First of all Howden provided a brand new fan solution to meet the performance demands. It was a considerably bigger fan of the type ANN-3200/1600B, speed of 740 rpm. The new and strong fabricated hub was provided with high pressure profiles of nodular cast iron. The maximum flue gas temperature had to be 160°C, the Test Block volume = 360m/sec and Test Block pressure = 2275 Pa. The new motor size was 1050 kW.
During the planning phase Howden presented three alternatives concerning the fan foundation:
- The first option was to place the new fan directly on a new standard foundation.
- The second option was to establish a support of springs between the new fan and a new foundation.
- The third option was to reuse the old foundation from 1995 and modify it to fit the new fan.
The plant had a very tight time schedule for the upgrade process. In order to meet that it was chosen to keep the existing foundation of the original fan from 1995, modifying it lightly with steel supports in each end – one for the new motor and another for the transport skates for the diffuser.
To secure that the foundation met all the requirements of stiffness and frequency, Howden also provided a thorough Foundation Test consisting of a Fan Survey, Balance Tests and Bump Tests.