Under operating conditions involving highly saline concentrated mother liquor, frequent wear and eventual perforation of the magnetic drive pump’s isolation sleeve constitute a composite failure resulting from the combined effects of medium corrosion, solid abrasion, operational defects, and the inherent characteristics of magnetic coupling. Rapid damage is rarely caused by a single factor; rather, it is typically accelerated by a combination of multiple conditions.

After concentration, the high-salt mother liquor approaches a saturated state, causing fine salt crystals to continuously precipitate within the system; these hard crystals remain suspended in the slurry. A narrow gap exists between the rotor and the isolation sleeve inside the magnetic drive pump, through which the medium continuously flows to provide cooling and lubrication. The slurry carrying salt crystals continuously erodes this gap, and the crystals exert a micro-abrasive effect on the outer surface of the isolation sleeve and the outer wall of the inner magnetic rotor. Prolonged operation gradually wears down the wall thickness of the isolation sleeve. Once the wall thickness continues to decrease, the isolation sleeve’s ability to withstand stress drops significantly, leading to tearing and perforation under the combined effects of internal medium pressure and alternating stress.

During the operation of the magnetic drive pump, the isolation sleeve is positioned between the inner and outer magnetic cores. The alternating magnetic field induces eddy currents in the metal isolation sleeve, which generate heat through eddy current heating. Under normal operating conditions, the material flowing through the gap can dissipate this heat. However, during mother liquor concentration, situations such as insufficient feed, low liquid levels, and blockages in the discharge piping often occur. This reduces the flow rate of material within the gap, causing the cooling effect to deteriorate sharply and leading to a rapid rise in local temperatures within the isolation sleeve. High temperatures not only reduce the strength of the metal material but also accelerate the electrochemical corrosion caused by high-salt media. The combined effects of high temperature and abrasion exponentially accelerate the rate of material failure.

High-salinity water is inherently highly conductive; when the metal isolation sleeve is immersed in a saline slurry, an electrochemical corrosion environment is created. If stray currents are present in the piping system or if contact between dissimilar metal components creates a potential difference, pitting corrosion will occur on the surface of the isolation sleeve, forming numerous microscopic pits. Crystal abrasion preferentially damages these weakened areas where pitting has already occurred; the pits continue to expand until they eventually penetrate the shell. In many operating conditions, it can be observed that the perforation site is not a uniformly worn area, but rather a point-corrosion hole that has cracked and extended outward.

During system operation, brief periods of dry running or semi-dry running are highly likely to occur. When the liquid level in the evaporation chamber is low or the circulation flow rate fluctuates, the discharge pump does not draw in sufficient material, resulting in a lack of medium for lubrication and cooling between the isolation sleeve and the inner magnetic rotor. Even brief periods of dry running can generate extremely high temperatures, causing localized, instantaneous overheating of the isolation sleeve and resulting in thermal deformation. This deformation leads to uneven clearance distribution, causing friction and scraping at specific locations, which directly produces scratches. These scratched areas then become weak points susceptible to subsequent corrosion and wear. In daily operation, brief periods of dry running are difficult to detect promptly, and damage accumulates over repeated occurrences.

Salt crystals in the slurry also tend to deposit within the narrow gap between the isolation sleeve and the inner magnetic rotor. The accumulation of crystals causes the gap to become blocked, narrowing the flow passage and obstructing the circulation of the cooling medium, preventing the dissipation of eddy current heat; In severe cases, solids can jam the rotor, causing it to operate with slight eccentricity. This eccentricity leads to continuous friction and impact, subjecting one side of the isolation sleeve to sustained wear, resulting in rapid thinning of the wall thickness on that side and localized damage.

Additionally, attention must be paid to the impact of start-up and shutdown shocks. The concentration section often operates in batch discharge mode, causing the magnetic drive pump to start and stop frequently. The magnetic coupling instantly transmits high torque, making the rotor prone to momentary eccentricity; each start-up carries a risk of scraping. While conventional clean water operations have limited impact, when the slurry contains hard salt crystals, every instance of eccentric friction leaves irreversible damage.

Once the isolation sleeve is perforated, high-salt mother liquor enters the motor chamber directly, causing a short circuit and burning out the stator windings, which can lead to more severe equipment failures. Corresponding improvement strategies can be tailored to operating conditions: prioritize the use of magnetic drive pumps with wide-clearance designs to enhance flow capacity through the clearance and reduce crystal retention; prevent the pump from running dry intermittently for extended periods by installing low-liquid-level interlock shutdown protection; if necessary, select non-metallic materials for the isolation sleeve to improve corrosion and wear resistance; install a simple filtration device at the pump inlet to prevent large crystal particles from entering the pump; and stabilize discharge conditions to reduce frequent starts and stops, thereby lowering the probability of eccentric friction on the rotor.