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Seal protection – part 1

Troubleshooting common seal failure modes

Industrial shaft seals play a key role in retaining lubricants and protecting bearings from contaminants. But there are several factors that negatively impact seal performance and reliability. The first post in this two-part series examines common failure modes and the causes behind them.

Although they are commonly seen as “low-value” components, seals are crucial for the protection of bearing arrangements. By keeping lubricants in and contaminants out, they improve bearing service life and reliability. In turn, this maintains the overall operating health of machinery. However, while seals can be made in a wide variety of different designs, profiles, and materials, there are a number of factors that have an adverse effect on their lifespan and performance. To help ensure that seals operate effectively, it is important to minimize friction and wear.

A significant proportion of seal failures in day-to-day operation are due to underlying root causes that do not necessarily originate from the seal itself. But you can often get to the bottom of the issue by looking for some telltale signs.

50% of premature bearing failures are related to sealing issues

It all starts with installation

Proper installation is decisive in seal performance and reliability. An otherwise suitable seal can have its lifespan significantly reduced by incorrect installation procedures. Nicks, scratches, or cuts in the lip contact area are strong indicators of installation issues. A potential cause could be damage from a sharp edge of a tool or improper packaging and handling of a seal before it is installed.

To prevent these issues, you should use the right installation tools for the procedure. It is also important to examine the seal and installation tools for damage and wear before installation and check that the bore chamfer meets the recommendations for the seal. It may be necessary to modify your installation procedure or use different tools.

Lubrication issues prevent smooth operation

Excessive wear is a common failure mode for seals – and there are many possible root causes. It could, for example, be the result of using the wrong seal material for the application. But excessive wear can also originate from insufficient lubrication. To prevent premature failure, you should check for contamination ingress, increase lubrication at the lip interface, or consider switching to a high-wear seal material as appropriate.

Sludge or other deposits on the seal lip or shaft are another indicator of a lubrication-related failure mode. In high-temperature operating environments, the lubricant can break down and lead to the accumulation of sludge. In this case, you should use seals designed for high temperatures, check that the lubricant is compatible or try to reduce the operating temperature if possible.

More issues beneath the surface?

The shaft itself can also have a negative impact on seal performance. If the shaft surface finish is irregular or damaged due to a poor shaft grinding process, the seal will encounter issues. An excessively rough shaft may accelerate lip wear, while an overly smooth shaft may result in leakage. To prevent these problems, you should ensure that the shaft is handled and installed properly and check for visible damage or irregular surface characteristics. It also pays to measure the seal’s surface finish and shaft lead and compare them to industry standards such as RMA and ISO.

While the aforementioned failure modes are some of the most commonly encountered, there are many more specific cases. To identify the root cause of a recurring issue, it may be necessary to contact your seal provider for a more thorough inspection.

Stay tuned for the next installment of this troubleshooting series for some tips to help you identify causes of failure and extend seal life.

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Dan Bannon
| 2019-07-11 | 15:10
WOW, 50% of premature bearing failures due to seals? That is a huge number. We will have to reduce the checking alignment, and balance, to spend more time checking seals.

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