Page 174 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

156 Major Process Equipment Maintenance and Repair

OlLlTE
BUSHING
-
AIR FLOW
CENTER CONTROL VIV
SLIDING BLOCK DESlGN
PATENT NO. 039588
Flgure 4-13. Center control variable inlet design vane. (Courtesy CWCP Ltd.)

and 12 in. water gauge pressure. Another design uses prelubricated ball
bearings rather than self-lubricated bushings. Here, the operating mecha-
nism inside the bell is completely shrouded with a dust cover. In yet an-
other design, the center control VIV is used on ID and clean, hot-gas
fans. The operating mechanism, a sliding block design, is connected to
the vanes outside the air flow next to the fan shaft as shown in Figure
4-13.

lumlng Gear

For applications such as gas recirculation, fans may stand idle for long
periods while exposed to temperatures as high as 800°F. Under such con-
ditions, a thermal set can result in the shaft, causing extreme vibration
upon startup.