Mechanical seals are critical for preventing leaks in centrifugal pumps. Proper assembly ensures reliability and longevity. Below is a step-by-step guide for installing a mechanical seal in a centrifugal pump.
New mechanical seal (correct type: single/double, balanced/unbalanced)
Dial indicator (check shaft runout)
Micrometer/caliper (measure seal dimensions)
Clean lint-free cloths
Isopropyl alcohol or degreaser (for cleaning)
Lubricant (silicone grease or compatible oil)
Torque wrench
Soft-faced hammer (if needed)
✔ Verify seal type matches pump specifications.
✔ Inspect shaft/sleeve for wear, scratches, or corrosion.
✔ Ensure shaft runout ≤ 0.05 mm (use dial indicator).
✔ Check seal faces for flatness (no cracks or scratches).
Drain the pump and remove the coupling.
Disassemble the gland plate (if applicable).
Remove the old seal:
For pusher-type seals, carefully extract rotating and stationary components.
For cartridge seals, unbolt and slide off the entire assembly.
Clean all surfaces (shaft, seal chamber, gland plate) with solvent.
Apply light lubricant to the O-ring/gasket.
Slide the stationary seat into the gland plate.
Ensure proper alignment (should seat flush without force).
Lubricate the shaft/sleeve to prevent O-ring damage.
Slide the rotating assembly onto the shaft:
For component seals, install the rotating face, spring, and collar separately.
For cartridge seals, slide the entire pre-assembled unit.
Hand-tighten set screws (do not fully torque yet).
Check manufacturer’s recommended compression (typically 3–5 mm for most seals).
For cartridge seals, no adjustment is needed (pre-set).
For component seals, ensure spring tension is correct.
Reinstall the gland plate with new gaskets.
Tighten bolts evenly in a crisscross pattern (use torque wrench).
✔ Ensure seal faces are parallel (no cocking).
✔ Rotate shaft manually—should turn smoothly without binding.
For wet seals, fill seal chamber with clean liquid before startup.
For dual seals, check barrier/buffer fluid pressure.
Start pump slowly and check for leaks.
Monitor:
Temperature near seal (should not exceed 70°C).
Vibration levels (< 2.5 mm/s RMS).
Leakage (a few drops/hour may be acceptable initially).
❌ Overtightening set screws (can distort seal faces).
❌ Dry running (always prime the pump).
❌ Using damaged O-rings/gaskets.
❌ Ignoring shaft/sleeve wear (causes premature failure).
| Type | Application | Key Feature |
|---|---|---|
| Single Seal | Non-hazardous liquids | Simple, cost-effective |
| Double Seal | Toxic/volatile fluids | Backup containment |
| Cartridge Seal | Easy installation | Pre-assembled, minimal adjustment |
| Balanced Seal | High-pressure (> 7 bar) | Reduces face loading |
Selection Rule: Match seal material (e.g., carbon vs. silicon carbide) to fluid compatibility.
Proper mechanical seal assembly prevents leaks and extends pump life. Always follow OEM guidelines for specific models.
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