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Halifax Fan has supplied 12 fans from its Flexible Bespoke range for a power generation project in Thailand.

The fans are rated up to 11kW, with narrow impellers and are complete with 12 full and 12 half backward-inclined blades, which boost the pressure while maintaining high efficiency.

They will be used to provide a ‘seal air’ system for Baltec’s diverter dampers, which in turn are used to control the flow of high-temperature exhaust gas from a gas turbine.

Using the diverter damper, gas flow can be split in any proportion between the heat recovery steam generator (HRSG) downstream of the diverter and a waste heat bypass.

The diverter consists of a flanged and braced plenum chamber that is internally lined with stainless steel and insulated with ceramic fibre.

This ensures, for safety and reliability reasons, that the equipment has an exterior temperature typically less than 50C, even with exhaust gas temperatures in excess of 600C.

Contained within the plenum, an insulated blade assembly contains two rows of seals around its perimeter; one to provide a seal on the HRSG side and the other to provide a seal on the bypass side.

The electrically driven blade assembly pivots from the top in a 90deg arc, providing any amount of opening from closed to fully diverted to the steam generator.

The seal air system operates in both the fully closed and fully open positions and supplies air, through inter-connecting pipe work, to the space between the two rows of seals at a pressure above that existing within the plenum, usually at least 250Pa above the plenum pressure.

This ensures that any gas leakage is into the plenum, not out of it, providing 100 per cent isolation of the gas turbine exhaust gases.

The differential pressure is measured by pressure transmitters and monitored by a PLC control system.

Halifax Fan’s Shenzhen factory completed the order for the 12 Brighouse-designed Flexible Bespoke fan assemblies to Baltec’s specification and on time, in just eight weeks from receipt of order.

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