Case History No. 12

Industry & Location:

A utility station in the west

Problem:

Inadequate capacity from an F.D. fan

Source of Detection:

One boiler generates 10 megawatts less than an adjacent identical boiler.

Cause of Problem:

Each identical boiler is equipped with identical F.D. fans which operate with vortex dampers and no inlet boxes. Because of the absence of the inlet boxes, the vortex dampers are very accessible for inspection and cleaning.

To a trained fan engineer, the obvious cause of reduced fan capability is the presence of prespinning at the fan or inadequate gap at the inlet cone. In this particular case, a trained eye detected the fact that one F.D. fan inlet vortex damper was not fully open. An open vortex damper must have the blades set at an angular position of 90 degrees. In this particular case, the vortex damper blades were only at an 85 degree position which caused prespinning and deteriorated the ability of the fan to develop static pressure.

Solution:

Because of continuous vibrations, the vortex damper linkages are exposed to continuous wear. Because of this wear, it is not uncommon for vortex dampers to develop slack in the linkages and not fully open. Vortex dampers require periodic maintenance and adjustment of these linkages during outages. The solution in this case was to replace worn parts and adjust the linkages of the vortex dampers so they could be positioned in the fully open setting.

Benefit:

Increase in megawatt capability so that both boilers produce the same power generation.

Vortex Dampers