Plzen - New fan on existing foundation

New boiler and FGD processes called for a total change of the ID booster fan.

Howden's solution was to install a complete new fan on the existing fan foundation reducing both costs and duration of the project.

Keeping the existing foundation ensured Plzenska energetika a.s that the erection time and costs were reduced to an absolute minimum.

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Axial fan new fan on existing foundation

The challenge

In 2008 the power plant of Plzen, Czech Republic, owned by Plzenska energetika a.s., planned to do a boiler refurbishment. At the same time the FGD from the mid-nineties had to be upgraded in order to comply with today's demands for bringing down emissions.

The changes in the power plant processes caused a demand for a total change of the performance of the ID/Booster fan.


he original ID/Booster fan which alone served all three boilers of the 346 MW power plant was delivered by Howden in 1995. It was a single stage fan type ANN-2500/1250N, speed of 990 rpm, and with medium pressure blade profiles of aluminium with wear noses and a cast hub.

The maximum operating temperature was 75°C, the Test Block volume = 198 m3/sec and Test Block pressure = 2469 Pa. The motor size was 750 kW.

The result

The power plant of Plzen obtained all the advantages of a brand new fan: optimum efficiency, improved operational reliability, performance suited for the actual operation values, and the latest developed fan technology.

And Plzen experienced savings by using the existing foundation: no demand for establishing a brand new foundation, minimum adjustment of existing foundation and ductwork, cut down on total erection time – minimum downtime, and huge price savings for the total project.

The solution

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.


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