6 Reasons for Why Mechanical Seals Fail

Figure 1: Faulty mechanical seal.

You might be asking yourself, why are my seals failing so fast, and how can I prevent this from happening? This topic rings true among operators and engineers in plants of all sizes and industries. A mechanical seal is often a "barometer" for the pump, helping maintenance and operators understand the health of the pump on which it's installed. Other times, failure is a result of poor selection or installation errors. Here are 6 of the most common reasons mechanical seals can fail.

1. Allowing the Pump to Run Dry

Allowing your pump to run dry can be very damaging to a mechanical seal. Under the right conditions, mechanical seals can experience thermal shock and shatter within 30 seconds or less.

2. Vibration

Pump vibration is caused by pump imbalance, improper alignment, operating the pump too far to the right or left of the BEP (Best Efficiency Point) on the performance curve, etc. Vibration hurts your equipment and can result in damaged seals and shortened seal life.

3. Hammering Couplings onto the Shaft

When it comes to pumps, hammers are not friends! Mechanical seal faces can be very fragile. Pounding couplings onto the shaft will damage the mechanical seal.

4. Operator Error

Skipping initial start-up procedures and installation errors are a big factor when it comes to mechanical seal failure. Improperly starting the pump can cause the motor to trip and the shaft to twist causing orbital movement, resulting in internal parts contact, seal failure, and shortened bearing life. Improperly installing the mechanical seal will cause damage to elastomers (o-rings or boots), along with a wide variety of other issues, as pictured to the right. Mechanical seals can be very sensitive because the faces are incredibly flat. Even a small amount of dirt or oil, even fingerprints, can cause the faces not to align.

Figure 2: Improper installation.

5. Improper Use of Mechanical Seal Flush Plans

A mechanical seal flush plan must be properly in place. No mechanical seal recommendation is complete without a coordinating flush plan. Be Aware: if no flush plan exists, dewatered product and contaminants can build up, causing excessive heat or erosion on the seal, resulting in shortened seal life.

6. Selecting the Wrong Mechanical Seal or Materials

Figure 3: Wrong materials.

Lack of knowledge and information accounts for the majority of mechanical seal installation errors. Consider normal operating conditions, the potential for off-design excursions, and non-process activities, such as cleaning, steaming, acid and caustic flushes. The picture to the right is an example of poor material choice for an abrasive liquid.

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