TM 5-3895-374-24-2
modate a normal amount of tooth wear without permitting
contact between lobes of the two impellers.
However. a high oil level will cause churning and
excessive heating, indicated by an unusually high temperature
at the bottom of the gear housing. Consequent heating of the
gears will result in loss of tooth-clearance or backlash. and
rapid wear of the gear teeth usually will develop. Continuation
of this tooth wear will eventually produce impeller contacts
(knocking), and from this point serious damage will be
unavoidable if blower operation is continued. A similar
situation can be produced suddenly by gear tooth fracture,
which is usually brought on by sustained overloading or
momentary shock loads.
Operating problems may also develop from causes other
than internal parts failure. Operating clearances within a
blower are only a few thousandths of an inch (hundredths of a
mm). This makes it possible for impeller interferences or
casing rubs to result from shifts in the blower mounting or from
changes in piping support. Foreign materials sucked into the
blower will also cause trouble. which can only be cured by
disconnecting the piping and thoroughly cleaning the blower
interior.
If this type of trouble is experienced, and the blower is
found to be clean. try removing mounting strains. Loosen
blower mounting bolts and reset the leveling and drive
alignment. Then tighten mounting again, and make sure that
all piping meets blower connections accurately and squarely
before reconnecting it.
A wide range of causes for operating troubles are covered
in the TROUBLE SHOOTING CHECKLIST. The remedies
suggested there in some cases need to be performed by
qualified mechanics with a good background of general
experience, using procedures detailed in this manual. Major
repairs generally are to be considered beyond the scope of
maintenance, and should be referred to the nearest Distributor
listed on the last page.
Warranty failures should not be repaired at all, unless
specific approval has been obtained through a Distributor or a
factory before starting work. Unauthorized disassembly within
the warranty period may void the warranty.
When a blower is taken out of service it may require
internal protection against rusting or corrosion. The need for
such protection must be a matter of judgment based on
existing conditions as well as length of downtime. Under
favorable conditions, protection will probably not be needed if
shut-down is not longer than a month. Under atmospheric
conditions producing rapid corrosion, the blower should be
protected immediately. If blower is to be shut down for an
extended period of time, see suggestions for corrosion
protection under installation.
It is recommended that major repairs, if needed, be
performed at a Dresser authorized service facility.
However, it is recognized that this may not always be practical,
especially when a spare blower is not available. If a blower is
out of the warranty period. mechanical adjustments and parts
replacement may be undertaken locally at the owner’s option
and risk. It is recommended that Factory Parts be used to
insure fit and suitability. The maintenance of a small stock of
on-hand spare parts can eliminate possible delays. When
ordering parts give Item Numbers and their word descriptions
from Figures 5 & 6. Also specify quantities wanted and the
blower size and serial number from the nameplate.
Repairs or adjustments are best performed by personnel
with good mechanical experience and the ability to follow the
instructions in this manual. Some operations involve extra
care and patience, and a degree of precision work. This is
especially true in timing impellers and in handling bearings.
Experience indicates that a high percentage of bearing failure
is caused by dirt contamination before or during assembly.
Therefore, the work area should be cleaned before starting
disassembly. and new or re-usable parts protected during
progress of the work.
In the following outlines of repair procedures. numbers
shown in brackets ( ) correspond to the Item Numbers used in
assembly drawing, Figures 1 & 13. It is recommended that the
procedure be studied carefully and completely, with frequent
reference to the drawings. before starting work. This will
produce better efficiency through an understanding of what
work is to be done. and the order of doing it. Before
disassembly. mark all parts so that they may be returned to
original locations or relative positions.
A-Replacing Timing Gears
1.
Drain all oil from the gearhouse by removing drain
plug (21) in the bottom. Remove gearhouse by taking
out all cap screws (23) in its flange. It may be
necessary to bump the sides with a wood block or
mallet to break the flange joint.
2.
Reach through one of the blower pipe connections
and place a chalk mark on the strip of one impeller
and the mating waist of the other. so that they may
easily be returned to their original relative positions.
Figure 5-Impeller Timing Viewed From Gear End
3. GEAR REMOVAL: For this operation. the impellers should
be wedged as shown in Figure 5. Back off gear clamping nuts
(17) about 1/4". Use a puller of the type shown in Figure 10.
Position it around the gear per Figure 9. As the puller set
screw is torqued, the puller will have a tendency to turn and
contact teeth of the other gear. To prevent this contact. hold
the puller corner nut with a wrench while torquing the set
screw. Once the gear is unseated, remove the puller.
Remove gear nuts (17) and the gear. Repeat same procedure
for the other gear. NOTE: Do not remove gear nuts (17)
completely before the gears are unseated from the taper
fits or damage/injury may result.
page 3-810
