Can high-temperature resistant pipe materials be replaced by insulating materials coated on ordinary carbon steel pipes?

At 500°C, chromium-molybdenum alloy steel can be considered. The internal insulation material should be something similar to castables; the cost is high, and there are many issues related to installation and maintenance.

The material chosen now is chromium-molybdenum alloy steel, but it’s very expensive. The client wants to save money and has proposed using ordinary carbon steel with a high-temperature resistant coating, suggesting that a cost comparison be made. Two questions: first, whether this approach is feasible; second, whether it is more economical than using alloy steel directly

In my opinion, using high-temperature resistant materials for internal coating is definitely useless. On the one hand, what is the thickness of the internal coating material? To what temperature can it provide relative insulation? Is the coating adhesion that strong? How to apply it at the weld area? The surface isn’t smooth, and it’s impossible to make it smooth – how should I apply it? On the other hand, even if you calculate the thickness correctly and apply the coating, unless your pipe has an extremely large diameter and consists only of straight sections without any other components, the cost of applying the coating inside it is still quite high.

Thank you for the thoughtful reply; we have also considered these issues. How could the client’s management think about so many things? I know it will definitely cause trouble, but the project currently lacks funds; that’s why I’m trying to cut costs and came up with this idea. The diameter of the pipe should be 1.4 meters. This still requires consultation with the insulation manufacturer: whether an insulating effect can be ensured in an environment of 550 degrees Celsius, whether the proposed solution is feasible, and whether there are any similar examples in China

OP, there’s a question I forgot to mention. If you insulate it internally, is it feasible from a technical standpoint? Are the fluid parameters still within the original calculation range? This still needs to be discussed with the people in charge of the manufacturing process.

This post was last edited by Yimi on 2016-1-7 at 14:10. High-temperature resistant coatings are not very practical; although some coatings can withstand high temperatures, it seems that no coating can prevent heat from being transferred to carbon steel pipes. The only feasible option might be using castable materials, but this is suitable for pipes with larger diameters and fewer branches. There are significant differences among different manufacturers in terms of the composition, thickness, and price of castable materials; it is best to obtain quotes from specialized manufacturers (usually, such manufacturers provide construction services as well). Personally, I think using 500°C for casting is quite strange; chromium-molybdenum steel costs only around ten thousand yuan... When converted to a price per meter, the latter might even be cheaper, so it’s definitely the latter that offers better value for money. Additionally, as mentioned on floor 8, even if we do not consider whether the coating or casting material is detrimental to the medium, we still need to take into account the resulting increase in pipe diameter, which also represents a cost.

Uh, I’m sorry; I didn’t notice earlier. With a diameter of 1.4 meters, chromium-molybdenum steel is indeed expensive. The elbows are the most costly part. Moreover, it seems that there are no standards yet for welding pipes made from this type of alloy steel. In that case, it might be worth considering using castables instead.

High-temperature resistant casting materials can be used, commonly known as linings

I would like to ask why chromium-molybdenum elbows are so much more expensive. We didn’t take elbows into account when preparing the budget; do we need to consider them separately? I called many manufacturers for inquiries, and the price for chromium-molybdenum alloy steel was 16,000 yuan per ton, excluding insulation and anti-corrosion measures. Compared to 31 thousand yuan per ton for carbon steel, the leadership clearly cannot afford it. When I started making a budget, I didn’t expect the prices to be so high. For 800 meters of piping with a diameter of 1.2 meters, using chromium-molybdenum material would cost 4 million.

Well, I saw that it was recommended earlier as well; I’m still not sure whether this approach is cheaper than using chromium-molybdenum alloy steel directly.