What causes leakage in the pigtail tube?
Thread Content
What is the cause of leakage in the pigtail pipe? We use natural gas as raw material, with an annual production capacity of 60,000 cubic meters; we use box-type furnaces, and the exit temperature at the first stage of the furnace is between 730 and 750 degrees. Our lower gas collection pipes have leaked several times already, and it leaked again today. What could be the reason? Is it due to welding issues? Or is it uneven temperature?
Uneven temperature leakage in the lower gas collection pipe is one aspect; the stress from lifting and the uneven stress generated during production should also be taken into consideration.
The main factors are. 1. Sharp variations in temperature differences; 2. Welding quality issues (poor welding, incomplete welding, slag); 3. Stress factors (temperature stress, welding stress, lifting stress).
There’s a bit of a mismatch between the topic and the content posted by the original poster; the working conditions of the pigtail pipe and the lower exhaust pipe are quite different. Small nitrogen fertilizer plants have a relatively long service life, but if leaks occur frequently, welding defects certainly need to be considered; however, a thorough analysis is probably the safest approach. 1. CAT. If the furnace tubes are in good condition, then factors such as coking, carbon deposition, carbon burning after deposition, and pulverization in the CAT can seemingly be ignored, but the original poster did not mention the operating condition of the furnace tubes. 2. Temperature of the lower gas collection duct wall. Reliance on historical records and specialized measurement tools (such as infrared). 3. Energy distribution in the furnace body. 4. Load. Are there any records of overs? 5. Start/stop records. Operation to check for the presence of values exceeding the design limits. 6. Normal operation data analysis. Relatively easy. 7. Stress analysis. 8. Maintenance records. 9. Technical upgrades. Including burners, internal insulation, etc. 10. Metallography, UT
1. During installation, the adjustment of the suspension springs should be verified. Generally, after installation, temperature fluctuations and thermal stress are not a problem, as they can be absorbed by the springs; in case of large temperature changes, simply shut down or restart the equipment. Therefore, it’s important to check whether there are any issues with the installation. 2. Welding quality: The pigtail tube has some flexibility, so thermal stress is not sufficient to cause it to crack, unless there are problems with the welding, such as cracks in the weld. 3. Insulation material: If the insulation at the junction between the conversion tube and the pigtail tube is damaged, large temperature differences will lead to changes in thermal stress, which can easily cause cracking