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Seal selection – part 4

Choosing shaft seals for heavy industrial applications

Regardless of the type of machinery you operate, a radial shaft seal should act as an impenetrable border between a bearing and the outside world. This means it is able to shut out contaminants while retaining appropriate oil or grease levels. In heavy industry, this becomes even more difficult to accomplish, given the harsh operating conditions a seal is faced with. Standard radial shaft seals are unlikely to overcome these challenges.

Heavy-duty solutions

To that end, SKF designs and supplies a range of seals which are specifically designed to deal with a wide range of temperatures, speeds, and abrasive contaminants found in heavy industrial applications, such as in metal, mining, oil drilling, or turbines – to name just a few examples. Aside from a typically robust design, they have a range of heavy industry-specific characteristics which improve sealing performance and help operators ensure a smooth operation.

These seals are the all-rubber HS and HSS, as well as the metal-cased option HDS. All of these can be custom made quickly and easily to fit any shaft and bore size over 4” (100 mm) without the need for tooling – thus speeding up lead time. Add-on features are available and SKF can also manufacture seals from scratch to meet the most demanding sealing requirements of many industries. In short, all seals are customizable in terms of design and dimension.

General considerations

However, which seal is eventually chosen hangs on a series of standard prerequisites, as follow:

• Housing design and dimensions: How will your seal fit? Does the housing feature a cover plate to clamp the seal into the housing?
• Installation and arrangement requirements: Are you performing a blind installation? A single installation or back-to-back installations? Are there any spatial limitations?
• Pressure differentials: What levels of pressure will the seal be exposed to? Will your application involve the use of a pressurized lubricant or process fluid? Does your intended system have a pressure release valve?
• Permissible speed: Is the seal design and sealing lip material equipped to deal with your application’s rotational and circumferential speeds?
• Lubrication requirements: Is sealing material compatible with the fluid? Does your seal require an oil retaining ring?
Once you are aware of these specifications, you will be a lot closer to finding the right radial shaft seals for your heavy industrial application. Now, Industrial Seals Expert explains the individual characteristics of the HS, HSS, and HDS ranges

Back in 2017, SKF customer Scanmaskin approached our team with a request for a heavy-duty seal, which would be used in the most robust floor grinder on the market. After in-depth analysis and consideration of all functions and operational factors. SKF presented a customized solution based on the HDS design, which was originally designed to exclude contamination from metal rolling mill chocks. Scanmaskin’s product is now capable of handling the toughest of environmental conditions.

Reveal the selection process in this article.

All-rubber seals (HS) and reinforced all-rubber seals (HSS)

Depending on your installation requirements, you have the option to choose from either a split or solid version of the HS and HSS. Standard solid HS seals can accommodate shaft diameters starting at 4” (100 mm), whereas a split execution is ideal if shaft removal is impractical. SKF Springlock is a standard feature of all of SKF’s heavy industrial shaft seals and will help to keep the spring in place when installing a seal. For blind installations, where spring displacement may go undetected, the SKF Springcover to retain the spring can be specified.

These seals are available in any size and in nitrile rubber (NBR), SKF Duralip (XNBR), SKF Duratemp (HNBR), or SKF Duralife (FKM). HSS seals follow the same design as the HS but features a reinforced seal body and optional lubrication grooves which simplifies regreasing runs and can speed up back-to-back installations.

Both HS and HSS seals also require a housing with a cover plate to axially clamp the seal.

Metal-cased seals (HDS)

These seals perform exceptionally well in the high-contamination environment of metal rolling mills, the pulp and wet section of paper mills, mining and construction machinery, and more universal industrial drive applications.

HDS seals are manufactured with a metal casing, which provides extra durability in heavy-duty applications and is self-retaining in the housing bore. As spring loss is a common cause of bearing failure in heavy-duty applications, an SKF Springcover can be added. Nitrile rubber is the standard material for the HDS seal designs, but both of them are also available in SKF Duralip, SKF Duratemp, and SKF Duralife.

Selected, sealed, delivered

For more detailed specifications of our seals for heavy industrial applications, refer to page 174 onwards of the SKF brochure ‘Industrial shaft seals’, or consult your local SKF engineer. We make your selection process simple. In around six weeks, we can manufacture and deliver a seal to your instructions.

Related articles

Tools & Guides
Seal selection – part 1
Find the right seal for different operating conditions
Tools & Guides
Seal selection – part 2
Choosing bespoke, machined sealing solutions
Tools & Guides
Seal selection – part 3
Shaft seals for general industrial applications