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14 February 2012 - Whatever the nature of the equipment, it is a safe assumption that its reliable operation depends, among other components, on seals, ranging from tiny O-rings to custom engineered large diameter roll-line seals.
Wherever there are aggressive operating conditions, seals form the first line of defense. If a seal fails to function effectively, the consequences can be expensive, including increased consumption of lubricant, clearing of hazardous waste and equipment failure. The bottom line: unplanned shutdowns and lost productivity.
SKF offer a wide range of standard and custom built seals, including all-rubber, metal cased, fabric reinforced and metal clamp seals, with spring loaded and springless sealing lips.
For example, in demanding roll line applications SKF large diameter seals with an elastomeric outside diameter provide a robust sealing solution. These seals effectively retain oil or grease and prevent the ingress of contaminants, improving bearing performance and reducing lubrication costs. The elastomeric outer also protects the housing bore and minimises the risk of damage during installation or removal, while the use of a springless lip seal, designed to pump contaminants away from the lip, enhances seal life and preserves the condition of lubricant and bearing.
Large diameter seals, between 203mm and upwards of several meters in diameter, offer a unique combination of properties, as they have to function under exceptionally high levels of stress for long periods of time without degradation, yet have to be easy to fit and replace.
It is therefore crucial to select large diameter seals that have been developed specifically for each application, as the use of incorrect designs or materials will rapidly lead to failure.
For example, when SKF were working on their Bearing Life Theory (adopted in ISO 281) their research indicated that up to 14% of all premature bearing failures could be directly attributed to contaminants entering bearings either via poorly designed or specified seals, or because the materials used were unsuitable for each application.
SKF's latest large diameter seals, are therefore manufactured from advanced engineering plastics, including PTFE (polytetrafluoroethylene) and HNBR (hydrogenated acrylonitrile butadiene rubber).
PTFE is a thermoplastic polymer with a chemical resistance that is far superior to that of any other material used in conventional seals. The operating temperature of PTFE extends from -70
| Product Model | Inside Diameter | Outside Diameter | Thickness |
| 418/414 NACHI | 38.1 | 88.501 | 29.083 |
| 3381/3320 NACHI | 38.1 | 80.167 | 30.391 |