Stokes Microvac 412H-11 User manual

Instruction Manual
Stokes Microvac
412H-11 Piston
Vacuum Pump

INSTRUCTIONS
PART I
Section
Page
1.
DESCRIPTION
1.1
General 1-1
1.2 Gas Ballast 1-1
1.3
Water System 1-2
1.4 Electrical System
1-2
1.5 Lubricants 1-2
1.6
Guards
1-2
1.7 Vacuum Break & Gage Ports \-2
2.
INSTALLATION
2.1 Locating and Mounting 2-1
2.2 Vacuum Piping 2-1
2.3 Exhaust Piping 2-2
2.4 Electrical Connections 2-2
2.5 Cooling 2-3
2.6 Lubrication
of Pump 2-4
3. OPERATION
3.1 Pre-Start Check 3-1
3.2 Pump Start 3-1
3.3 Checking Oil Level 3-1
3.4 Operation
of Gas Ballast 3-2
3.5 Pump Stop 3-3
3.6 Operating Notes 3-3
4.
CHECKING
4.1 Poor Vacuum 4-1
4.2 Localizing Leakage 4-1
4.3 Repairing Small Leaks 4-1
4.4 Pump Activity Record 4-1
5.
MAINTENANCE
5.1
Initial Servicing 5-1
5.2 Pump Disassembly 5-3
5.3 Troubleshooting Guide 5-11

6. MAJOR ATTENTION ITEMS BULLETIN AND MAINTENANCE CHECK LIST
7. PARTS LIST
8. STOKES SUPPLEMENTARY DATA
Parts Ordering Infonnation
Recommended Replacement Parts Kit
Stokes Microvac 2-Year Warranty
Pumping Hazardous Gases Sheet
Pumping Fluids, Lubricants'and Grease Bulletin
ILLUSTRATIONS
Figure
I. Pump Cross Section View
2. Vacuum Piping (Pump Below System)
3.
Vacuum Piping (Pump Above System)
4.
Exhaust Piping
5.
Wiring Diagram
6. Gas Ballast Check Valve
7. Standard Vacuum System Piping
8. Exhaust Valve Assembly
9. Taper Lock Bushing, Installation
10. Rotary Oil Seal
II. Exploded View
of Pump
12. Specifications
Page
1-1
2-1
. 2-1
2-2
2-3
3-2
4-1
5-2
5-3
5-5

1.0 DESCRIPTION
1.1 GENERAL (Principle of Operation)
.. The Stokes Model 412..:11 Microvac Pump is a self-contained, rotary, oil sealed piston type unit. The piston is driven
by an eccentric mounted on the drive shaft and the piston slided
is guided by two floating hinge bars that are free to
oscillate in the pump housing. Facing the drive
end:the piston assembly rotates clockwise. Air enters the pump through
the intake and then through the piston slide until the piston completes its stroke. At this point all air previously en-
trapped
is in front of the piston as it begins another stroke. As the piston continues to rotate, the air in front of it is
compressed and discharged through the exhaust valve and fmally out the exhaust outlet. As the piston nears the top
center position the intake port
is closed, separating the system from the pump (See Figure I). The exhaust valves are of
the corrosion-resistant, heavy duty, poppet type. When the pump is in operation, lubrication of the internal parts is
completely automatic. Oil is forced by atmospheric pressure from the reservoir through the oil lines to the shaft
bearings. The oil
is then fed into the pump to provide the necessary piston-to-cylinder oil seal. Finally, the oil is
forced out through the exhaust valve with the air and returns to the reservoir. A solenoid valve automatically prevents
oil from flooding the pump
in the event of a power failure, or when the pump is shutdown without vacuum being
broken.
EXHAUST
I-i.+--- OIL SEPARATOR
OIL
POPPET VALVE
PISTON Ell SLICE
HINGE BARS
eCCENTRIC
FiQ I
1.2 GAS BALLAST
The pump is provided with a manually operated gas ballast valve to overcome the adverse affect on vacuum resulting
from oil contamination. Contamination occurs when water vapor or other gaseous components enter the pump and
condense within the pump mixing with the oil
as emulsified droplets. The condensate will mix with the oil and "flash"
. into vapor again as the oil circulates into high vacuum in the pump cylinder limiting the vacuum to the Vapor pressure
of the condensed water. Gas Ballast is a controlled bleed of air from the atmosphere. This air caries the water vapor
through the compression cycle without it condensing to liquid and mixing with oil. Thus, the water vapors are ex-
hausted without contaminating the pump oil. Other contaminates are also removed by ballasting except those that
dissolve in the oil.
NOTE: Never use gas ballast when pumping gases or gas mixtures that are explosive or flammable.
1-1

1.3 WATER SYSTEM
A supply of cooling water at 85° F. and 2 G.P.M. maximum is needed at the water inlet for efficient performance. See
Section 2.5 for additional information.
1.4 ELECTRICAL SYSTEM
The main power supply is 230/460V., 60 Cy., 3 Ph. and should be wired through a suitable fused motor starter. Power
for the oil solenoid is taken from any two of the motor leads. Check both motor and solenoid nameplates to insure
proper voltage.
1.5 LUBRICANTS
Refer to Section 2 for recommended high vacuum grease and pumping fluids.
1.6 GUARDS
The standard pump is with a totally enclosed belt guard to cover the motor pulley, pump pulley and belts.
1.7 VACUUM BREAK & GAGE PORTS
The pump is provided with a 112" FPT Vacuum Break & a 1/4" FPT Gage Port, as shown in Fig. II.
IMPORTANT: When using Gage Port, provided a 90° elbow and at least 12" of vertical pipe
to the gage sensor.
1-2

2.0 INSTALLATION
2.1 LOCATING AND MOUNTING
Locate the pump as near as possible to the equipment being evacuated so that the Vacuum, Water and Exhaust
connections can be conveniently made. Provide for adequate space for convenient servicing where possible.
2.1.2 The
pump should be mounted on a rigid foundation, such as a concrete floor, and made level by shimming or
grouting, if necessary. Bolt pump to foundation without putting a strain or twist in the pump housing. See Figure 12
for foundation bolting dimensions.
2.1.3 Remove cap from exhaust and intake openings only when ready to make a pipe connection. Also remove the
plastic plug (by unscrewing) from the Gas Ballast valve. When pump is to be subjected to temperatures below freez-
ing, drain water jacket through the housing drain plug to prevent cracking the housing, then blowout waterjacket.
Follow this same procedure for storage.
2.2 VACUUM PIPING
All pipe lines should be as short as possible and should be no smaller than the inlet to the pump. (If it is absolutely
necessary
to run a long line, the pipe size should be increased 50% in diameter, or more, than the inlet to the pump.)
Conductance of long lines must be checked and the line sized large enough or pumping speed of system will be
seriously decreased. When connecting pump to the system, provide a vertical pipe at least.2 ft. long between the pump'
and the system, if the pump is below the system inlet."· If the pump is above or level with the system inlet, provide an
inverted "U" pipe to serve as a trap for dirt from the system and to prevent migration of pump oil toward the system
inlet. Be sure all vacuum piping is tight If an inline filter is being used it should be installed as noted below. It is
advisable to install a flexible connection between pump intake and vacuum piping to eliminate vibration. (See Figures
2 &3).
r-----
i.O·MIN.
PUMP.
Close/Lonq Radius
Elbow
""'2
PUIIP BELOW SYSTEII ••
..........FLEXIBLE CONNECTOR
PUM-P--H+R-;~!~L-..~:/~~~:;' .~ ._11 II
F1 v-3 ~TEM
PUMP ABOVE SYSTEM
A high vacuum valve (full opening type preferred) is recommended to facilitate start-up and for checking pump blank
off pressure.
CAUTION:
Make sure the system to be evacuated and connecting lines are clean and free of weld
splatter, dirt, or grit.' Foreign matter' entering the pump can cause failure and possibly
damage the internal parts. To prevent this it is recommended that a 16 mesh wire
screen be installed at the inlet connection. After 20 hours of operation the screen must
be removed.
2.2.1 TYPES OF PIPING JOINTS
A. Standard wrought piping with welded joints makes the best vacuum piping system.
B. Copper piping with sweated fittings andjoints can also be made vacuum tight and has the advantage
of providing a neat, clean vacuum installation.
2-1

C. Standard threaded piping, however, is satisfactory and more readily installed. The piping should be
carefully hammered to loosen any scales or chips.
Blowout the resultant with compressedair prior
to installation. All male threaded joints should
be carefully doped, screwed up tight and NEVER
"backed-off' to make parts align -this is apt to cause a leak. Paint thejoints while the system is
under vacuum until the paint is no longer drawn in, G.E.
12Ol-B, Glyptal or equivalent is
recommended for painting all connections.
2.2.2 LOCATION OF GAGE PORT
A vacuum gage connection is located at the upper left hand side of intake side of pump. (See Figure 12). The pipe plug
found at this location should be replaced with a small vacuum ball valve to which the gage can be connected. When a
Stokes McLeod Gage is used a synthetic, thick wall, smooth bore tubing, such as Tygon, makes a very satisfactory
flexible connection.
2.3 EXHAUST PIPING
2.3.1 It is recommended that the exhaust be piped horizontally as short distance and tied into a vertical exhaust pipe.
The vertical exhaust pipe must
be at least I ft. long and the bottom end of the vertical exhaust pipe terminated with a
plug or a drain cock to allow removal
of moisture and contaminated oil before it can accumulate sufficiently to drain
back into pump oil reservoir. See Figure 4.
£XHAUST PIPING
Figur~ 4
2.3.2 The exhaust pipe should be no smaller than the exhaust outlet and as short as possible. Run the pipe outside
the building where the pump exhaust vapors will not be objectionable
.. Point the outside end of the exhaust pipe
downward to prevent the entrance
of rain water.
2.3.3 Closed circuit Oil Mist Separators are available from Stokes which can eliminate oil fog
in the majority of
applications. The separator will not remove noxious or toxic gases and n;lust be run outside the bUilding. For operating·
continually under conditions of higher pressure an electro-static precipitator is recommended. Contact Stokes for.
specifics.
CAUTION: NEVER
PLACE A VALVE IN THE EXHAUST LINE. IF A VALVE
MUST BE INSTALLED IN THE LINE, A RELIEF VALVE MUST ALSO
BE INSERTED IN THE LINE BETWEEN THE RESERVOIR AND THE
VALVE. THE RELIEF VALVE SHOULD BE EQUAL IN SIZE TO THE
LINE, AND SET TO OPEN AT 2 PSIG.
2.4 ELECTRICAL CONNECTIONS (See Figure 5)
CAUTION: BE SURE
PUMP IS PROPERLY LUBRICATED BEFORE STARTING.
2.4.1· Install a motor starter with safety device within easy reach
of the operator.
2.4.2 Connect the solenoid valve as in Figure
5.
2.4.3 Connect motor so that pump shaft rotates clockwise when viewed from driven end. See 3.1 for Pre-Start
Check.
2-2

NOTE:
MAKE SURE THE PROPER VOLTAGE, STARTERS AND OVERLOADS ARE
SUPPLIED TO THE MOTOR. MAKE SURE THAT THE SOLENOID COIL LEADS
ARE CONNECTED FOR PROPER VOLTAGE. BOTH MAY FAIL TO OPERATE IF
VOLTAGE IS LESS THAN 90% OF RATED.
230/'I6O/~~0 V.,60 CY., 3 PH.
LINE vOLTAGE
230/460/5SDV., 50/60 CY.,3Ft!.
LINE
VOLTAGE
LI
LI
L2
L3
1
1I
230/460/550 V., SO/60 cv., I PH. or 115 II, SO/60 CY., I PH.
L~' CON~~\ VOLTAG: L2
STOP M
2 3
O<JAL VOLTAGE COIL CONNECTiONS
WI·TH 115
11
.,50/60 CY.,IPH.
. CONTIIOL VOLTAGE
L2 1
230V.
460 V.
WIRING OIAGRAM
Fi(Jllr~ 5
Blk Red
2.5 COOLING
2.5.1 This pump is water cooled and must be connected to a water supply.
2.5.2 The
112" water inlet connection is located in the pump housing on the drive side near the bottom.
2.5.3 ·Insert a valve in the water inlet line and regulate the water flow so that the temperature
of the oil in the
reservoir
is between 140 Deg. and 160 Deg. F. Oil temperature kits are available that automatically control the water
flow to maintain the proper oil temperature (Consult factory).
Ifpump is outside and subjected to freezing tempera-
tures, water tank and circulating pump should be installed with anti-freeze in the water.
2-3

CAUTION:
DO NOT START PUMP WHEN OIL TEMPERATURE IS BELOW 55° F.
2.5.4 The V2" water outlet is located in the pump housing on the opposite side of the water inlet.
2.5.5 The water outlet SHOULD be connected to an open drain to permit the operator to check the flow and
temperature
of the outlet water periodically. There SHOULD NOT be a valve or back pressure in this line. In some
cases, coolingwater must be discharged to a pressure drain. In such cases, discharge pressure must
not exceed 50
P.S.I.G. and no block valve should be placed
in discharge line unless a 50# reliefvalve is provided to protect pump
from high inlet pressure.
NOTE: IF CONDENSABLES ARE PRESENT IN GAS BEING PUMPED AND GAS
BALLAST IS USED THROTTLE THE COOLING WATER TO RAISE OPERATING
TEMPERATURE TO THE LEVEL NEEDED FOR GAS BALLAST (SEE SECT. 3).
2.6 LUBRICATION OF PUMP
The successful operation of this pump depends largely on the type of oil used. An initial charge of ojl is included with
each pump. This standard oil
is V-Lube (Label F) which is recommended for general operating conditions in a
relatively clean environment. The oil
is a multigrade petroleum oil, fortified for·oxidation protection, containing
detergent dispersants, with excellent flow characteristics at low temperature.
It has a viscosity of 430 SSU at 100 Deg.
F., and 82 SSU at 2lO Deg. F., with a vapor pressure
of 0.0001 mm Hg. at 145 Deg. F.
If the pump is to be operated at vacuum levels that cause the oil temperature to exceed 160 Deg. F. for extended
. periods
of time, a heavier grade oil should be used, Stokes V-lube (Label G) is available for oil temperatures up to 200
Deg.F .
. Special operating conditions may require the use of Special oils. We have listed the·most used special lubricants on the
back page
of the Bulletin enclosed, Greasing and Pumping Fluids for Vacuum Components. Consult Stokes for
specific recommendations when other than regular petroleum oils are being used.
2.6.1
INITIAL FILL
The microvac pump is shipped with ail Initial charge of oil (12 gallons) inthe reservoir. Bt;:fore connecting the suction
manifold slowly rotate the pump thru two revolutions. This will distribute the oil throughout the pump interior.
NOTE: STARTING
THE MICROV AC PUMP WHEN OIL TEMPERATURE IS BELOW 55 .
DEG. F., CAN RESULT IN EXCESSIVE WEAR AND GALLING DAMAGE TO
THE MOVING PARTS.
'When changing oil, refer to SectionS, page 5~1 of manual, Service and Maintenance.
2-4

3.0 OPERATION
3.1 PRE-START CHECK
NOTE: REMOVE BELT GUARD COVER. TURN PUMP OVER BY HAND AT LEAST TWO
REVOLUTIONS.
3.1.1 A.
B.
NOTE:
Jog the motor momentarily while observing pump rotation. If the pump does not rotate in a
clockwise direction, interchange any two of the three-phase leads.
Make sure the oil solenoid valve operates properly by checking the oil flow indicator. The
ball in the Oil Flow Indicator bowl should rise after system pressure is below 600 mm Hg.
(6" Hg. Suction).
IF INDICATOR BALL DOES NOT RISE, STOP PUMP IMMEDIATELY. (1) CHECK
OPERATION OF SOLENOID. (2) CHECK OIL LINES FOR BLOCKAGE
3.1.2 DRIVE BELT TENSION
A.
B.
NOTE:
At approximately the center of the span, between drive and driven pulleys, apply 5 to 7
pounds pressure on the belt.
Iftension is correct, the resulting deflection should be 112".
Adjust, if necessary, by raising or lowering the location nuts on the motor support eyebolt
(39). Tighten these nuts securely after adjustments.
MAINTENANCE OF PROPER BELT TENSION IS IMPORTANT. TOO TIGHT ANY
ADJUSTMENT IS
HARMFUL TO THE SHAFT BEARINGS. TOO LOOSE AN
ADJUSTMENT
ALLOWS THE BELT TO SLIP.
3.2 PUMP START
3.2.1 Tum cooling water ON.
3.2.2 Depress "start" button and check solenoid valve for proper operation.
CAUTION: DO NOT START PUMP WHEN OIL TEMPERATURE IS BELOW 55° F.
3.2.3 Be sure the equipment being evacuated is properly cleaned and all openings closed. Open intake valve.
NOTE: REMOVE PLASTIC PLUG FROM EXHAUST PORT BEFORE OPERATING PUMP
3.3 CHECKING OIL LEVEL
3.3.1 Check oil level each day.
3.3.2 The oil level should be at center
of sight glass or in lower half while pump"is operating at high vacuum.
Level will change depending on suctiori pressure. In most cases, oil is added after operating the pump for a short
while.
3.3.3 To avoid blowing oil out the fill hole, do not add oil to the pump when in operation unless pump is at I
torr or less without Gas Ballast.
NOTE: When pumping gases that contain water vapor it may be necessary to remove the water that
condenses in the pump reservoir sump. This can be done by opening the oil drain valve and
draining out water, and closing valve when oil starts to flow. The interval for this must be
determined for each specific operation and depends on the amount of water vapor and oil temperature.
Operating the pump with the oil temperature in the 160 Deg. F., temperature range will tend to
minimize formation
of water, but will not eliminate it.
3-1

3.4 OPERA TION OF GAS BALLAST
3.4.1 Open the Gas Ballast valve fully for maximum efficiency. For a lesser degree of ballasting, tum valve toward
close position. Full gas ballast will cause pump temperature to rise but this
is nonnal. For maximum effect of gas
ballast, pump should
be run approximately at 160 Deg. F. Operating temperature can be raised by throttling cooling
water. Oil Temperature Control Kits are available, consult factory.
NOTE: Be sure to remove the plastic plug in the Gas Ballast
air intake lines. This plug is used for
shipping and storage purposes ONLY
3.4.2 If pumping water vapor in excessive quantities and the oil has become contaminated, it can be purified by
running the pump with Gas Ballast valve full open while the pump
is shut-offfrom the system. When excessive
contaminants are present, indicated
by high oil level, or thinning, formation of varnish, etc., the oil should be replaced.
NOTE: In dirty applications
where condensable contaminants (asphalt, pitch, epoxies, etc.) other than
water vapor are present, the pump should be operated in the range of 160 Deg. F.
CAUTION: Gas Ballast should never be used ifvapors being pumped are explosive, e.g. Methane
Gas, Hydrogen, and certain solvent vapors. When gases of an explosive nature are being
handled. the safest procedure is to remove the gas ballast valve entirely and plug or cap
the pipe to which the gas ballast valve is attached.
Opening the gas ballast slightly will quiet valve noise when pump is blanked-off, but will prevent reaching the lowest
final pressure.
3.4.3 The check valve used for Gas Ballast should be inspected at least every six months for
we.ar or a broken spring
when operating on an (8) hour a day basis; every 3 months for (24) hour a day operation.
TEFLON BACK· UP lUNG \ &
STATIC "0" RING \ \ ~
t"\~ >
~\J'-J,~,/
L)~ "-""'.'C"O" .,,'
~ \.. .. ,,"'
SCREEN (nor r.".,vall/e 1
GAS BALLAsr CHECK VALVE
Flgur.6
3.4.4 The gas ballast valve should be closed when the pump is stopped.. If the valve is open, gas will be sucked into
the pump through the valve·and the vacuum manifold will be pressurized with atmospheric air. This air
goir).g through
the pump will carry the oil in the pump cylinder system. A solenoid valve attached to the gas ballast piping and
connected across the motor can be used to tum the gas ballast automatically on pump shutdown. Contact local Stokes.
representative for additional infonnation.
3.4.5 When a pressurized gas is used to ballast the pump, the pressure must be reduced to 2 psi maximum. The used
of higher pressures may damage the pump.
3.4.6 When pumping an explosive gas, (Le. hydrogen, silane, methane) or corrosive gas, (cl,
f, ccl4, etc.) the pump
must be ballasted with an inert gas (nitrogen, argon). The used
of air for ballasting under the above conditions can ..
result in an explosion or excessive corrosion inside the pump.
3-2

3.5 PUMP STOP
3.5.1 Close intake valve to system.
3.5.2 Stop
the motor and break vacuum unless system dictates otherwise ..
NOTE: The solenoid valve closes automatically when the pump is stopped or in case of power failure,
thus preventing pump and vacuum system from being flooded with oil.
3.6 OPERATING NOTES
3.6.1 If large amounts of air pass through the pump, it may become warm and under severe conditions may become
hot. This does not indicate trouble. The pump is designated for high vacuum work and should not be operated at
pressures above 600 mm Hg. for more than 15 minutes or at intermediate vacuums for periods which cause oil tempera-
ture to exceed 200 Deg. F. For optimum pump operation the oil temperature of the oil in the reservoir should be
between 140 Deg. F. and 160 Deg. F. with the pump operating on the system or process. Oil temperature can be
-measured by inserting a thermometer in the fill hole or by contact pyrometer on oil line near the solenoid. If the pump
is to be operated with oil temperature in excess of 160 Deg. F. the use of a heavier viscosity oil is recommended. (See
Section 2.6.)
3.6.2 When starting the pump or when handling large amounts of air, oil vapor in the form of smoke will issue from
the exhaust. Again this is no indication of trouble, as the volume of smoke will decrease as the vacuum in the system
improves.
NOTE: Stokes closed type oil mist separator is available to alleviate exhaust oil smog ..
3.6.3 If the pump has been shut down for an extended period, always turn over at leasttwo (2) revolutions by hand
before starting to insure free movement
of parts.
3.6.4 Low .oil temperature can.cause overloading when starting the pump and possibly prevent the pump from
sealing. Microvac pumps should not be started.when the oil temperature.is below 55 Deg. F.*Optimum operating oil..
. temperature after starting is between 140 Deg. F. to 160 Deg. F. Opening the Gas Ballast valve will help warm-up the
oil.
A Water Miser is recommended to automatically control the oil temperature.
*THIS APPLIES ONLY IF STOKES V-LUBE "F" IS USED. CONSULT FACTORY IF OTHER OILS ARE
USED.
3-3

4.0 CHECKING
4.1 POOR VACUUM
No pump will give good results on a poor vacuum system. If the vacuum in the system is unsatisfactory, the usual
cause is leakage. To check for this condition, a methodical approach will usually resolve the.problem in the least
amount
of time.
4.2 LOCALIZING LEAKAGE
A leak rate will help localize a vacuum leak. Such a test is easily made by successively isolating and evacuating each
section
of the system. The in-leakage rate of the isolated section is then noted.
4.2.1 A vacuum leak detector will speed up the process of the locating leaks.
VACUUM CHAMBER
-po
iROUGHING VAL~~
-----:-------1"..ft .... t-:-----------"
---------t,.'" '.1------------, \
.. - ___ ALTERNATE LDCATIONS I :
--- FOR CHAMBER GAGE PORT I t
VAPOR PUMP
I 1- ROUGHING LINE
I .
I I
I
. I I
I I
\
F SEPARATE
HOLD : I
PUMP
IS NEEDED I .
CONNECT HERE/tfl FORELINE VALVE
I t (Required if separate
I I roughin9 line is used I
--~----t'-.J:J""!I"-....I......(
-GAGE PORT
-AIR INLET VALVE
PORT
MECH.
FOREPUMP.
STANOARO VACUUM SYSTeM PIPING
Figur~ 7
4.3 REPAIRING SMALL LEAKS
To repair small leaks orto close pores, use Sealing Compound, Stokes Part No. 4-927. When replacing plug type
valves
(if used) use Locktite Pipe Sealer No. 714-1 to help seal them. Gate, Ball or Butterfly type high vacuum valves.
are preferred for high vacuum service.
NOTE: Use of Teflon Tape for sealing is not recommended. Material is often drawn into system,
causing
premature wear and damage to moving parts.
4.4 PUMP ACTIVITY RECORD
A record of oil changes, work done on pump, and changes or additions to the system will be of value in checking for
leaks or poor vacuum.
NOTE:A sample mechanical vacuum pump preventive maintenance check list along with a summary
of major attention items is enclosed for your review.
4-1

CAUTION
WHEN REASSEMBLING PUMP BE
CERTAIN ALL MOVING PARTS ARE
CLEAN AND LUBRICATED.
BEFORE STARTING PUMP POUR 10%
OF THE REQUIRED AMOUNT OF OIL
INTO INLET WHILE SLOWLY
ROTATING PUMP THRU TWO (2)
REVOLUTIONS. POUR REMAINDER OF
- OIL INTO THE RESERVOIR.
NOTE:
THE JOINT BETWEEN THE RESERVOIR
AND HOUSING MAY BE SEALED BY
THE FACTORY WITH A GASKET OR
LOCTITE GASKET ELIMINATOR.
CONTACT FACTORY IF NEED ARISES
TO REMOVE RESERVOIR THAT HAS
BEEN SEALED WITH GASKET
ELIMINATOR.
~ ..

5.0 MAINTENANCE
The Stokes 412-11 Microvac Pump is of rugged construction and designed for trouble free performance. However, to
insure effiCient performance and minimum wear the following procedures are recommended:
5.1 INITIAL SERVICING
5.1.1 First Three Weeks of Operation
A. Check oil level daily and also its condition. (See Paragraph 5.1.3). Maintain oil level at
center
of sight glass with pump in operation.
B. Check belt tension weekly (See Paragraph 3.1.2).
C. Check the foundation bolts weekly.
5.1.2 After First Three Weeks of Operation
A. Check oil level daily.
B. Check "V" belts, tension and wear every 3 months
C. Tighten all flange side cover bolts and foundation bolts at regular intervals.
5.1.3 Changing Oil and Cleaning Pump Reservoir (See Figure 11)
Change oil every 300 hours of operation and clean reservoir every 600 to 900 hours of operation .. For dirty applica-
tions decrease bil change intervals. Also
if the oil becomes contaminated (indicated bydarkening in color and/or poor
pump performance) it should be drained. Drain the reservoir and exhaust valve chamber. Wipe the reservoir clean
before filling with new oil. Milky appearance
of oil indicates water contamination. Use Gas Ballast to clear oil, or
change oil. Also most water can be removed
by draining water from pump before starting pump.
To change oil and clean reservoir proceed as follows:
A. With pump running, close intake valve to system and open vacuum break valve-to.pump or
open intake valve and admit atmosphere to the system so that atmospheric pressure forces
oil
from the pump interior up into the reservoir. Run pump for approximately 30 seconds, then
tum pump OFF.
B. Drain oil by opening drain cock (51).
C. After oil has been drained remove oil reservoir cover (32) being careful·not to damage gasket
(31).
D. Thoroughly wipe out oil reservoir, DO NOT flush the reservoir with Kerosene, Gasoline or
any other solventthat may, if not completely removed, contaminate the pump oil. Use only
clean, dry, lint-free towels.
E. Replace gasket (31) and cover (32) and tighten securely.
5.1.4 Cleaning Exhaust Valve Assemblies and Chamber
When the oil is badly contaminated the exhaust valves and chamber should be cleaned. Referring to Figure 11 proceed
as follows:
A. Repeat Steps 5.1.3, A to D.
B. .Remove oil baffle (28) and valve cover plate gasket (27).
5-1

NOTE:
C. Drain the oil from the valve chamber by removing the plug on the dead end side of the pump
housing. (See Figure 12)
D.
E.
F.
G.
'----26A
_--::;""::::;.J
-----268
'-----260
VALVE ASSEMBLY
Figurtt8
Remove valve assembly (26), by removing the six cap screws, and valve gasket (25).
To disassemble valve assembly (26), remove center cap screw, lift off valve cap (26 A),
remove spring (26 B) and valve disc (26 C).
Clean and inspect valve parts, and wipe out valve chamber with clean, dry lint-free towels.
Reassemble valve assemblies
by reversing the disassembly steps described above. It is
. advisable to use a new valve gasket (31) when reinstalling valve assemblies.
Replace valve
chamber plug.
5.1.5
Care of Exhaust Valves
The valves are the poppet type and corrosion resistant construction. These valves operate many millions of cycles per·
year in nonnal operation and should be inspected at least once every six months even though the pump is operating
satisfactorily, and more frequently where. duty on pump is severe .. The valve should be disassembled and cleaned ill
accordance with Section 5.1.4. At the time ofthe inspection, it is advisable to replace the entire set of springs and valve
discs. This
procedure will increase the reliability of the pump, avoiding the possibility of additional spring failure.
5.1.6
Solenoid Valve
Check Solenoid Valve, which prevents oil from flooding the pump in case of a power failure, at regular
intervals; See page 3-1 para. 3.1.B. In the event the solenoid valve stays closed,after the pump is started,.the oil cannot
circulate.
This is indicated by poor perfonnance and if the conditjon is allowed to continue for any length of time, the
pump may suffer damage.·. The pump work-in period .establishes the nonnal preventive maintenance checks according
to the type
of system (clean or dirty) being pumped down and the continuous pumping time (light of heavy).
In a clean and light pumping situation, the exhaust valve springs and discs should be replaced every six months. At
this time the reservoir should. be checked for sludge accumulation and foreign particles. Use a magnet to detect
presence of foreign metal particles. The presence of.sludge and/or foreign particles in the reservoir indicates the same
condition exists in
the oil solenoid valve. This condition will cause the solenoid valve to stick in the open or closed
position. Disassemble and clean the solenoid valve.· Replace any worn parts. If the pump is used in a dirty and heavy
pumping situation, the preventive maintenance checks should be perfonned sooner.
It is strongly suggested that a spare oil solenoid valve be on hand at all times to keep pump downtime at an absolute
minimum.
When operating with
pump oils other than that supplied, special gasket material may be needed in the solenoid valve -
consult factory.
The visual flow indicator on latest pumps makes this check simple by indicating flow when pressure is
below 600
mm Hg. (6" Hg. Suction) 5-2

5.2 PUMP DISASSEMBLY
5.2.1 Removal of Shaft Seal- Flywheel End (See Figures 10& 11)
The shaft seal used on this pump are the mechanical face type. Since their efficiency depends on the highly fmished
. surfaces, it is extremely importantto handle them with care. They should require little or no attention, but if excessive
leakage
occurs, they can be removed for service as follows:
NOTE:
NOTE:·
A. To remove the pUlley.
B.
c.
D.
E.
F.
1) Unclasp (4) hinge locks on belt guard.
2) Lower the adjusting nut on motor support eye bolt (39) to relieve all tensions on
the drive belts.
3) Remove the belts.
4) Insert screw in hole that is threaded through bushing side (See Figure 9).
One screW in each hub is left over and not used in loosening operation.
5) Tighten screws alternately until bushing is loosened in hub. If bushing does not
loosen immediately, tap on hub.
\
OA INSTALLATION ~
'~---1
. I
1-- ~
rAPER-LOCK BUSHING INSrALLAriON
.";(lu~ 9
To assure proper seal assembly, check exploded view, Figure II, for proper orientation...
Remove Key (14) from the shaft and remove any burrs around the keyway.
Remove (4) 5116-18 Screws
and Plastic washers which hold belt guard back plate in place.
Disconnect the oil line from
the hub of side cover (12).
Take out screws
that secure end cap (5) to the side cover and remove the end cap and "0"
ring (6).
Inspect the face
of seal port (7e) retained by the end cap.
5-3

NOTE: The inner seal ring (7e) may be removed from the seal outer seal ring (7b) for inspection. (7b)
is pressed in the end cap(s). Depress and rotate the seal ring (7e) releasing the bayonet lock,
and remove from outer ring (7b). Inspect the "0" ring (7c) and spring (7d) for possible
damage. Removal of the outer ring (7b) is not recommended unless replacing the entire oil
seal.
G. Remove the seal matting ring (7g) with a slight back and forth rocking motion. Earlier model
pumps have a socket head cap screw in the ring, if so, loosen screw halfway then remove
mating ring (7g).
H. Whenever the pump is disassembled and the rotary seal parts 7e & 7g are separated, it is
advisable that these parts be lapped to a 2-lightband flatness or replaced. If the normal ridge
on member (7e) is worn flat, replace this part. Always check bearing (11) for wear and
replace if necessary. Also, if a leaking seal is replaced, it is advisable to replace the bearing (11).
IMPORTANT: Before replacing the seal, lubricate the shaft and seal members and "0" ring with a thin
coat of vacuum grease or pump oil. Replace the sealmating ring on the shaft using a slight
back and forth motion. However, the seal mating ring should still maintain slight free
movement on the shaft.
1. The seal is reassembled by reversing the disassembly procedure.
J. Replace the Pulley.
I. CLEANthe bushing, shaft, and bore of pulley.
2. Place bushing in hub and match halfholes to make complete holes. Place the
screws loosely in holes that are threaded on hub side. (see Figure 9).
3. Make sure bushing is·free in hub and slip the assembly onto the shaft locating it in
the position desired. BE SURE.to counterweight is opposite the bushing keyway
. to avoid imbalance.
4. Tighten screws alternately and evenly until all are pulled up VERY TIGHTLY.
Use a piece of pipe or wrench to increase leverage. (Wrench torque is 430 pounds
-inches).
5.· Hammer against large end of bushing being careful to use a block or sleeve to
avoid damage to the bushing. The screws can now be turned a little more using the
specified wrench torque. REPEAT THIS ALTERNATE HAMMERING AND
SCREW RE-TIGHTENING UNTIL THE SPECIFIED WRENCH TORQUE NO
LONGER TURNS THE SCREWS.
[)~
(\)\~ \ \(Place toward unlor
(\~\J~\ \ ' .. _.,
V \ c
\ B
A
HOrAI7Y OIL ~AL
FigUl"t! 10
5-4

,"'PLY A L,,"Y COAY DF
YAc;UUM MUW. TO TIIII
"D" IIIN8 ONLY -----~"""'"~
INSTALLATIONNOTES
1. Remove existing seal from shaft and in counter bore of end cap.
2. After removing seal from package, make sure the spring fits freely inside carbon seal and over
the lip on
the spring retainer.
3. Make sure the "0" ring retainer (which fits between the "0" ring in the carbon seal and the spring).
fits freely over the pump shaft.
4. Clean the counter bore of the end cap. This counter bore should be free of oil and all foreign matter.
5. .. Before inserting static seat, coat the back surface and approximately up 1/8" of the lower portion of the
counter bore with Loctite 620, adhesive Loctite *PrimerN to be used before applying.the Loctite 620.
6. Clean static seat and polished surface of tool with a lint free cloth. Apply Primer "N" to back surface
of the static seat. Gently press seat into end cap using fmger pressure only. Make sure the polished
surface is facing toward you. Take care to protect this surface since this forms the seal when in contact
with the carbon face. Gently place the polished undercut end
of the tool* on the static seat surface.
(This surface must be flat within two light bands). Apply finn pressure, do
not exceed 25 lbs. Hold for
two minutes to setLoctite. The
"0" ring on the static seat will keep the Loctite from oozing out and
forming on the polished surface. The Loctite forms a
vacuum seal between the static seat and end cap.
** Tool can be purchased from Stokes Vacuum, Inc., part No. A-427-740-l or made as per Figure 2.
7. . Slide the·spring retainer, spring, and carbon seal with "0" Ring and "0" Ring retainer in place as
shown, onto the pump shaft, making sure the
"0" Ring passes over the taper on the shaft and the·
spring retainer rests against the threaded shoulder on the shaft. Be careful not to nick or scratch theshaft
since this will affect the seal
of the carbon "0" Ring.
8. Replace end cap with "0" Ring. Coat the "0" Ring in end cap only with vacuum grease.

NOTE: *It is very important the Primer "N" is used. The combination of 620 Adhesive and PrimerN Gives a
bond with a shear stress that permits the static seal to be pressed out. Also this combination will allow the Loctite to be
removed from the parts when the bond is broken. Primer "N" to dry 2 to 5 minutes. Apply adhesive 620 to counter
bore only.
It is recommended that the static seat be installed within 10 minutes after adhesive 620 is applied over
primer.
fjg.::1.
f~ ~~U=~~=T~.
STATIC SEAT /L
kR
.
+.010
2.172",000
SURFACE "A" O'G.
NOTES-
I
6'4
R
,- MAr'L.--f'-fOH.R. STEEL, HEAT TREAT
TO RC52-S$
2- 6-- F.A.O. EXCEPT AS NOTED.
3- SURFACES MARKED V MUST BE
PARAULL WITHIN .002.
-f- SURFACES ·MARKED "AN TQ BE FLAT
WITHIN TWO LIGHT BANds & FREE
OF SCRATCHES.
F..!.g.-.L
5-6