Do not block the exhaust port. Pressure will build up with the
potential of oil case bursting with possible injury to personnel.
WARNING
Pumps being run continuously above 1 torr should use an
exhaust oil recycler.
WARNING
Pumps not recommended for filtration, aspiration or drying
electrophoresis gels.
Gardner Denver Welch Vacuum Technology, Inc.
5621 W. Howard Street
Niles, IL 60714
Phone: (847) 676-8800
Fax: (847) 677-8606 (Technical Support)
E-Mail: welchvacuum@gd-thomas.com Part No. 67-1483R2.5
Web-Page: www.welchvacuum.com Printed in USA
For outside of U.S. and Canada, contact your local
Gardner Denver sales office, see back page
INSTRUCTION
WARNING AND CAUTION
PLEASE READ BEFORE OPERATION
While reading your manual, please pay close attention to areas labeled:
WARNING AND CAUTION.
The description of each is found below.
WARNING
Warnings are given where failure to observe instruction could
result in injury or death to people.
CAUTION
Cautions are found where failure to observe the
instruction could result in damage to the equipment,
associated equipment and process.
These units conrm to the SI International system of units of measurement.
The following symbols (with recommendation of IEC1010 ) of warning will be found on the pump.
Caution - refer to accompanying documents
Caution - risk of electrical shock
Caution - hot surface
WARNING
Motor includes a self resetting thermal cutout and the pump could
restart without actuation under fault condition.
2
TABLE OF CONTENTS
SECTION PAGE
Section 01 - Installation 05
1.01 Unpacking 05
1.02 Pump Mounting 05
1.03 Pump Location / Environmental Conditions 05
1.04 Exhaust Provisions 05
1.05 Electric Power 06
1.06 Vacuum Connections 07
1.07 Vacuum Gauges 07
1.08 Vacuum Pump Oil 07
Section 02 - Pump Features & Principles of Operation 08
2.01 General Description 08
2.02 Principles of Vacuum Pump Operation 09
2.03 Effects of Continued Pressure Reduction 09
2.04 Ultimate Pressure 09
2.05 Pump Mechanism Description 09
2.06 Intake Anti-Suckback Protection 10
2.07 Pump Lubrication 10
2.08 Exhaust Filter 10
2.09 Gas Ballast Valve 10
2.10 UNIBARBTM Intake Fitting 11
Section 03 - Specications 12
3.01 Specication Chart 12
Section 04 - Motor Power Specications / Features 14
4.01 Motor Specications Chart 14
4.02 Changing the voltage setting; 8907, 8912 & 8917 “A” Models 15
4.03 Changing the voltage setting; 8907, 8912 & 8917 “C” Models 15
4.04 Changing the voltage setting; 8905, 8920 & 8925 “A” Models 16
(Includes instructions to attach solenoid valve)
4.05 Other Electrical Congurations 16
4.06 Explosion Proof Pumps 16
Section 05 - Operation 17
5.01 Starting Procedure 17
5.02 High Pressure Operation 17
5.03 Shutdown Procedures 17
3
TABLE OF CONTENTS
SECTION PAGE
Section 06 - Maintenance 18
6.01 Vacuum Problems 18
6.02 Oil Change 19
6.03 Developing a Maintenance Schedule 19
6.04 Lip Seal / Gasket Change 20
Section 07 - Trouble Shooting 24
7.01 Leak Detection Problems 24
7.02 Trouble Shooting Guide 25
Section 08 - Specications 26
8.01 Shaft Seal Replacement 26
8.02 Minor Repair Kits 26
8.03 Major Factory Repair 26
Section 09 - Accessories 27
9.01 Pump Oil 27
9.02 Exhaust Filter 27
Section 10 - Drawings and Speed Curve 28
10.10 Speed Curve 28
10.20 Dimensional Drawing 29
10.30 Pump Exploded Views and Parts List 30
10.40 Module Exploded Views and Parts List 36
10.50 Oil Case Exploded View and Parts List 39
Section 11 - Warranty 40
Section 12 - MSDS Sheet for 8995P 41
4
Section 1: INSTALLATION
1.01 Unpacking
Carefully remove the pump from the shipping carton. Keep all paperwork and inspection tags for future
reference. If shipping damage has occurred, a claim must be led with the carrier immediately; keep the
shipping container for inspection by the carrier.
1.02 Pump Mounting
Rubber bumpers are supplied with the pump base. They isolate noise and eliminate creeping. For more
rigid mounting requirements the pump base can be bolted directly to a surface by removing the bumpers
from the base and using the mounting holes and slots featured on the base.
1.03 Pump Location / Environmental Conditions
The pump should be located in a clean and well-ventilated area and adequate space should be provided
wherever possible for routine maintenance such as oil changes. For best performance, the pump should
be located as closely as possible to its system. Determining factors for pump location should include
length and size of connections, the number of bends, and the type of exhaust connections.
1.04 Exhaust Provisions
Exhaust connections will be determined by the type of system to be exhausted and the desired
cleanliness of the air surrounding the pump. Under normal pumping conditions the optional exhaust
lter will be adequate. Refer to Section 9, Accessories for available exhaust lters. Where extreme
exhaust conditions are encountered, it is best to pipe the exhaust out of the building. Always use thick
walled rubber vacuum hose, wire reinforced PVC tubing or metal pipe for exhaust lines to avoid the
possibility of the line becoming crimped or collapsing resulting in dangerous exhaust line blockage.
The exhaust connection is a 1”-20 threaded port for all Models except 8905 which is 3/4”-20. The port
is located on top of the oil reservoir. See section 9.02 Exhaust Filters to nd the correct lter for each
pump. If a hose nipple is preferred for the exhaust port, use part number 1393K for models 8907, 8912
and 8917.
Call Welch customer support (847) 676-8800, ext. 1, prior to start-up if you have any questions.
WARNING
Never block or impede air flow from the exhaust port. High
pressure can build up within the oil reservoir if the exhaust port
is blocked. Check frequently, especially if exhaust is piped
out of the building.
5
1.05 Electric Power
For Model 8905
Compare the pump motor rating, printed on a label on the side of the motor and on the serial number tag,
to the power source, to be sure they agree in voltage, phase, and frequency. Pump installation must
comply with local electrical codes which dictate appropriate protection devices such as fuses or circuit
breakers. Know the location of the circuit breaker protecting the electrical outlet for the pump.
For Models 8907, 8912 & 8917
Compare the pump motor rating, printed on a label on the side of the motor and on the serial number tag,
to the power source, to be sure they agree in voltage, phase, and frequency. Pump installation must
comply with local electrical codes which dictate appropriate protection devices such as fuses or circuit
breakers. Know the location of the circuit breaker protecting the electrical outlet for the pump.
Only the Models 8907C, 8912C and 8917C have “global motors” that operate over a wide range of
voltages (100-120V, 200-30V). They also operate at frequencies of 50Hz and 60 Hz.
Power is single phase.
For Models 8920 & 8925
Compare the pump motor rating, printed on a label on the side of the motor and on the serial number tag,
to the power source, to be sure they agree in voltage, phase, and frequency. Pump installation must
comply with local electrical codes which dictate appropriate protection devices such as fuses or circuit
breakers. Know the location of the circuit breaker protecting the electrical outlet for the pump.
CAUTION
Make certain the power settings on the pump match your power
source before attempting to operate the pump.
(Additional information can be found in section 4: Motor Power).
6
1.06 Vacuum Connections
TM
The pump inlet is equipped with a UNIBARB
7/16” and 13/16” hose tting. The inlet is located
next to the pump handle. It contains a screen to collect any debris from getting into the pump. An
extensive line of vacuum pump ISO ttings, hoses, traps, etc. is available from Welch to meet the
requirements of most vacuum systems. For the best vacuum, use a hose clamp in conjunction with a
vacuum hose to hose nipple connections. Welch offers a number of different types of vacuum tubing
and connectors.
See Section 9 - Accessories or call Welch customer support (847) 676-8800, Extension 1.
The choice of connections and ttings can have a very marked effect on the pumping speed at the
vacuum chamber. Any connection placed between the pump and the chamber creates an impedance to
the ow of gas. This is particularly true at low pressures in the millitorr range where the gas ow is
substantially molecular in character. The gas ow is then dependent upon the kinetic activity of the
molecules to bring it to the pump intake. This impedance is described by the term “conductance”.
The conductance of a tube is proportional to the cube of its diameter and inversely proportional to its
length. Therefore, connecting lines should be as large in diameter and as short in length as practical.
For best results the diameter of the connecting tube should be at least as large as the diameter of the
pump intake. To avoid a large reduction in pumping speed at the vacuum chamber, the conductance of
the line must be considerably greater than the speed of the pump. Sharp bends in vacuum lines also
contribute to conductance. To avoid reductions in pumping speed, minimize the number of 90º angles
in the vacuum system.
1.07 Vacuum Gauges
The type of vacuum gauge to be used in a system is determined largely by the pressure range to be
measured. A thermocouple or pirani gauge is recommended for measuring pressures in the range
produced by these pumps. See Website or call for additional information.
1.08 Vacuum Pump Oil
WARNING
The vacuum pump is shipped witout oil inside to prevent possible
spillage during shipment. Oil must be added prior to use.
Filling with Fresh Oil
Be sure the pump is lled with oil to the level indicated on the oil ll window. When additional oil is
required, use only DIRECTORR® Gold Vacuum Oil , pump performance is not guaranteed with other
brands of oil. Do not overll the pump, and be sure to replace the oil ll plug.
Remove the oil ll plug located on the top of the oil case and add the oil supplied in a bottle packaged
with each pump.
WARNING
Use only DIRECTORR® Premium or Gold Vacuum Pump Oil.
The ll plug has a raised middle section and a center slot for easy turning either by hand or with a
screwdriver. After the pump has been running for at least 15 minutes, check the oil level again. The oil
level should be maintained at the “full” mark on the oil level window while the pump is operating. Do
not overll, excess oil tends to be splashed out the pump exhaust.
Guidelines for the frequency of oil changes and the oil changing procedure can be found in
Section 6-2: Oil Change
7
Section 2: PUMP FEATURES AND PRINCIPLES OF OPERATION
2.01 General Description
All of the Welch Vacuum Pumps are two-stage, rotary-vane, oil sealed vacuum pumps.
These Vacuum Pumps offer a number of features that improve performance, or protect the pump or
vacuum system under specic operating conditions.
2.02 Principles of Vacuum Pump Operation
The main purpose of a vacuum pump is to reduce the pressure in a vessel or a closed system. The
degree of pressure reduction is dependent upon the requirements of the application and the type of
vacuum pump employed. Rotary vane, oil-sealed vacuum pump operation is described in this section.
Pressure reduction in a closed system is accomplished by repeatedly removing a portion of the
original volume of gas contained in the system. Removal is performed by the action of the rotating
elements of the pump which cause a given space to be successfully enlarged and diminished. Figure 2.1
illustrates a section through a typical stage of rotary-vane pump. Note that this gure is not intended to
illustrate exactly the internal components of the pumps; its purpose is to illustrate the general operating
principles of vacuum pumps.
The rotary action of the pump creates a hollow space of chamber (1) which expands as the pump rotates.
As the chamber expands, the pressure in the chamber decreases. As a result, gas is drawn into the
chamber due to the difference in pressure between the chamber and the inlet (4) to the chamber. (The
inlet is the only place where gas can ow into the chamber.) Once the vane (3) moves past the inlet (4),
it seals the inlet against the chamber (1) and the gas becomes trapped between the vanes (2 and 3). The
chamber (1) formed by the enclosed space between the vanes then begins to decrease in volume as the
rotor revolves, compressing the gas. The pressure of the compressed gas becomes greater than
atmospheric pressure. When the vane (2) moves past the exhaust port (5) the compressed gas in the
chamber is forced out through the exhaust port.
This expansion/compression cycle constitutes one complete cycle of the pump operation. This cycle is
repeated as the vane (2) passes the intake port and seals it against the atmosphere. Therefore, two pump
cycles are performed during each revolution of the pump rotor.
8
2.03 Effects of Continued Pressure Reduction
The quantity of gas in the vessel (6) is reduced with each evacuation cycle. The gas remaining in the
vessel expands to ll the vessel and consequently with each cycle the pressure in the vessel is reduced.
This is a manifestation of Boyle’s Law which states that, for a constant temperature, the volume of a
body of gas is inversely proportional to its pressure; i.e., if the volume is enlarged the pressure must be
reduced.
As the amount of gas in the vessel is steadily diminished, its pressure is correspondingly reduced. The
action of the pump must therefore compress a successively smaller quantity of gas with each cycle to
something greater than atmospheric pressure in order to expel it from the pump.
At the beginning of an evacuation sequence, the compression ratio is very small. In the rst cycle of
operation the pump draws in a volume of gas at atmospheric pressure and expels it at approximately
atmospheric pressure. In contrast, near its ultimate pressure, a pump draws in gas at (for example) 30
millitorr and must compress it to more than 760,000 millitorr (atmospheric pressure) in order to expel it
from the pump. Since the exhaust valve is generally spring loaded to provide a good seal, the pressure
required to open it is somewhat greater than atmospheric pressure. Therefore, at an ultimate pressure
of 1.3 x 10-4 mbar 0.1 millitorr, (1 x 10-4 Torr) the compression ratio performed by the pump is greater
than 1,000,000 to 1.
2.04 Ultimate Pressure
As described previously, a quantity of gas is removed from the system with each cycle of the pump.
Therefore, the pressure of the gas remaining in the system is reduced with each pump cycle. Since the
pump can remove only a small portion of the gas with each pump cycle, it is obvious that this method of
evacuation can never completely remove all the gas in the vessel. In addition to this, all the components
of the system contain minute sources of gas leakage which are impossible to seal completely against
atmospheric pressure. Outgassing of materials within the system provide additional sources of gas.
As a result, after prolonged pumping, a state of equilibrium is reached in which the gas introduced from
all the leakage sources is balanced by the ability of the pump to remove gas from the system. This state
of equilibrium is referred to as the ultimate pressure or blankoff pressure of the pump and its system.
No matter how much additional pumping time is provided, no further reduction in system pressure will
be accomplished once ultimate pressure is attained.
2.05 Pump Mechanism Description
This vacuum pump incorporates two in-line rotary-vane stages with interconnecting ports. When in
operation, the intake stage is at lower pressure and the exhaust stage is at higher pressure relative to each
other. Each stage contains a rotor assembly consisting of a rotor with two vanes and a stator. The two
rotors are combined on one shaft, and the two stators are combined in a common housing. The pump
shaft turns the rotors, causing the vanes in each section to sweep the surface of their stators. The vanes
are pressed against the stators by centrifugal force.
Each stage has an exhaust valve. Gas expelled from the rst stage exhaust passes through an interstage
port to the intake of the second stage. The second stage compresses the gas further, then expels it from
the second stage exhaust valve to the atmosphere.
An adjustable gas ballast valve is located in the pump’s exhaust stage. The purpose of the gas ballast is
to reduce or eliminate vapor condensation in the pump. The function of the gas ballast valve is
described later in this section.
The pump is mounted inside an oil case which is a reservoir for the oil that lubricates the pump. The
electric motor shaft drives the pump shaft via a coupling. There is a coupling body on the end of each
shaft; a coupling spider between the two coupling bodies transfers the power from the motor shaft to the
pump shaft.
9
2.06 Intake Antisuckback Protection
When power to the pump is turned off, this device closes automatically, maintaining vacuum in the
system being evacuated, and vents the inside of the pump to atmospheric pressure.
2.07 Pump Lubrication
To ensure efcient operation and proper maintenance, and to minimize noise and oil vapors, it is
important to use the correct type and quantity of oil. DIRECTORR® Gold Vacuum Oil has been
especially developed to have the proper viscosity, low vapor pressure, and chemical stability needed to
produce peak pumping efciency. The ultimate vacuum guarantee on Welch pumps applies only when
this oil is used. Therefore, DIRECTORR® Gold Vacuum Oil is the only oil recommended for use with
these pumps. Each pump is supplied with sufcient oil for lling. Additional oil is available.
See Section 9: Accessories.
2.08 Exhaust Filter
Any oil-sealed vacuum pump tends to discharge oil mist from its exhaust port when the pump operates
under high-ow conditions, such as when the pump’s intake is at or near atmospheric pressure.
Typically, oil mist in the form of a white puff of “smoke” can be seen from the exhaust port when no
lter is used. Once the vacuum level and the corresponding air ow through the pump are reduced, very
little, if any, oil mist will be emitted.
An exhaust lter is recommended for any vacuum pump installation where the pump operates at high
intake pressures for a prolonged period of time. Oil droplets entrained in the pump’s exhaust are
removed by the exhaust lter element. Use of an exhaust lter typically reduces or bafes pump noise
as well. Exhaust lters are sometimes referred to as Oil Mist Eliminators. See Section 9 - Accessories.
2.09 Gas Ballast Valve
The gas ballast valve can increase the pump’s water vapor tolerance. (The gas ballast valve is sometimes
referred to as a vented exhaust valve.) In many vacuum pump applications the gases being pumped
from a system are a combination of permanent gases and undesirable vapors such as water vapor. Under
some conditions, the vapors condense in the second stage of the pump and contaminate the oil. The gas
ballast valve reduces oil contamination by decreasing or eliminating vapor condensation.
Vapor condensation is most likely to take place when the gas compression ratio is high, i.e. when the
pump compresses a relatively large volume of gas to a small volume. Whether or not condensation takes
place is dependent upon several factors, including the proportion of permanent gases to vapors at the
pump intake. If the gases being pumped consist entirely of vapors, condensation will denitely occur
unless the gas ballast valve is opened. The gas ballast valve adds a small amount of air at atmospheric
pressure to the gas being compressed in the second stage. This reduces the compression required to
push the gas out past the exhaust valve (less reduction in volume is required), and therefore reduces or
eliminates condensation.
When the gas ballast valve is open, the pump has to work a little harder, resulting in a slight increase in
operating temperature. The increase in temperature is small, however, and is not harmful to the pump.
Also, the pump is slightly noisier, and the pump’s ultimate pressure is somewhat reduced. Therefore, the
gas ballast valve should be kept closed when it is not needed. Note that the gas ballast is not equally
effective on all diffrent types of chemical vapors, so it may not always eliminate condensation
completely.
10
2.10 UNIBARB
TM
Intake Fitting - Simplies Small Hose Connections
The Unibarb intake tting allows the user to be able to use either 7/16” or 13/16” ID hose to connect to
this system. However, the choice of hose size can have a very marked difference on pumping speed. It
is the best to have the largest connection I.D.(internal diameters) as possible. However, we recognize
many lab appliances use hose barbs accepting small I.D. hose.
The conductance of a tube is proportional to the cube of its diameter and inversely proportional to its
length. Therefore, connecting line should be as large in diameter and short in length as practical.
Included is a free hose clamp to hold the hose in place.