106.How to know reverse flow in the case of GR Fan and how to handle it?

A reverse flow of flue gas in the GR system will produce high temperature at the outlet of GR duct after the fan.

A shut of damper as close as possible at the inlet to furnace will stop the reverse flow. However during operation of GR fan a positive feedback from the shaft of fan end will ensure no reverse flow in the GR system. This is a must when hydraulic coupling or equivalent methods are used to control the speed of the fan.