TM 5-3895-374-24-2
started, gradually close the discharge unloading valve to
apply working pressure. At this point it is recommended
that a good 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 or
in the process to which air is being supplied. Refer to the
TROUBLE SHOOTING CHECKLIST for suggestions on
various problems that may appear.
The blower should now be ready for continuous duty
operation at full speed. 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,
verify 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 unloading vent valve. Never rely on the
pressure relief valve as an automatic vent. Such use
may cause the discharge pressure to become excessive
and can also
TROUBLESHOOTING CHECKLIST
TROUBLE
ITEM
POSSIBLE CAUSE
REMEDY
No Air Flow
1
Speed too low
Check by tachometer and compare with speed
shown on Roots Order Acknowledgment.
2
Wrong rotation
Compare actual rotation with Figure 2.
Change driver if wrong.
3
Obstruction in piping
Check piping, screen, valves. silencer, to assure
an open flow path.
Low capacity
4
Speed too low
See item 1. If belt drive, check for slippage and
readjust tension.
5
Excessive pressure
Check inlet vacuum and discharge pressure,
and compare these figures with specified
operating conditions on Order.
6
Obstruction in piping
See item 3.
7
Excessive slip
Check inside of casing for worn or eroded sur-
faces causing excessive clearances.
Excessive Power
8
Speed too high
Check speed and compare with Roots Order
Acknowledgment.
9
Pressure too high
See item 5.
10
Impellers rubbing
Inspect outside of cylinder and headplates for
high temperatures areas, then check for-im-
peller contacts at these points. Correct blower
mounting, drive alignment.
Overheating of
11
Inadequate lubrication
Restore correct oil levels in gearbox and
Bearings. or Gears
lubricate.
12
Excessive lubrication
Check gear oil level. If incorrect, drain and refill
with clean oil of recommended grade.
13
Excessive pressure rise
See item 5.
14
Coupling misalignment
Check carefully. Realign if questionable.
15
Excessive belt tension
Readjust for correct tension.
16
Speed too low
Speeds lower than the minimum recommended
will overheat the entire blower.
Vibration
17
Misalignment
See item 14.
18
Impellers rubbing
See item 10.
19
Worn bearings, gears
Check gear backlash and condition of bearings.
20
Unbalanced or rubbing
Scale or process material may build up on cas-
impellers
ing and impellers. or inside impellers. Remove
build-up to restore original clearances and im-
peller balance.
21
Driver or blower loose
Tighten mounting bolts securely.
22
Piping resonances
Determine whether standing wave pressure
pulsations are present in the piping. Refer to
Distributors.
page 3-808
