How to Repair Mechanical Seal

Repairing a mechanical seal involves identifying failure signs, cleaning and inspecting components, and replacing damaged parts. Key steps include addressing leaks, noise, or excessive heat, focusing on seal faces, O-rings, and gaskets.

For minor issues, repairing O-rings and secondary seals may suffice. More extensive damage might require full replacement, so consider repair costs versus a new seal.

Signs a Mechanical Seal Needs Repair

Leakage of fluid or gas from the seal area

Visible drips, sprays, or puddles around equipment signal problems. Even small leaks warrant attention. Wear on seal faces, damaged O-rings, or improper installation often cause leakage.

Assess leak severity first. Some applications tolerate a few drops per minute, but continuous leakage demands action. Identify the leaking fluid type to pinpoint the issue source and severity. Oil leaks suggest worn bearings, while process fluid leaks point to seal face problems.

Excessive noise like squealing or grinding

Squealing or grinding sounds from a mechanical seal warrant immediate investigation. These noises typically signal friction between seal faces or components that should not contact each other.

Insufficient lubrication or seal face misalignment usually cause squealing sounds. This can lead to rapid wear and damage if not addressed quickly. Grinding noises suggest debris entry into the seal area or severe component wear or damage.

Increased temperature around the seal indicating friction

Increased temperature around the seal area often indicates excessive friction in mechanical seals. Heat radiating from the seal housing or steam emanating from the area are common signs of this problem. Lack of lubrication, misalignment, or worn-out seal faces typically cause this excessive heat.

Excessive shaft vibration signaling misalignment or wear

Excessive shaft vibration indicates mechanical seal issues. Equipment produces unusual noises or shakes during operation due to misalignment between shaft and seal or component wear.

Identify vibration using a vibration analyzer or by feeling for abnormal movement. Inspect the shaft for visible wear signs like scoring or pitting. Check seal faces for uneven wear patterns suggesting misalignment.

Visible corrosion or pitting on seal components

Chemical reactions between seal materials and the sealed fluid, or inadequate material selection for the operating environment, often cause these issues. Inspect seal faces, metal components, and elastomers thoroughly for corrosion or pitting signs.

Examine seal faces for discoloration, rough patches, or small holes. Check metal parts for rust or oxidation.

Repairing corroded or pitted mechanical seals typically requires replacing affected components. Select materials resistant to the specific corrosive elements in your system. Upgrade to corrosion-resistant alloys or ceramics for metal parts and choose compatible elastomers. Some cases may require seal design modifications or additional protective measures, such as coating vulnerable components or improving the system’s chemical balance to reduce corrosiveness.

The Mechanical Seal Repair Process

Disassembly, cleaning and inspection of seal components

Document the seal’s assembly order and orientation before disassembly, using photos if needed. Remove components gently with soft tools to avoid surface damage. Clean each part thoroughly, eliminating old lubricants, debris, and process fluids with appropriate solvents and lint-free cloths. Focus on sealing faces, O-rings, and gaskets. Use ultrasonic cleaning or gentle abrasives for stubborn deposits.

Inspect components under good lighting, using magnification when necessary. Look for wear, corrosion, pitting, and heat damage. Check sealing faces for flatness and smoothness. Examine O-rings and gaskets for deformation or degradation. Measure critical dimensions to ensure they meet tolerances.

Failure analysis to determine root cause and prevent recurrence

Thorough failure analysis prevents future mechanical seal breakdowns. Examine failed components for wear, damage, or abnormalities. Look for scoring on seal faces, excessive O-ring wear, or thermal damage evidence. Check for contamination or debris causing failure.

Review operating conditions at failure time. Consider temperature, pressure, speed, and pumped fluid properties. Compare these to seal design specifications to identify discrepancies. Analyze installation and maintenance records to ensure proper procedure adherence.

Replacing damaged parts like seal faces, O-rings, springs etc

Mechanical seal repair requires replacing damaged components identified through failure analysis. Remove faulty seal faces, O-rings, and springs carefully.

Select replacement parts matching original specifications or upgrade to more durable materials if appropriate.

Lapping and polishing of seal faces to restore flatness

Begin by placing a lapping plate on a flat surface and applying a thin layer of lapping compound. Position the seal face on the plate and move it in a figure-eight pattern with gentle pressure. Continue for several minutes, rotating the seal face periodically for even lapping.

Assess flatness using a precision straightedge or optical flat. Repeat lapping if necessary. Once desired flatness is achieved, switch to a finer grit lapping compound and repeat the process to smooth the surface.

For final polishing, use a polishing cloth and diamond paste. Apply paste to the cloth and polish the seal face using circular motions.

Clean the seal face regularly with solvent to remove debris during the process. Avoid over-lapping or polishing to prevent altering significant seal face dimensions.

Reassembly and pressure testing of the repaired seal

Reassembly of the repaired seal begins with thorough cleaning of all components using solvent to remove debris and contaminants. Inspect each part again for overlooked damage. Reverse the disassembly order to reassemble the seal. Apply a thin layer of compatible lubricant to O-rings and gaskets before installation. Align components carefully, ensuring snug fits without force. Pay close attention to repaired seal faces, verifying proper seating and alignment.

Pressure testing verifies seal integrity after reassembly. Set up a testing rig mimicking the seal’s operating conditions. Increase pressure gradually while monitoring for leaks. Depressurize the system, disassemble the seal, and address any detected leaks.

When to Repair vs Replace a Mechanical Seal

Minor issues like O-ring wear can be repaired

Minor issues like O-ring wear can be repaired in mechanical seals. O-rings prevent leaks and maintain seal function. Signs of wear include small cuts, deformations, or loss of elasticity. Replacing worn O-rings restores seal effectiveness without full replacement.

To repair O-rings, remove the old one using a plastic pick to avoid damaging the seal surface. Clean the O-ring groove thoroughly. Select a new O-ring of the same size and material, ensuring compatibility with operating conditions. Apply a thin layer of compatible lubricant to the new O-ring before installation to prevent damage and improve sealing performance.

Other minor repairs include cleaning or replacing secondary sealing elements, such as gaskets or shaft sleeves.

Extensive damage to seal faces or metal components warrants replacement

Mechanical seal replacement becomes necessary when damage exceeds repair capabilities. Inspect seal faces for deep scratches, chips, cracks, significant pitting, warping, or uneven surfaces. Metal components like springs, drive pins, or retaining rings showing corrosion, deformation, or breakage indicate replacement need.

• Excessive leakage or persistent performance issues unresolved by basic maintenance suggest internal damage requiring seal replacement.
• Seals subjected to harsh environments or operating beyond expected lifespan often need replacement.
• Critical applications where seal failure poses safety hazards or costly downtime warrant proactive replacement.

Consider cost-benefit of repair vs replacement

Repair costs include labor, parts, and downtime. Compare these to new seal prices and installation fees. Replacement often proves more cost-effective when repair expenses exceed 50-60% of a new seal’s cost.

Criticality of the application and seal reliability requirements

Application criticality and seal reliability requirements drive the decision to repair or replace mechanical seals. Highly critical processes with costly or dangerous downtime often necessitate seal replacement. This approach ensures a new component less prone to unexpected failure.

Less critical applications may allow for seal repair. However, repaired seals typically have shorter lifespans than new ones, potentially leading to more frequent maintenance. Assess the consequences of seal failure in your specific application, including product contamination, environmental hazards, and safety risks.

FAQs

Can a Mechanical Seal Be Repaired While the Equipment Is Still Running?

Repairing a mechanical seal while equipment is operational is not feasible. It poses safety risks and would be ineffective. Proper procedure requires shutting down and isolating the machinery before conducting any seal repairs or replacements.

How Often Should Mechanical Seals Be Inspected for Potential Issues?

Mechanical seals should be inspected quarterly.

What Are the Common Causes of Premature Mechanical Seal Failure?

Common causes of premature mechanical seal failure include improper installation, misalignment, dry running, contamination, excessive pressure or temperature, vibration, and chemical incompatibility.

Are There Specific Tools Required for Mechanical Seal Repair?

Mechanical seal repair requires specialized tools: seal removal tools, torque wrenches, alignment devices, cleaning supplies, gasket scrapers, and measuring instruments. Manufacturers’ guidelines should be consulted for specific equipment requirements.