What to do when the circulating water pipes are corroded
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Last week, our company experienced a major shutdown. The main reason was corrosion of the pipes by circulating water; 12 out of 14 heat exchangers were leaking. There were more than 20 defects in the DN50 pipes, and the surfaces of the DN200 main pipes were also severely corroded. We have now decided to replace all the DN50 pipes and switch the heat exchangers to stainless steel ones. However, there is disagreement regarding whether to replace the DN200 pipes, as some of them are buried underground, making replacement a time-consuming process. The company wants to resume operations as soon as possible, as it experiences significant losses whenever it is shut down for even one day – losses of over 2 million per day. Replacing the main pipes would take at least another month, resulting in losses of nearly 50 million. On the other hand, if we don’t replace them, there is a risk of leaks in the main pipes once operations resume. At present, the main question is: under the same conditions that caused defects in the DN50 pipes, to what extent are the DN200 pipes corroded? I’m hoping that some colleagues in this forum have encountered similar situations and can offer some advice
How many years has the pipeline been in use? It’s still necessary to identify the root cause: what are the corrosive components in the circulating water? Additives or specific treatment methods can be used to neutralize them and reduce corrosion
The replacement cycle is too long. Keep it running despite the issue, but increase inspections. For a leak in the trachoma system, first plug it with wire. The DN200 pipe might perform better than the DN50 one, as its wall thickness is greater. If there is time to treat the circulating water, shut down the machine for 3 days to coat the inside of the circulating water as well as the pipes in the heat exchangers, and then restart it. But in the end, it is still necessary to address the problem at its root, investigate the causes of severe corrosion, and enhance water quality analysis. It is advisable to consider replacing the DN200 pipeline. If the downtime required for replacement is long, then explore the possibility of creating a bypass line, allowing the existing pipeline to continue in use while the sections that need to be replaced are laid new. Interfaces are reserved for the branch line; once the entire branch line is completed, work will be stopped to make the connections and remove the existing pipes. This solves the problem without causing long downtime.
Is it corrosion of the circulating water system itself, or has material entered the circulating water pipes? Corrosion of the circulating water can be addressed by adjusting the dosage formula; generally, the type and formula of corrosion inhibitors and scale inhibitors are determined based on the heat exchange equipment in the system ； In the other case, it becomes more complicated; the heat exchange equipment needs to be reselected by comparing it with the relevant materials. Replacing the main circulating water pipe is definitely not feasible at the moment. The idea mentioned above of setting up an additional pipeline also doesn’t seem workable. It’s better to identify the root cause of the problem, take appropriate measures, and keep production going; we can discuss this again next year!
It is possible to check for corrosion in the main pipeline; a conclusion can be drawn based on the results of that inspection. Moreover, it isn’t necessary to shut down the system for an extended period of time in order to replace the pipeline – the pipeline can be prepared in advance, with only the connection parts left, and shutdown can take place during installation, thus minimizing the downtime as much as possible.
The analyses from those upstairs are quite good. I believe the key is to analyze the water quality in order to determine the cause of corrosion. If acidic substances have mixed in, such as catalytic liquid hydrocarbons, it is possible to identify and eliminate the leakage points, followed by neutralization treatment. Strengthen water quality testing, as problems in public utility systems can have a significant impact.
Our company has a corrosion inhibitor that, when added to circulating water, can completely eliminate corrosion.
Check it.............................
Find a company specialized in water treatment to provide on-site services. In a normal water system, chemical treatment is necessary; otherwise, various forms of corrosion will occur severely once the system starts operating. Our group uses NALCO’s water treatment solutions, and after seven or eight years of operation, there has been basically no corrosion, with only some pitting in certain areas. Regarding your situation, the colleagues above have already discussed it in detail. The best approach is to shut down the system for a few days to carry out pre-coating, thereby controlling the current level of corrosion. Simple measures can be taken to address the existing problems, and afterwards, a secondary line should be set up. When there’s another opportunity to shut down the system, production can be shifted to this secondary line. Remember, the secondary line must also have water treatment in place.
The analyses from those upstairs are quite good. I think the cause of this situation must be some abnormality in certain aspects of the work, or simply illegal operations. Because as long as it is a standard design and operated properly, utility systems generally do not experience such issues during the design lifespan ； I don’t know what material the heat exchanger used by the original poster is made of, nor what the operating conditions are In my opinion, it’s not just a matter of corrosion in the circulating water pipes; the root cause of the problem must be identified. Our company has also encountered similar problems: In the case of enamel disk-type condensers, the rubber gaskets failed to be properly treated, and as a result they swelled and aged due to organic solvents, which caused leaks in the distillation section. Workers tried to tighten the screws more forcefully, which led to the compression of the two enamel disks and the loss of their enamel coating. Acidic substances then corroded the carbon steel layer; pitting and perforations occurred, allowing these substances to enter the circulating water and corrode the inner carbon steel surface of the normal disks. This in turn caused the enamel to peel off and form perforations, creating a vicious cycle. Fortunately, it was detected early and work was stopped promptly. There were 154 enamel disc-type condensers in total, of which 31 had perforations – resulting in a total of 67 holes. 57 discs showed mild localized enamel loss, while the inner surface of the carbon steel suffered severe pitting corrosion. Two water pipes had corrosion-induced perforations of about 5 cm in length. Finally, the water pipes and enamel discs were replaced, rubber gaskets were wrapped with thick PTFE tape, and regular inspections and replacements were carried out. After nearly 3 years of operation, it is still in good condition. This incident is certainly different from the original poster’s situation, but I hope it can provide some reference for them. It’s important to first analyze the reasons behind the problem, so as to avoid treating only the symptoms rather than the root cause. Wish the original poster a speedy resolution to the issue, and a great year-end bonus!