How Long Do Mechanical Seals Last

How Long Do Mechanical Seals Last

On average, mechanical seals last between 18 months to 2 years under normal operating conditions. However, some high-quality seals designed according to API 682 standards can last up to 3 years with proper installation and maintenance.

Variations Based on Seal Type

1. Single mechanical seals: These seals consist of a single seal face and are typically used in less demanding applications. They have an average lifespan of 12 to 18 months.
2. Double mechanical seals: Featuring two seal faces, double mechanical seals provide enhanced reliability and are suitable for more critical applications. These seals can last up to 3 years or more, depending on the operating conditions.
3. Cartridge mechanical seals: Pre-assembled and easy to install, cartridge seals offer improved performance and longer lifespans compared to traditional component seals. They can last between 2 to 5 years, depending on the application and maintenance practices.
4. Split mechanical seals: Designed for easy installation and maintenance without disassembling the equipment, split seals are ideal for large, difficult-to-access equipment. Their lifespan ranges from 18 months to 3 years, depending on the application and operating conditions.
5. Gas-lubricated mechanical seals: These seals use gas as a barrier fluid, making them suitable for high-temperature and high-pressure applications. Gas-lubricated seals can last up to 5 years or more with proper maintenance and operating conditions.
6. Dry-running mechanical seals: Designed to operate without lubricating fluids, dry-running seals are used in applications where liquid lubrication is not possible or desirable. These seals typically have shorter lifespans, ranging from 6 to 18 months, due to the lack of lubrication and cooling.

Factors Affecting Seal Lifespan

Operational Conditions

The lifespan of a mechanical seal is significantly influenced by the operational conditions it is subjected to.

• High temperatures can cause thermal expansion, leading to increased wear and tear on the seal faces.
• Similarly, excessive pressure can cause deformation and damage to the seal components.
• The speed at which the shaft rotates also affects seal life, with higher speeds generally resulting in faster wear.
• Chemical compatibility is another critical factor, as exposure to incompatible fluids can cause corrosion, swelling, or degradation of the seal materials.

Fluids

The type and characteristics of the fluid being sealed play a vital role in determining seal life.

• High-viscosity fluids can generate excessive heat and cause increased wear on the seal faces.
• Abrasive fluids, such as slurries or those containing solid particles, can erode the seal faces and cause premature failure.
• Additionally, the fluid’s chemical properties, such as pH and reactivity, can affect the seal materials and lead to degradation over time.

Material

Seal faces are typically made from hard, wear-resistant materials such as silicon carbide, tungsten carbide, or ceramic.

Secondary seal components, such as O-rings and gaskets, must also be compatible with the fluid and able to withstand the operating conditions.

Using high-quality, application-specific materials can significantly extend the life of a mechanical seal.

Installation and Maintenance

During installation, it is crucial to ensure that the seal is correctly aligned and that the seal faces are properly lubricated. Misalignment or improper installation can lead to premature failure.

Regular maintenance, including cleaning, inspection, and replacement of worn components, can help extend seal life. Following the manufacturer’s recommended maintenance schedule and procedures can prevent minor issues from escalating into major failures.

Lubrication

The lubricating fluid, often the process fluid itself, helps to reduce friction between the seal faces and dissipate heat. Insufficient lubrication can lead to increased wear, overheating, and premature failure. In some cases, an external lubricating system may be used to provide a clean, cool, and compatible lubricant to the seal faces. Maintaining proper lubrication levels and ensuring the lubricant remains free of contaminants can significantly extend seal life.

Seal Face Deflection and Sensitivity to Transients

The seal faces of a mechanical seal are designed to maintain a small gap between them, allowing for a thin film of lubricating fluid. However, seal faces can be sensitive to deflection and transient conditions. Deflection occurs when the seal faces are subjected to uneven pressure or thermal gradients, causing them to deform and lose their flatness. Transient conditions, such as sudden changes in pressure, temperature, or speed, can also cause temporary distortions in the seal faces.

Seal Environment and Support Systems

Seal environmental controls, such as temperature and pressure regulation, help to maintain stable operating conditions and prevent excessive stress on the seal components. Properly designed and maintained support systems, including barrier fluid systems, cooling systems, and filtration systems, can extend seal life by providing a clean, cool, and compatible environment for the seal to operate in.

How Do I Know if My Mechanical Seal Is Broken

• Leakage: Visible leakage of process fluid from the seal gland is a clear sign of seal failure. Seals may leak before total failure as faces wear.
• Excessive Vibration: Seal failure can sometimes cause the shaft to wobble or vibrate excessively. This may indicate severe seal face damage or secondary seal issues.
• Overheating: Failed seals generate excess heat due to increased face friction. Overheated seal components or fluids point to potential failure.
• Decreased Pump Performance: Seal failure can allow air to enter the pump, causing loss of prime, cavitation, and reduced flow or pressure.
• Unusual Noise: Squealing, grinding, or squeaking noises emanating from the seal area indicate face contact and damage.