Increasing energy efficiency and reducing downtime are two of the most sought-after goals in many industrial environments. Multiple improvements can be made to machinery to help achieve these goals; one example is the switch from elastomer lip seals to bearing isolator seals.

Efficiencies can be gained in certain applications that use process pumps and motors, as elastomer seals in these applications exert significant torque whereas isolator seals exert almost zero torque.

In addition to increased equipment efficiency, facilities using isolator seals can also save precious resources otherwise lost to equipment downtime. Industries that use numerous types of rotating equipment in critical production operations feel the pinch of a shutdown that can cost thousands of dollars. Since some equipment downtime is caused by failure due to contaminants reaching bearings, isolator seals can contribute greatly to a decrease in production downtime as they are more effective at preventing contaminants from reaching the bearing. The direct result is a bearing that operates longer and keeps equipment running smoothly.

Isolator Seal Advantage

Whether classified as an elastomer lip or isolator, a seal is essentially a bearing protection device that eliminates cross-contamination between the lubricant and the external environment as it protects the bearing by preventing lubricant leakage and contaminant ingress.

While both seal types share a common purpose, the design and engineering behind the isolator seal enables it to operate both more effectively and efficiently than the elastomer lip seal in applications where the lubricant level resides below the seal. Elastomer lip seals are, of course, essential in applications where lubricant levels come up to the bottom of the rotating shaft.

Seal Design

The bearing isolator seal is a labyrinth seal that is made up of two non-contacting components, and these two metal components -- a rotor and stator -- are separated by a durable PTFE-ring. Together, these components create a torturous labyrinth path that prevents contaminants from entering and lubricants from exiting the isolator seal in both directions.

In comparison, a single lip seal is designed to seal in only one direction and requires two opposing lips to seal in both directions.

Although considered one of the more superior bearing seals on the market today, the first isolator seals had a very basic labyrinth pathway made up of 90 degree turns that, in certain cases, still allowed contaminants to work their way through to the bearing. To build upon this innovation and improve its effectiveness, the isolator was redesigned with a more torturous labyrinth path that included a less direct route through the seal.

Today, the isolator is made up of both an ingress and a retention labyrinth path. The ingress path prevents contaminants from reaching the bearing by redirecting them to the expulsion port at the bottom of the seal. Conversely, the retention path redirects the lubricant back to the bearing through its separate bottom expulsion port.

This use of such a torturous labyrinth path removes the need for an elastomer lip seal, and solves two common problems:

1. Increased torque and temperature from friction caused by the elastomer seal lip contacting the shaft.
2. Contaminant entry allowed by elastomer lip wear.

With no rubbing parts to contend with, isolators do not wear away, and their design life is extremely long. Plus, unlike elastomer lip seals, isolators do not require lubrication because they do not have contacting components. Most importantly, isolator seals exert little to zero torque, making them a contributor to electrical energy savings in many plants.

Other advantages in the newest isolator seals include an interference fit of the rotor component to the shaft by using two fluoroelastomer o-rings that allow it to rotate with the shaft. There are also two additional o-rings set into grooves on the stator; these grooves are cut on an incline to securely trap the o-rings when they are forced to move in an opposite direction.

Industry Applications

A variety of industries can benefit from the isolator seal, such as primary metals, power generation, food and pharmaceutical, pulp and paper, and process industries. Within these industries, isolators are used in the top two types of rotating equipment in the world: motors and pumps. While isolator seals meet the many demands of these two main applications, they are also applicable in gearboxes, conveyors, mixers, agitators, centrifuges, and other heavy equipment. Bearing isolator seals are also an excellent choice for dry applications and those that require both lubricant retention and contaminant exclusion.

Isolators are particularly suitable for use in electric motor applications to keep contaminants out. Most electric motors reside in dirty environments and must get washed down with high-pressure washers. In this environment, an isolator must prevent both water and dust from reaching the motor bearing.

The performance of isolator seals has been tried and tested, and advanced isolator seals have performed well in tests such as the Institute of Electrical and Electronic Engineers (IEEE) IEEE-841 Dust Exclusion testing and IEEE-841 Water Exclusion test. Both tests subjected the isolator seal to rigorous dust and water conditions, and the isolator seal performed well by preventing both types of contaminants from passing through the seal.

Many pumps in use today come standard with isolator seals, including American National Standards Institute (ANSI) chemical and general service pumps, and API 610 refining and petrochemical pumps.

In many types of manufacturing facilities, isolators are also used to replace standard seals on split pillow blocks (SPB) – specifically, the labyrinth excluder ring (LER) or Taconite seals. In this application, no modification is required on the SPB housing because the isolator seals fit into the existing LER groves.

An entire family of isolator seal designs is available for many applications. While all utilize the same basic technology, each offers characteristics specific to the application. For example, the small-cross-section isolator is designed for applications where little room exists for a standard seal, and a vertical design is suitable for applications with vertical shafts. Also available are flangeless and split pillow block designs in addition to the standard design.

Product Offerings

Both metallic and non-metallic isolators are available. Both can be utilized in electric motors and pumps, and each offers unique characteristics suited to specific environments. Specifically, both types:

• Provide bearings with an extra layer of protection from contaminants;
• Do not require lubrication during operation; and
• Are easy to install by hand in the repair shop or in the field, without the use of an arbor press.

Metallic Design: Bronze construction is standard, but designs are also available in other metals. The metallic isolator includes the engineered PTFE-ring, which prevents metal-to-metal contact. The surface speed rating of metallic isolators is up to 12,000 fpm, and most metallic isolator designs meet IP56 testing standards. Also available is a special metallic isolator with a microcellular filter, which is effective in highly contaminated environments such as mining.

Non-metallic Design: The non-metallic isolator design is an ideal alternative to elastomer lip seals in non-flooded oil or grease applications. Made from materials such as PTFE, the non-metallic isolator provides greater chemical resistance.

Other types available include a unique isolator design that features no “top” or “bottom” orientation, allowing the isolator to be installed in any rotational position.

Designed for many applications within many industries, the bearing isolator seal is a remarkable advancement in bearing protection. Its highly engineered design makes it a true innovation in friction management, and a reputable contributor to savings in both equipment efficiency and plant downtime.

For more information or advice on bearing isolator seals, visit www.timken.com/industrialseals.