TL;DR
Seal leakage is usually dry-running damage or face wear. Drain the tank to isolate the seal, inspect both seal faces, and replace any face showing chipping, scoring, or heat marking.
What you might see
- liquid weeping at the shaft-to-tank entry point
- process fluid dripping down the shaft
- seal flush flow losing pressure
- seal faces showing heat discoloration on removal
Likely causes
Seal face wear from dry running during tank drawdown or start-up without liquid
Shaft runout exceeding the seal's misalignment tolerance, leading to face-opening and leak
Process solids or abrasives scoring the seal faces
Incorrect seal flush pressure or loss of flush supply
Required tools
- Torque wrench with socket for gland bolts
- Clean lint-free cloths
- Caliper to verify seal set dimension
- Replacement seal cartridge per Lightnin XE part numbers
- LOTO kit
Safety first
- Drain or isolate the tank before working on the seal. Hot or hazardous fluid above the seal entry poses a burn and chemical exposure hazard.
- Do not run the mixer without liquid present. Even a few seconds of dry running can destroy new seal faces.
Procedure
- 1
Stop the mixer and lock out the motor disconnect.
- 2
Drain the tank to below the shaft entry point or isolate the nozzle if a separate seal chamber is used.
Warning: Process fluid in the tank may be hot or hazardous. Follow the process safety procedures for the specific fluid before draining. - 3
Remove the gland plate bolts and slide the gland assembly back along the shaft per the Lightnin XE seal installation drawing for the applicable shaft size.[1]
- 4
Inspect the rotating seal face and the stationary seat. Look for radial scoring, chipping at the face edge, and heat discoloration (blueing on carbon faces).
- 5
If either face shows any damage, replace the complete seal cartridge. Mixing face materials from different seal sets is not permitted.
- 6
Clean the shaft at the seal running zone with a clean cloth. Verify there are no burrs or scale that could damage the new seal elastomers.
- 7
Install the new seal cartridge per the Lightnin instruction: seat the stationary ring in the gland, slide the rotating element onto the shaft, and compress the spring to the correct set dimension.[1]
- 8
Torque the gland bolts evenly in a cross pattern to the value in the Lightnin IOM for this shaft diameter.
- 9
Fill the seal flush system first if fitted, then re-fill the tank and run the mixer at slow speed for 10 minutes before returning to full load.
Sources
SPX Lightnin XE Series Industrial Mixer Installation, Operation & Maintenance Manual, SPX Lightnin
SPX Lightnin XE Series Industrial Mixer Installation, Operation and Maintenance Manual, mechanical seal installation and replacement (general)
View source
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