H2S Corrosion-proof controllers

[NorfolkEIT]

I've got a pump station with excessive corrosion in the PLC due to excessive H2S levels that really can't be mitigated at this point. Does anyone have suggestions for a controller brand that handles these conditions better? Or maybe some sort of other idea on how to keep the H2S at bay and out of the box? Thanks.

 

[NorfolkEIT]

I guess I put this in the wrong forum. I'm not sure where the collection systems fit in the forum categories

 

[bimr]

If it is not possible to relocate the controller, another solution is to install a purging system for the control panel. You can add an air purging system to the control panel to blow clean dry air through the panel. You will need a source of dry instrument air.

Lift station areas are generally defined as a Hazardous Class 1, Div. 2 Classification areas.

http://www.bebcoeps.com/typez.jsp

Do yourself a favor and save money/headaches in the long run. Fit a purge kit on either the existing panel that houses the controller or install the controller in a purged enclosure. Allowing corrosive air into such a panel is not a good idea no matter.

It is also possible to an inert gas instead of air, but the inert gas carries with it further hazards.

http://www.google.com/url?sa=t&rct=...e=web&cd=11&cad=rja&ved=0CG0QFjAK&url=http://

http://www.eiga.org/index.php?id=17...bc7iZLTDIEYIBN1NA&sig2=NfeSAYVmoxsuUsXeTlE1GQ

 

[NorfolkEIT]

Thank you. That is actually a very good suggestion that I never considered. I need to see if retrofitting existing controllers with these is a cost-effective measure. I think in the case of rehab, an encapsulated circuit board might be a better application Too bad I can only find one vendor who does this. I think one of these purge boxes is just one more thing in a PS for the mechanics to maintain and the less we give them to maintain, the better. Do you know of anyone who has used one of these boxes specifically in a pump station application?

 

[dicksewerrat]

Why is the panel inside the manhole? Where is the electic service panel for this PS? That is an explosive environment. I'd move all that out to the power panel and only have sensors in the pit. They are easier to replace if they fail.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[bimr]

I am sure that there are many installations with enclosure purges. Here are a few suppliers.

http://www.wastechengineering.com/products/explosion_proof_panels.html

http://www.wastech.com/pages/explosion-proof

http://www.tpcusa.com/

The only O & M for these devices is to make sure that the device is working.

An encapsulated board will work for the controller, but if you have H2S exposure, then everything else in the control panel will suffer from corrosion as well.

 

[NorfolkEIT]

This controller is not in a manhole. The station is a large collection station with 5 smaller stations lifting to it. The control panel is in a building on top of the wet well/dry well. The poor design of the wet well creates a lot of turbulence and the subsequent H2S issue. I'm actually considering using chemical odor control to mitigate some of the H2S, coupled with some sort of measure to protect the controllers. Thanks for the vendor info. I'm working my first job as an engineer. Any help from more experienced professionals is greatly appreciated.

 

[bimr]

Not sure that odor control will solve the hydrogen sulfide problem. Increased ventilation will help to some extent.

You may consider adding nitrate compounds into the feed lift stations. This method has proven to be successfull in minimizing hydrogen sulfide in similar installations when repumping from force mains.

http://www.webpages.uidaho.edu/ce432/h2s-newea.pdf

http://www.webpages.uidaho.edu/ce432/WET-CaNO3-Feb 2001.pdf

http://www.h2o2.com/products-and-services/us-peroxide-technologies.aspx?pid=114&name=Nitrates

 

[QualityTime]

I am not sure how big this pump station is or how many I/O there is but don't fool arond with a sewage pump station. The last thing you need is to put in some interim solution HOPING that it will work and the controller fails...let alone the H2S levels may exceed allowable health & saftey levels. The moment that controller fails and people's homes get flooded out...yikes....,

 

[QualityTime]

How is the H2S migrating to the room? Are there openings in the floor? Is there conduit where the interior is not sealed. Is the HVAC not keeping the room pressurized. Chemical odor control is a waste of time.