First clarify: whether the magnetic drive is suitable for the medium
The magnetic pump transmits torque through the magnetic coupling. The pump shaft does not need to pass through the pressure-bearing shell, which can eliminate the leakage path of the traditional rotating shaft seal. Therefore, it is suitable for process transportation that requires higher leakage control. Before selection, you must also confirm whether the medium contains particles, whether it is easy to crystallize, whether it is possible to vaporize, and whether continuous liquid supply can be guaranteed on site. If it is idle for a long time, the internal circulation is blocked or the medium vaporizes locally, the bearings and isolation sleeves may be damaged.
Flow rate: Determine the operating range based on actual working conditions
The purchaser should provide normal, minimum and maximum flow rate, the unit is uniformly m³/h, and explain the continuous operation time, adjustment method and future expansion needs. The manufacturer should mark each operating point on the performance curve and check efficiency, power and allowable operating range.
Do not oversize your pump solely by maximum flow. If the pump deviates from the suitable operating area for a long time, it may increase the risk of internal backflow, vibration and temperature rise. For solutions that use transported liquid for internal lubrication and cooling, it should also be verified whether the internal circulation is reliable under low flow conditions.
Head: Calculate the entire system, not just the height of the equipment
The required head should comprehensively calculate the difference in suction and discharge liquid levels, the resistance along the pipeline, the resistance of valves and filters, and the pressure difference between the inlet and outlet containers. The density of the liquid will affect the required shaft power. In particular, the torque of the motor and magnetic coupling should be calibrated according to the highest density working condition.
At the same time, the minimum suction liquid level, maximum operating temperature and inlet pressure are provided. The manufacturer will check the cavitation head NPSHa of the device and the cavitation head NPSHr required by the pump. For media close to the boiling point or with high vapor pressure, the suction conditions are often more worthy of confirmation than the nominal head.
Temperature: Check the material and internal heat.
Temperature selection cannot only fill in an "operating temperature". The normal, maximum, minimum and starting and stopping temperatures should be stated respectively, taking into account the ambient temperature, preheating method and temperature change speed. High temperature may change the viscosity and vapor pressure of the medium, and may also affect the working conditions of magnetic components, isolation sleeves and bearings.
There are transmission losses and liquid circulation heat inside the magnetic pump. When transporting easily vaporized media, you should focus on confirming the temperature rise near the isolation sleeve, the circulating fluid path and necessary cooling or monitoring measures; the specific upper temperature limit must be confirmed based on the selected model and configuration, and the parameters of a certain magnetic pump cannot be applied to all products.
Materials: determined according to complete medium conditions
Wetted materials should be selected based on the medium name, concentration, water content, chloride ions and other impurities, temperature and corrosion data, rather than simply classifying according to "acid" and "alkali". When making an inquiry, you should also confirm the materials of the pump casing, impeller, isolation sleeve, bearings and seals.
For example, whether stainless steel can be used must be judged based on the specific corrosion environment; for particles or easily crystallized media, the risk of bearing wear and internal flow channel blockage must also be assessed. If the composition of the medium changes from batch to batch, the most adverse working conditions should be provided so that the supplier can explain the basis for material selection and usage restrictions.
Typical Applications and Frequently Asked Questions
Magnetic pumps can be used as candidates for petrochemical intermediates, fine chemical solvents and other delivery points that require strict leakage control. But no shaft seal does not mean no leakage under any working conditions: the shell, static seal and connecting parts still need to be checked according to the design pressure, temperature and on-site requirements.
**Can low traffic run for a long time? **Should be based on the continuous operating range allowed by the specific model, as well as internal cooling and lubrication conditions, and cannot be judged solely on the basis that the motor is not overloaded.
Can it be used if it contains a small amount of particles? **Particle content, particle size, hardness and settling or crystallization characteristics need to be provided, and the manufacturer will evaluate the bearings, internal circulation channels and wear-resistant solutions; it is not appropriate to default to ordinary magnetic pumps.
Purchasing suggestions and Feiyue Pump Industry solutions
When sending inquiry information, it is recommended to provide at one time: medium composition and concentration, density, viscosity, vapor pressure, particle conditions; normal and extreme flow, required head, inlet pressure and liquid level; normal and extreme temperature, design pressure; power supply, explosion-proof requirements, continuous operation time, and the API 685 version to be adopted. Suppliers are requested to submit performance curves, operating range, bill of materials, power and NPSH verification results with their quotations, and clarify internal circulation and monitoring configurations.
Feiyue Pump website has API 685 magnetic pump product classification. The purchaser can contact its engineering team based on the above working condition data to further confirm the flow head range, material configuration and applicable boundaries of the specific model. The selection principles in this article do not replace the technical data sheets or project acceptance documents for individual pumps.
