Corken 91 Instruction manual

Model 491-107
Installation, Operation
& Maintenance Manual
Plain Style Compressors for Liquid
Transfer-Vapor Recovery
Solutions beyond products...
ORIGINAL INSTRUCTIONS IE101K
Warning: (1) Periodic inspection and maintenance of Corken products is essential. (2) Inspection, maintenance and installation of
Corken products must be made only by experienced, trained and qualified personnel. (3) Maintenance, use and installation of Corken
products must comply with Corken instructions, applicable laws and safety standards. (4) Transfer of toxic, dangerous, flammable or
explosive substances using Corken products is at user’s risk and equipment should be operated only by qualified personnel according
to applicable laws and safety standards.

Warning
Install, use and maintain this equipment according to Corken’s instructions and all applicable federal, state, local laws
and codes. Periodic inspection and maintenance is essential.
Corken One Year Warranty
CORKEN, INC. warrants that its products will be free from defects in material and workmanship for a period of
one year from date of installation, provided that the warranty shall not extend beyond twenty-four (24) months from
the date of shipment from CORKEN. If a warranty dispute occurs, the DISTRIBUTOR may be required to provide
CORKEN with proof of date of sale. The minimum requirement would be a copy of the DISTRIBUTOR’S invoice to
the customer.
CORKEN products which fail within the warrant period due to defects in material or workmanship will be repaired or
replaced at CORKEN’s option, when returned, freight prepaid to CORKEN, INC., 3805 N.W. 36th St., Oklahoma City,
Oklahoma 73112.
Parts subject to wear or abuse, such as mechanical seals, blades, piston rings, valves and packing, and other parts
showing signs of abuse, neglect or failure to be properly maintained are not covered by this limited warranty. Also,
equipment, parts and accessories not manufactured by CORKEN but furnished with CORKEN products are not
covered by this limited warranty and the purchaser must look to the original manufacturer’s warranty, if any. This
limited warranty is void if the CORKEN product has been altered or repaired without the consent of CORKEN.
All implied warranties, including any implied warranty of merchantability or fitness for a particular purpose, are
expressly negated to the extent permitted by law and shall in no event extend beyond the expressed warranty period.
CORKEN DISCLAIMS ANY LIABILITY FOR CONSEQUENTIAL DAMAGES DUE TO BREACH OF ANY WRITTEN OR
IMPLIED WARRANTY ON CORKEN PRODUCTS. Transfer of toxic, dangerous, flammable or explosive substances
using CORKEN products is at the user’s risk. Experienced, trained personnel in compliance with governmental and
industrial safety standards should handle such substances.
Important notes relating to the European Union (EU) Machinery Directive
Pumps delivered without electric motors are not considered as machines in the EU Machinery Directive. These
pumps will be delivered with a Declaration of Incorporation. The fabricator of the machinery must assure and declare
full compliance with this Directive before the machine in which the pump will be incorporated, or of which it is a part,
is put into service.
Contacting the Factory
Before you contact the factory, note the model number and serial number of your pump. The serial number directs
us to a file containing all information on material specifications and test data applying to your specific pump. When
ordering parts, the Corken service manual or Operations, Installation and Maintenance (IOM) manual should be
consulted for the proper part numbers. ALWAYS INCLUDE THE MODEL NUMBER AND SERIAL NUMBER WHEN
ORDERING PARTS.
The model and serial numbers are shown on the nameplate of the unit. Record this information for future reference.
Model No.
Serial No.
Date Purchased
Date Installed
Purchased From
Installed By
2

Table of Contents
Chapter 1—Introduction........................................................................4
1.1 Liquid Transfer By Vapor Differential Pressure ...................................................5
1.2 Residual Vapor Recovery....................................................................5
1.3 Compressor Construction Features ...........................................................6
Chapter 2—Installing Your Corken Compressor....................................................8
2.1 Location .................................................................................8
2.2 Foundation ...............................................................................8
2.3 Piping ...................................................................................8
2.4 Liquid Traps .............................................................................11
2.5 Driver Installation / Flywheels ...............................................................12
2.6. Crankcase Lubrication ....................................................................12
2.7 Relief Valves .............................................................................14
2.8 Truck Mounted Compressors ...............................................................15
2.9 Shutdown/Alarm Devices...................................................................15
Chapter 3—Starting Up Your Corken Compressor.................................................16
3.1 Inspection After Extended Storage ...........................................................16
3.2 Flywheel and V-belt Alignment ..............................................................16
3.3 Crankcase Oil Pressure Adjustment ..........................................................16
3.4 Startup Check List ........................................................................17
Chapter 4—Routine Maintenance Chart .........................................................18
Chapter 5—Routine Service and Repair Procedures...............................................18
5.1 Valves ..................................................................................18
5.2 Heads..................................................................................20
5.3 Piston Rings and Piston Ring Expanders ......................................................20
5.4 Pistons .................................................................................21
5.5 Piston Rod Packing Adjustment .............................................................22
5.6 Cylinder and Packing Replacement ..........................................................22
5.7 Bearing Replacement for Crankcase and Connecting Rod ........................................25
5.7.1 Wrist Pin Bushing Replacement ..........................................................25
5.7.2 Replacing Connecting Rod Bearings ......................................................25
5.7.3 Replacing Crankcase Roller Bearings .....................................................25
5.8 Oil Pump Inspection ......................................................................26
Chapter 6—Extended Storage Procedures .......................................................27
6.1 Repair Kits ..............................................................................27
6.2 Gasket Sets .............................................................................28
Appendices
A. Model Number Identification Code and Available Options..........................................30
B. Specifications ............................................................................32
C. Compressor Selection......................................................................38
D. Outline Dimensions ........................................................................42
E. Parts Details .............................................................................58
Model 91 and F91 .........................................................................58
Model 291 and F291 .......................................................................66
Model 491 and F491 .......................................................................74
Model 691 and F691 .......................................................................82
Model D891 and FD891 ....................................................................90
F. Troubleshooting ...........................................................................98
3

Connections:
Available in threaded NPT or Class 300
RF flanges.
High-efficiency valves:
Valves are quiet and highly durable. Special
suction valves tolerating small amounts of
condensate are available.
O-ring seals:
Easy to install O-ring seals head and cylinder.
Ductile iron construction:
Cylinder and head are made of ductile iron
for maximum thermal shock endurance.
Self-lubricating PTFE piston rings:
State-of-the-art piston ring designs to
provide the most cost-effective operation
of compressors for non-lube service. The
step-cut design provides higher efficiencies
during the entire life of the piston ring.
Positively locked piston:
Simple piston design allows end clearance
to be precisely set to provide maximum
efficiency and long life.
Piston rod seals:
Seals constructed of PTFE incorporating
special fillers to maximize leakage control.
Spring loaded seal design self adjusts to
compensate for normal wear.
Nitrotec
®1 coated piston rods:
Impregnated nitride coating provides
superior corrosion and wear resistance.
Cast-iron crosshead:
Durable cast-iron crossheads provide
superior resistance to corrosion and galling.
Pressure-lubricated crankcase with filter:
Self-reversing oil pump ensures proper
lubrication regardless of directional rotation to
main and connecting rod bearings. Standard
10-micron filter ensures long-lasting bearing
life (not available on Model 91).
1 Registered trademark of TTI Group Ltd.
Chapter 1—Introduction
Construction Details—Model F291 Compressor
4

1.1 Liquid Transfer By Vapor
Differential Pressure
Corken LPG/NH3compressors are designed to transfer
liquefied gases such as butane/propane mixtures
(liquefied petroleum gas or LPG) and Anhydrous Ammonia
(NH3) from one tank to another. Liquefied gases such as
LPG and NH3are stored in closed containers where both
the liquid and vapor phases are present.
Figure 1.1A: Typical nameplate
(also serves as the packing adjusting screw cover)
There is a piping connection between the vapor
sections of the storage tank and the tank being
unloaded, and there is a similar connection between
the liquid sections of the two tanks. If the connections
are opened, the liquid will seek its own level and
then flow will stop; however, by creating a pressure
in the tank being unloaded which is high enough
to overcome pipe friction and any static elevation
difference between the tanks, all the liquid will be
forced into the storage tank (see figure 1.1B). The
gas compressor accomplishes this by withdrawing
vapors from the storage tank, compressing them
and then discharging into the tank being unloaded.
This procedure slightly decreases the storage tank
pressure and increases the pressure in the other tank,
thereby causing the liquid to flow.
The process of compressing the gas also increases the
temperature, which aids in increasing the pressure in the
tank being unloaded.
1.2 Residual Vapor Recovery
The principle of residual vapor recovery is just the
opposite of liquid transfer. After the liquid has been
transferred, the four-way control valve (or alternate
valve manifolding) is reversed so that the vapors are
drawn from the tank just unloaded and discharged into
the receiving tank. Always discharge the recovered
vapors into the liquid section of the receiving tank.
This will allow the hot, compressed vapors to condense,
preventing an undesirable increase in tank pressure (see
figure 1.2A).
Residual vapor recovery is an essential part of the value
of a compressor. There is an economical limit to the
amount of vapors that should be recovered, however.
When the cost of operation equals the price of the
product being recovered, the operation should be
stopped. For most cases in LP-Gas and Anhydrous
Ammonia services, this point is reached in the summer
when the compressor inlet pressure is 40 to 50 psig
Figure 1.1B: Liquid transfer by vapor differential pressure.
Compressor reduces
pressure in storage tank
by removing vapor
Compressor increases
pressure in tank car by
adding vapor
Pressure difference between
tanks causes liquid to flow out of
the tank car into the storage tank
Four Way Valve Position 1
Vapor Line
Vapor Line
Liquid Line
5

Vapor is
bubbled
through liquid
to help cool and
recondense it
Removing vapor from
tank causes liquid heel
to boil into vapor
Liquid line is valved closed
during vapor recovery.
Four Way Valve Position 2
Vapor Line
Vapor Line
Liquid Line
(3.8 to 4.5 bars). A good rule of thumb is not to operate
beyond the point at which the inlet pressure is one-
fourth the discharge pressure. Some liquids are so
expensive that further recovery may be profitable, but
care should be taken that the ratio of absolute discharge
pressure to absolute inlet pressure never exceeds 7 to
1. Further excavation of very high value products would
require a Corken two-stage gas compressor.
Invariably, there is some liquid remaining in the tank
after the liquid transfer operation. This liquid “heel”
must be vaporized before it can be recovered, so
do not expect the pressure to drop immediately.
Actually, more vapor will be recovered during the first
few minutes while this liquid is being vaporized than
during the same period of time later in the operation.
Remember that more than half of the economically
recoverable product is usually recovered during the
first hour of operation on properly sized equipment.
1.3 Compressor
Construction Features
The Corken liquid transfer-vapor recovery compressor
is a vertical single-stage, single-acting reciprocating
compressor designed to handle flammable gases
like LPG and toxic gases such as ammonia. Corken
compressors can handle these potentially dangerous
gases because the LPG/NH3is confined in the
compression chamber and isolated from the crankcase
and the atmosphere. A typical liquid transfer-vapor
recovery compressor package is shown in figure 1.3A.
Figure 1.3A: 107-style compressor mounting.
Corken gas compressors are mounted on oil lubricated
crankcases remaining at atmospheric pressure. Crankshafts
are supported by heavy-duty roller bearings and the
connecting rods ride the crankshaft on journal bearings.
With the exception of the small size model 91 compressor,
all compressor crankcases are lubricated by an automotive
type oil pressure system. An automatically reversible gear
Figure 1.2A: Residual vapor recovery.
6

type oil pump circulates oil through passages in the
crankshaft and connection rod to lubricate the journal
bearings and wrist pins (see figure 1.3B). Sturdy iron
crossheads transmit reciprocating motion to the piston.
Corken’s automatically reversible oil pump design
allows the machine to function smoothly in either
direction of rotation.
Corken compressors use iron pistons locked to the piston
rod. The standard piston ring material is a glass-filled
PTFE polymer specially formulated for non-lubricated
services. Piston ring expanders are placed behind the
rings to ensure that the piston rings seal tightly against
the cylinder wall.
Figure 1.3B: Pressure lubrication system (not available on Model 91).
Piston rod packing is used to seal the gas in the
compression chamber and prevent crankcase oil from
entering the compressor cylinder. The packing consists
of several PTFE V-rings sandwiched between a male and
female packing ring and held in place by a spring (see
figure 1.3C).
The typical Corken compressor valve consists of a seat,
bumper, one or more spring/s and one or more valve/s
discs or plates as shown in figure 1.3D. Special heat-
treated alloys are utilized to prolong life of the valve in
punishing non-lubricated services. The valve opens
whenever the pressure on the seat side exceeds the
pressure on the spring side.
Gasket
Adjusting
screw
Relief ball spring
Relief ball
Suction valve
seat
Valve plate
Spacers
Washer
Spacers
Washer
Valve spring
Suction valve
post
Suction valve
bumper
Valve gasket
Gasket
Bolt
Discharge valve
bumper
Valve spring
Valve plate
Discharge valve
seat
Valve gasket
Suction Valve
Spec 3
Discharge Valve
All Specs
Figure 1.3C: Compressor sealing system
Figure 1.3D: Compressor sealing system
7

Chapter 2—Installing Your Corken
Compressor
2.1 Location
NOTE: Compressor must be installed in a well
ventilated area.
Corken compressors are designed and manufactured
for outdoor duty. For applications where the compressor
will be subjected to extreme conditions for extended
periods such as corrosive environments, arctic
conditions, etc., consult Corken. Check local safety
regulations and building codes to assure installation will
meet local safety standards.
Corken compressors handling toxic or flammable
gases such as LPG/NH3should be located outdoors. A
minimum of 18 inches (457.2 mm) clearance between the
compressor and the nearest wall is advised to make it
accessible from all sides and to provide unrestricted air
flow for adequate cooling.
NOISE. Corken vertical compressors sizes model 91
through 891 should not exceed an 85 DBA noise level at
a distance of one meter (3.3 ft.) when properly installed.
2.2 Foundation
Proper foundations are essential for a smooth running
compression system. The concrete slab should be
at least 8 inches thick with a 2 inch skirt around the
circumference of the baseplate. The total mass of the
foundation should be approximately twice the weight of
the compressor system (compressor, baseplate, motor,
etc.). For Models 91, 291, 491, and 691, the baseplate
should be secured to the foundation using 1/2" diameter
x 12" long “J” bolts. Use 3/4" x 12" anchor bolts for 891.
NOTE: Be sure to use all anchor holes.
Hex nut
Washer
Compressor
baseplate
NOTE: Locate “J” bolts per compressor outline
dimension drawings.
8" minimum
Grout beneath
base
1/2"“J” bolts
12"long
2" minimum
all sides
Concrete foundation
with reinforcements
should be used on
all models
Figure 2.2A: Recommended foundation details for Corken
compressors 91–691.
After leveling and bolting down baseplate and/or skid,
the volume beneath the channel iron baseplate must
be grouted to prevent flexing of the top portion of the
baseplate and the “J” bolt that extends beyond the
foundation. The grout also improves the dampening
capabilities of the foundation by creating a solid interface
between the compressor and foundation.
See ED410: Compressor Foundation Design for more
information.
2.3 Piping
Proper piping design and installation is as important as
the foundation is to smooth operation of the compressor.
Improper piping installation will result in undesirable
transmission of compressor vibration to the piping.
DO NOT SUPPORT PIPING WITH THE COMPRESSOR.
Unsupported piping is the most frequent cause of
vibration of the pipe. The best method to minimize
transmission of vibration from the compressor to the
piping is to use flexible connectors (see figure 2.3A).
Concrete
foundation
Grouted
baseplate
Pipe
support
Pipe
support
Flexible
connections
Flexible
connections
Ground level
Baseplate should
be a maximum
of 4"high
Figure 2.3A: On –107 mountings, the flexible connectors should be
located near the four way valve.
Pipe must be adequately sized to prevent excessive
pressure drop between the suction source and the
compressor as well as between the compressor and the
final discharge point. In most cases, piping should be
at least the same diameter as the suction nozzle on the
compressor. Typically, LPG/NH3liquid transfer systems
should be designed to limit pressure drops to 20 psi (1.4
bar). Appendix C shows recommended pipe sizes for
each compressor for typical LPG/NH3installations.
Care must be taken if a restrictive device such as a valve,
pressure regulator, or back-check valve is to be installed
in the compressor’s suction line. The suction line volume
between the restrictive device and the compressor suction
nozzle must be at least ten times the swept cylinder volume.
See Appendix B for details on cylinder and stroke.
8

107 style compressors are usually connected using a five-
valve (figure 2.3B) or three-valve manifold (figure 2.3C).
The five-valve manifold allows the storage tank to be
both loaded and unloaded. The three-valve manifold only
allows the storage tank to be loaded. Adequate sizing of
the liquid and vapor lines is essential to limit the pressure
drop in the system to a reasonable level (20 psi or less).
The line size helps determine the plant capacity almost
as much as the size of the compressor, and liquid line
sizes are a bigger factor than vapor lines. If the pressure
gauges on the head indicate more than a 15 to 20 psi
(1.0 to 1.4 bars) differential between the inlet and outlet
pressures, the line sizes may be too small or there is too
much piping restriction. The less restriction in the piping,
the better the flow. Appendix C shows recommended
pipe sizes for typical LPG/NH3compressor installation.
A tank car unloading riser should have two liquid hoses
connected to the car liquid valves. If only one liquid
hose is used, the transfer rate will be slower and there
is a good possibility that the car’s excess flow valve
may close.
Since the heat of compression plays an important part in
rapid liquid transfer, the vapor line from the compressor to
the tank car or other unloading container should be buried
or insulated to prevent the loss of heat and the compressor
should be located as near as possible to the tank being
emptied. In extremely cold climates, if the line from the
storage tank to the compressor is over 15 feet (4.6 meters)
long, it should be insulated to lessen the possibility of
vapors condensing as they flow to the compressor. The
vapor recovery discharge line should not be insulated.
Placing the compressor as close as possible to the tank
Hydrostatic relief valve Back check valve
Relief valve
4-Way valve
C
Vapor line to liquid phase
in storage tank
B
Vapor line to truck
trailer or tank
(local transport)
Vapor line to
rail car
(inbound bulk
transport)
Vapor line to gas phase
in storage tank
D
E
A
Bury or
insulate in
cold climate
areas
4-Way Valve
Position 1
E B
D A C
4-Way Valve
Position 2
Service to Perform Valve Position
4-way A B C D E
1. Unload tank car
into storage tank
Position
One Open Open Close Close Close
2. Recover vapors
from tank car into
storage tank
Position
Two Close Open Open Close Close
3. Unload transport
or truck into
storage tank
Position
One Open Close Close Close Open
4. Recover vapors
from transport or
truck into storage
tank
Position
Two Close Close Open Close Open
5. Load truck or
field tank from
storage tank
Position
Two Open Close Close Close Open
6. Load truck or field
tank from tank car
Position
One Close Open Close Open Close
7. Equalize between
tank car and
storage tank
without using
vapor pump
—Open Open Close Open Open
8. Equalize between
truck or field tank
and storage tank
without using
vapor pump
—Open Close Close Open Close
4-way Valve Operation
Figure 2.3B: Five valve manifold piping system.
9

being unloaded will minimize heat loss from the discharge
line for the best liquid transfer rate.
Unloading stationary tanks with a compressor is quite
practical. Delivery trucks and other large containers can
be filled rapidly if the vapor system of the tank to be
filled will permit fast vapor withdrawal, and if the liquid
piping system is large enough. Many older trucks (and
some new ones) are not originally equipped with vapor
excess flow valves large enough to do a good job and
these should be replaced by a suitable size valve. The
liquid discharge should be connected to the tank truck
pump inlet line rather than the often oversized filler valve
connection in the tank head.
It is of extreme importance to prevent the entry of
liquid into the compressor. The inlet of the compressor
should be protected from liquid entry by a liquid trap
(see section 2.4). It is of equal importance to protect the
discharge of the compressor from liquid. This may be
done by installing a check valve on the discharge and
designing the piping so liquid cannot gravity-drain back
into the compressor. Make sure to install a check valve
on vapor lines discharging to the liquid space of the tank.
All piping must be in accordance with the laws and codes
governing the service. In the United States, the following
codes apply:
For LP-Gas — The National Fire Protection Association
Pamphlet No. 58, Standard for the Storage and Handling
of Liquefied Petroleum Gases.
For Ammonia — The American National Standards
Institute, Inc., K61.1-1999, Storage and Handling of
Anhydrous Ammonia.
Back check valve
Hydrostatic releif valve
A
B
C
Vapor line rail car
(in-bound
bulk transfer)
Bury or insulate in
cold climate areas
4-Way valve
Relief valve
Vapor line to gas
phase in storage
Vapor line to liquid
phase in storage
4-Way Valve
Position 1
B
A C
4-Way Valve
Position 2
Service to
Perform
Valve Position
4-way A B C
1. Unload
tank car into
storage tank
Position
One Open Open Close
2. Recover
vapors from
tank car into
storage tank
Position
Two Close Open Open
4-way Valve Operation
Figure 2.3C: Three valve manifold piping system.
10

109 and 107 compressor mountings (see Appendix D for
details on standard Corken compressor mountings).
When the compressor will not be under more-or-less
constant observation an automatic trap is recommended.
The automatic trap replaces the float with electrical float
switches. If the liquid level should rise too high, the level
switch will open and disconnect the power to the motor
starter, stopping the compressor. This design ensures
the machine will be protected even when it is not under
close observation and is standard in the 109A and 107A
mounting configurations.
Corken’s most sophisticated trap provides the most
thorough liquid separation. This trap is larger and is
ASME code stamped. It contains two level switches, one
for alarm and one for shutdown. In some cases the alarm
switch is used to activate a dump valve (not included
with trap) or sound an alarm for the trap to be manually
drained by the operator. This trap also contains a mist
pad. A mist pad is a mesh of interwoven wire to catch fine
liquid mists. The ASME code trap is standard in the 109B
and 107B mounting configurations.
A typical wiring diagram for the liquid level switch is
shown in figure 2.4B.
Install, use and maintain this equipment according to
Corken instructions and all applicable federal, state, and
local laws and previously mentioned codes.
2.4 Liquid Traps
Compressors are designed to pressurize gas, not to pump
liquids. The entry of even a small amount of liquid into the
compressor will result in serious damage to the compressor.
On liquefied gas applications, a liquid trap must be used
to prevent the entry of liquid into the compressor.
Corken offers three types of liquid traps for removal of
liquids in the gas stream (see figure 2.4A). The simplest is
a mechanical float trap. As the liquid enters the trap the
gas velocity is greatly reduced, which allows the liquid
to drop out. If the liquid level rises above the inlet, the
float will plug the compressor suction. The compressor
creates a vacuum in the inlet piping and continues to
operate until the operator manually shuts it down. The
trap must be drained and the vacuum-breaker valve
opened before restarting the compressor, to allow the
float to drop back. This type of trap is only appropriate
for use where the operator keeps the compressor under
fairly close observation. This trap is provided with the
Figure 2.4A: Liquid traps.
Standard liquid trap with
mechanical float assembly
and drain valve.
Sizes: • 1-1/4" x 1-1/4" NPT
• 1-1/4" x 1-1/2" NPT
Automatic liquid trap, with one
NEMA 7 liquid-level switch for
compressor shutdown and
drain valve.
Sizes: • 1-1/4" x 1-1/4" NPT
• 1-1/4" x 1-1/2" NPT
Class 300 RF flange code-stamped
automatic liquid trap with two NEMA 7 liquid-
level switches for compressor shutdown and
alarm. Equipped with relief valve, pressure
gauge, demister pad, and drain valve.
Sizes: • 1-1/2" x 1-1/2" NPT
• 2" x 2" Class 300 RF flange
Standard Liquid Trap Automatic Liquid Trap ASME Automatic Liquid Trap
11

Typical Float Switch Wiring Diagram
1 = Common, black
2 = Normally closed, blue
3 = Normally open, red
Figure 2.4B: Typical float switch wiring diagram.
NOTE: The level switch MUST be removed from
the trap before grounding any welding devices to
the trap or associated piping! Failure to do so will
damage the switch contacts.
If your compressor is equipped with a liquid trap
of other than Corken manufacture, make sure it is
of adequate size to thoroughly remove any liquid
present in the suction stream.
2.5 Driver Installation / Flywheels
Corken vertical compressors may be driven by either
electric motors or combustion engines (gasoline, diesel,
natural gas, etc.). Corken compressors are usually V-belt
driven but they are also suitable for direct drive applications
as well. Direct drive applications require an extended
crankshaft to allow the attachment of a rigid metal coupling.
Note: Flexible couplings are not suitable for reciprocating
compressors. Never operate a reciprocating compressor
without a flywheel.
Drivers should be selected so the compressor operates
between 350 to 825 RPM. The unit must not be operated
without the flywheel or severe torsional imbalances will result
that could cause vibration and high horsepower requirement.
The flywheel should never be replaced by another pulley
unless it has a higher WK
2value than the flywheel.
A humid climate can cause problems, particularly in
explosion proof motors. The normal breathing of the
motor, and alternating between being warm when running
and being cool when stopped, can cause moist air to be
drawn into the motor. This moist air will condense, and
may eventually add enough water inside the motor to
cause it to fail. To prevent this, make a practice of running
the motor at least once a week on a bright, dry day for an
hour or so without the V-belts. In this period of time the
motor will heat up and vaporize the condensed moisture,
driving it from the motor. No motor manufacturer will
guarantee their explosion proof or totally enclosed
(TEFC) motor against damage from moisture.
For installation with engine drivers, thoroughly review
instructions from the engine manufacturer to assure the
unit is properly installed.
2.6. Crankcase Lubrication
Non-detergent oil is recommended for Corken vertical
compressors. Detergent oils tend to keep wear particles
and debris suspended in the oil, whereas non-detergent
oils let them settle in the bottom of the crankcase.
When non-detergent oils are not available, detergent
oils may usually be successfully substituted, although
compressors handling ammonia, amine, or imine gases
are notable exceptions. These gases react with the
detergent and cause the crankcase oil to become
corrosive and contaminated. Figures 2.6A and 2.6B show
recommended oil viscosities and crankcase capacities.
Acceptable Crankcase Oil Products
for Corken Compressors
Constant Weight - Non-Detergent - R&O Inhibited
Oil product ISO VI SAE Ambient Temp.
Exxon®
TERESSTIC
100 95 30 65° – 100° F
68 95 20+ 45° – 70° F
46 95 20 35° – 50° F
Mobil®
RARUS 427
Reciprocating
Compressor Oil
100 95 30 65° – 100° F
DTE Oil Heavy Medium 68 95 20+ 45° – 70° F
Dectol R&O Oil 46 95 20 35° – 50° F
Conoco®
Dectol R&O Oil
100 98 30 65° – 100° F
68 97 20+ 45° – 70° F
46 99 20 35° – 50° F
Texaco®
Regal R&O Oil
100 92 30 65° – 100° F
68 97 20+ 45° – 70° F
46 102 20 35° – 50° F
Sun®
SunVis 900 Oil
100 100 30 65° – 100° F
68 100 20+ 45° – 70° F
46 100 20 35° – 50° F
Figure 2.6A: Oil selection chart.
Compressor
Model
Approximate
Quarts Capacity Liters
91 0.9 0.8
291 1.5 1.4
491 3.0 2.8
691/891 7.0 6.6
Figure 2.6B: Oil capacity chart.
Synthetic lubricants are generally not necessary. Please
consult your lubricate supplier if you are considering the
use of synthetic oil. To add oil, remove the name plate
and pour through the opening.
General Notes on Crankcase Oil
Corken gas compressors are used for a wide variety of
gases in a multitude of operating conditions. They are
used in all areas of the world from hot dusty deserts, to
humid coastal areas, to cold arctic climates. No single
crankcase oil or maintenance schedule is right for every
compressor installation. Availability of brands and grades
12

of oil varies from one location to another. These factors
can make it challenging for a Corken compressor user to
select a suitable crankcase oil.
It is safe to say that purchasing a quality crankcase oil,
and changing it regularly, is significantly less costly than
the repair bill and downtime associated with a lubrication
failure in any gas compressor. Given the relatively
small volume of oil used in the crankcase of a Corken
compressor, and the critical nature of the services
where these compressors are typically used, selecting
the appropriate high-quality oil is the most economical
choice. It will help ensure the dependability and longevity
of the compressor.
Oils to Avoid
Selecting a crankcase oil based on low price or easy
availability is seldom the most economic decision.
Following are oils to avoid.
• Do not use engine/motor oil with an API Service SA
through SH.
• Do not use any oil with a viscosity index below 95.
• Do not use any oil with a pour point less than 15ºF
(8ºC) lower than the anticipated minimum ambient
temperature (unless a crankcase oil heater is used).
See below for additional detail on each of these parameters.
Industrial Oils
Corken recommends using industrial oils (rather than
engine oil or “motor oil”). Industrial oils have additives
specifically selected and blended for specific purposes.
Many are designed specifically for the conditions
inherent in compressor crankcases. Such industrial
oils are required for Corken compressors operating in
continuous duty or heavily loaded applications.
Industrial oils do not receive an API service designation
like an engine oil does.
Critical Oil Characteristics
Viscosity
The viscosity of a crankcase oil is a measure of its
resistance to flow. Viscosity is the most important
physical property of lubricating oil. Oils with higher
viscosity (ISO 100 and ISO 150) are thicker and are
used for higher ambient temperatures. Oils with lower
viscosity (ISO 68, ISO 46, and ISO 32) are thinner and
are used at lower ambient temperatures. However, oils
with a high viscosity index (see below) can be used at
wider ambient temperature range compared to oils with
a lower viscosity index.
Viscosity Index
Viscosity Index (VI) is a measure of how much the
oil’s viscosity changes as its temperature changes. A
low viscosity index is an indication that the viscosity
changes more as the temperature changes. A high
viscosity reflects a more stable viscosity, and is generally
preferred for Corken compressors.
Oil with a low viscosity index tends to thin out as the oil
temperature increases. This can cause lubrication failure
as well as unstable oil pressure. The minimum Viscosity
Index for oils used in Corken compressors is 95 (VI is
a unit-less number). This is particularly important when
operating at high or low temperature extremes, or at a
variety of ambient temperatures (seasonal changes).
Pour Point
The pour point of an oil is the lowest temperature at
which the oil flows. At temperatures below the pour
point, the oil is very thick and can’t freely flow to the
compressor’s bearings and other wear surfaces, or even
to the compressor’s oil pump.
In low ambient temperature operation, the oil’s pour point
is critical. An oil should have a pour point at least 15ºF
(8ºC) below the lowest expected ambient temperature.
For example, if the minimum ambient temperature is
expected to be 0ºF (-18ºC), the pour point must be no
higher than -15ºF (-26ºC).
Do not assume the pour point of an oil is low enough.
Consult the oil’s technical data sheet. Many oils have a
pour point around 0 to 10ºF (-18 to -12ºC) which is too
high for low ambient temperatures. Synthetic oils often
have a lower pour point than conventional oils.
Engine Oils (Motor Oils)
Engine oils are formulated for use in internal combustion
engines and contain additives that specifically counter
the contaminants created by the combustion of fuel
(soot, CO2, water, etc.). A gas compressor crankcase
is a different environment than an engine crankcase.
Thus, engine oils are not necessarily the best oils to use
in a gas compressor. They are by far the most readily
available oils.
If a suitable industrial oil is not available, engine oils can be
used in Corken compressors used in intermittent service.
Heavily loaded compressors or those in continuous duty
service should always use high quality industrial oil. If
engine oil is used, it is critical that the engine oil have an
adequate API Service Grade.
13

API Service
The American Petroleum Institute (API) grades motor
oils (oils designed for use in engines in cars and trucks)
with a two letter classification. Oils with API grades “SA”
through “SH” are obsolete and should never be used
in modern engines or gas compressors. Unfortunately,
motor oils with an “SA” and “SB” ratings are still readily
available at parts stores, service stations, and other
retail outlets at low prices. These are low quality oils and
should NEVER be used in Corken compressors. If motor
oil is used in a Corken compressor, it should have an
API Service of SJ or better. Multigrade motor oils such
as 10W-40 tend to have a higher viscosity index.
A
P
I
S
E
R
V
I
C
E
S
N
E
N
E
R
G
Y
C
O
N
S
E
R
V
I
N
G
SAE
5W-30
API (American
Petroleum Institute) Quality rating
Service classification
S=gasoline engine
C=diesel engine
Example of API “Donut” symbol used on motor oil.
Oil suppliers post product data sheets on line that
contain various physical properties of the oil , and the
API Service classification. If there is any doubt, do not
use the oil.
Oil Change Intervals
Oil change intervals can vary significantly depending
on local environmental conditions, the gas being
compressed, and the oil being used. Unless there are
factors that shorten the life of the oil, the following
recommendations apply:
Conventional oil: 2200 hours or 6 months – whichever
comes first
Synthetic oil: 6000 - 8000 hours* or one year –
whichever comes first
*Oil change intervals in this range should be confirmed via oil analysis.
Factors that shorten the life of the oil:
• Dirty or dusty environmental conditions that cause the
oil to become dirty or discolored
• Oil dilution caused by condensation or other liquids in
the gas stream (see below)
• Change in viscosity for any reason (various oil additives
can break down over time)
• Changing ambient temperature may cause the need for
a different viscosity
The oil should be changed as often as necessary
to maintain clean, undiluted oil. Each time the oil is
changed, the oil filter (Corken part number 4225) should
also be changed.
Ammonia Services
Never use a detergent oil in a compressor in ammonia
service. Ammonia will react with the detergent and cause
lubrication failure.
Oils that can be used in ammonia compressors:
• Royal Purple: Uni-Temp
• Phillips 66: Ammonia Compressor Oil
• Chevron: Capella P68
Crankcase Oil Heater Option
Corken offers a crankcase oil heater as an option on
all models except the small model 91. This heater is
available in 110V and 220V versions and is rated for Class
1, Division 1 and 2, Group B, C, D service. The heater
includes a thermostat set at 70°F (21.1°C).
If a crankcase heater is desired, it is best to order the
heater with the compressor (crankcase specification
“MH”). The mounting hole for the heater is not drilled
unless the heater is ordered with the compressor. It is
also possible to order the compressor with the hole
drilled (1" NPT), but without the heater (crankcase
specification “MR”). With this option, a customer can
supply their own heater.
2.7 Relief Valves
An appropriate relief valve must be installed at the
compressor discharge. On Corken 107-style mounted
units a relief valve should be fitted in the piping between
the compressor discharge and the four-way valve (see
figure 1.3A). Relief valves should be made of a material
compatible with the gas being compressed. Local codes
and regulations should be checked for specific relief
valve requirements. Also, relief valves may be required at
other points in the compressor’s system piping.
14

2.8 Truck Mounted Compressors
Corken compressors may be mounted on trucks to perform
liquid transfer operations as described in section 1.1. The
compressor should be mounted so the inspection plate is
accessible for packing adjustment. The compressor must
be protected against liquid as explained in section 2.4
and a relief valve must be installed in the discharge piping
before the first downstream shutoff valve.
Three types of mountings are typically used. The inside
mounting (figure 2.8A) drives the compressor directly off
the PTO shaft. The PTO must be selected to drive the
compressor between 400 and 800 RPM. An extended
compressor crankshaft is required so the U-joint yoke
may connect to the compressor without removing the
flywheel. Do not operate the compressor without a
flywheel. Use a U-joint with a splined joint and make sure
the connections are parallel and in line. The U-joint angle
should be less than 15 degrees (see figure 2.8B). Always
use an even number of U-joints.
Figure 2.8A: Inside transport mounting.
Figure 2.8B: U-joint drive for compressor.
Depending on the truck design, the compressor may be
outside or top mounted as shown in figures 2.8C and
2.8D to be V-belt driven. Power is transmitted through
a U-joint drive shaft, jackshaft with two pillow block
bearings, V-belt sheave and V-belts. An idle pulley may
be used under the truck frame.
Figure 2.8C: Outside transport mounting
Figure 2.8D: Top transport mounting.
2.9 Shutdown/Alarm Devices
For many applications, shutdown/alarm switches will
provide worthwhile protection that may prevent serious
damage to your compressor system. All electronic
devices should be selected to meet local code
requirements. Shutdown/alarm devices typically used on
Corken compressors are as follows:
1. Low Oil Pressure Switch: Shuts down the unit if
crankcase oil pressure falls below 12 psi due to oil
pump failure or low oil level in crankcase. The switch
or the compressor controller must have a 30 second
delay on startup which allows the compressor to
build oil pressure in the crankcase.
2. High Discharge Temperature Switch: This switch
is strongly recommended for all applications. Both
the High Discharge Temperature switch (HDT) and
compressor have an operating pressure range. It is
preferable that the switch set point be midpoint in its
range and 30°F (-1°C) above the normal discharge
temperature, but below the maximum design
temperature for the compressor of 350°F (176.7°C).
3. Low Suction Pressure Switch: Shuts down the
unit if inlet pressure is not within the preset limit (set
point). In some cases, it is important not to pull a
vacuum because of the potential of pulling oil from the
crankcase into the gas stream.
4. High Discharge Pressure Switch: Shuts down the
unit if the outlet pressure reaches a preset limit (set
point). Both the switch and the compressor have an
operating range. The set point of the pressure switch
should be as follows:
15

Greater than the normal operating pressure for the
compressor.
Less than 90% of the relief valve set point pressure.
Less than the maximum operating pressure of the
compressor.
Midpoint of the pressure switch range.
5. Vibration Switch: Shuts down the unit if vibration
becomes excessive. Recommended for units mounted
to a portable skid.
Chapter 3—Starting Up Your
Corken Compressor
NOTE: Before initial startup of the compressor be
sure the principal of using a compressor for liquid
transfer by vapor differential pressure is understood
(see section 1.1). Read this entire chapter, then
proceed with the startup checklist.
3.1 Inspection After
Extended Storage
If your compressor has been out of service for a long period
of time, you should verify the cylinder bore and valve areas
are free of rust and other debris (see chapter 5 of this IOM
manual for valve and/or cylinder head removal instructions).
Drain the oil from the crankcase and remove the
nameplate and crankcase inspection plate. Inspect the
running gear for signs of rust and clean or replace parts
as necessary. Replace the crankcase inspection plate
and fill crankcase with the appropriate lubricant. Squirt
oil on the crossheads and rotate the crankshaft by hand
to ensure that all bearing surfaces are coated with oil.
Rotate unit manually to ensure running gear functions
properly. Replace nameplate and proceed with startup.
3.2 Flywheel and V-belt Alignment
Before working on the drive assembly, be sure that the
electric power is disconnected. When mounting new
belts, always make sure the driver and compressor are
close enough together to avoid forcing.
Improper belt tension and sheave alignment can cause
vibration, excessive belt wear and premature bearing
failures. Before operating your compressor, check alignment
of the V-grooves of the compressor flywheel and driver
sheave. Visual inspection often will indicate if the belts are
properly aligned, but use of a square is the best method.
The flywheel is mounted on the shaft via a split, tapered
bushing and three bolts (refer to figure 3.2A). These bolts
should be tightened in an even and progressive manner until
torqued as specified below. There must be a gap between
the bushing flange and the flywheel when installation is
complete. Always check the flywheel runout before startup
and readjust if it exceeds the value listed in Appendix B.
Hub
Size
Diameter
in. (cm)
Bolt Torque
Ft-lb (kg-meter)
Set Screw
Torque Ft-lb
(kg-meter)
SF 4.625 (11.7) 12-18 (1.7–2.5) 22 (3.1)
E6.0 (15.2) 30-36 (4.1–4.9) 22 (3.1)
J7.25 (18.4) 75-81 (10.3–11.1) 10 9 (15.1)
Figure 3.2A: Flywheel installation.
Tighten the belts until they are taut, but not extremely
tight. Consult your V-belt supplier for specific tension
recommendations. Belts that are too tight may cause
premature bearing failure. Refer to figure 3.2B.
Figure 3.2B: Belt tension.
3.3 Crankcase Oil Pressure
Adjustment
Corken compressor models 291 through 891 are
equipped with an automatically reversible gear type oil
pump (if your compressor is the splash lubricated Model
16

91, proceed to section 3.4). It is essential to ensure
the pumping system is primed and the oil pressure is
properly adjusted in order to assure smooth operation.
Before starting your compressor, check and fill the
crankcase with the proper quantity of lubricating oil.
(Refer to section 2.6)
When the compressor is first started, observe the
crankcase oil pressure gauge. If the gauge fails to
indicate pressure within 30 seconds, stop the machine
and loosen the oil filter. Restart the compressor and run
until oil comes out and tighten the filter.
The oil pressure should be about 20 psi (1.4 bars)
minimum for normal service. If the discharge pressure
is above 200 psi (13.8 bars) the oil pressure must be
maintained at a minimum of 25 psi (1.7 bars). A spring-
loaded relief valve mounted on the bearing housing
opposite the flywheel regulates the oil pressure. As
shown in figure 3.3A, turn the adjusting screw clockwise
to increase the oil pressure and counterclockwise to
lower it. Be sure to loosen the adjusting screw locknut
before trying to turn the screw and tighten it after making
any adjustment.
Oil Pressure Gauge
Oil Level Bayonet
Lock Nut
Oil Pressure
Adjusting
Screw
+
-
Oil Pump Cover
Figure 3.3A: Oil pressure adjustment.
3.4 Startup Check List
Please verify all of the items on this list before
starting your compressor! Failure to do so may result
in a costly (or dangerous) mistake.
Before Starting the Compressor
1. Become familiar with the function of all piping
associated with the compressor. Know each line’s use!
2. Verify that actual operating conditions will match the
anticipated conditions.
3. Ensure that line pressures are within cylinder
pressure ratings.
4. Clean out all piping.
5. Check all mounting shims, cylinder and piping
supports to ensure that no undue twisting forces exist
on the compressor.
6. Verify that strainer elements are in place and clean.
7. Verify that cylinder bore and valve areas are clean.
8. Check V-belt tension and alignment. Check drive
alignment on direct drive units.
9. Rotate unit by hand. Check flywheel for wobble or play.
10.Check crankcase oil level.
11. Drain all liquid traps, separators, etc.
12. Verify proper electrical supply to motor and panel.
13.Check that all gauges are at zero level reading.
14. Test piping system for leaks.
15.Purge unit of air before pressurizing with gas.
16.Carefully check for any loose connections or bolts.
17. Remove all stray objects (rags, tools, etc.) from
vicinity of unit.
18.Verify that all valves are open or closed as required.
19. Double-check all of the above.
After Starting Compressor
1. Verify and note proper oil pressure. Shut down and
correct any problem immediately.
2. Observe noise and vibration levels. Correct
immediately if excessive.
3. Verify proper compressor speed.
4. Examine entire system for gas, oil or water levels.
5. Note rotation direction.
6. Check start-up voltage drop, running amperage and
voltage at motor junction box (not at the starter).
7. Test each shutdown device and record set points.
8. Test all relief valves.
9. Check and record all temperatures, pressures and
volumes after 30 minutes and 1 hour.
10.After 1 hour running time, tighten all head bolts, valve
holddown bolts, and baseplate bolts. See Appendix B
for torque values.
17

Item to Check Daily Weekly Monthly Six
Months Yearly
Crankcase oil pressure
Compressor discharge pressure
Overall visual check
Crankcase oil level 1 1
Drain liquid from accumulation points 2
Drain distance pieces
Clean cooling surfaces on compressor and
intercooler (if any)
Lubricator supply tank level (if any)
Check belts for correct tension
Inspect valve assemblies
Lubricate motor bearings in accordance with
manufacturers’ recommendations
Inspect motor starter contact points
Inspect piston rings
13
Chapter 4—Routine Maintenance Chart
1 Change oil every 2,200 hours of operation or every 6 months, whichever occurs first. If the oil is unusually dirty, change it as often as needed to maintain a
clean oil condition. Change replacement filter 4225 with every oil change.
2 Liquid traps should be drained prior to startup.
3 Piston ring life varies greatly, depending on application, gas, and operating pressures. Consult factory for additional recommendations for your specific
application.
Chapter 5—Routine Service and
Repair Procedures
CAUTION: Always relieve pressure in the unit
before attempting any repairs. After repair,
the unit should be pressure tested and checked for
leaks at all joints and sealing surfaces.
If routine maintenance is performed as listed in chapter
4, repair service on your Corken gas compressor is
generally limited to replacing valves or piston rings.
When it comes time to order replacement parts, be sure
to consult the part details appendix in the back of this
Installation, Operation & Maintenance (IOM) manual for a
complete list of part numbers and descriptions.
5.1 Valves
Test the compressor valves by closing the inlet piping
valves while the unit is running; however, do not allow
the machine to operate in this way very long. If the
inlet pressure gauge does not drop to zero almost
immediately, one or more of the valves is probably either
damaged or dirty. It is possible, of course, that the
pressure gauge itself is faulty.
Inspect valves for breakage, corrosion, debris, and
scratches on the valve disc. In many cases, valves may
simply be cleaned and reinstalled. If the valves show
any damage, they should be repaired or replaced.
Replacement is usually preferable, although individual
parts are available. If valve discs are replaced, seats
should also be lapped until they are perfectly smooth.
A maximum of .005 inch can be removed during the
lapping process. If more than .005 inch must be removed
to achieve a smooth surface, the valve should be
discarded. If discs are replaced without relapping the
seat, rapid wear and leakage may occur.
Each suction and/or discharge valve assembly is easily
removed as a unit for inspection. If any part of the valve
assembly is broken, the valve assembly should be replaced.
See valve assembly parts details in the appendices for a
complete list of part numbers and descriptions.
If a valve is leaking due to dirt or any other foreign
material that keeps the valve plate and seat from sealing,
the valve may be cleaned and reused. New gaskets and/
or O-rings should be used to assure a good seal.
The valve holddown assemblies and valve assemblies on
the following pages show the various specifications used
on models 91, 291, 491, 691 and 891 compressors. Since
more than one suction valve arrangement is available for
each model of compressor, it is necessary to know your
complete model number so you can identify the valve
18

type specification number (see examples listed below).
In most cases for liquid transfer and/or vapor recovery
compressors, the valve type will be spec 3 or 3P.
Model number 491AM 3 FBANSNN
Valve type = spec 3
Model number 691AM 3P FBANSNN
Valve type = spec 3P
Valve Holddown Assemblies: Depending on your model
of compressor, the valve holddown assembly has all or a
combination of the following:
1. Valve cap / cover
2. Valve cap O-ring
3. Holddown screw
4. Valve cover plate
5. Valve cover plate bolts
6. Valve cover plate O-ring
7. Valve spacer (model 491 only)
8. Valve cage
9. Valve assembly
10.Valve gasket
Valve Assemblies: Depending on your valve specification,
the valve assembly has all or a combination of the following:
1. Gasket
2. Adjusting screw
3. Relief ball spring
4. Relief ball
5. Valve seat
6. Valve plate
7. Spacers
8. Washer
9. Valve spring
10.Suction valve post
11. Valve bumper
12. Valve gasket
See valve holddown and valve assembly part details
in the appendix for a complete list of part numbers
and descriptions.
Valve Inspection and/or Replacement for Models
91 and 291 Compressors
Before removing and inspecting the valves, begin by
depressurizing and purging (if necessary) the unit.
Disassembly
1. Unscrew the valve cap and remove O-ring.
2. With the special wrench supplied with your compressor
at time of purchase, remove the holddown screw.
3. After the holddown screw has been removed, the
valve assembly and valve gasket can be lifted out.
4. Carefully inspect for dirt or broken/damaged parts.
5. Inspect valves for breakage, corrosion, debris and
scratches on the valve disc or plate. In many cases,
valves may simply be cleaned and reinstalled. If the
valves show any damage, they should be repaired or
replaced. Replacement is usually preferable although
repair parts are available. If valve plates are replaced,
seats should also be lapped until they are perfectly
smooth. If more than .005 in. must be removed
to achieve a smooth surface, the valve should be
discarded. If plates are replaced without relapping the
seat, rapid wear and leakage may occur.
Assembly
1. Insert metal valve gasket into the suction and/or
discharge opening of the head. The metal valve
gasket should always be replaced when the valve
is reinstalled.
2. Insert cleaned or new valve assembly. Make sure the
suction and discharge valves are in the proper suction
and discharge opening in the head. NOTE: The spec
3 suction valves for a model 91 and 291 compressor
are pre-set so no adjustments to liquid relief pressure
are necessary.
3. Replace the holddown screw and tighten to the value
listed in Appendix B to ensure the valve gasket is
properly seated. NOTE: Gaskets and O-rings are not
normally reusable.
4. Replace the O-ring and valve cap and tighten to the
value listed in Appendix B. O-rings sealing the valve
caps should be replaced.
5. Check bolts and valve holddown screws after first
week of operation. Re-torque if necessary. See
Appendix B for torque values.
Valve Inspection and/or Replacement for Models
491, 691 and 891 Compressors
Before removing and inspecting the valves, begin by
depressurizing and purging (if necessary) the unit.
19

Disassembly
1. Unscrew the valve cap/nut and remove the O-ring
from the coverplate.
2. Remove the valve cover plate, O-ring and holddown
screw by removing each of the four bolts. NOTE:
Since the holddown screw has been secured with an
impact wrench at the factory, you will probably need
to wait to remove the holddown screw until after the
cover plate has been removed. At this point in time,
the holddown screw can be easily removed from the
cover plate. The holddown screw on model 691 and
891 is most easily removed with the special wrench
supplied with your compressor at time of purchasing.
3. After the cover plate and O-ring have been removed,
the valve spacer (model 491 only), valve cage, valve
assembly and valve gasket can be lifted out.
4. Inspect valves for breakage, corrosion, debris,
and scratches on the valve plate. In many cases,
valves may simply be cleaned and reinstalled. If the
valves show any damage, they should be repaired or
replaced. Replacement is usually preferable although
repair parts are available. If valve plates are replaced,
seats should also be lapped until they are perfectly
smooth. If more than .005 in. must be removed
to achieve a smooth surface, the valve should be
discarded. If plates are replaced without relapping the
seat, rapid wear and leakage may occur.
Assembly
1. Insert metal valve gasket into the suction and/or
discharge opening of the head. The metal valve gasket
should always be replaced when the valve is reinstalled.
2. Insert cleaned or new valve assembly. Make sure the
suction and discharge valves are in the proper suction
and discharge opening in the head.
3. Insert the valve cage and valve spacer (NOTE: spacer
applies to model 491 compressor only).
4. Replace the O-ring and valve cover plate. Torque
bolts to the value listed in Appendix B. CAUTION: Be
sure the holddown screw has been removed.
5. Insert the holddown screw and tighten to the value
listed in Appendix B to ensure the valve gasket is
properly seated. NOTE: Gaskets and O-rings are not
normally reusable.
6. Replace the O-ring (or gasket) and valve cap/nut and
tighten to the value listed in Appendix B. O-rings
sealing the valve cap should be replaced if they show
signs of wear or damage. Valve caps sealed by flat
metals gaskets should be reinstalled with new gaskets.
7. NOTE: The Model 491 Spec 3 suction valve has an
adjusting screw to set the liquid relief pressure. To set
the liquid relief pressure, the screw bottom must be
tightened to 1.8" from the top of the valve body.
8. Check bolts and valve holddown screws after first
week of operation. Re-torque if necessary. See
Appendix B for torque values.
5.2 Heads
A compressor head very seldom requires replacement
if the compressor is properly maintained. The primary
cause of damage to a head is corrosion and the entry
of solid debris or liquid into the compression chamber.
Improper storage can also result in corrosion damage to
the head (for proper storage instructions see chapter 6).
Many compressor repair operations require removal of the
head. While the compressor is disassembled, special care
should be taken to avoid damage or corrosion to the head. If
the compressor is to be left open for more than a few hours,
bare metal surfaces should be coated with rust preventative.
When reassembling the compressor, make sure the bolts
are retightened as shown in Appendix B.
5.3 Piston Rings and Piston Ring
Expanders
Piston ring life will vary considerably from application to
application. Ring life will improve dramatically at lower
speeds and temperatures.
1. To replace the piston rings, depressurize the
compressor and purge if necessary.
2. Remove the head to gain access to the compressor
cylinder.
3. Loosen the piston head bolts. Remove the piston as
shown in figure 5.3A by pinching two loose bolts together.
Figure 5.3A: Piston removal
4. Piston rings and expanders may then be easily
removed and replaced. Corken recommends replacing
expanders whenever rings are replaced. To determine
if rings should be replaced, measure the radial
thickness and compare it to the chart in Appendix C.
20