Have you ever wondered why mechanical seals fail prematurely? Seal failure can lead to costly downtime and repairs in industrial settings.
In this blog post, we’ll explore the top 15 reasons behind mechanical seal failure. By understanding these common causes, you’ll gain valuable insights into preventing seal failure and ensuring optimal performance in your equipment.
Dry Running
Dry running occurs when a mechanical seal operates without proper lubrication. This can happen due to insufficient liquid in the seal chamber or improper installation. Dry causes increased friction and heat generation, leading to rapid wear and damage to the seal faces.
Prolonged dry running can result in complete seal failure. To prevent this, ensure that the seal chamber is filled with the appropriate liquid and that the seal is installed correctly.
Chemical Attack
Chemical attack happens when the mechanical seal is exposed to incompatible or aggressive chemicals. These chemicals can degrade the seal materials, causing them to soften, swell, or crack. This deterioration compromises the seal’s ability to maintain a proper sealing interface.
To avoid chemical attack, select seal materials that are compatible with the process fluid. Consult with the seal manufacturer or refer to compatibility charts to choose the appropriate materials for your application.
Excessive Pressure
Mechanical seals are designed to operate within a specific pressure range. Exposing the seal to excessive pressure can cause deformation of the seal components, leading to increased leakage and premature failure.
High pressure can also result in the seal faces opening up, allowing the process fluid to escape. To prevent this, ensure that the seal is rated for the maximum pressure expected in the system and maintain the pressure within the specified range.
Shaft Runout or Vibration
Shaft runout and vibration can cause the seal faces to lose contact, resulting in increased leakage and wear. Runout occurs when the shaft is not perfectly straight, causing it to wobble as it rotates. Vibration can be caused by improper alignment, unbalanced rotating components, or bearing issues.
To minimize shaft runout and vibration, ensure that the shaft is properly aligned and balanced. Regular maintenance, including checking and correcting alignment and replacing worn bearings, can help prevent these issues from causing seal failure.
Excess Heat
Excess heat can cause mechanical seal failure. High temperatures can damage seal materials and cause them to degrade faster. This can lead to increased wear and leakage.
To prevent excess heat, ensure that the seal is operating within its specified temperature range. Proper cooling and heat dissipation methods should be employed to maintain acceptable temperatures.
Improper Installation
Improper installation is a common cause of mechanical seal failure. Incorrect installation can result in misalignment, damage to seal components, or inadequate sealing.
To avoid installation issues, follow the manufacturer’s installation instructions carefully. Ensure that the seal is properly aligned and that all components are correctly assembled.
Shaft Movement
Shaft movement can cause mechanical seal failure. Excessive shaft movement, such as axial or radial displacement, can cause the seal faces to lose contact or become misaligned. This can result in increased leakage and wear.
To minimize shaft movement, ensure that the shaft is properly supported and guided. Use appropriate bearings and coupling devices to maintain proper shaft alignment and stability.
Worn Shaft
A worn shaft can cause mechanical seal failure. As the shaft wears, it becomes uneven and can cause the seal faces to lose contact. This can result in increased leakage and accelerated wear of the seal components.
To prevent shaft wear, ensure that the shaft is made of a suitable material and is properly hardened.
Ingress of Abrasive Particles
The ingress of abrasive particles can cause mechanical seal failure. Abrasive particles, such as dust, dirt, or process media, can enter the seal chamber and damage the seal faces. This can result in increased wear, leakage, and premature failure.
To prevent the ingress of abrasive particles, use appropriate sealing arrangements, such as labyrinth seals or dust excluders. Ensure that the process media is properly filtered to remove abrasive particles. Regularly clean and inspect the seal area to remove any accumulated debris.
Hammering Couplings onto the Shaft
Hammering couplings onto the shaft can cause mechanical seal failure. This improper installation practice can damage the shaft, seal components, and bearings. It can also cause misalignment and uneven stress distribution.
To avoid this issue, use proper installation techniques and tools. Follow the manufacturer’s instructions for coupling installation. Use appropriate heating methods, such as induction heating, to expand couplings for installation instead of hammering.
Incorrect Operation
Incorrect operation of the mechanical seal can lead to failure. Operating the seal outside of its specified parameters, such as pressure, temperature, or speed, can cause damage and premature wear.
To ensure correct operation, follow the manufacturer’s guidelines for the mechanical seal. Monitor and maintain the operating conditions within the specified ranges. Provide proper training to personnel responsible for operating and maintaining the equipment with mechanical seals.
Cavitation
Cavitation can cause mechanical seal failure. It occurs when the fluid pressure drops below its vapor pressure, creating vapor bubbles. When these bubbles collapse near the seal faces, they can cause erosion and damage to the seal components.
To prevent cavitation, ensure that the fluid pressure is maintained above the vapor pressure. Proper system design, including adequate net positive suction head (NPSH), can help avoid cavitation conditions.
The Wrong Flush Plans
Using the wrong flush plan can lead to mechanical seal failure. Flush plans are designed to provide the appropriate fluid environment for the seal. Incorrect flush plans can result in inadequate cooling, lubrication, or debris removal.
To select the correct flush plan, consider factors such as the process fluid, temperature, pressure, and the presence of abrasive particles. Consult with the seal manufacturer or refer to industry standards, such as API 682, for guidance on selecting the appropriate flush plan.
The Wrong Mechanical Seal or Materials
Using the wrong mechanical seal or seal materials can cause failure. Seals and their materials must be compatible with the process fluid and operating conditions. Incorrect seal selection can result in premature wear, leakage, or chemical attack.
To choose the right mechanical seal and materials, consider the fluid properties, temperature, pressure, and chemical compatibility. Consult with the seal manufacturer and refer to compatibility charts to select the appropriate seal and materials for your application.
Lack of Maintenance
Lack of maintenance can lead to mechanical seal failure. Regular maintenance is essential to ensure that the seal is operating correctly and to identify potential issues before they cause failure.
Establish a regular maintenance schedule that includes inspections, cleaning, and replacement of worn components. Follow the manufacturer’s recommendations for maintenance intervals and procedures. Keep accurate records of maintenance activities and seal performance to help identify trends and potential problems.
FAQs
What the most common cause of mechanical seal failure
The most common cause of mechanical seal failure is improper installation, which can lead to misalignment, incorrect seal face loading, and damage during the installation process.
How does the presence of entrapped air affect mechanical seal performance
Entrapped air can cause seal face opening, leakage, and potential dry running conditions, leading to premature seal failure.
How can improper storage and handling impact mechanical seal performance
Improper storage and handling can cause seal face damage, distortion, or contamination before installation, leading to premature failure once in service.
How can improper seal balance ratio selection affect seal performance
An improper seal balance ratio can result in either excessive or insufficient seal face loading, causing increased wear, leakage, or seal face damage.
Can seal face flatness deviations contribute to mechanical seal failure
Yes, seal face flatness deviations can cause uneven loading, increased leakage, and accelerated wear of the sealing surfaces.
Can improper shaft or housing dimensions cause mechanical seal failure
Yes, improper shaft or housing dimensions can result in incorrect seal fitment, misalignment, and inadequate support, all of which can contribute to seal failure.
Conclusion
Understanding the common causes of mechanical seal failure is crucial for maintaining efficient and reliable equipment operation. By addressing these 15 factors proactively, you can significantly extend seal life and reduce costly downtime.
Take action now to assess your mechanical seals and implement preventive measures. Your diligence will pay off in improved performance and cost savings.
