DI sewer force main lining 1

[vodeni]

In your experience, is double cement mortar lining with asphaltic coating adequate for sewer force main or would it be prefered some sort of epoxy liner/coating?

thanks

 

[rconner]

I believe cementitious pipes and linings have carried domestic sewage/sewerage in many areas for a very long time. However, if pipelines do not flow full for extended periods of time i.e. are not continuously rising mains or with other profiles otherwise dependably designed to flow full (and other conditions such as H2S generation, temperature, length of main/detention time, flow rate etc. are amenable to same), there are many references including ASCE Manuals and Reports on Engineering Practice #37 and #69 (and also EPA manuals), which discuss the mechanisms by which corrosion can occur in some specific circumstances in the “crown” areas or above the flow-wetted perimeter of some sewers. This corrosion occurs as a result of the conversion of hydrogen sulphide (H2S) into very low pH sulphuric acid (H2SO4) by various aerobic bacteria. References going back many years state that the specific wall moisture pH values of the sulfuric acid produced by the aerobic bacteria can be in “the 0.5 to 2 range”. At least as early as the Fifth Printing (1970) ASCE MOP No. 37 (WPCF MOP No. 9) stated, “In some instances where air has been trapped in high places in the main and where the treatment has not been sufficient to keep the main free from sulfide all along its length, damage to the pipe has occurred.” Of course if extremely low pH sulfuric acid is to be produced, even double thickness cement mortar linings (and maybe even a lot of other materials, less obvious?) will not withstand its attack for very long service life, and other special linings with suitable performance are therefore required in such cases.

 

[vodeni]

Hello everyone.
I am designing a baffle wall inside a concrete aeration tank. The baffle is to create a separate anoxic zone for the denitrification. Any suggestions regarding the material, construction and type of flow (over or under the wall)would be appreciated. Thank you

 

[dicksewerrat]

Is this force main going to be buried? How much pressure? cement lining will deteriorate over time. less than 25 years probably. HDPE or fusible PVC may be better options

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[rconner]

Ummhhh. I remember reading a paper published in ASCE only 30 years ago that stated Portland cement concrete was then the major constructional material used in the developed countries of the world. It was also stated in that paper (and is otherwise well known) that concrete pipes long before that were used by the Romans for water and drainage, and parts of systems apparently were found to be in “reasonable condition” after more than 1,800 years! Cementitious pipes do not have quite as long a history in the USA, as this article also mentioned the first concrete sewer pipes in the USA were not installed until ~1842.
I believe cast iron pipe has an even longer history of use in the USA, and I guess even most of the early stuff without protective linings. Information concerning this is available from the sites cispi.org and dipra.org, and from the former portal I noticed the quite interesting (though maybe at least some dated, as e.g. quite a few old pipelines are replaced at least due to inadequate size etc.) statement on the page at

http://www.cispi.org/corrosion_resistance.htm

that “Over 95 percent of all cast iron pipe that has ever been installed in underground service in the United States is still in use.” There are also some perhaps useful comments made on the FAQ #3 “Longevity” at

http://www.cispi.org/faq.htm.

Does this mean that these materials are immune to all forms of chemical/biological attack? NO, as is explained on these sites, many other engineering references such as ASCE manuals etc., and as I explained briefly in my initial response there can be problems in some quite aggressive exposures (dictating other precautions). Durability or pipeline performance for all pipeline materials is of course dependent on specific exposures, and I will note on many other determining factors in the manufacturing, shipping/handling, construction and life cycle of pipelines.
I do not offer these comments to challenge you to furnish equal performance history (considering all aspects I talk about, and I suspect others maybe equally meaningful) for the e.g. “fusible” plastic pipes you propose as an alternate to what the original inquirer is using, nor do I ask you the question have there ever been any problems of any nature with plastic sewer pipes in general that may shorten their life spans. I believe all available materials should be given appropriate consideration.
However, given the overall body of work I do not think it is fair to claim or imply that a chosen traditional pipe will not last 25 years, and one may not necessarily want to "throw the baby out with the bath water" (so to speak).

 

[dicksewerrat]

Well we are lining one of those DIP cement lined pipes right now. they were installed about 30 years ago.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com