RWB II ROTARY SCREW COMPRESSOR UNITS
MAINTENANCE
S70-200 IOM
Page 31
Pressure Gauge - Discharge Port
1. High reading would indicate:
a. High viscosity and small and/or long discharge line.
b. Gate valve partially closed.
c. Filter plugged.
d. Vertical head did not consider a high specifi c gravity
liq uid.
e. Line partially plugged from buildup on inside of pipe.
f. Liquid in pipe not up to temperature.
g. Liquid in pipe has undergone a chemical reaction and
has solidifi ed.
h. Relief valve set too high.
2. Low reading would indicate:
a. Relief valve set too low
b. Relief valve poppet not seating properly.
c. Too much extra clearance.
d. Pump worn.
3. Fluttering, jumping, or erratic reading:
a. Cavitation.
b. Liquid coming to pump in slugs.
c. Air leak in suction line.
d. Vibrating from misalignment or mechanical prob-
lems.
Some of the following may also help pinpoint the prob-
lem:
1. Pump does not pump.
a. Lost its prime - air leak, low level in tank.
b. Rotating in wrong direction.
c. Motor does not come up to speed.
d. Suction and discharge valves not open.
e. Strainer clogged.
f. Relief valve set too low, relief valve poppet stuck
open.
g. Pump worn out.
h. Any changes in the liquid system, or operation that
would help explain the trouble, e.g. new source of
sup ply, added more lines, inexperienced operators,
etc.
i. Tighten end clearance.
j. Head position incorrect.
2. Pump starts, then loses its prime.
a. Low level in tank.
b. Liquid vaporizing in the suction line.
c. Air leaks or air pockets in the suction line; leak ing air
through packing or mechanical seal.
d. Worn out.
3. Pump is noisy
a. Pump is being starved (heavy liquid cannot get to
pump fast enough). Increase suction pipe size or
re duce length.
b. Pump is cavitating (liquid vaporizing in the suction
line). Increase suction pipe size or reduce length; if
pump is above the liquid, raise the liquid level closer
to the pump; if the liquid is above the pump, increase
the head of liq uid.
c. Check alignment.
d. May have a bent shaft or rotor tooth. Straight en or
re place.
e. May be a foreign object trying to get into the pump
through the suction port.
4. Pump not up to capacity
a. Starving or cavitating - increase suction pipe size or
reduce length.
b. Strainer partially clogged - clean.
c. Air leak in suction piping or along pump shaft.
d. Running too slowly - is motor the correct speed and
is it wired up correctly
e. Relief valve set too low or stuck open.
f. Pump worn out.
g. Tighten end clearance.
h. Head position incorrect.
5. Pump takes too much power.
a. Running too fast - is correct motor speed, reducer
ra tio, sheave size, etc. be ing used.
b. Liquid more viscous than unit sized to handle - heat
the liquid, increase the pipe size, slow the pump down,
or get a bigger motor.
c. Discharge pressure higher than calculated - check
with pressure gauge. Increase size or reduce length of
pipe, re duce speed (capacity), or get bigger mo tor.
d. Pump misaligned.
e. Extra clearance on pumping elements may not be
suffi cient for operating conditions. Check parts for
evidence of drag or contact in pump and increase
clear ance where nec es sary
6. Rapid Wear.
Examination of a pump that has gradually lost its abil i ty
to deliver ca pac i ty or pressure would show a smooth
wear pattern on all parts. Rapid wear shows up as heavy
groov ing, galling, twisting, breaking, or sim i lar severe
signs of trouble.
PREVENTATIVE MAIN TE NANCE
Performing a few preventative maintenance procedures will
extend the life of your pump and reduce the cost per gallon
pumped.
1. Lubrication - Grease all zerks after every 500 hours of
operation or after 60 days, whichever occurs fi rst. If service
is severe, grease more often. Do it gently with a hand gun.
Use #2 ball bearing grease for normal applications. For hot
or cold applications, use appropriate grease.
2. Packing Adjustment - Occasional packing adjustment
may be required to keep leak age to a slight weep; if im pos -
si ble to reduce leakage by gentle tightening, replace pack-
ing or use different type. See Technical Service Manual on
par tic u lar model se ries for details on repacking.
3. End Clearance Adjustment - After long service the run-
ning clearance between the end of the rotor teeth and the
head may have increased through wear to the point where
the pump is losing capacity or pressure. Resetting end clear-
ance will normally improve pump performance. See Tech ni cal
Service Manual on particular model series for pro ce dure on
adjusting end clear ance for the pump involved.
