Grundfos MTS Screw Pumps

Monthly inspection of seal faces for surface roughness exceeding Ra 0.8μm, visible scoring, corrosion pitting, and leakage rate. Check springs for >15% compression loss or corrosion. For marine saltwater environments, verify electropolished 304-grade stainless steel material. Accept minor imperfections <0.05mm depth only (polish out), deeper damage requires shaft sleeve and seal renewal.

Quarterly monitoring of bearing condition via vibration analysis (compare to baseline), bearing housing temperature (target <80°C for normal operation), audible noise (grinding, squealing indicates wear), and lubricant oil samples for metal wear particles. Use thermocouples for direct bearing outer ring temperature measurement. Premature failure typically caused by lubrication starvation, contamination, or misalignment - check bearing clearances and shaft alignment within 0.1mm on coupling concentricity.

Yearly inspection of internal screw and casing clearances: rotor-to-bore maximum 0.2mm, between rotor flanks maximum 0.4mm. Use borescope or remove inspection covers to check for internal scratches, scoring, or corrosion pitting. Casing material examination for stress corrosion cracking in cemented carbide components. Complete overhaul required not exceeding 3 years. Discard rotors with scoring exceeding 0.2mm depth.

Check strainer and inlet screen monthly by monitoring suction pressure reduction (gradual drops indicate clogging). Verify suction piping for blockages, air leaks into suction line, and adequate net positive suction head (NPSH). Prime pump completely with working liquid before startup. Inlet pressure must not exceed 25-75 PSIG depending on pump type. Cavitation creates vapor bubbles causing noise, vibration, and rotor/impeller damage - verify pump inlet pressure at <6 bar (self-priming design requirement).

Pre-installation: verify pump and motor shaft concentricity within 0.1mm on coupling outer circle, maintain 2-4mm gap between coupling planes (0.3mm tolerance). Post-installation: periodic inspection of foundation bolts torque, coupling wear, and shaft seal integrity (leakage should not exceed 10 drops per hour). Rotate pump-motor coupling by hand to confirm smooth operation. Any resistance or grinding indicates internal bearing damage. Replace shaft seals if leakage is excessive.