Howden Contact Seals

Rotary Heater leakage reduction


For decades, there has been a wish for flexible contact seals for rotary heat exchangers as a simple method of minimising the direct leakage gaps between the hot end of the rotor and the sectorplates, which separate the air and gas flows. 

Every few years another type of contact seal comes on to the market as the quick means of leakage reduction. The constant flexing as they contact the sectorplates, coupled with steam sootblowing forces and pressure differentials between the air and gas, quickly fatigues the thin flexible seals. Leakage rapidly increases and they have to be replaced with standard seals.

Recognising this user demand, Howden carried out an extensive development programme to optimise contact seals for suitable applications.

Howden contact seals provide major leakage reductions – particularly when combined with new parabolic sectorplates on large rotary heaters or on package heaters. 
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Results of theoretical analysis and testing

Finite Element Analysis and classic theoretical calculations were also carried out to assess the seal resistance capabilities to repeated contact with sectorplates (Figure 4) and cyclic loading from air/gas or gas/gas pressure differentials (Figure 5). The conclusion of all of this theoretical work along with the practical test rig testing and prototype testing within operating heaters; was that contact seals were only suitable for closing small even gaps.

However, this is the type of leakage gap that exists when Howden's new actuated parabolic sectorplates are installed. This enhanced combination provides a radical reduction in the hot end radial leakage.

Benefits would be typically around a 20% overall leakage reduction relative to standard actuated sectorplates without contact seals.

In smaller package heaters, where rotor turndown is too small to adjust sectorplates these new Howden contact seals are also effective.

Key Applications

  • In large rotary heaters, when combined with hot end parabolic sectorplates, which provide small even gaps, Howden contact seals are effective in reducing the direct leakage
  • In package heaters, where rotor turndown is minimal and leakage gaps are small and even, Howden contact seals are also effective in reducing the direct leakage

Contact Seals - Rotary Heater leakage reduction

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