4
Before operating a blower under power for the first time,
recheck the unit and the installation thoroughly to reduce the
likelihood of avoidable troubles. Use the following procedure
check list as a guide, but consider any other special condi-
tions in the installation.
1. Be certain that no bolts, tools, rags, or debris have been
left in the blower air chamber or piping.
2. If an outdoor intake without filter is used, be sure the
opening is located so it cannot pick up dirt and is pro-
tected by a strong screen or grille. Use of the temporary
protective screen as described under INSTALLATION is
strongly recommended.
3. Recheck blower leveling, drive alignment and tightness
of all mounting bolts if installation is not recent. If belt
drive is used, adjust belt tension correctly.
4. Turn drive shaft by hand to make sure impellers still
rotate without bumping or rubbing at any point.
5. Ensure oil levels in the main oil sumps are correct.
6. Check lubrication of driver. If it is an electric motor, be
sure that power is available and that electrical overload
devices are installed and workable.
7. Open the manual unloading valve in the discharge air
line. If a valve is in the inlet piping, be sure it is open.
8. Bump blower a few revolutions with driver to check that
direction of rotation agrees with arrow near blower
shaft, and that both coast freely to a stop.
After the preceding points are cleared, blower is ready for
trial operation under “no-load” conditions. The following
procedure is suggested to cover this initial operation test
period.
a.
Start blower, let it accelerate to full speed, then shut
off. Listen for knocking sounds, both with power on
and as speed slows down.
b.
After blower comes to a complete stop, repeat
above, but let blower run 2 or 3 minutes. Check for
noises, such as knocking sounds.
c.
After blower comes to a complete stop, operate
blower for about 10 minutes unloaded. Check oil
levels. Observe cylinder and headplate surfaces for
development of hot spots such as burned paint,
indicating impeller rubs. Be aware of any noticeable
increase in vibration.
Assuming that all trials have been satisfactory, or that neces-
sary corrections have been made, the blower should now
have a final check run of at least one hour under normal
operating conditions. After blower is restarted, gradually
close the discharge unloading valve to apply working pres-
sure. At this point it is recommended that a pressure gauge
or manometer be connected into the discharge line if not
already provided, and that thermometers be in both inlet and
discharge lines. Readings from these instruments will show
whether pressure or temperature ratings of the blower are
being exceeded.
During the final run, check operating conditions frequently
and observe the oil levels at reasonable intervals. If excessive
noise or local heating develops, shut down immediately and
determine the cause. If either pressure rise or temperature
rise across the blower exceeds the limit specified in this
manual, shut down and investigate conditions in the piping
system. Refer to the
TROUBLESHOOTING CHECKLIST
for
suggestions on various problems that may appear.
The blower should now be ready for continuous duty opera-
tion at full load. During the first few days make periodic
checks to determine whether all conditions remain steady, or
at least acceptable. This may be particularly important if the
blower is supplying air to a process system where conditions
can vary. At the first opportunity, stop the blower and clean
the temporary inlet protective screen. If no appreciable
amount of debris has collected, the screen may be removed.
See comments under
INSTALLATION
.
At this same time, veri-
fy leveling, coupling alignment or belt tension, and mounting
bolt tightness.
Should operating experience prove that blower capacity is a
little too high for the actual air requirements, a small excess
may be blown off continuously through the manual unload-
ing or vent valve. Never rely on the pressure relief valve as
an automatic vent. Such use may cause the discharge pres-
sure to become excessive, and can also result in failure of
the valve itself. If blower capacity appears to be too low, refer
to the
TROUBLESHOOTING CHECKLIST
.
See pages 15 and
19 for additional troubleshooting information regarding DVJ
and DPJ units.
Vibration Assessment Criteria
With measurements taken at the bearing locations on the
housings, see chart below for an appropriate assessment
guide for rotary lobe blowers rigidly mounted on stiff foun-
dations.
In general, blower vibration levels should be monitored on a
regular basis and the vibration trend observed for progres-
sive or sudden change in level. If such a change occurs, the
cause should be determined through spectral analysis.
As shown on the chart below, the level of all pass vibration
will determine the need to measure discrete frequency vibra-
tion levels and the action required.
Operation
All Pass Vibration Discrete Frequency
Action
(in/sec)
Vibration (in/sec)
0.45 or less
N/R
Acceptable
Greater than 0.45
0.45 or less @
Acceptable
but 1.0 or less
any frequency
Greater than 0.45 @
Investigate
any frequency
Greater than 1.0
Less than 1.0
Investigate
Greater than 1.0
Investigate
