Material selection for process pipelines and valves in sodium hypochlorite systems
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In our company’s production process for sodium hypochlorite, the temperature is kept around 40 degrees. The pipes and valves used are made of CPVC material, but leaks occur frequently; not only at the plastic welds, but also the pipes and tees can become corroded and perforated. I wonder if anyone knows what type of material could be used to prevent corrosion in cases of sodium hypochlorite production, thereby extending its service life! Thank you! !
Tubes and pipe fittings made of titanium can last at least 20 years
Titanium is used in high-temperature conditions; using it at around 40°C might be a bit excessive. It would be better to consider using PVDF material. However, our company uses PVC + fiberglass, and it seems to be quite acceptable.
For sodium hypochlorite transfer pumps, fluoroplastic-lined materials are generally used. For pipes and valves, PVDF or PE can be considered as options.
It seems that for sodium hypochlorite, PVC has better corrosion resistance than CPVC. Does anyone agree?
Obviously, the key issue is that titanium materials are very expensive; small organizations can’t afford to use them
CPVC itself is fine; the problem lies in the perforations in the pipes, which are a quality issue.
Tower-type continuous production of sodium hypochlorite features a high degree of automation, requires less space for equipment, and offers high production capacity along with stable quality.
Keep the temperature around 40 degrees: circulating water should be used for heat exchange, as hyposodium decomposes easily when its concentration exceeds 30; pay attention to controlling the reaction rate and the amount of chlorine gas used. If possible, try using water at 7 degrees. There are leak points in the welds, tees, and pipes: check the cause. Is the local operating pressure too high? Generally, 3–4 kg is sufficient ； Has the pipe support worked effectively? Is there any stress? Is it necessary to install π-shaped bends or expansion joints? ； Then there’s the issue of material procurement. For items that tend to leak, we plan to try a different brand or material. PVC/FRP or carbon steel lined with fluoropolymer are both good options. However, when the pipe diameter is small, PVC/FRP can easily deform over time. Therefore, we intend to switch everything to carbon steel lined with fluoropolymer; this will incur considerable costs.