Reasons for Frequent Wear-Through of the Isolation Sleeve in Magnetic Drive Pumps for High-Salinity Concentrated Slurries

1. Hard salt crystal particles become lodged in the narrow gap of the isolation sleeve, causing continuous abrasion that thins the sleeve.

The clearance between the inner and outer magnetic cores and the isolation sleeve is extremely small (typically only 1–3 mm), and the salt crystals in the saturated mother liquor are very hard:

During operation, fine crystals are flushed into the gap. As the rotor spins at high speed, the particles continuously scrape against the inner wall of the isolation sleeve, uniformly thinning the wall thickness; larger particles cause localized cutting, forming pits that lead to stress concentration and rapid cracking, ultimately resulting in perforation.

Ordinary clean water without solid phases exhibits almost no such wear, whereas the wear rate in high-salt slurries increases exponentially.

2. Highly conductive concentrated brine generates significant eddy current heat, weakening the strength of the isolation sleeve

Concentrated brine has a high ion concentration and strong electrical conductivity; the magnetic cutting process continuously generates eddy current heat within the metal isolation sleeve:

The flow rate of the interlayer cooling medium is limited, causing heat to accumulate and the temperature of the isolation sleeve to rise significantly; the strength and toughness of the stainless steel decrease, and its wear resistance plummets, making it prone to damage even from slight crystal friction.

Alternating hot and cold cycles also generate thermal fatigue microcracks, which continue to expand under the grinding action.

3. Narrow liquid level range, frequent emptying and dry grinding, and instantaneous high-temperature scorching of the isolation sleeve

The buffer range for the concentrated liquid level is small, making it extremely prone to low liquid levels toward the end of discharge, resulting in brief periods of liquid shortage in the pump chamber:

The jacket loses its cooling and lubricating medium, preventing the dissipation of eddy current heat, causing the isolation sleeve to overheat and soften within a short time; the magnetic steel rubs directly against the isolation sleeve under dry friction, wearing through it within a few hours.

At high temperatures, residual salt crystals sinter and harden, further enhancing their cutting and grinding capabilities.

4. Low-flow intermittent operation: Salt crystals settle and cause concentrated wear at the bottom of the jacket

During intermittent start-stop cycles and low-flow conditions, salt crystals accumulate by gravity in the dead corners of the lower half of the isolation sleeve;

Each time the pump starts, high-speed flow scours and compresses the bottom, causing the vast majority of perforations to concentrate in the lower half of the isolation sleeve, where localized wall thickness loss is far greater than in the upper section.

5. Synergistic under-deposit corrosion caused by chloride ions and abrasion (metal isolation sleeve)

High-salt mother liquor contains a large amount of chloride ions; crystal abrasion damages the passivation film on the stainless steel surface;

A confined corrosion environment forms within the abrasion pits, where mechanical grinding occurs alongside electrochemical pitting corrosion. Under this dual action, the rate of wall thickness reduction accelerates significantly, causing small holes to rapidly expand and lead to leaks.

6. Silica Gel and Organic Flocs Act as Adhesive Abrasive Media

Trace amounts of silicate colloids and flocculation residues in the raw solution adhere to salt crystals, forming composite scale that firmly adheres to the inner wall of the isolation sleeve;

Water flow cannot flush these away, so they persist as abrasive media over the long term, continuously eroding the wall thickness of the isolation sleeve.

Consequences Following Perforation

High-salinity mother liquor infiltrates the permanent magnet chamber, corroding the permanent magnets and sliding bearings, causing the magnetic drive to fail and the pump to seize up and shut down; the leakage of saline slurry contaminates the entire evaporator system, accelerating scaling and corrosion in the plate heat exchanger.