Q. What is Forced Draft Fan?

Fan shall comply with API 673 as supplemented by the following: (para. references are to API 673).

Where the intake air is unfiltered, the Vendor shall provide a fan cleaning facility using compressed air at 120 psig (828 kPag). Cleaning system shall function with fan in operation without adverse affects to fan or Steam Generator performance. System shall be manually activated.

Steam Generator Vendor shall be responsible for demonstrating that loads imposed on the fan from ducting under all operating scenarios are acceptable to fan Vendor.

Riveted fan wheels are not permitted

Torsional response studies are not required

Fan and motor balancing shall be done without the coupling half in place. A half key of equal length to that used to secure coupling half shall be used during balancing.

A spot faced 1 inch diameter area shall be provided in three planes at each bearing location (as permitted by access) for mounting magnetic vibration probes.

Fan shall meet the following requirements at its rated point:

• Rated air flow shall be 115% of the air flow by weight required by the units operating at maximum design heat release, and firing mixing fuel gas at 15% excess air.
• Fan shall be rated at 70^oC design air temperature and summer design relative humidity.

Fans shall be direct driven by constant speed electric motors.