Can a tubular axial type lug be designed for a hydrogenation reactor?
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Hydrogenation reactors are all lifted using lid-type lugs; I haven’t seen shaft-type lugs used for this purpose. Why is that? Is it because the cylinder requires that pipe-axis type lugs cannot be used for welding, or is there some other reason?
The shell of a hydrogenation reactor is usually made of thick plates or forgings of chromium-molybdenum steel; if tubular shaft-type lugs are used, these lugs must be welded to the shell via fillet welds. Welding chromium-molybdenum steel tends to cause cracks, so welds are generally avoided as much as possible.
The second issue is that the reactors are extremely heavy (many hydrocracking reactors weigh around 2,000 tons; the heaviest ones can reach 2,600 tons each). If shaft-type lifting lugs are used, they need to be very large, and the strength requirements for such lugs are also very high. Overall, the lid is more cost-effective, and it can be reused.