Canned pump use
Thread Content
Our unit mainly uses canned pumps. The medium used is mainly benzene. During use, the pump often stops suddenly. I would like to ask my colleagues what are the main reasons for this phenomenon in canned pumps. Thank you.
It is mainly caused by an error in the medium density provided during the design. It causes an overload trip. Just increase the current setting value of the motor.
It may be that the material temperature changes, causing the material density to change, or the temperature is too high, causing benzene to vaporize, causing the motor's protection device to act and stop the pump.
Regarding the issues mentioned by the poster, they are discussed in the following links, which are now provided for reference. Attached link: http://bbs.hcbbs.com/thread-31891-1-1.html (canned pump operating procedures), http://bbs.hcbbs.com/thread-367298-1-1.html (Please ask whether the outlet valve should be closed like an ordinary centrifugal pump when starting and stopping the canned pump).
The reason why the pump stops may be that the temperature of the benzene material rises, cavitation occurs in the pump and the material cannot be pumped, causing the temperature of the canned pump to rise beyond the specified value and the protection device interlocks to stop the pump.
The tripping of the canned pump is due to the vaporization of the material, which leads to insufficient liquid inlet into the pump, causing the motor undercurrent protection to trip. From a process analysis, underflow can easily cause a lack of liquid in the pump, causing the bearing assembly to burn.
The protection device of the motor operates and the pump stops, which may be mainly caused by the vaporization of benzene.
Is your canned pump sealed and heated? If it is a canned pump with closed heating and insulation, I analyze the following reasons. First, the interlocking problem. The interlocking between the pump and the DCS and the flow meter is not set properly. You can ask the instrument person to repair it, or you can try to remove the interlocking. Second, there is a process problem. There is no pressure relief in the pipeline. Every time the material is pumped, the pressure must be released. The return line must be fully opened, and the feed port and feed port should be opened by one-third. Third, the temperature of the heating wire is too high, and the material vaporizes in the pipeline, causing cavitation. The semi-hot temperature of the material can be appropriately adjusted. Generally, the semi-hot temperature of the pipeline is 5 to 10 degrees higher than the melting point of the material. 4. The pointer of the canned pump may point to the red area, the pointer indicates that it can be used in the green area, the pointer indicates that there may be a problem with the equipment in the red area and cannot be started, and the pointer points to the yellow area, the pump must not be started.
Our process is that the material comes out of the kettle and passes through the tank, which goes to the canned pump, to the filter, and then to the kettle. Our unit usually adds filter aids to the tank. Our filter aid is diatomaceous earth, but the section from the tank to the pump is always blocked. When filtering the material, we turn off the heat trace to prevent the material from vaporizing. However, it is still blocked after half-heating is turned off, and there is also cavitation. Why is this? Would it be better if filter aids were added to the kettle? Is there another reason for the reaction between diatomaceous earth and alkali? The main component of diatomite is silica, and our material is alkaline.