed enclosure containing a VFD is the volume of air necessary to keep the VFD from cooking itself inside. I once did a study for a 40HP VFD in a NEMA4 enclosure to be cooled by I-air; it looked OK on paper until you factor in the compressor power it took to provide that much air. In this case, it took 7.5HP worth of compressor power to cool a 40HP VFD! The numbers can sneak up on you...
 
But the instrument air which is supplied by the air compressor in this remote lagoon area will also be having the corrosive component in it..

Otherwise the compressor has to be installed in a separate area and I-air brought to the site...
 
Jraef said:
The problem with using I-air on a sealed enclosure containing a VFD is the volume of air necessary to keep the VFD from cooking itself inside. I once did a study for a 40HP VFD in a NEMA4 enclosure to be cooled by I-air; it looked OK on paper until you factor in the compressor power it took to provide that much air. In this case, it took 7.5HP worth of compressor power to cool a 40HP VFD! The numbers can sneak up on you...
Click to expand...

I have made this point over and over to the Owner of this forum, but he keeps continuing to promote its use without the discalimer. I believe that Vortex air coolers are one of the most energy inefficient devices EVER invented and should be outlawed. The makers are selling it for obscene profits as these are very simple devices.

However in this case only pressurization was proposed and the amount of air used is miniscule when comnpared to the vortex air coolers. The amount of air used greatly depend on how well the enclosure is sealed and proper regulation of the air pressure.
 
weressl said:
I have made this point over and over to the Owner of this forum, but he keeps continuing to promote its use without the discalimer. I believe that Vortex air coolers are one of the most energy inefficient devices EVER invented and should be outlawed. The makers are selling it for obscene profits as these are very simple devices.

However in this case only pressurization was proposed and the amount of air used is miniscule when comnpared to the vortex air coolers. The amount of air used greatly depend on how well the enclosure is sealed and proper regulation of the air pressure.
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You and I see eye to eye on Vortex coolers. Over hyped and under scrutinized.

As to this application, pressurizing a box with the controls and panelboards would work. But not the VFD unless it is a small VFD in a very large box, which most lagoon drives are not. VFDs require a lot of cooling air flow, not just pressurization. A VFD with "fins out the back" of a sealed enclosure would work for a while (along with pressurization of course), but the fins are typically un-anodized aluminum and corrode very quickly themselves, which reduces their effectiveness so much, so rapidly that the drives will start tripping on OT within about a year (my direct experience). I would have recommended an Air Conditioner, but I have yet to see one of those that holds up well in lagoon environments either (same problem with aluminum). But they are slightly less expensive than the VFDs to replace!

I have been involved in a lot of VFD applications in "Brown Trout Farms", and lagoon drives are always problematic. Conformal coating of the PC boards and locating them in a de-humidified room have been the only reasonably successful practices I have observed.
 
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Jraef said:
You and I see eye to eye on Vortex coolers. Over hyped and under scrutinized.

As to this application, pressurizing a box with the controls and panelboards would work. But not the VFD unless it is a small VFD in a very large box, which most lagoon drives are not. VFDs require a lot of cooling air flow, not just pressurization. A VFD with "fins out the back" of a sealed enclosure would work for a while (along with pressurization of course), but the fins are typically un-anodized aluminum and corrode very quickly themselves, which reduces their effectiveness so much, so rapidly that the drives will start tripping on OT within about a year (my direct experience). I would have recommended an Air Conditioner, but I have yet to see one of those that holds up well in lagoon environments either (same problem with aluminum). But they are slightly less expensive than the VFDs to replace!

I have been involved in a lot of VFD applications in "Brown Trout Farms", and lagoon drives are always problematic. Conformal coating of the PC boards and locating them in a de-humidified room have been the only reasonably successful practices I have observed.
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Application recommendation:

1. The ASD would need to be mounted in an unconventional way. If the heat sink removable then you would remove it, coat the surface with heat transfer material and bolt the ASD chassis directly to the back of the box. Then mount the heat sink, again with heat-transfer material applied, on the other side of the back-panel. (Should strip the paint off of the panel.)
2. Install a thermostat inside and wire it to an alarm. Set it to the maximum ambient operating temperature minus 2 Centigrade of the ASD.
3. In many corrosive atmospheres COPPER-FREE aluminum will perform excellent, but you need to know what corrosive materials involved and select your material for the heat sink accordingly.
4. You don't have to use the manufacturer?s heat sink, just make sure it has the equivalent surface area. (There are many manufacturers of heat sinks.)
5. You can coat the heat sink with appropriate material selected for the specific corrosives involved. When you coat it, consult the HS manufacturer how much the coating will reduce the heat transfer and oversize the HS accordingly. Or just replace the heat sink whenever the temperature alarm starts going off.
6. Oversize the ASD, if you needed a 40HP, use a 50HP. It will not reduce the amount of heat generated, but the larger physical size will results in a cooler running ASD.
7. Passive heat transfer devices, such as Nortec heat pipes can be a viable substitute for regular AC units. They have no moving parts and available in various materials of construction so they are good choice in a corrosive environment. Their remove heat, but can not create lower temperature than the ambient air. They are passive devices.
8. ...and of course pressurize it as recommended earlier.
 
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