The FSA Mechanical Seal Technical Committee
December 30, 2013
- Excessive vibration transmitted to the seal chamber caused by cavitation, internal recirculation or asymmetrical wear
- Cavitation (vaporization) of the fluid in the seal chamber (and, therefore, vaporization of the fluid film)
- Temperature increase in the seal chamber under low-flow conditions causing vaporization of fluid in the seal chamber
- Insufficient cooling flow from the mechanical seal support system (such as process flush or barrier fluid circulation)
Critical Seal Components
Within the seal design, the components that are most sensitive to vibration and insufficient lubrication are typically the mating pair of seal rings. The seal ring materials are selected based on the defined conditions of the environment being sealed. Those conditions include factors—such as temperature, the media being contained, system pressures and interface surface speeds.
The seal components’ interface conditions can change quickly and dramatically with exposure to vibration, insufficient seal face lubrication or other upset circumstances. While the sealing system design incorporates features to regulate the interface conditions, the seal faces can become damaged when off-design pump operation forces them into settings for which they were not designed. Slight damage can result in a leakage at the sealing interface that is caused by systemic issues unrelated to the materials or the seal design.
Seal performance degradation is often caused by improperly operated pumping equipment. Energy and maintenance costs and unplanned downtime may be saved if a proactive systems approach is taken to pump system efficiency and investment is made in process modifications and system upgrades to mitigate the root causes of these failures. While properly selected mechanical seal designs help increase the seal’s tolerance, the most reliable approach is a pumping system with a strong focus on eliminating or minimizing these root causes of reduced mechanical seal service life.
Next Month: How can creating a cross-functional team improve pump and valve sealing?
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