FScurtis RS Series User manual

CAP303
REV Q
SEPT 2020
RS Series
OIL-INJECTEDROTARY SCREW COMPRESSORS
OPERATOR
MANUAL
RSB-15 RSB-20 RSB-25
RSB-30 RSB-40 RSB-50

CAP 303
SECTION 1
GENERAL SAFETY
As with any piece of rotating equipment
common sense and safety precautions
should be used in the operation of this rotary
screw air compressor. Carelessness can be
very hazardous to personnel.
In addition to the obvious safety rules, we
recommend additional safety precautions as
listed below. Please read and follow these
precautions for the safe day-to-day
operation of your compressor.
1. Read and understand all the instructions found in this manual before operating your compressor.
2. Disconnect the main power source before working on or performing any maintenance procedures
on this unit. Use a lock out and tag out process.
3. Do not attempt to remove any parts, break any connection, loosen oil fill plug or drain plug until the
unit has been shut down and air pressure has been relieved.
4. Do not operate the compressor in excess of its rated pressures and speeds indicated on the
compressor nameplate.
5. Do not remove guards, shields, or screens while the compressor is in operation. If removed for
maintenance replace before resuming operation.
6. Observe the delivery pressure gauge daily to be sure the automatic control system is operating
within proper limits.
7. Periodically check all safety and relief devices for proper operation.
8. Use compressed air properly. Pressurized air can cause serious injury to personnel.
9. Be sure that no tools, rags or loose parts are left in or on the compressor or drive parts.
10. Do not use flammable solvents for cleaning parts.
11. Exercise cleanliness during maintenance and when making repairs. Keep dirt away from parts and
exposed openings by covering with clean cloth or Kraft paper.
12. Do not install a shut-off valve in the discharge line without installing a pressure relief valve
between the shut-off and the compressor package.
13. Do not operate the compressor in areas where there is a possibility of flammable or toxic
substances entering the system.
14. Never disconnect (or jump) the air discharge temperature switch or any other safety device and
attempt to operate the compressor.
15. Know what mode of operation the compressor is in before working around the unit. The power
may be on but the machine not running if it is in the auto restart mode. Adhere to note #2 above..
Make sure to follow the local code
requirements in your area to ensure
compliance prior to installing the
compressor.
The owner, lessor or operator of this
compressor is hereby notified and fore-
warned that failure to observe these
safety precautions may result in injury
and/or property damage.
Curtis-Toledo does not mean to imply that
the preceding list of safety precautions is all-
inclusive or that the observance of this list
will prevent all injury or property damage.
Cutis-Toledo expressly disclaims respon-
sibility or liability for any injury or property
damage caused by failure to follow these
specified precautions or by failure to exer-
cise ordinary caution and due care required
in operating or handling this equipment even
though not expressly specified.
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CAP 303
2
SAFETY DECALS
Your compressor is posted with several safety
decals to inform the user of hazards associated
with its operation. These decals are positioned
where the hazard is most prevalent on the
compressor. Refer to the figures below for the
decals used and their location on the
compressor.
Figure 1-1
Safety Decal Locations
(Open units)

CAP 303
3
Figure 1-2
Safety Decal Locations
(Enclosed units)

CAP 303
SECTION 2
GENERAL DESCRIPTION
COMPRESSOR
The compressor assembly is an oil flooded
positive displacement, single stage, helical
screw type unit consisting of two rotors or
screws supported axially by roller bearings and
enclosed in a housing or stator as depicted in
the sectional view Figure 2-1.
Figure 2-1
Compressor Assembly
In operation as depicted below in the
compression cycle (Ref. Figure 2-2), air
entering the compressor through the inlet
port becomes trapped between the helical
lobes of the main rotor and the matching
grooves of the secondary rotor (A). As the
rotors turn air is trapped in the cavity created
by the meshing lobe and groove and
reduced in volume or “compressed”. It is
then pushed through the successive cavities
(B) until it reaches the discharge end of the
compressor (C) and is sent to the oil
separator.
During the compressor cycle, oil is injected
into the compressor for the purpose of
dissipating the heat of compression and to
seal the internal clearances. The
compressed air laden with oil leaves the
compressor through the discharge port and
enters a reservoir where the oil and air are
separated. This process delivers a smooth
flow of compressed air at the desired
pressure.
INLET
DISCHARGE
MAIN ROTOR
SECONDARY
ROTOR
ABC
Figure 2-2
Compression Cycle
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CAP 303
AIR/OIL FLOW
Air enters the compressor through the air filter
and air inlet valve and into the air end where it is
mixed with oil. After compression the air/oil
mixture is discharged into the oil separator
where its velocity is reduced causing most of the
oil to drop to the bottom. The remaining oil is
removed as the air passes through the separator
element. Oil collected at the bottom of the
separator element is returned to the inlet of the
compressor through the scavenger line that is
equipped with a sight glass for monitoring the
flow of oil to determine when separator
replacement is necessary. The coalesced air
then passes through the minimum pressure
valve set to maintain a minimum of 65-70 PSI in
the oil separator to ensure a sufficient flow of oil
to the compressor. The compressed air then
enters the aftercooler where it is cooled and
discharged into the compressed air system.
A sufficient amount of oil is stored in the oil
separator tank and is forced by the pressure of
compression from the separator to the thermal
by-pass valve, which regulates its flow into the
oil cooler depending on the temperature of the
oil. The thermal by-pass valve will open when
the oil reaches a predetermined temperature
allowing the hot oil to enter the cooler. Oil, which
has not reached this temperature setting, will by-
pass the cooler.
The oil is then filtered and sent to the
compressor to initiate the compression cycle.
The oil also serves as lubrication for the
compressor bearings.
Air/Oil Flow
Figure 2-3
5

CAP 303
SECTION 3
INSTALLATION
GENERAL
Upon receipt of your compressor, inspect for
freight damage. Report any damage as soon as
possible. See “FREIGHT DAMAGE PROCED-
URES” at the end of this section.
We recommend that the compressor remain on
its shipping skid until it reaches the final
installation site.
The base of the compressor is equipped with
lifting notches for forklift removal from the
shipping skid. If a crane is used to lift the
compressor we recommend the use of a
spreader bar and chains
Allow at least three (3) feet clearance on all
sides of the compressor to facilitate
maintenance and allow for free circulation of air.
The unit should be located in a clean, well-
lighted area that will not be exposed to ambient
temperatures exceeding105°F.
LOCATION
Your Curtis Rotary Screw compressor unit does
not require a special foundation to operate.
However, it is necessary that the floor be level
and that the base of the unit be adequately
supported. Consult the “SPECIFICATIONS”
section of this manual for the weight and
dimensions of your model. We also recommend
the compressor be bolted to the floor.
OUTDOOR INSTALLATION – The standard
R/S Series was designed for indoor applications
only. Installation in an outdoor, unsheltered area
should be avoided. The unit must be protected
against rain, snow and freezing temperatures. If
outdoor installation is unavoidable contact the
factory for modifications. Failure to obtain factory
approval will void the warranty.
Lift the compressor unit by the base plate
only. Do not attempt to lift the unit using such
places as the motor, compressor or discharge
piping as lifting points.
Any unsheltered installation must have at least
the following modifications:
•NEMA 4 controls
•TEFC motors
•Weather resistant cabinet
•Freeze protection (If applicable, see “COLD
WEATHER OPERATION”)
COLD WEATHER OPERATION – The unit
should be installed inside a shelter heated to
temperatures above freezing (32° F). If
installation must be in an unheated area the
following conditions must be met to keep the
compressor warranty intact:
The eyebolts provided on the motor are for 1. All control lines and drain lines must be
heated to avoid freezing.
lifting the motor only and should not be used to
lift any additional weight. All eyebolts must be 2. The oil separator must be heated to
maintain viscosity during idle periods.
securely tightened. When lifting the motor the
lifting angle must not exceed 15°. Failure to 3. FS CURTIS MaxFluid FSC-8000
synthetic oil must be used.
observe this warning may result in damage to
the equipment and/or personal injury.
Low temperature kits are available through the
factory. Contact your local FS Curtis compressor
distributor for details.
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CAP 303
INLET AIR
A clean air supply is required for the satisfactory
operation of your compressor.
The inlet air filter supplied with the compressor
is of sufficient size and design to meet all normal
operating conditions
\
If it is necessary for inlet air to be taken from an
outside source, the piping should be at least the
diameter of the air filter inlet. If the distance is
over twenty (20) feet the diameter needs to be
enlarged to reduce restriction. The piping must
be corrosion resistant and cleaned thoroughly
after fabrication. The inlet must be protected to
prevent rainwater and small animals from
entering the inlet piping.
AIR DISCHARGE
Your compressor is equipped with an oil/air
cooler. On air-cooled units the cooling fan is of
sufficient size to provide adequate cooling of the
compressed air and the compression oil passing
through this cooler. We recommend a thorough
cleaning of the cooler fins periodically by
vacuum or compressed air to insure a restriction
free flow of air from the cooling fan through the
oil/air cooler.
WATER-COOLED UNITS
The cooling water supply should be checked to
make sure the flow is sufficient. The chart shown
in Figure 3-1 lists approximate minimum water
flow rates in U.S. gallons per minute at various
temperatures into the heat exchanger(s). The
water flow rate shown will cool the compressor
oil to approximately 140° F. The compressor
discharge temperature should be maintained at
160° F to 180° F under most conditions. The
water outlet temperature from the heat
exchanger will be approximately 110° F, which is
the maximum recommended to prevent heat
exchanger tube fouling and corrosion. Higher
than listed water flow rates will decrease the
water outlet temperature.
Inlet air must not contain any flammable
or toxic gases. These gases will be
concentrated by the compressor and
could result in property damage, personal
injury or death.
Inlet air containing reactive gases will
cause failure of the lubricant and
compressor. Insure an air supply that is
well clear of any reactive gases.
HP Inlet Water Temperature
60°F 70°F 80°F 90°F
15 1.6 2.0 2.8 4.0
20 2.2 2.8 3.7 5.5
25 2.8 3.3 4.3 6.5
30 3.1 4.0 5.5 8.0
40 4.4 5.5 7.3 1.0
50 5.5 6.5 8.5 13.0
Figure 3-1
Water Flow Rates (U.S. gal/min)
The size of the incoming water supply piping
should be at least equal to the connections
provided with the compressor.
ELECTRICAL CONNECTIONS
All internal wiring has been done at the factory.
Wiring of the power supply to the compressor
should be done by a qualified electrician to
comply with the National Electric Code, state
code and any local codes in accordance with the
wiring diagram specific to your compressor
model shown in the “SPECIFICATIONS” section
of this manual.
Inadequate airflow will cause the
compressor to run hot which can cause
damage to the compressor and increase
oil carryover.
Water-cooled units must not be exposed to low
temperatures below 40°F, 4.4°C.
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CAP 303
The power supply should be adequate and free
of parasitic loads that will cause an under
voltage condition during compressor operation.
The power source should be connected through
a fusible disconnect and properly grounded in
accordance with the National Electric Code and
any other applicable codes.
We recommend the use of time delay fuses in
the fusible disconnect for isolating the unit. Per
the National Electric Code the fuse should be
sized at 175% of the full load amp draw. Consult
the Code if using another style of branch circuit
protection.
COMPRESSOR ROTATION
After the electrical wiring has been properly
connected check for proper rotation by
momentarily starting and stopping the motor. A
directional arrow is affixed to the compressor
drive end.
OIL LEVEL CHECK
Electrical shock can cause severe injury
or death. Disconnect all power supplies,
lockout and tag before working on unit.
Your compressor was shipped from the factory
charged with the correct amount of compressor
oil. However, the oil level must be checked at
installation and again prior to start-up. The
combination oil fill and sight glass is located on
the side of the separator tank. The oil level
should be at the center of the mark when the
unit is off (Figure 3-2).
Oil level must be at
center of sight glass
Failure to properly ground the
compressor package could result in
controller malfunction. Figure 3-2
Oil Fill – Sight Glass
STORAGE
In some cases it may be necessary to store the
compressor for extended periods of several
months before putting it into service. When this
is required observe the following
recommendations.
1. Cover and seal all machine openings to
prevent the entrance of water and dirt.
2. Cover all openings in open drip proof
motors.
3. If the storage conditions are below freezing,
drain the aftercooler, traps, water-cooled
heat exchangers and associated piping. We
do not recommend outside storage.
4. Cover with a waterproof tarpaulin that can
easily be removed for in storage inspection
and maintenance.
Reverse rotation will cause air end damage.
Never allow the compressor to run in
reverse rotation as property damage or
personal injury may occur.
5. While in storage, rotate the compressor and
motor by hand every thirty to sixty days to
prevent flat spots on the bearings that can
lead to premature failure.
At the end of the storage period follow the
uncrating and start-up procedures. If the unit has
been stored for more than eighteen months
contact the factory before starting the
compressor
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CAP 303
FREIGHT DAMAGE PROCEDURES
1. The customer or his agent MUST inspect
each shipment for damage at the receiving
point.
2. If the shipment is damaged, the customer
should so note the damage on the freight
bill.
3. The customer should request an inspector
from the freight carrier to inspect the
equipment immediately. It is best to send a
confirming letter with the following
information.
a. Freight bill number.
b. Date delivered.
c. Shippers name and address.
d. Description of damage (a photograph if
possible).
e. A copy of your invoice for the equipment
4. After inspection (before the inspector
leaves).
a. Get a copy of the inspection report.
b. Request the unit be shipped back to
the factory at the freight carrier’s
expense.
c. Request a credit for the original
freight bill.
5. Call the factory and:
a. Get a Return Material Authorization
(RMA) number.
b. Give a purchase order for repair. The
P.O. should refer to the item and
trucker claim.
6. Curtis-Toledo will accept the shipment back,
repair the damage (under normal conditions)
and return the unit within (7) working days.
7. We will invoice the customer for the repair,
which will then become part of your claim.
The invoice must be presented to the freight
carrier’s claim department along with their
completed claim form.
If the damage can be repaired at the receiving
point, follow procedure steps 1 through 4a.
Repair the unit and present a detailed invoice to
the freight carrier showing labor hours, labor
rate, materials used and cost of the materials.
9

SECTION 4 CAP 303
10
OPERATION
GENERAL
Every Curtis Rotary Screw compressor has been
pre-wired for the voltage specified at the time the
order was placed.
The unit has been thoroughly tested at the factory
to assure it will operate at its rated capacity and
is in good working order. The user needs only to
connect the unit to the correct power supply and
to the compressed air system (and to the
appropriate water supply on water cooled units,
refer to SECTION 3 “INSTALLATION”).
The purpose of this section is to familiarize the
user with the controls, their function and how they
operate. We strongly suggest that you read and
understand this section before starting your
compressor.
OPERATING MODES
The RS Series compressors are equipped with
an automatic dual control operating system
consisting of a load/unload control (constant) and
a start-stop control with delay off timer
(automatic). These control methods are achieved
through the use of a pressure switch, a two-
position selector switch, a three way normally
open solenoid valve and a two way air operated
blow down valve shown schematically in
Figure 4-9 “Load/ Unload Control”.
The mode of operation is selected using the
switch marked CONST/AUTO located on the
compressor control panel (Figure 4-1).
Figure 4-1
Control Panel
LOAD/ UNLOAD CONTROL
Selecting the CONST position puts the unit into
the load/ unload control mode which allows the
motor to run continuously while the compressor
loads and unloads as determined by the high and
low settings of the pressure switch. This mode of
operation is best used in high air demand
systems to reduce energy consumption.
START – STOP CONTROL
With the selector switch in the AUTO position the
motor is allowed to start and stop as dictated by
the pressure switch. When system pressure
reaches the high setting of the pressure switch a
timer is energized which will shut down the unit
after a selected time period (factory set at 10
minutes) if system pressure does not fall to the
low setting of the pressure switch. If the system is
allowed to shut down the amber standby light on
the control panel will illuminate to alert personnel
that the unit may restart at any time. When the
system pressure does fall to the low setting the
unit will restart turning off the standby light.
Hours

CAP 303
MINIMUM PRESSURE VALVE
An internally loaded check valve that prevents
the back flow of air from system pressure when
the unit stops, unloads or is shut down. This
valve also maintains approximately 65 PSI in the
oil reservoir (Figure 4-2).
THERMOSTATIC CONTROL VALVE
This valve, located in the oil return line (Figure
2-3), incorporates a thermostat to control the
temperature of the compressor lubricant.
When the compressor is started and the unit is
cold the valve is open to the by-pass at port B
allowing the oil entering at port A to flow directly
from the oil separator tank through the oil filter to
the compressor.
As the oil heats up the thermostat senses the
temperature and gradually closes the valve to
port B and opens it to port C through which the
heated oil will flow to the oil cooler before
entering the oil filter and compressor. The
thermostat is fully opened at 170° F to prevent
moisture contamination in the oil system (Figure
4-3).
OUT
IN
Figure 4-2
Minimum Pressure Valve
Figure 4-3
C
B
AA
B
C
TO COOLER
BY-PASS
INLET INLET
PISTON
SPRING
THERMOSTAT SLEEVE
PORT
OPEN TO COOLER
OPEN TO BY-PASS
Thermostatic Control Valve
11

CAP 303
INITIAL START-UP
After completing the initial start-up checks, as
noted in SECTION 3 “INSTALLATION”, the
machine is ready to start. Turn the switch
marked UNLOAD /LOAD to the unload position
then press the START button. When the unit
reaches full speed and separator pressure
reaches 25-30 PSI, turn the UNLOAD/LOAD
switch to the load position (Figure 4-1). The
minimum pressure valve will allow 65 PSI to
build in the oil separator tank before permitting
air to flow downstream.
Watch the following measurements carefully at
the instrument panel while the compressor is
running:
1. Compressor discharge temperature should
range between 160° to 180° F when running
at full speed.
2. Oil separator tank pressure should be
approximately 1-2 PSI higher than system
gauge pressure.
3. Receiver pressure should register actual
system pressure – approximately 1-2 PSI
lower than separator tank pressure.
SHUTTING DOWN THE COMPRESSOR
Before shutting down the compressor, turn the
UNLOAD/LOAD switch to unload and allow the
separator tank time to blow down i.e. 45 to 60
seconds. When the separator tank pressure
gauge reads 30-40 PSIG press the Stop button
to turn off the compressor.
Failure to follow this procedure when
shutting down the compressor will lead to oil
carry over.
12

CAP 303
13
Figure 4-4
Flow Diagram
Load/Unload Control

CAP 303
SECTION 5
MAINTENANCE
GENERAL
Your Curtis Rotary Screw Compressor has been
designed to require a minimum amount of
maintenance. However, as with any piece of
mechanical equipment, the implementation of a
good maintenance program is recommended for
smooth day-to-day operation of your compressor
and for the longevity of your compressed air
system.
This section will provide the user with instructions
for maintenance and/or replacement of the
serviceable components.
NOTE: Some components of your unit may be
equipped with service indicators that alert the user
when service on these items is required
AIR FILTER
Frequency of servicing the air filter will depend on
the environmental conditions under which the
compressor is operating. Service the air filter
element under any of the following conditions,
whichever comes first.
•Check the air filter element weekly and
change if outside surface of the element
appears to be coated with dust.
•Change every two thousand (2000) hours
of operation or every six (6) months.
•Under unusually dirty ambient conditions
change the element as required.
•When differential pressure gauge reads 25”
H2O vacuum, service is required.
Standard air filter replacement (Figure 5-1)
1. Clean the exterior surfaces of the filter
canister.
2. Loosen the wing nut and remove the air filter
cover.
3. Remove the element and clean the interior
surfaces.
4. Inspect and/or replace the element.
5. Replace the cover and retighten the wing nut.
*Consult the appropriate parts list for
element part number
COV
WING
ELE
BASE
ER
NUT
MENT*
PRE-
ELEM
FILTER
ENT
Before performing any maintenance be sure
the electrical supply has been disconnected,
locked and tagged and that all pressure has
been relieved from the compressed air
system.
Figure 5-1
Heavy-Duty air filter replacement (Figure 5-2)
1. Clean the exterior surfaces of the filter
canister.
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Cap 303
15
2. Remove the filter cover.
3. The heavy-duty filter consists of two
elements, a main element with a safety
element inside. Remove the element then
the main element form the filter body.
4. Using a damp cloth clean the interior
surfaces of the filter body and cover. Do not
attempt to blow dirt out with compressed air.
5. Inspect and/or replace the elements.
6. Replace the cover and tighten the wing nut.
7. Reset the maintenance indicator if applic-
able.
BODY
SAFETY ELEMENT
MAIN ELEMENT
COVER
*Consult the appropriate parts list for
element part numbers
Figure 5-2
Air filter inspection and cleaning
It is recommended that the air filter element(s)
be changed every six (6) months or 2000 hours.
However the filter element(s) should be
inspected and cleaned if necessary on a weekly
basis in conjunction with your maintenance
program. Instructions for inspecting the
element(s) are as follows:
1. Shine a bright light through the element from
the inside to inspect for damage. If cracks or
pinholes are detected, discard the element.
2. If element(s) appear in good condition return
them to the filter housing per previous filter
replacement instructions.
LUBRICANT
Your compressor has been tested and shipped
with a full charge of FS CURTIS LUBEPLUS
FSC-8000 synthetic oil. This lubricant has been
specially formulated to extend the service life of
your compressor and is formulated for high
temperature operation, easy start-up when cold,
reduced sludge and lacquer buildup and is
completely compatible with all seals, gaskets
and other compressor materials.
Change the lubricant as noted in the
“Maintenance Schedule” located on page 26 of
this manual. Between changes check the oil
level daily and add as necessary.
When operating in severe conditions it will be
necessary to change the lubricant more
frequently. Temperature of operation has the
most significant effect on the life of the lubricant.
The following chart shows the decrease in
interval based on temperature.
Checking level and adding compressor oil.
(Ref. Figure 5-3)
1. Shut down the unit.
2. Wait one (1) minute after the compressor
stops to allow the pressure to be relieved
and the lubricant to settle.
3. Observe the lubricant level. It should be at
the center of the sight glass.
4. To add lubricant, disconnect the power,
lockout and tag to prevent accidental
restarting.
5. Clean dirt from around the fill cap.
Discharge
Temperature
FSC-8000
Up to 180° F
8000 Hrs.
180° to 190° F
6000 Hrs.
190° to 200° F
4000 Hrs.
200° to 210° F
2000 Hrs.
Hot oil under pressure can cause severe
injury, death and/or property damage. Be
sure the compressor is shutdown and the
pressure is relieved before attempting to
change or add lubricant.

CAP 303
16
6. Loosen the cap and make sure any additional
pressure is relieved through the vent holes,
then remove.
7. Add lubricant to the proper level.
8. Replace cap and tighten securely.
Figure 5-3
Changing lubricant (Ref. Figure 5-3)
1. Shut down the unit, disconnect the power,
lockout and tag to prevent accidental
restarting.
2. Wait one (1) minute after the compressor
stops to allow the pressure to be relieved.
3. Clean the dirt from around the fill plug.
4. Loosen the fill plug and make sure any
additional pressure is relieved through the
vent hole, then remove.
5. Remove the drain plug from the end of the
drain line at the bottom of the separator tank.
6. Open the ball valve and allow the oil to drain.
7. When the oil has completely drained close
the ball valve and replace the drain plug.
8. Refill with FS CURTIS LUBERPLUS FSC-
8000 Compressor lubricant. (Consult the
specifications section for the proper amount
of lubricant for your model).
9. Replace the fill cap and tighten securely.
10. Restart the unit and allow the lubricant to
circulate through the system.
11. Shutdown the unit and follow the steps for
checking the lubricant level.
Oil filter replacement
Change the oil filter element after the first five
hundred (500) hours of operation. Then under
any of the following conditions:
Every six (6) months or two thousand (2000)
hours whichever occurs first
Every lubricant change
When differential pressure gauge reads 15
PSID.
Change as follows: (Ref. Figure 5-4)
1. Shut down the unit, disconnect the
power, lockout and tag to prevent
accidental restarting.
2. Wait one (1) minute after the compressor
stops to allow for the pressure to be
relieved.
3. Using a strap wrench remove the old
filter from the filter head.
4. Clean the gasket contact surface on the
inside of the filter head.
5. Apply a light film of the compressor oil to
the gasket surface on the new element.
6. Hand tighten the new element until the
gasket is seated in the gasket groove.
7. Continue tightening the element by hand
an additional ½ to ¾ turn.
8. Restart the unit and check for leaks.
Do not attempt to remove the fill cap, drain
plug or any other components while the
compressor is running or pressurized.
FILL CAP
SIGHT GLASS
DRAIN VALVE
DRAIN PLUG
Over filling the oil reservoir can cause oil
carryover and damage the compressor. Do
not fill above the full mark in the sight
glass.
Mixing lubricants can damage the
compressor and will void the warranty. Use
only FS CURTIS lubricants.

CAP 303
*Consult appropriate parts list for correct
element part number.
Figure 5-4
SEPARATOR ELEMENT
The air/oil separator element never “wears out”
but it does lose its effectiveness due to being
plugged with dirt. To obtain long separator life, it
is important to change the air inlet filter and the
lubricant filter as suggested in the maintenance
schedule.
Change the separator element under any of the
following conditions, whichever comes first:
•Whenever pressure drop between system
and separator exceeds 10 PSI.
•Once a year.
•Every four thousand (4000) hours.
•When excessive oil appears in the air
discharge line.
•When differential pressure gauge reads 10
PSID.
Separator element replacement
(Ref. Figure 5-5)
1. Shut down the unit; disconnect the power,
lockout and tag to prevent accidental restart.
2. Allow one (1) minute after the compressor
stops to allow the pressure to be relieved and
the oil in the sump to settle.”
FILTER
ELEMENT*
GASKET
FILTER HEAD
(W/ BY-PASS)
SET 25 PSI 3. Disconnect the main air line and the
scavenger tube from the separator cover.
4. Disconnect the control air lines after noting
their connection points. Tag the lines if
necessary.
5. Use a suitable wrench and remove the bolts
that hold the separator cover and lift the
cover from the separator tank.
6. Lift the element up and out of the separator
tank and discard.
7. Carefully lower the new element into the
separator tank and center.
8. Clean and replace the cover, align the holes
and install the bolts. Tighten the bolts in a
cross pattern to prevent over tightening one
side of the cover (See bolt torque
specifications).
9. Install the main air line and the control air
lines.
10. Install the scavenger tube making sure the
end is touching the bottom of the separator
element.
11. Clean the orifice located at the end of the
scavenger tube where it enters the inlet valve
or air end.
12. Reconnect the power, restart the unit and
check for leaks.
Separator, piping and control lines may be
very hot immediately after shut down. Allow
the unit to cool before attempting service.
SCAVENGER LINE OIL SIGHT GLASS
During loaded operation there should be a visible
mist of lubricant in the sight glass. If no flow is
visible then the orifice is blocked or restricted.
The orifice is located in the scavenger line were it
enters the inlet valve or air end. (Ref. Figure 5-5)
NOTE: After installation of a new separator
element, lubricant will not necessarily appear in
the sight glass for the first several hours of
operation. If clogging is suspected remove the
orifice and clean in a suitable solvent.
17

CAP 303
SCAVENGER TUBE
COVER BOLT
ELEMENT*
SIGHT GLASS
SEPARATOR
TANK
ORIFICE
COVER
*Consult appropriate parts list for element
part number Figure 5-5
THERMOSTATIC CONTROL VALVE
In normal operation the thermostatic valve controls
the oil temperature and prevents moisture
contamination of the oil. Malfunction of this valve
may result in moisture in the oil system that can
damage the compressor and cause oil carry-over.
A failure of the element in the closed position will
divert the lubricant from the oil cooler and result in
the unit shutting down due to high temperature.
A repair kit is available for this valve to replace the
wearable components. Consult the parts list for
your compressor to obtain the part number for this
repair kit.
Thermostatic Control Valve Repair
(Figure 5-6)
1. Place a spill pan under the valve.
2. Remove the snap ring from the top of
the valve body. The valve is spring
loaded and the cap may pop up when
the ring is removed.
3. Remove the cap and internal parts
taking care to note the orientation of the
spring, piston and element.
4. Reassemble with the renewal parts.
Take care when replacing the cap not to
cut the “O” ring or put undue stress on
the attached piping.
5. Replace any lost lubricant.
6. Return the unit to service.
SNAP RING
CAP
O RING
SLEEVE
SPRING
BODY
PISTON
W/ ELEMENT
Figure 5-6
MINUMUM PRESSURE VALVE
Before performing any maintenance be sure
the electrical supply has been cut off, locked
The minimum pressure valve is a non-adjustable
spring loaded check valve designed to maintain
a minimum of 65 PSI in the separator tank.
and tagged and that all pressure has been
relieved from the compressor system.
18

CAP 303
19
Air exiting the vent hole in the cap indicates “O”
ring failure, allowing air to leak into the spring
cavity inside the cap, which will effect the
operation of the valve.
Consult the appropriate parts list for part number
of the kit available to repair this valve, depicted
in Figure 5-7, as follows.
1. Carefully unscrew the spring loaded valve
cap.
2. Remove the piston and seat assembly.
3. Inspect the valve body for scratches and
deterioration of the seating surfaces.
4. Replace the “O” ring on the piston taking
care not to damage it.
5. Reassemble the piston with the new seat
assembly and spring and replace in the
valve body.
6. Replace the spring and tighten the cap.
7. Return the unit to service
Figure 5-7
INLET VALVE
See CAP303-1 Manual Supplement.
DRIVE SYSTEM
Routine examination of the drive system is
recommended to insure maximum compressor
life. Check the belts weekly for condition and
tightness. The slack created by initial operation
should be taken up after the first one hundred
(100) hours.
Do not operate the compressor with the fan
or belt guard removed. Exposed fan and
belts can cause injury to personnel.
Check and tighten the belts as follows:
(Ref. Figure 5-8)
1. Disconnect the power, lock out and tag out,
and allow all pressure to be relieved.
2. Remove the belt guard.
3. Inspect for any fraying or cracking. If found
replace the belts. (See “Belt Replacement”)
4. Check the tension. The deflection should be
about 1/64” per inch of span between the
sheaves with about 4-6 pounds of downward
force.
5. To adjust the tension, loosen the bolts
holding the motor to the slide base and
using the take-up bolts move the motor until
the belts are tight per number 4 above, then
retighten the motor bolts.
6. Replace the belt guard and return the
compressor to service.
BODY
CV ASSEMBLY
CV SPRING
PISTON
O RING
SPRING
CAP
Before performing any maintenance be sure
the electrical supply has been cut off, locked
and tagged and that all pressure has been
relieved from the compressed air system.
Changing the belts: ( Ref. Figure 5-8)
1. Disconnect the power and relieve all
pressure to the system.
2. Remove the belt guard.
3. Loosen the bolts holding the motor to the
slide base.
4. Using the take-up bolts move the motor
toward the air end to relieve the tension.
5. Remove the belts.