Consultation regarding magnetic pump issues

The magnetic pump lost its magnetism; that’s a flaw of magnetic pumps, but I didn’t expect it to stop working after just a few days.

What is the reason for demagnetization? I hope it can be analyzed. . .

Is the motor wiring reversed? Please check it.

It was adjusted during the pump testing, and there was no reverse rotation; it’s highly likely that demagnetization for an unknown reason caused this issue. Thank you all. I checked it, and the references below are very helpful. The performance of domestic pumps still has significant issues. Repost: Operation of Magnetic Pump Published: 2008-9-28 10:17 | Author: liushuhai | Source: Haichuan Chemical Forum Our company currently has several magnetic pumps lined with PTFE, with a flow rate of 100 cubic meters per hour; the fluid involved is dilute acid water containing a small amount of benzene. These pumps often lose their magnetism during operation, and sometimes there is no pressure at the pump outlet. The magnetic pumps in question were manufactured by Jiangsu Taicang. Please help analyze the reasons for this issue. Deep Sea (2008-9-28 10:32:29) 1. Preventing the entry of particles: (1) Ferromagnetic impurities and particles must not enter the magnetic drive units and bearing friction pairs. (2) After transporting media that are prone to crystallization or precipitation, it is necessary to rinse the pump promptly (fill the pump chamber with clean water after stopping the pump, and then drain it completely after running for 1 minute) in order to ensure the service life of the sliding bearings. (3) When transporting a medium containing solid particles, filtration should be performed at the inlet of the pump suction pipe. 2. Prevent demagnetization (1) The magnetic torque should not be designed to be too small. (2) It shall operate under specified temperature conditions; it is strictly prohibited for the medium temperature to exceed the limits. A platinum resistance temperature sensor can be installed on the outer surface of the magnetic pump’s isolation sleeve to monitor the temperature rise in the gap area, so as to trigger an alarm or shut down the pump when the temperature exceeds a set limit. qingqingdehaife (2008-10-03 17:04:15) The quality of domestically produced heavy-duty magnetic pumps is still not up to standard; smaller magnetic pumps, on the other hand, are generally problem-free. Our factory uses magnetic pumps manufactured by Anhui Wanflulong Pump Valve Co., Ltd.; the flow rate of these pumps is 80 cubic meters. Due to design flaws, the shafts have broken twice, and two isolation covers have had to be replaced. But the small pump is much better. I’ve also encountered the same issue as the original poster: after opening it for inspection, nothing was damaged, and it worked fine once it was reassembled; however, the problem appeared again after some time. It seems to be a case of demagnetization. By using imported magnetic pumps, the situation improves significantly, with little to no need for maintenance. (America’s success is inevitable; after all, the most powerful imperialist powers in the world are built on a solid material foundation.) cwillow (2008-10-03 17:12:48) That’s easy to handle! Check the instructions or contact the manufacturer! Let them help you solve it – after all, they are professional manufacturers! If they can’t even solve such minor problems, then it’s better to just have them close down. ztfzh (2008-10-04 09:34:02) The main issues are excessive magnetic torque, as well as temperatures that are too high in the isolation sleeves and inner magnets. haixuan (2008-10-04 10:00:05) Our factory has purchased 7 new units; they’ve been in use for just a few days yet 4 of them have already broken down. I think poor maintenance on our part is one factor, but the quality of these units is also substandard. henantianjin (2008-10-04 14:49:07) Our factory has also encountered the problem of demagnetization of magnetic pumps; the reason for this was that, during operation, the pipes became suddenly blocked, which caused the pump to stop receiving fluid and led to an increase in its temperature. Therefore, it is necessary to prevent material breakage during operation. congrong72 (2008-10-05 00:18:53) Main reason ； Idle operation of the pump can cause demagnetization of the internal magnetic assembly, or the maximum magnetic torque of the magnetic coupling may be too low; under actual operating conditions such as certain voltage levels, the pump’s operating point, or situations involving jamming, it is easy for the internal and external magnets to separate from each other. liu4122222 (2008-10-05 08:59:45) It’s best to buy magnetic pumps made abroad. dangqi (2008-10-05 10:57:02) Our factory used several domestic magnetic pumps in the past, but we ended up switching to fluoroplastic centrifugal pumps all of them, as the isolation sleeves of those magnetic pumps broke down frequently. WSL01218 (2008-10-06 11:25:11) Demagnetization is mainly caused by excessive power and too high medium temperature. bsslys (2008-10-06 12:07:48) Steps to start a magnetic pump: (1) Start the motor. Once the magnetic pump is running properly, check the outlet pressure gauge and the inlet vacuum gauge to ensure that appropriate pressures are being displayed; then gradually open the gate valve, while also monitoring the motor’s load. (2) If the outlet pressure is unstable and decreasing, it indicates the presence of gas inside the pump; the pump should be stopped immediately, and the pump should be refilled with fluid and degassed again. (3) Pay attention to whether there are any abnormalities in the sound of the pump; if a metallic scraping sound is heard, stop the pump and wait for a fitter or equipment technician to check it. (4) If the pressure is normal, there are no abnormal noises, and the vibration is normal, open the outlet valve and adjust the outlet flow to the desired level.

The fundamental reason for demagnetization is that the internal magnetic temperature exceeds the design temperature of the magnetic material. Since both the inner and outer magnetic rotors of magnetic pumps are made of permanent magnetic materials, such as samarium-cobalt, demagnetization occurs when the temperature exceeds 350 degrees; neodymium-iron-boron materials lose their magnetism at temperatures above around 180 degrees. Precautions to prevent the internal magnetic rotor from overheating: 1. Prevent hard or iron particles from entering, as these particles can wear out the seals, leading to leaks or jamming of the impeller and rotor. To avoid this issue, install a filter screen at the inlet; or refrain from using magnetic pumps ； 2. Avoid running idle or in reverse for long periods ； During idling, the induced currents generated by the inner and outer magnets produce a large amount of heat; if there is no medium to carry away this heat, the temperature will rise sharply, leading to demagnetization ； Based on what you’ve described: the flow rate is low. If there is no leakage, it definitely isn’t a problem with the seal (the isolation sleeve), as the isolation sleeve of a magnetic pump provides a static seal. If your pump does not operate continuously, special attention should be paid to the starting and stopping process; improper operation of these processes can lead to demagnetization issues. Another possible reason for insufficient flow is improper selection – the torque of the magnetic pump rotor is not sufficient, which leads to loss of rotation ；

If it is necessary to start and stop the magnetic pump frequently, it should be noted that the inlet valve must remain open. Once the pump is started and pressure is detected on the outlet pressure gauge, the outlet valve should be opened as soon as possible, generally within one minute. It is not advisable to allow pressure to build up for an extended period, as this can cause the internal magnet to heat up and lose its magnetism.

Be careful when running the device idly; prolonged idling can cause the temperature to rise and lead to demagnetization. Do not operate the pump in a sealed condition when starting it, for the same reason.

This post was last edited by Taohuadao on 2009-7-18 at 11:04; it goes without saying that it has lost its magnetism. You’re using the 40CQ-32P made of 304 material, right? The temperature of this ordinary stainless steel magnetic pump must not exceed 90 degrees! For a temperature of 100 degrees, it’s best to use Foplastic.

Demagnetization of magnetic pumps is a major problem associated with them. Firstly, the magnetic materials used in such pumps should be neodymium oxide, as iron oxide is of poorer quality for this purpose； Secondly, magnetic pumps are most vulnerable to demagnetization due to overheating, and overheating is mainly caused by the pump running idle or having insufficient flow; this must be taken into account during operation.

It is recommended to install an anti-idling protection device for pumps, which will automatically shut down the pump within 2 seconds when it is idling, thus protecting the pump from damage. The address for the electronic brochure is: http://www.dnpump.com/PicUp/200910162202501.pdf. If you want to minimize maintenance efforts, it’s better to choose a protection device designed specifically to prevent idling – it makes things easier!