Page 173 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Positive Displacement and Dynamic Blowers 155

Variable Inlet hnes (VIV’s)

Variable inlet vanes regulate fan capacity using moveable vanes in the
fan inlet. A common linkage joins the vanes together so they operate in
unison when the control lever is moved. See Figure 4-12.
VIV’s are completely assembled in the inlet bell and adjusted at the
factory for operation.
To meet a range of conditions, fan manufacturers provide several VIV
designs. In one design, the vanes are cantilevered with the operating
mechanism inside the fan. They are easily serviced by removing the inlet
bell that includes the VIV assembly. Each vane shaft is supported by two
self-lubricating bushings separated by a steel sleeve. The area between
the steel sleeve and vane shaft is packed with graphite grease to prevent
the shaft from seizing. Service conditions for this design are up to 150°F

Figure 4-12. Common linkage variable inlet vanes (Vlv). (Courtesy CWCP Ltd.)