Introduction to corrosion prevention methods for heat exchanger tube bundles
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Anti-corrosion treatment of heat exchanger tube bundles is a challenging task to carry out, and poor execution can affect the performance of these tube bundles. This set of images shows the methods commonly used by ordinary anti-corrosion companies. The construction process is as follows: 1. Surface preparation, including alkali washing, acid washing, and neutralization; thereafter, sandblasting is carried out on both the inside and outside of the metal surface to achieve a Sa2.5 grade (the outside of the tube does not need to be fully treated, as it has already been chemically treated). 2. Coating: The inner wall of the tube bundle is generally coated by pouring, with the tube bundle being tilted at a certain angle as coating is applied from top to bottom. Coating is applied to the outer wall of the tube bundle at a certain angle, from top to bottom. It can be painted multiple times as needed. 4. Homogenization treatment, primarily to improve the leveling of the paint film and prevent issues such as paint bumps and sagging. 5. Quality inspection. 6. Repair: Fix any items that fail the inspection. 7. High-temperature curing (not required for some).
Applying anti-corrosion coatings to the surface of the tubes significantly affects the performance of the heat exchanger. Moreover, due to thermal expansion and contraction as well as long-term use, surface cracking may occur; rusting can then start from these cracks. This approach is not highly recommended. It would be much better to use a different material, or to assess how long the unit can function without any protection. If time permits, it’s advisable to purchase spare parts for regular replacement
In petrochemical plants, the investment in heat exchange equipment accounts for about 30% of the total investment in the plant. Among them, heat exchange equipment has the shortest service life, mostly due to corrosion of the tube bundles in the heat exchangers. In fact, the selection of the heat exchanger tube bundle is based on the production process conditions. Practice has shown that carbon steel is generally used for the coil tubes of water coolers in chemical processing units. If ordinary stainless steel tube bundles are used, corrosion still occurs to some extent, and it also increases production costs. However, the use of carbon steel tube bundles presents the problem of metal corrosion; therefore, over the years engineers have been working hard to find better anti-corrosion coatings to address this issue in heat exchanger tube bundles. This is just a basic method for addressing tube bundle corrosion. The issue of whether coatings can provide thermal insulation has now been resolved; by modifying conventional coatings with graphene, the thermal conductivity can reach 250 W/m·K, which is comparable to that of aluminum.
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This post was last edited by wengjingqq on 2019-4-9 09:45. I would like to ask the moderator: what is the typical lifespan of the anti-corrosion coating shown in the image? What type of coating is being used? On our tube sheet surfaces, after sandblasting, an epoxy resin coating is applied, which completely peels off within 1 year. Material: carbon steel plates and tube bundles; medium: water; temperature: 40–100°C. Are there any better and more cost-effective corrosion prevention strategies?
This type of metal-polymer alloy coating can be used, and it yields much better results than epoxy resin coatings.