Why are galvanized pipes used for some instrument pipelines in the purification section?
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While reviewing the piping schedule provided by the design institute, I noticed that in a very small number of sections related to the conversion process, instrument pipelines use Q235-A galvanized pipes. Why is that? Can 20# steel be used as a substitute?
Galvanized steel pipes utilize the principle of electrochemical corrosion, primarily through cathodic protection by consuming an anode. When carbon steel comes into contact with zinc, the carbon steel acts as the cathode while zinc functions as the anode; this prevents the carbon steel from corroding. They are generally used in process instruments or process water pipelines, and are usually connected using threads, for pipelines operating at low temperatures and pressures without hazardous substances. Another advantage of galvanized pipes is that there is less residue inside them, which is why they are commonly used for instrument air pipelines. :P
I don’t know the specific materials and requirements for the pipelines. Instrument piping, instrument air? The reason for choosing galvanized pipes of Q235-A is likely the requirement for clean materials. It doesn’t work well; use 20# as a substitute. For some of the instrument air pipelines in our facilities, we also opt for 304 material pipelines.
The reason is simple: carbon steel pipes are prone to rusting, while galvanized pipes do not rust
I think there’s a misunderstanding on the 4th floor; what the original poster meant was whether it’s possible to replace the galvanized Q235-A with galvanized 20#, rather than using 20# steel pipes
Considering only electrochemical corrosion and not stress corrosion, galvanized pipes can be used to reduce costs. It depends on the fluid conditions and application requirements.