A lot of equipment will have internal cannulas, the outer cannulas are welded with the shell, and the flange cover of the internal extension pipe and the outer pipe are welded.
This design is because the internal cannula is expected to be pulled out from the external pipe during maintenance. Therefore, we should pay attention to the following situations in the design of endotracheal intubation
1. It is necessary to check whether the internal cannula can be pulled out from the external cannula, draw a 1:1 drawing to simulate the action of pulling out, and have a certain margin. If necessary, it is necessary to draw a drawing on the drawing. Once in the project, 3 “pipes could not be pulled out from 10″ pipes. Therefore, the internal cannula with elbow must be carefully checked. If it can not be pulled out, it can be solved by changing the structure, enlarging the outer pipe, shortening the extension length of the outer pipe, increasing the threaded connection of the elbow, installing from the inside of the manhole or unscrewing the connecting pipe (this is the worst way).
2. When the diameter of the intubation pipe is large, it is generally spliced by the plate, and there is a spray hole. If the spray port of the extension pipe is opened in the weld, it is very unsightly. In the design, the position of weld can be marked to avoid opening.
3. The internal cannula is generally divided into up and down. In order to facilitate the installation and maintenance in the future, it is better to mark the words “this side up, down” on the flange. Avoid reverse installation.
4. Many endotracheal pipes also need local stress check. It is generally recommended to use the nozzle load of large pipe to check. On the one hand, it is conservative; on the other hand, the pipe stress can be calculated to the connecting pipe on the outer wall of the cylinder, which is generally checked according to the connecting pipe welded on the cylinder. Moreover, through communication with the pipeline stress specialty, although the force is transmitted from the small pipe, the load of the outer pipe on the cylinder is generally greater than that of the small pipe on the flange cover. If the small pipe load is used to check the local stress of the large pipe, the allowable external load will be too low.