Brush seals are a particularly good choice for replacing steel strip seals for circumferential, radial and axial seals on rotary APHs. Each brush consists of thousands of high-temperature, corrosion resistant metal filaments that form a high-integrity seal and provide a high degree of abrasion resistance, flex life and bend recovery. Each filament is independent and flexible, allowing deflection to conform to irregularities and gap variations and recovery to its original position.
The inherent elasticity of the brush design dissipates stress under deformation, reducing drag and wear. In addition to the dense barrier of the thousands of filaments, an independent flexible stainless steel membrane is nested within the thousands of filaments. This flexible membrane is designed for deflection that conforms to any irregularities and gap variations and recovers to its original position to ensure a tight seal is maintained. This membrane increases the sealing power of the brush seal by up to 80%, without sacrificing seal flexibility.
In areas where soot blowers are used, where blasts of steam of 400° F can be focused directly on the seal, the brush seal is equipped with an integrated protective shield configured at an angle to deflect the direct blast.
Click here to see the condition of axial brush seals after 135 days in service.
Click here to see how the brush system deals with a pronounced turndown condition of the cold end outer radial seal.
Strip steel vs. brush seal.
A worn strip steel seal compared to a new brush seal. The brush seal is flexible, allowing it to conform to smaller gaps and then return to its original position to seal larger gaps. The strip steel seal simply wears away to the smallest gap size, leaving larger gaps unsealed.
The adaptive brush design is built around a malleable alloy foil membrane (stainless steel) nestled within the brush filaments. This additional seal provides a 70% to 80% reduction in leakage without sacrificing overall seal flexibility.
Installed seals Click on thumbnail below