Recommendation for Coating to Protect Concrete Force Main from H2S Corrosion

[ziptron]

Hi Everyone,

As the thread subject says, I'm hoping to get some recommendations for a coating to coat a concrete force main and protect it from H2S gas produced by bacteria in the sewage. I expect H2S gas levels of around 400 ppm Past experiences/stories would be appreciated and names of coating manufacturers as well as coating types would be appreciated as well.

Thanks in advance,

 

[dicksewerrat]

Cured in Place pipe liner, HDPE liner. both should be able to handle that. Are there lots of bends in the line? what kind of pressure, surge pressure vacuum? Where is it? Diameter, length?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[bimr]

New installation or repair of an existing force main? Diameter and length?

 

[ziptron]

Thanks for your quick replies.

Pipe is rather large, 900 mm. Not many bends. It would be a new install.

Going through a brain storm session on this project at the moment. I arbitrarily picked that ppm, but I'd like for it to sustain that based on some things that I am reading. Another thing I worry about is it may sit not completely full. I've read in the past that H2S will come out of the water solution and form H2S04 in the head space above the fluid. That may chew up the coating heavily no?

Anyone have experience with the above?

 

[cvg]

coatings are not the best recommendation. lined pipe is better. non-corrosive pipe is the best. keeping the velocity high and ppm low is better. avoid head space. aerate or oxygenate if necessary

 

[bimr]

Hobas pipe is one product that will work in that application.

http://www.hobaspipe.com/case-histories/wwtp/illinois-wwtp-plant-expansion/

 

[dicksewerrat]

36 inch pipe is not a problem to line. there are liners out there that can do the job. What is the GPM and pressure of the force main when the pumps are running?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[dicksewerrat]

Is the RCP already purchased? Get a variance in the spec to allow HDPE and fusible PVC. they can be installed by Directional drilling. No coating needed.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[ziptron]

I see several of you are suggesting pipe lining even though I mentioned that there would at times be some empty head space from the pipe not being full. Are there liners that will withstand that? Would they be an epoxy?

If so, could you recommend some pipe lining products for me to look into? Something odd to me about a force main with empty head space being OK as a design.

Should I simply be suggesting that we ensure it is always full instead of trying to find a coating that will likely fail anyway?

Thanks in advance,

 

[bimr]

If there is head space, then it is not a force main, it is a gravity sewer.

 

[ziptron]

True, I see your point. What would you coat a gravity sewer with then?

 

[cvg]

coating is really not recommended. epoxy is a coating, not a lining

as recommended above, linings are superior to coatings. but non-corrodible pipes are even better

 

[rconner]

It is well known concrete is for various reasons a quite a difficult material to line for dependable long term service in such applications, with the best performance to date with well installed liners that are not really bonded as normal paint, but instead mechanically locked to the substrate. Even so, such liners are in practice not impermeable, and present other vulnerabilities in the real world e.g. as noted at

http://www.wwdmag.com/pipe/preventing-problems-liners

etc.
As it appears you are now delving into issues of basic system design, you also may be interested in perspectives contained in past discussions of perhaps similar challenges e.g.

http://www.eng-tips.com/viewthread.cfm?qid=194951

and

http://www.eng-tips.com/viewthread.cfm?qid=24447

etc.

 

[ziptron]

Stupid question, but why are liners better? Is it just easier to get a continuous surface without holidays in a liner than in a painted epoxy?

If you paint two times.. (two separate layers) and paint over the holidays, would you not have a good enough coating and be as good as a PVC liner for example?

 

[bimr]

A “coating” generally implies a thinner spray, brush or roller applied material, while a lining is considered to be thicker, usually trowel applied. Some linings are applied as sheets. Many linings today, are in fact, thicker layers of material that are also spray applied.

 

[ziptron]

Ahh I see.

Is there a rule of thumb as to what thickness constitutes a liner? I have here in my specs a '20 mill' coating. Seems somewhat thick to me.. hence the confusion.

 

[rconner]

fyi see

http://www.epoxyproducts.com/fail4u.html,

and particularly pages 19-20 at

https://www.chlor-rid.com/saltinfo/Pipeline Corrosion Protection by Guan page 17.pdf

with regard to some experience and challenges of coating/lining concrete pipe (understanding this is from a coating manufacturer).

 

[bimr]

20 mil is the thickness of the elephant rubber that you line your trash can with.

Imagine if you tried to clean a forcemain with 20 mil liner? The liner would probably be ripped off the wall.

See the attachment, page 5.

https://www3.epa.gov/npdes/pubs/force_main_sewers.pdf

 

[ziptron]

Sorry, it actually says 40 mill coating.. not sure where that 20 mill came from. Though in retrospect, even that seems a bit too thin based on what you guys are saying (and based on what common sense should have dictated to me from the start).

Thanks everyone for your kind replies. This website is truly a gem!

 

[dicksewerrat]

Call some local lining contractors. there are liners out there that will hold 100 psi. I know. I have been designing them for 20 years now. And there are new products out every couple years. We are are not allowed to sell our products here or I would be all over it.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com