Seeking help with pump selection
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Our factory uses magnetic pumps to transport 33% dilute sulfuric acid at 100°C, but these pumps lose their magnetism frequently, which causes the motors to burn out. Could anyone with expertise suggest other types of pumps that could serve as a better alternative?
Does the manufacturer of the magnetic pump you use employ permanent magnets made of high-temperature samarium-cobalt?
If neodymium-iron-boron is used, it is prone to high-temperature demagnetization
The temperature resistance they provided for us is 200 degrees; the material isn’t specified
Please provide the pump model; is it lined with fluoropolymer?
The highest grade of neodymium-iron-boron can withstand temperatures of 150 degrees
Magnetic pump, indeed – the external magnet uses triple-cobalt permanent magnets, offering high temperature resistance.
Which company designed this? There’s clearly a design flaw here. In such an environment, it’s necessary to take into account the temperature rise that occurs when the magnets are in use. Even if the operating temperature is below the magnet’s Curie temperature and seems to be within a safe range, the temperature rise can still cause a gradual transition from ferromagnetic to paramagnetic behavior. Over time, as the pump continues to operate, most of the magnets will transform into a paramagnetic state. If the operating temperature (the temperature of the material plus the temperature rise due to the magnets’ operation) is close to the Curie temperature, then a significant paramagnetic transformation will occur. If the temperature is above the Curie temperature, then the transformation to a paramagnetic state will be much more rapid, meaning demagnetization will occur. It’s advisable to check the demagnetization curve; therefore, ask the manufacturer which grade of magnets they are using and what their Curie temperature is Different grades vary; you should measure the temperature of the surface of the pump inlet pipe under normal conditions, as well as the external temperature of the coupling. Alternatively, you can calculate the actual temperature of the magnet in a static state using heat transfer principles. Add the operating temperature of the magnet and include some margin, and then you can select a magnet with an appropriate Curie temperature. High-temperature magnets such as samarium-cobalt permanent magnets, samarium-iron-nitrogen magnets, and aluminum-cobalt-nickel magnets can all be used. In my opinion, taking half of the Curie temperature, adding the temperature rise, and subtracting the margin will give you a suitable choice. Try not to use it in areas close to the Curie temperature. Where did you measure 100°C? Normally, inside the pump casing, due to the need for pressure elevation, the pump rotates at high speed, which inevitably involves work being done; this results in a conversion of mechanical energy into internal energy. Therefore, this temperature change also needs to be taken into account, not just the temperature of the fluid. It’s best to measure the temperature inside the fluid, using a thermometer or a thermal resistor – an infrared thermometer only measures the surface temperature.
Centrifugal pumps made entirely of PTFE are used; the pump shaft is lined with PTFE, the mechanical seal is also made of PTFE, and the O-rings are covered with PTFE
It’s not lined with fluoroplastic; thank you. Using a centrifugal pump has resolved the issue now