Mechanical Seal Inspection

A mechanical seal prevents fluid leakage in rotating equipment like pumps and compressors by creating a barrier between moving and stationary parts.

Regular inspection of these seals prevents catastrophic equipment failure, reduces downtime, and saves thousands in repair costs. The inspection process requires systematic examination of all seal components, from operational signs to dimensional measurements.

This guide provides a comprehensive approach to mechanical seal inspection that maintenance professionals can follow.

Inspection Process

The mechanical seal inspection process follows a systematic approach to identify potential issues before they lead to equipment failure. This structured methodology ensures thorough examination of all critical components while maintaining safety and accuracy throughout the inspection.

1. Review Operational Signs

The first step involves checking for warning signs while the equipment is still running. These indicators often reveal seal problems before complete failure occurs:

• Leaks – Visible fluid around the seal area indicates primary seal face damage or secondary seal deterioration
• Unusual Noise or Vibration – Grinding sounds or excessive vibration suggest misalignment or damaged seal faces
• Temperature Anomalies – Higher than normal temperatures point to excessive friction between seal faces

2. Isolate and Drain the Equipment

Safety requires complete equipment isolation before inspection begins. Lock out and tag out procedures prevent accidental startup.

Drain all process fluids from the pump or equipment housing. This step protects personnel from chemical exposure and allows clear access to seal components.

3. Disassemble to Access the Seal

Remove the pump casing or equipment housing to expose the mechanical seal assembly. Document the seal orientation and component positions with photographs before removal.

Careful disassembly prevents damage to seal components that might mask the root cause of problems.

4. Clean Components for Inspection

Clean all seal parts with appropriate solvents to remove process residue and deposits. Proper cleaning reveals surface conditions that indicate wear patterns and failure modes.

Use lint-free cloths to avoid contaminating precision seal faces.

5. Inspect Seal Faces (Primary Rings)

The primary seal faces require detailed examination as they perform the main sealing function:

• Surface Condition – Check for scratches, pitting, or heat checking that compromises sealing ability
• Wear Pattern – Uniform wear indicates proper operation while uneven patterns suggest misalignment
• Cracks or Chips – Physical damage requires immediate seal replacement
• Flatness & Fit – Use optical flats or precision gauges to verify face flatness within manufacturer specifications

6. Inspect Secondary Seals

Secondary sealing elements prevent leakage along static surfaces and accommodate shaft movement:

• O-Rings and Gaskets – Examine for compression set, chemical attack, or physical damage
• Bellows – Check metal or elastomer bellows for cracks, corrosion, or loss of flexibility
• Gaskets and Static Seals – Verify proper seating and absence of extrusion or deformation

7. Inspect Springs and Metal Parts

Metal components provide mechanical force and structural support for the seal assembly:

• Corrosion or Erosion – Chemical attack weakens springs and reduces sealing force
• Wear Marks – Contact patterns reveal misalignment or improper installation
• Alignment Features – Verify drive pins, slots, and keys remain within tolerance

8. Dimensional Checks

Precise measurements confirm components meet specifications:

• Shaft or Sleeve Diameter – Verify proper fit within seal bore tolerances
• Seal Face Thickness – Measure remaining material to determine service life
• Spring Height or Compression – Confirm proper spring force for effective sealing
• Axial End Play – Check shaft movement stays within acceptable limits

9. Examine Seal Support Systems (if applicable)

Many mechanical seals require auxiliary systems for proper operation:

• Flush Lines – Inspect for blockages or flow restrictions that cause seal overheating
• Barrier/Buffer Fluid Systems – Verify proper fluid levels and absence of contamination
• Quench and Drain – Ensure atmospheric side protection functions correctly
• Cooling Systems – Check heat exchanger effectiveness and coolant flow rates

What Is the Standard for Mechanical Seal Testing

Mechanical seal testing follows internationally recognized standards that ensure consistent performance evaluation across manufacturers and industries. The primary standard is API 682, developed by the American Petroleum Institute for seals in petroleum and chemical processing applications.

API 682 specifies qualification testing procedures including hydrostatic testing, dynamic testing, and cyclic testing. These tests verify seal performance under various pressure, temperature, and speed conditions.

ISO 21049 provides additional testing guidelines for general industrial applications. This standard covers type testing for new seal designs and production testing for quality assurance.

Testing requirements typically include pressure tests at 1.5 times maximum operating pressure and temperature cycling to verify thermal stability. Dynamic tests run seals at specified speeds while monitoring leakage rates, face temperatures, and vibration levels.

Manufacturers must document test results showing seals meet specified leakage limits, typically less than 3 ml/hour for most applications. Qualification tests often run for extended periods, sometimes exceeding 1000 hours, to demonstrate long-term reliability.