Reasons for air coil leakage
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I’ve been troubled lately as there’s a leak in the air coil – it’s on the stainless steel pipe that connects to the coil, specifically at the upper part of that pipe, where there’s a crack. My boss asked us to analyze the cause; I think it’s due to steam expanding there. I wonder if there are any cases like this? Thank you
Explain the situation clearly! Is it the early stage of driving? Does it still occur during normal production?
I think your question isn’t clear enough; theoretically, steam expansion shouldn’t cause the pipes to crack, unless the design is extremely unreasonable. It is recommended that you clarify the working conditions so that others can help you analyze them.
During normal operation, the amount of air cannot be adjusted proportionally to control the hydrogen-to-nitrogen ratio, and this amount keeps increasing; eventually, 3000 units of air are used for every 6000 units of hydrogen. It is initially suspected that there is a leak in the coil, and upon shutting down the equipment for inspection, it was found that the stainless steel tube through which air enters the coil had cracked, allowing air to leak out. As a result, there was no change in the temperature of the furnace. Our facility started operating in April 2001, and there have been two instances where operations had to be stopped due to problems with the air coil. The temperature of the air exiting the coil is below 540 degrees, while the temperature inside the furnace is below 880 degrees.
I think it’s mainly a problem with the material of the air coil. The common stainless steel material is 0Cr18Ni9. We used this type for our air coils in the past, and leaks did occur as well. Since this material contains no titanium metal, its heat resistance is approximately around 600 degrees. If it is replaced with 0Cr18Ni9Ti stainless steel, there should be no problem. Go and check the material of your air coil, its design temperature, and so on. We have not encountered any leaks since switching to 0Cr18Ni9Ti stainless steel coils. Personal opinion.
I think it’s mainly a problem with the material of the air coil. The common stainless steel material is 0Cr18Ni9. We used this type for our air coils in the past, and leaks did occur as well. Since this material contains no titanium metal, its heat resistance is approximately around 600 degrees. If it is replaced with 0Cr18Ni9Ti stainless steel, there should be no problem. Go and check the material of your air coil, its design temperature, and so on. We have not encountered any leaks since switching to 0Cr18Ni9Ti stainless steel coils. Personal opinion.
Another key issue is the quality control of steam; it is necessary to ensure that all waste boilers and steam generators discharge wastewater in accordance with regulations, and to keep the Si content in the deionized water within the specified limits. If substances such as SiO2 in the steam accumulate inside the coil, it can also cause damage to the coil; we have experienced such accidents before.
If it’s due to silicon in the steam, then not only is the air coil damaged, but there will also be scaling on the catalyst and the waste heat boiler, and the back pressure after the first stage of the turbine is likely to change as well.
If it is under normal production conditions, the possibility of water hammer is low; I still think there is a problem with the material. Generally, after a certain amount of soot accumulates and the thermal resistance increases, local overheating occurs.
Thank you. There should be no problem with our steam – there is a separator before the steam enters the coil, and it is drained on schedule. I think we should start by checking the material used.