Seals Gone Bad: The Most Common Causes of Mechanical Seal Failure
Mechanical seal failures often stem from errors during design, installation, operation, or maintenance. Each stage introduces unique risks that can compromise the seal’s integrity, causing leakage, exacerbating wear, and leading to operational inefficiencies, compromised performance, and, potentially, failure. Here is an overview of the most common errors and their direct effects:
DESIGN ERRORS
Incorrect Specification: Using a seal not suited to the operating environment (e.g., pressure, temperature, or chemical incompatibility)
RESULTS: Warping, puckering, coning, drying, cracking, or other degradation of the seal materials
Inadequate Face Loading: Improper design of the spring or other loading mechanisms
RESULTS: Pressure failure leading to leakage or uneven wear of the seal faces
Failure to Factor in Thermal Expansion: Ignoring the potential for thermal expansion in materials
RESULTS: Distortion of seal faces leading to misalignment and loss of sealing capability
Improper Seal Housing Design: Poorly designed housings where seal faces are not properly seated
RESULTS: Increased stress, leading to vibration and/or premature and uneven wear
INSTALLATION ERRORS
Misalignment: Failure to properly align the rotating and stationary parts of the seal
RESULTS: Vibration, uneven wear, rapid seal face deterioration.
Over-Tightening or Under-Tightening: Excessive or insufficient torque during assembly
RESULTS: Deformation of sealing components or improper contact of seal faces
Contamination During Installation: Introduction of dirt, debris, or grease to the seal faces or components.
RESULTS: Scoring or scratching of seal faces, increasing leakage
Improper Lubrication: Using insufficient or incompatible seal lubricant
RESULTS: Dry running and overheating of the seal faces, dissolution of seal face materials.
OPERATIONAL ERRORS
Dry Running: Operating sealing equipment without sufficient fluid to lubricate the seal faces.
RESULTS: Overheating and rapid wear or cracking of the seal.
Exceeding Design Limits: Running the pump or industrial equipment at higher speeds, temperatures, or pressures than the seal is rated for.
RESULTS: Thermal or mechanical stress leading to deformation or cracking.
Cavitation or Excessive Vibration: Caused by equipment or process operation issues.
RESULTS: Misalignment, seal face chipping, or fatigue failure.
Improper Start-Up/Shutdown Procedures: Abrupt pressure changes can damage seals.
RESULTS: Seal faces separate or crack under the sudden load.
MAINTENANCE ERRORS
Neglecting Scheduled Maintenance: Failing to inspect and replace seals regularly, according to manufacturer recommendations.
RESULTS: Seal components wear out, causing any number of issues that can lead to immediate or eventual failure.
Using Non-OEM Parts: Substituting lower-quality parts that may not meet design specifications.
RESULTS: Poor fitment or compromised quality can cause premature wear, vibration, and incompatibility issues, leading to failure down the road.
Improper Cleaning: Using abrasive materials or harsh chemicals
RESULTS: Abrasion, chapping, and cracking of seal surfaces leading to performance degradation, leakage, and failure.
Inadequate Repairs: Merely replacing a failed seal without diagnosing or addressing the underlying cause of failure
Replacing seals without addressing the underlying problem (e.g., misalignment or vibration)
RESULTS: Repeated failures
Failure Prevention Vs. Failure Remediation
Mechanical seals, like most any other mechanical system, require a degree of maintenance in order to run at optimal efficiency and productivity. As such, there is a cost associated with keeping your seals in top shape. The cost for this can be considerable. However, when compared to the potential costs of seal failure, money spent on proper seal maintenance is well spent, indeed.
Consider the potential cost of shutting down operations completely while a seal is diagnosed and repaired or replaced. New parts may need to be sourced, and sometimes custom machined, out of materials which may be vulnerable to global supply chain issues.
It is potentially far less costly to adhere to a seal manufacturer’s recommended schedule of seal inspections and part replacements while observing best practices at every stage of your seal’s life, including:
Design Stage: Collaborate with seal manufacturers to ensure correct seal selection. Consider operating conditions like pressure, temperature, and fluid properties.
Installation Stage: Train technicians on proper installation practices. Follow OEM guidelines for alignment, torque, and lubrication.
Operational Stage: Avoid dry running by ensuring adequate lubrication. Operate equipment within the design limits. Monitor for unusual vibrations or noises.
Maintenance Stage: Establish a preventive maintenance schedule. Use high-quality, OEM-recommended components. Investigate and address root causes of failures.
