The impeller cover of the centrifugal pump has fallen off!
Thread Content
The two urea melting pumps in our factory are equipped with auxiliary impellers and packing seals. Since they were put into operation, the back caps have fallen off three times, which has affected production. Do any of the technicians have any good solutions to completely resolve this issue?
I’m not quite clear about the specific way in which your impeller is installed. Could you draw a simple diagram?
There are many reasons for the loosening of the impeller back cap, the main ones being: 1. Insufficient locking force of the back cap； 2. Reversal caused by operational reasons ； 3. Corrosion 4. Is a gasket installed between the back cap and the impeller? The gasket has aged and lost its elasticity
Has the original poster noticed whether the rotation direction of the impeller is opposite to the direction in which the cover is tightened? If not, the hood will fall off easily.
Our inspection process: 1. Check whether the rotation direction of the impeller is opposite to the tightening direction of the back cap. 2. Check whether the pre-tightening force is insufficient. 3. Check whether the gasket has been replaced. After no issues were found in these checks, considering that the back cap is too large and may cause excessive inertia during shutdown, leading to its detachment, the back cap was remanufactured to reduce its weight. It is required to follow the procedures during operation to prevent backflow after the pump stops. In the end, the problem was solved.
One more thing: Is the cap on the impeller regular and in line with hydrodynamic design? Does the internal structure of the pump’s large cover create resistance to the rotation of the impeller cover.
Has the impeller been corroded by the medium, and is there any looseness in the threaded connection between the impeller and the shaft?
In some parts of our factory, we use locks that are manufactured by us; after locking them in place, two points are welded together. Hehe, it’s a bit troublesome to remove them since grinding is required
How long has it been running? Did both lose their nuts? Please carefully inquire with the operator about the conditions of the work on site to see if the operating procedures were not followed Are the pump’s flow rate and head normal? (Is the wire connected backwards?) ) Pumps from regular manufacturing plants generally do not experience such problems!
Under normal circumstances, following the rotation direction of the pump, if the nuts are tightened, check the direction of the threads to see if there is any slippage, and whether reverse rotation at high speed occurs over an extended period of time
Thank you all for your advice. We have also analyzed the reasons: each time the cover becomes loose, it happens after the chemical flushing pump is used, and the main cause is reverse rotation of the impeller; moreover, the tightening force is not sufficient either, so the cover becomes very loose once it is screwed on
Is it corroded? If it is corroded, a new nut or shaft needs to be replaced. If it’s not corrosion, it’s likely an improper or damaged gasket.
I have also encountered such a situation; the solutions are as follows: 1. Remove the rotor and machine the shaft end to ensure the accuracy of the threading. 2. Replace the nut and add lock washers. 3. If that doesn’t work, make a slight modification to the structure by adding a pin behind the nut.
The person on the 3rd floor explained it more clearly. But sometimes I really do it the way I did on the 8th floor. :lol :lol But I suggest that you could design something like a braking ring depending on the specific circumstances. :victory:
Another option is to consider adding a locknut.
Methods to prevent thread loosening: 1. Use double nuts； 2. Add a stop washer ； 3. Use a threaded locking agent, choosing the detachable type. (It is mainly used on the piston lock caps of compressors in our factory)
These problems are encountered frequently, and many solutions have been devised. Summarized into the following 4 points. 1. First, consider the design to address the issue of the pump’s rotation direction and the threading direction of the shaft nut. It can only get tighter as it keeps turning. 2. Fine-thread pitch should be used for the shaft end threads. 3. Anti-loosening connection of the shaft end. There are three methods: spot welding at several points, adding shimming pads, and providing screw holes for the shaft end nuts. 4. A lock-type wire screw sleeve is installed in the internal thread of the shaft nut.
Just replace the shaft back cap with one whose rotation direction is opposite to the current one
The 16th floor shows that work has been done on it, and this is exactly what we do as well. If the conditions permit, we repair the threads by processing the shaft ends; if not, we skip using the original cap and instead use two nuts to secure it tightly. If there isn’t enough space for two nuts, then we still use the original cap, adding just a little thread-sealing agent. They come in red housings and are available on Taobao. Don’t apply too much of the sealant, otherwise it will be very difficult to remove it during future maintenance