Page 189 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

Positive Displacement and Dynamic Blowers 171

Table 4-1. Continued

Fan Component Check For
temperature, a good machinery paint may be used.
If moisture is excessive, or if fans are exposed to
the weather, bitumastic paints are available.
Corrosive fumes require all internal parts to be.
wire brushed, scraped clean and repainted with an
acid-resistant paint. Seek competent advice when
corrosive fumes are present.
Scroll and Housing Liners Worn? Replace because damaged liners can break
free and severely damage the wheel. Liners are
either bolted or welded to the housing.
Bearings Excessive temperature or chatter? High-speed fan
bearings are designed to run hot (100°F to 200°F).
Do not replace a bearing simply because it feels
hot. Check the pillow block temperature with a
pyrometer or contact thermometer. Ball or roller
bearing pillow blocks that are operating normaliy
can have surface temperatures of 200°F.
Ring-oiled sleeve bearings operate up to 170°F (oil
film temperature) before the cause of high
temperature need be investigated. For water-cooled
bearings, check that exit cooling water temperature
is about 100°F (unless your system is designed for
higher water temperature). If the water
temperature is too cool, condensation in the oil is
a possibility. If roller or ball bearings are to be
removed, follow the procedure in applicable
section of operating manual.
Rexible Couplings Lubricate all metal couplings (Fdk Steelflex, Fast
gear and similar types). Other types of flexible
couplings such as the Thomas disc, and rubber
insert styles such as T. B. Wood and hole, do not
need lubrication but must be inspected for pin and
bushing wear.
Motors Blow out open motor windings with low-pressure
air to remove dust or dirt. Air pressures above 50
psi can cause insulation damage and blow dirt
under loosened tape. Dust can cause excessive
insulation temperatures. Check load motor against
amperage rating on manufacturer’s nameplate.
Keep motors dry. Lubricate. When motors are idle
for a long time, single-phase heating or small
space heaters might be necessary to prevent water
condensation in the windings. Excessive starting of
large motors may burn out the motor. Consult the
manufacturer for maximum allowable number of
starts per hour.