Mechanical Seal Installation and Removal

1. Purpose of the liquid film between seal faces

A thin liquid film between the mating seal faces performs several essential functions:

1. It supports the majority of the hydraulic pressure load on the seal.

2. It lubricates the faces and reduces frictional heat generation.

3. It minimizes rough contact, thereby reducing wear rate.

4. It acts as a heat transfer medium to carry heat away from the immediate seal-face region.

2. Pre-disassembly considerations (what to think about before removing the seal)

Before disassembling a mechanical seal, confirm and record the following:

1. Where is the primary leakage located? (shaft, gland, stuffing box, piping connection)

2. Are there fragments or debris on external components?

3. Is there observable eccentricity of the shaft or the rotating seal parts?

4. Are there system-related vibrations/noise (e.g., cavitation, misalignment)?

5. Is there localized heat generation at the pump or seal?

6. Is the leakage intermittent under different operating conditions (for example at different temperatures or pressures)?

7. What is the leak form — spray, fine droplets, stream, or routed into piping?

8. Is there axial play in the bearings (shaft axial clearance)?

9. For dual-face seals, is the quench/flush or barrier fluid supply intact and at the correct pressure/flow?

10. What is the relative axial position of the seal on the shaft (set/location)? Record any reference marks.

3. Inspections and checks to perform during disassembly

While removing the seal, pay attention to and record:

1. Condition of gaskets/braided packing and mating/run-in faces (visual wear, glazing, scoring).

2. Shaft condition and critical dimensions (diameter, run-out, scars).

3. Presence of blockage, cavitation evidence, or foreign material in the machine.

4. How tight or loose the seal was mounted on the shaft (ease of removal).

5. Signs of corrosion on machine parts.

6. Presence of seal fragments inside the machine or housing.

7. Whether there were alignment/reference marks showing the installed position.

8. Relative hardness of the shaft surface at the seal location (for compatibility with seal faces).

4. Best practices while removing seals (damage control & root-cause preservation)

1. During removal, be extremely careful to avoid introducing new damage that could obscure the original cause of failure. Preserve evidence.

2. Observe and document each component as it is removed — take photos, label parts, and record measurements before proceeding to the next step.

3. Categorize observed failure modes (e.g., abrasive wear, dry running, thermal damage, face chatter/noise) to aid root-cause analysis.

5. Installation — preparation & preconditions

1. Ensure the seal chamber and surrounding area are clean and free of foreign material.

2. Verify mating shaft or sleeve dimensions and finish: correct diameter, smooth surface finish, good straightness, free of burrs, sharp edges, scores or deep scratches.

3. Plug or seal any holes in the seal chamber that are not used during seal operation.

4. Seal chamber faces must be clean, flat and perpendicular to the shaft axis.

5. For horizontal split-case pumps the two halves must align properly and use a full gasket between housings; remove any sharp corners or burrs on the seal chamber surfaces.

6. Check wear ring / impeller clearances are correct. The shaft must rotate freely — friction or incorrect clearances that cause vibration will shorten seal life.

7. If a shaft sleeve is used, ensure the sleeve is properly sealed to the shaft to prevent leakage beneath the sleeve.

8. Confirm all fasteners are present and fit correctly. If set screws or drive screws are used to drive the seal to the shaft, countersunk or pilot holes may be required to secure the connection.

9. Use an evenly distributed gland with at least four equally spaced bolts where possible. For non-guiding glands, precise alignment is critical — check clearances with feeler gauges.

6. Assembly & bolting practice

1. When tightening the gland or cover bolts, tighten smoothly and evenly in a cross pattern to avoid bending the gland. Do not apply spring-like preload to the gland.

2. Use feeler gauges to check the gap between the gland and the shaft; this is particularly important when the seal chamber does not guide the gland. The gland must be accurately centered.

3. When possible, use four or more evenly spaced bolts for the gland.

4. If tightening studs are used to drive the seal relative to the shaft, provide the recommended pilot/countersink or thread engagement to prevent slippage.

5. After coupling alignment is completed, perform final tightening of the gland. Tighten bolts uniformly to prevent tilt — check multiple points with a feeler gauge or a dedicated alignment tool; final deviation should not exceed 0.05 mm.

6. Check the clearance/concentricity between the gland ID and the shaft (or sleeve) OD at several points around the circumference; allowable variation ≤ 0.10 mm.

7. Inspection of parts and specification verification (before final assembly)

1. Verify seal model, specification and quantity against design/drawing requirements.

2. Inspect all parts, especially the seal faces and secondary seals (o-rings, elastomeric parts), for damage, deformation or cracking — replace any defective parts.

3. Check machine tolerances for run-out, wobble and deflection:

   • Shaft axial runout (axial float) typically should not exceed ±0.5 mm.

   • Shaft wobble at the rotating seal ring should not exceed 0.06 mm.

   • Maximum shaft deflection should not exceed 0.05 mm.

   • Allowable non-perpendicularity of the seal cover gasket contact face to centerline: 0.03–0.05 mm.

4. Confirm the seal chamber dimensions conform to installation drawings and that the seal cover and shaft are perpendicular.

8. Pre-start testing and commissioning

1. Before starting the pump, perform a static pressure test of the seal under pressure where possible; while pressurized, make small adjustments to gland nuts to prevent leaks at the gland/gasket area.

2. Do not run a mechanical seal dry. Always ensure a lubricating/flushing medium is present on the faces during rotation.

3. Follow the manufacturer’s instructions for any flush, quench, or cooling connections required for the specific seal type.

4. Ensure pump suction and discharge valves are open and that a positive liquid head/pressure exists at start-up. This prevents cavitation and dry running.

5. Verify rotation direction and motor electrical connections before full operation.

9. Final checklist & common troubleshooting cues

Final installation checklist (minimum):

• Seal parts correct model and undamaged.

• Shaft/sleeve surface finish and diameter confirmed.

• Shaft run-out, wobble and deflection within limits.

• Gland/cover perpendicular and evenly bolted; clearances checked with feeler gauges.

• Static pressure test completed; minor gland adjustments made as required.

• Flush/flush plan, quench or barrier fluid (if applicable) connected and functioning.

• Positive suction head present at start-up; no dry starts.

Common early failure signs:

• Excessive leakage immediately after start: misalignment, incorrect gland tightening or damaged faces.

• Overheating of faces: inadequate lubrication/flush, dry running, or mismatch of materials.

• Noise or face chatter: misalignment, excessive run-out, or poor surface finish.

• Abrasive wear: debris ingress, poor filtration, or contaminated barrier fluid.

10. Notes on documentation and traceability

• Photograph key steps and final assembly orientation. Mark and record the axial position of the seal on the shaft.

• Record part numbers, batch codes for seal faces and elastomers, and operating conditions at installation (temperature, pressure, job ID). These data aid future root-cause analysis and continuous improvement.