High Efficiency Flexible Air Preheater Seals

• Flexible Radial Seals

• Flexible Axial Seals

• Flexible Bypass Seals

• Flexible Circumferential Seals

The flexible seal was developed to reduce normal leakage caused by the thermal expansion of the rotor while the unit is operating.  Although expansion characteristics vary per individual heater, typical differential expansion in rotary type air heaters causes the rotor to pull away from the hot side and move towards the cold sector plates.  This rotor expansion opens up areas of direct air to gas leakage that can be greatly reduced by installing our flexible seals.  In today's power market, with new emission control systems requiring air heaters to run more efficiently than ever before, our flexible seals can help your units reduce stack emissions, increase fan reserve, heat rate and overall efficiency.

 The method of installation of the “Flexible” seal is no different than that of the original seal other than the degree of clearance set at cold conditions and the preparation of the sector plate edge.

 Since this is an interference or contact seal, the wear life is not expected to exceed 18 months of continuous operation in severe cases.  During this time the “Flexible” seal will allow all of the benefits of lower air heater leakage to its user.  In some cases flexible seals have lasted 5-6 years. These benefits may range as follows:

• Fan requirements will be reduced while maintaining maximum air heater efficiency resulting in better overall boiler heat rate.  
• Lower fan horsepower and/or higher fan reserve when air heater plugging is experienced.
• Reduced corrosion and fouling potential at the air heater cold end element layer and downstream ductwork due to undiluted exit gas flow.
• Less exit gas volume (velocity), which would result in maintaining a lower pressure drop through the air heater.
• Flexible seals come in a variety of designs and material compositions depending on the harshness of the operating environment. Some Designs feature a replaceable flexible “pack” which can be quickly replaced without resetting the seal body, resulting in a minimal amount of required outage time and maintenance.
• With the installation of “Flexible” seals, a 38% to 50% reduction in present leakage may be obtained, with the total leakage being reduced to a minimum of 6% to 7% in most cases. Some air preheater designs may benefit even further.

Note: Flexible seals are not designed to be installed under soot blowers.