How to fix loose bolts on the distributor in a reactor?
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In one reactor, the distributor is of the tubular type; the main pipe of this tubular distributor is connected to its branch pipes via flanges. The fluid flowing within the distributor is gas, with the inlet gas temperature at 200°C. The temperature inside the reactor ranges from 480°C to 500°C. After 10 days of operation, the reactor was opened for inspection, and it was found that all the bolts were loose. The nuts used were single-nut types that had not been spot-welded. How can this situation be resolved? Experts with experience in designing similar high-temperature reactors are welcome to discuss solutions; thank you!
Is it because the high temperature causes excessive thermal expansion and contraction, leading to the loosening of the bolts?
Bolts elongate at high temperatures and cannot return to their original size at normal temperatures; is there a good solution?
Using high-temperature resistant screws and nuts such as 309S can solve the problem.
We’re using 316S for the bolts, but it still doesn’t solve the problem. Are there any other methods?
While considering the material, whether increasing the bolt diameter would also have some effect.
We haven’t tried this one. We’ve encountered many problems with this distributor abroad; one set of them became unusable, and although this one is new, issues still persist.
Install spring washers and use lock nuts
It may be caused by high-temperature creep, and structures that rely on elastic deformation to maintain their connection become unreliable. Weld it; cut it off during maintenance.