What’s the best material for pipes used in chlorination?
asked 8 March 2017 asked by polonium210 (420 points)
Hi, In my experience, there aren't many options. I would say you have to go with stainless steel, but watch out for the grade: it should be 316L or higher. However, welded joints will be weak points. You will need to tell your supplier or manufacturer that you are using the pipes for chlorination, so that any welding alloys that may be required are appropriate to the circumstances.
Pipes must be made of metal if they convey pressurized chlorinated. But this practice is uncommon. In most current facilities that rely on a hydro-injector, only the section between the chlorine tank or container and the membrane on the pressure regulator is actually pressurized. Everything else is in a vacuum, so suitable plastic pipes are more than adequate to the job. This reduces risk in the advent of a breakage—it's air entering the pipe and not the chlorine escaping. The metallic component containing pressurized chlorine is usually provided by the supplier and is constructed with special alloys. If you do have chlorine under pressure but do not need to extract dozens of kg of chlorine per day, changing your equipment might be the solution.
I recommend you order pamphlet no. 6 from the Chlorine Institute available in the link below. I have had bad experiences with stainless steel at the mixing point with water. https://bookstore.chlorineinstitute.org/mm5/merchant.mvc?Session_ID=60ac95a0cbdb19928801463bdad1fdd2&Store_Code=ci2store&Screen=PROD&Category_Code=SPHP&Product_Code=SPHP0006-HC& According to the technical sheet I have on hand, courtesy of a major chlorine supplier, screwed connections, with welded sockets or welded end to end, are recommended along with grade B, schedule 80 carbon steel.
You only need to look at Flint, Michigan, to know that stainless is the way to go, another idea might be UV treatment prior to distribution. Contact me if you are looking for a chemical free alternative
The pipes in flint were old but fine till the decided they needed to switch getting water from Detroit and get it from the Flint river. The Flint River has a high concentration of chloride which made the pipes corrode and leach the harmful chemicals. The problem is that because detected coliform bacteria the had no choice to dump in more chlorine. Pipes were already old and working well. Because they changed their water source that's what screwed them up. They weren't prepared enough.
Ductile iron pipe class 52 or 53. It has a concrete lining. We just rebuilt a chlorination building in a neighborhood. It was schedule 80 pvc. It must be threaded because the chlorine makes the pvc brittle. Switch to hypochloride for ease, price, and regulatory purposes.
What is your ppm of your Chlorine? Is it Gas or Sodium Hypo? We use CPVC and it has not been an issue. We use Sodium Hypo Onsite Generation. Our system has been in use for over 10 years and we have only had minor issues with the Sched 80 PVC parts that convey the hypo to the pre and post treatment sections.
Don't mix chlorine and ozone in a stainless steel pipe. It will pit the stainless steel and destroy the metal. FYI