Axial Fan Blade Failure

The depth and length of the cracks and the rapid increase in vibration from the fan speed apparently from the fan blade flexing at the crack s during rotation led to the conclusion that at least one blade was on the way to catastrophic failure.

Axial fan blade failure.

The fdf blade has been run for 5 years and before its failure the fdf experienced high vibration 14 mm s. An axial fan is a type of fan that causes gas to flow through it in an axial direction parallel to the shaft about which the blades rotate. The forced draft fan fdf blade in a 300 mw coal fired power plant that experienced catastrophic failure has been investigated. The forced draft fan is an axial flow fan horizontally in front of the boiler and the fan is single stage.

Axial flow fan impellers will also be subject to centrifugal forces and thus the various elements will be stressed. Kushwaha studied failure analysis and technique of averting fracture in the generator s fan blade. Visual inspection metallographic analysis chemical composition and hardness test were carried out to find the cause of the failure. Axial fans are divided into three groups propeller tube axial and vane axial whereas centrifugal fan are classified as airfoil blade radial fans forward curved fans and backward inclined curved fan.

Causes of inadequate airflow to the fan include a backwards installed or running impeller improper blade angle setting missing cut off an impeller not centred with inlet collars slow fan speed dirty or clogged inlet improper running clearance or improper inlet cone to wheel fit. This paper includes the affects on the performance of axial fan due to the failure of different parts. The flow is axial at entry and exit. 7 8 stressing of axial impellers 7 8 1 introduction.

The fan is designed to produce a pressure difference and hence force to cause a flow through the fan factors which determine the performance of the fan include the number and shape of the blades. There were two main locations of the blade damage namely damage at. Fan performance is wrong. As in most cases the blades are cantilevered and only supported at the end adjacent to the hub fluctuating stresses are more important.

Wtw bill cory in fans and ventilation 2005. An axial fan blade can be considered as cantilever beam on which air pressure and centrifugal force are applied blade failure due to different forces during its operation is analysed by fixing its one end at hub by v block as shown in fig.