Corrosion problem of heat exchanger tube bundles
Thread Content
The corrosion of our heat exchanger tube bundles is mainly caused by under-scale corrosion resulting from the accumulation of sludge on the tubes. Cathodic protection of heat exchangers: 1. The sacrificial anode is made of magnesium blocks; should these blocks be placed on the tube bundle or inside the shell head? 2. External current method: The heat exchanger is protected by external current cathodic protection; which companies use this method, and are there any organizations responsible for promoting this technology?
This post was last edited by Wang Genrong on 2019-10-10 at 16:16. The issue of equipment corrosion is indeed a headache. Why not exchange knowledge with each other?
Let’s say I see that they have added it to the inner shell of the cover
The best approach is to regularly clean and replace the tube bundle
When we talk about heat exchangers that use electrochemical protection, we are generally referring to water coolers and the metal surfaces in contact with water. Because only water can be protected using electrochemical methods, while oil-based media cannot. It is generally recommended to first apply a coating for corrosion protection to the tube bundle; after one cycle of use of the coating (about 3 years), if the coating becomes damaged, sacrificial anode protection is then employed. Because when the tube bundle is not corrosion-resistant, there is significant current loss on the metal surface, resulting in poor performance. Only by using coating and sacrificial anode methods can satisfactory results be achieved. Generally, we do not recommend the method of applying an external current.
It’s not on the tubes or the cylinder; instead, the supports for the anode blocks are welded to the tube box and end caps (taking care to arrange the anode blocks properly). This method is generally used for water flow. For the best results, a combination of coating protection and a sacrificial anode is recommended. If the coating provides good protection and remains undamaged (steam cleaning should be carried out in accordance with technical specifications), only the anode block needs to be replaced in the next cycle. This approach proved very effective during Qingdao Refining & Chemical’s first major maintenance campaign. Do not choose coatings that contain iron oxide or are brittle; various coating test bars can be used for impact tests. Those with obvious damage at the impact site or extremely small cracks should not be used. Don’t use anything else; when it comes to anti-corrosion coatings, be sure to choose reputable large manufacturers – otherwise, it’s better not to use them at all. The suggestions of expert Wang Wei should be taken as an important reference.
Check water quality/raw material issues by examining the sludge adhering to the tubes. The magnesium block is placed in the cover
Electrochemistry has no effect on bacteria and sludge; use side filtration to control suspended solids, and add bactericides as necessary
Try to lower the temperature, increase the flow rate, or enhance turbulence to reduce the adhesion of sediment.
Your problem is what’s known as sediment corrosion; one should first address the water quality... If there are issues with the water quality today, then the same problems will occur in other equipment as well. Furthermore, can filters be installed before the water enters the equipment? What is the flow rate of the water entering that heat exchanger? These are all things that should be considered first
If the pressure is not high, impervious graphite can be used; it offers better heat transfer than stainless steel, and no such complex protection is required