Powmat Ltd. - Brush Seal

Brush Sealing Technolgy for Gas Turbines

Introduction
Powmat Ltd. has established itself as one of the leading independent suppliers of quality new parts for GE Frame 3, 5, 6, 7 and 9 gas turbines. Since 1975, we have worked continuously to provide our customers with a level of service that is second to none. A new product that we are offering that will greatly benefit your engine performance is the brush seal. We have selected Pratt & Whitney as our source for brush seals based on their level of experience, commitment to service and continual development of this technology. After you have reviewed the information below, we hope that you will consider us as your source for brush seals.

Brush Seals Introduction

A brush seal is an air-to-air seal that provides an alternative to labyrinth or honeycomb seals. The seal is comprised of thousands of densely packed wire filaments fused between two metallic plates. Brush seals offer many advantages when compared with traditional seals. Unlike the labyrinth seal, a brush seal is designed to come in contact with the rotor to provide a positive seal. The flexibility of the hair-like wires enables the seal to automatically adjust to accommodate rotor excursions typically encountered during start-up, shutdown or even passing through critical vibrations during normal operation. As early as the first start-up, the labyrinth seal could be compromised if it contacts the rotor. The brush seal will maintain its sealing capabilities with no significant loss in performance for up to 10,000 hours. Jet engines outfitted with brush seals can realize a 50% reduction in leakage compared to similar engines utilizing only labyrinth seals. All of this translates into at least a 1% increase in your engine performance – we guarantee it!

History of Brush Seals at Pratt & Whitney

In 1988, Pratt & Whitney began its development of brush seals for the aerospace market in their PW4000 family of engines. The PW4000 is used on the Boeing 777, 767 and 747; Airbus A300, A310 and A330; and on the McDonnell Douglas MD11. In these engines, Pratt & Whitney realizes between 30-70% improved sealing capabilities over prior labyrinth seals, depending on application. Performance improvements of 2% were attributed to the addition of brush seals in these engines.

In 1990, Pratt & Whitney’s North Berwick facility began production of brush seals to support the PW4000 family of engines, as well as other applications. Since then, the latest in technology have been incorporated into the design and manufacturing process to keep pace with the introduction of new and improved engine models. Shaft speeds of 10,000 RPM and temperatures of 1200°F are well within Pratt & Whitney’s current brush seal experience. These advances have led to many more applications for brush seals. Pratt & Whitney’s current production is in excess of 4000 brush seals annually.

Pratt & Whitney has established itself as the largest OEM and designer of brush seals in the world. A record of over 4 million hours of operation in production environments has been established with no service incidents related to brush seals.

Brush Seal Applications for Land-Based Turbines

Through close interfacing with their customers, Pratt & Whitney has designed and developed several unique applications for brush seals. They hold patents covering their implementation of brush seals in land based turbines. At the compressor discharge, they have successfully installed a brush seal upstream of the existing labyrinth teeth.

One benefit to the P&W compressor discharge brush seal is the fact that the seal can be easily removed for inspection without removing the rotor. This is made possible by its three-piece design, which installs easily in the compressor discharge inner casing. This feature alone will translate into substantial savings on your maintenance budget. Additional savings are also realized by the fact that they will install this brush seal into your existing barrel.

There is a lot of research that goes into the design, manufacture and installation of brush seals. Take the compressor discharge as an example. The air exiting the compressor discharge is the "most expensive" air in the engine and you want to put as much of it as you can through the turbine. However, some of this air is required to cool the first stage forward wheel space. The brush seal system must be carefully designed, manufactured, and installed to attain the maximum benefit without risking over-temp.

Pratt & Whitney is committed to remaining an industry leader in the design and implementation of brush seals. As brush seal technology advances, and new applications are explored, we will be working with Pratt & Whitney to bring these improvements to GE frame size gas turbines. Each of our brush seal packages is customized for individual applications. Seal locations are individually measured and the seals are manufactured to customer specifications. To some this attention to detail might seem excessive, but to us it’s imperative to provide our customers with the best brush seal package for their specific application.

Invitation to Our Customers

We have made a commitment to provide custom fitted, aircraft quality brush seals at a competitive price. We would like the chance to help you increase your gas turbine performance. Please feel free to contact us with any questions you may have regarding brush seal technology. We look forward to hearing from you.

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