Page 182 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

164 Major Process Equipment Maintenance and Repair

Inlet Bells or VlV's

Attach inlet bells to the housing (bolting from the outside of the hous-
ing). Do not tighten the bolts completely. Adjust the wheels and inlet
bells for correct alignment with one another. For included draft service,
the wheels should overlap in the inlet bell on the drive side to allow clear-
ance on the opposite side for shaft growth at operating temperatures. For
each 100°F increase in temperature, a steel shaft expands .008 in. per ft
of shaft length. For example, a 5 ft, 6 in. fan shaft operating at 570°F
would lengthen .22 in. (Room temperature at start is 70", so increase is
500". Expansion would be .008 in. X 5 X 5.5 in. or .22 in.) Thermal ex-
pansion clearances are shown on your assembly drawing. For forced
draft service fans, check the assembly drawing for the correct gap on
each side. For fans which use clearance fit, standard taper, or taper lock
collar hubs, the wheel can be moved on the shaft slightly to align the inlet
bells.
Proceed to pull down the foundation bolts on the housing and inlet box
support legs. If the foundation is slightly high or low, these support legs
can deflect the housing, making alignment of the wheel and inlet bell dif-
ficult. Shim if necessary. Double check inlet bell location and tighten in-
let bell bolt completely.
Now, tighten the hub set screws. First tighten the set screw over the
key, which should be in the six o'clock position before tightening. Next,
tighten the set screw that leads rotation.

Stufflng Box Installation

Packing is usually factory-installed for fans that use stuffing boxes.
However, stuffing boxes require the following break-in procedure:

1. With a feeler gauge, check that the clearance between the housing
stuffing box and fan shaft is uniform. The shaft must be centered in
the box.
2. Check for lubricant in the grease cup when a grease ring is sup-
plied. Use a good grade of temperature resistant packing grease.
3. If the stuffing box is water-cooled, connect flexible water line with
a valve in the drain return line to regulate flow. Discharge the cool-
ing water into an open funnel so visual inspection will show water
flowing. Adjust water flow to conditions.
4. Tighten the gland nuts finger tight. The packing should not be so
tight that the shaft cannot be turned by hand.
5. After all erection procedures have been followed, start the fan and
run for 15 minutes. If the stuffing box gets too warm or you see
smoke, stop the fan and loosen the gland.