GORMAN-RUPP 12D-1B20 FT4 Application guide

OM-06788-01
August 24, 2015
GORMAN‐RUPP PUMPS
www.grpumps.com
e2015 Gorman‐Rupp Pumps Printed in U.S.A.
INSTALLATION, OPERATION,
AND MAINTENANCE MANUAL
WITH PARTS LIST
10 SERIES PUMP
MODEL
12D-1B20 FT4

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Please record your pump model and serial number in the
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needs this information when you require parts or service.
Pump Model:
Serial Number:
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product contains chemicals
known to the State of California to
cause cancer, birth defects or
other reproductive harm.

TABLE OF CONTENTS
i
INTRODUCTION PAGE I - 1.................................................
SAFETY ‐ SECTION A PAGE A - 1............................................
INSTALLATION - SECTION B PAGE B - 1....................................
PREINSTALLATION INSPECTION PAGE B - 2............................................
POSITIONING PUMP PAGE B - 2.......................................................
Lifting PAGE B - 2.................................................................
Mounting PAGE B - 2.............................................................
Clearance PAGE B - 2.............................................................
SUCTION AND DISCHARGE PIPING PAGE B - 2.........................................
Materials PAGE B - 2..............................................................
Line Configuration PAGE B - 3......................................................
Connections to Pump PAGE B - 3..................................................
Gauges PAGE B - 3...............................................................
SUCTION LINES PAGE B - 3...........................................................
Fittings PAGE B - 3...............................................................
Strainers PAGE B - 3..............................................................
Sealing PAGE B - 3...............................................................
Suction Lines In Sumps PAGE B - 3.................................................
Suction Line Positioning PAGE B - 4................................................
DISCHARGE LINES PAGE B - 4........................................................
Siphoning PAGE B - 4.............................................................
Valves PAGE B - 5................................................................
Bypass Lines PAGE B - 5..........................................................
OPERATION - SECTION C PAGE C - 1......................................
PRIMING PAGE C - 1.................................................................
STARTING PAGE C - 1................................................................
OPERATION PAGE C - 1..............................................................
Lines With a Bypass PAGE C - 2....................................................
Lines Without a Bypass PAGE C - 2.................................................
Leakage PAGE C - 2..............................................................
Liquid Temperature And Overheating PAGE C - 2.....................................
Strainer Check PAGE C - 2.........................................................
Pump Vacuum Check PAGE C - 2..................................................
STOPPING PAGE C - 3................................................................
Cold Weather Preservation PAGE C - 3..............................................
TROUBLESHOOTING - SECTION D PAGE D - 1..............................
PREVENTIVE MAINTENANCE PAGE D - 3...............................................
PUMP MAINTENANCE AND REPAIR ‐ SECTION E PAGE E - 1.................
STANDARD PERFORMANCE CURVE PAGE E - 1........................................
PARTS LISTS:
Pump Model PAGE E - 3..........................................................

TABLE OF CONTENTS
(continued)
ii
Pump End Assy PAGE E - 5........................................................
PUMP AND SEAL DISASSEMBLY AND REASSEMBLY PAGE E - 6.........................
Suction Check Valve Disassembly PAGE E - 6........................................
Back Cover Removal PAGE E - 6...................................................
Pump Casing Removal PAGE E - 7.................................................
Impeller Removal PAGE E - 7......................................................
Seal Removal and Disassembly PAGE E - 7..........................................
Seal Reassembly and Installation PAGE E - 7........................................
Impeller Installation And Adjustment PAGE E - 9......................................
Pump Casing Installation PAGE E - 9................................................
Back Cover Installation PAGE E - 9.................................................
Suction Check Valve Installation PAGE E - 9.........................................
Final Pump Assembly PAGE E - 10..................................................
LUBRICATION PAGE E - 10.............................................................
Seal Assembly PAGE E - 10.........................................................
Engine PAGE E - 10................................................................

10 SERIES OM-06788
PAGE I - 1INTRODUCTION
INTRODUCTION
Thank You for purchasing a Gorman‐Rupp pump.
Read this manual carefully to learn how to safely
install and operate your pump. Failure to do so
could result in personal injury or damage to the
pump.
Because pump installations are seldom identical,
this manual cannot possibly provide detailed in
structions and precautions for every aspect of
each specific application. Therefore, it is the re
sponsibility of the owner/installer of the pump to
ensure that applications not addressed in this
manual are performed only after establishing that
neither operator safety nor pump integrity are com
promised by the installation. Pumps and related
equipment must be installed and operated ac
cording to all national, local and industry stan
dards.
If there are any questions regarding the pump or
its application which are not covered in this man
ual or in other literature accompanying this unit,
please contact your Gorman‐Rupp distributor, or
The Gorman‐Rupp Company:
The Gorman‐Rupp Company
P.O. Box 1217
Mansfield, Ohio 44901-1217
Phone: [phone]
or:
Gorman‐Rupp of Canada Limited
70 Burwell Road
St. Thomas, Ontario N5P 3R7
Phone: [phone]
For information or technical assistance on the
power source, contact the power source manufac
turer's local dealer or representative.
HAZARD AND INSTRUCTION
DEFINITIONS
The following are used to alert maintenance per
sonnel to procedures which require special atten
tion, to those which could damage equipment, and
to those which could be dangerous to personnel:
Immediate hazards which WILL result in
severe personal injury or death. These
instructions describe the procedure re
quired and the injury which will result
from failure to follow the procedure.
Hazards or unsafe practices which
COULD result in severe personal injury
or death. These instructions describe
the procedure required and the injury
which could result from failure to follow
the procedure.
Hazards or unsafe practices which COULD
result in minor personal injury or product
or property damage. These instructions
describe the requirements and the possi
ble damage which could result from failure
to follow the procedure.
NOTE
Instructions to aid in installation, operation, and
maintenance or which clarify a procedure.

10 SERIES OM-06788
PAGE A - 1SAFETY
SAFETY ‐ SECTION A
This information applies to 10 Series en
gine driven pumps. Refer to the manual
accompanying the engine before at
tempting to begin operation.
Because pump installations are seldom
identical, this manual cannot possibly
provide detailed instructions and pre
cautions for each specific application.
Therefore, it is the owner/installer's re
sponsibility to ensure that applications
not addressed in this manual are per
formed only after establishing that nei
ther operator safety nor pump integrity
are compromised by the installation.
Before attempting to open or service the
pump:
1. Familiarize yourself with this man
ual.
2. Shut down the engine and take
precautions to ensure that the
pump will remain inoperative.
3. Allow the pump to completely cool
if overheated.
4. Check the temperature before
opening any covers, plates, or
plugs.
5. Close the suction and discharge
valves.
6. Vent the pump slowly and cau
tiously.
7. Drain the pump.
This pump is designed to handle most
non‐volatile, non‐flammable liquids
containing specified entrained solids.
Do not attempt to pump volatile, corro
sive, or flammable liquids which may
damage the pump or endanger person
nel as a result of pump failure.
After the pump has been installed, make
certain that the pump and all piping or
hose connections are tight, properly
supported and secure before operation.
Do not operate the pump against a
closed discharge valve for long periods
of time. If operated against a closed dis
charge valve, pump components will
deteriorate, and the liquid could come
to a boil, build pressure, and cause the
pump casing to rupture or explode.
Do not remove plates, covers, gauges,
pipe plugs, or fittings from an over
heated pump. Vapor pressure within the
pump can cause parts being disen
gaged to be ejected with great force.
Allow the pump to completely cool be
fore servicing.
Overheated pumps can cause severe
burns and injuries. If overheating of the
pump occurs:
1. Stop the pump immediately.
2. Ventilate the area.
3. Allow the pump completely to cool.
4. Check the temperature before
opening any covers, plates,
gauges, or plugs.

10 SERIESOM-06788
PAGE A - 2 SAFETY
5. Vent the pump slowly and cau
tiously.
6. Refer to instructions in this manual
before restarting the pump.
Do not operate an internal combustion
engine in an explosive atmosphere.
When operating internal combustion
engines in an enclosed area, make cer
tain that exhaust fumes are piped to the
outside. These fumes contain carbon
monoxide, a deadly gas that is color
less, tasteless, and odorless.
Fuel used by internal combustion en
gines presents an extreme explosion
and fire hazard. Make certain that all
fuel lines are securely connected and
free of leaks. Never refuel a hot or run
ning engine. Avoid overfilling the fuel
tank. Always use the correct type of fuel.
Never tamper with the governor to gain
more power. The governor establishes
safe operating limits that should not be
exceeded. The maximum continuous
operating speed for this pump is 3600
RPM.
Pumps and related equipment must be in
stalled and operated according to all na
tional, local and industry standards.

10 SERIES OM-06788
PAGE B - 1INSTALLATION
INSTALLATION - SECTION B
Review all SAFETY information in Section A.
Since pump installations are seldom identical, this
section offers only general recommendations and
practices required to inspect, position, and ar
range the pump and piping.
Most of the information pertains to a standard
static lift application where the pump is positioned
above the free level of liquid to be pumped.
If installed in a flooded suction application where
the liquid is supplied to the pump under pressure,
some of the information such as mounting, line
configuration, and priming must be tailored to the
specific application. Since the pressure supplied
to the pump is critical to performance and safety,
be sure to limit the incoming pressure to 50% of the
maximum permissible operating pressure as
shown on the pump performance curve (see Sec
tion E, Page 1). If the pump is fitted with a Gorman‐
Rupp double grease lubricated seal, the maximum
incoming pressure must be reduced to 10 p.s.i.
For further assistance, contact your Gorman‐Rupp
distributor or the Gorman‐Rupp Company.
Pump Dimensions
See Figure 1 for the approximate physical dimen
sions of this pump.
OUTLINE DRAWING
Figure 1. Pump Model 12D-1B20 FT4

OM-06788 10 SERIES
PAGE B - 2 INSTALLATION
PREINSTALLATION INSPECTION
The pump assembly was inspected and tested be
fore shipment from the factory. Before installation,
inspect the pump for damage which may have oc
curred during shipment. Check as follows:
a. Inspect the pump and engine for cracks,
dents, damaged threads, and other obvious
damage.
b. Check for and tighten loose attaching hard
ware. Since gaskets tend to shrink after dry
ing, check for loose hardware at mating sur
faces.
c. Carefully read all tags, decals, and markings
on the pump assembly, and perform all duties
indicated.
d. Check levels and lubricate as necessary. Re
fer to LUBRICATION in the MAINTENANCE
AND REPAIR section of this manual and per
form duties as instructed.
e. Check for the discharge elbow shipped loose
with the pump.
f. If the pump and engine have been stored for
more than 12 months, some of the compo
nents or lubricants may have exceeded their
maximum shelf life. These must be inspected
or replaced to ensure maximum pump serv
ice.
If the maximum shelf life has been exceeded, or if
anything appears to be abnormal, contact your
Gorman‐Rupp distributor or the factory to deter
mine the repair or updating policy. Do not put the
pump into service until appropriate action has
been taken.
POSITIONING PUMP
Lifting
Pump unit weights will vary depending on the
mounting and drive provided. Check the shipping
tag on the unit packaging for the actual weight, and
use lifting equipment with appropriate capacity.
Drain the pump and remove all customer‐installed
equipment such as suction and discharge hoses
or piping before attempting to lift existing, installed
units.
Mounting
Locate the pump in an accessible place as close as
practical to the liquid being pumped. Level mount
ing is essential for proper operation.
The pump may have to be supported or shimmed
to provide for level operation or to eliminate vibra
tion.
If the pump has been mounted on a moveable
base, make certain the base is stationary by setting
the brake and blocking the wheels before attempt
ing to operate the pump.
To ensure sufficient lubrication and fuel supply to
the engine, do not position the pump and engine
more than 15_off horizontal for continuous opera
tion. The pump and engine may be positioned up
to 30_off horizontal for intermittent operation
only; however, the engine manufacturer should be
consulted for continuous operation at angles
greater than 15_.
Clearance
When positioning the pump, allow a minimum
clearance of 18 inches (457,2 mm) in front of the
back cover to permit removal of the cover and easy
access to the pump interior.
SUCTION AND DISCHARGE PIPING
Pump performance is adversely effected by in
creased suction lift, discharge elevation, and fric
tion losses. See the performance curve and notes
on Page E‐1 to be sure your overall application al
lows pump to operate within the safe operation
range.
Materials
Either pipe or hose maybe used for suction and
discharge lines; however, the materials must be
compatible with the liquid being pumped. If hose is
used in suction lines, it must be the rigid‐wall, rein
forced type to prevent collapse under suction. Us
ing piping couplings in suction lines is not recom
mended.

10 SERIES OM-06788
PAGE B - 3INSTALLATION
Line Configuration
Keep suction and discharge lines as straight as
possible to minimize friction losses. Make mini
mum use of elbows and fittings, which substan
tially increase friction loss. If elbows are necessary,
use the long‐radius type to minimize friction loss.
Connections to Pump
Before tightening a connecting flange, align it ex
actly with the pump port. Never pull a pipe line into
place by tightening the flange bolts and/or cou
plings.
Lines near the pump must be independently sup
ported to avoid strain on the pump which could
cause excessive vibration, decreased bearing life,
and increased shaft and seal wear. If hose‐type
lines are used, they should have adequate support
to secure them when filled with liquid and under
pressure.
Gauges
Most pumps are drilled and tapped for installing
discharge pressure and vacuum suction gauges. If
these gauges are desired for pumps that are not
tapped, drill and tap the suction and discharge
lines not less than 18 inches (457,2 mm) from the
suction and discharge ports and install the lines.
Installation closer to the pump may result in erratic
readings.
SUCTION LINES
To avoid air pockets which could affect pump prim
ing, the suction line must be as short and direct as
possible. When operation involves a suction lift, the
line must always slope upward to the pump from
the source of the liquid being pumped; if the line
slopes down to the pump at any point along the
suction run, air pockets will be created.
The maximum vertical suction lift for this pump is
25 ft. (7,6 m). It is not designed to be operated at a
higher lift.
Fittings
Suction lines should be the same size as the pump
inlet. If reducers are used in suction lines, they
should be the eccentric type, and should be in
stalled with the flat part of the reducers uppermost
to avoid creating air pockets. Valves are not nor
mally used in suction lines, but if a valve is used,
install it with the stem horizontal to avoid air pock
ets.
Strainers
If a strainer is furnished with the pump, be certain
to use it; any spherical solids which pass through a
strainer furnished with the pump will also pass
through the pump itself.
If a strainer is not furnished with the pump, but is
installed by the pump user, make certain that the
total area of the openings in the strainer is at least
three or four times the cross section of the suction
line, and that the openings will not permit passage
of solids larger than the solids handling capability
of the pump.
This pump is designed to handle up to 1‐3/16 inch
(30 mm) diameter spherical solids.
Sealing
Since even a slight leak will affect priming, head,
and capacity, especially when operating with a
high suction lift, all connections in the suction line
should be sealed with pipe dope to ensure an air
tight seal. Follow the sealant manufacturer's rec
ommendations when selecting and applying the
pipe dope. The pipe dope should be compatible
with the liquid being pumped.
Suction Lines In Sumps
If a single suction line is installed in a sump, it
should be positioned away from the wall of the
sump at a distance equal to 1‐1/2 times the diame
ter of the suction line.
If there is a liquid flow from an open pipe into the
sump, the flow should be kept away from the suc
tion inlet because the inflow will carry air down into
the sump, and air entering the suction line will re
duce pump efficiency.

OM-06788 10 SERIES
PAGE B - 4 INSTALLATION
If it is necessary to position inflow close to the suc
tion inlet, install a baffle between the inflow and the
suction inlet at a distance 1‐1/2 times the diameter
of the suction pipe. The baffle will allow entrained
air to escape from the liquid before it is drawn into
the suction inlet.
If two suction lines are installed in a single sump,
the flow paths may interact, reducing the efficiency
of one or both pumps. To avoid this, position the
suction inlets so that they are separated by a dis
tance equal to at least 3 times the diameter of the
suction pipe.
Suction Line Positioning
The depth of submergence of the suction line is
critical to efficient pump operation. Figure 2 shows
recommended minimum submergence vs. veloc
ity.
NOTE
The pipe submergence required may be reduced
by installing a standard pipe increaser fitting at the
end of the suction line. The larger opening size will
reduce the inlet velocity. Calculate the required
submergence using the following formula based
on the increased opening size (area or diameter).
Figure 2. Recommended Minimum Suction Line Submergence vs. Velocity
DISCHARGE LINES
Siphoning
Do not terminate the discharge line at a level lower
than that of the liquid being pumped unless a si
phon breaker is used in the line. Otherwise, a si
phoning action causing damage to the pump
could result.
Valves
If a throttling valve is desired in the discharge line,
use a valve as large as the largest pipe to minimize
friction losses. Never install a throttling valve in a
suction line.
A check valve in the discharge line is normally rec
ommended, but it is not necessary in low dis
charge head applications.
With high discharge heads, it is recommended that
a throttling valve and a system check valve be in

10 SERIES OM-06788
PAGE B - 5INSTALLATION
stalled in the discharge line to protect the pump
from excessive shock pressure and reverse rota
tion when it is stopped.
If the application involves a high discharge
head, gradually close the discharge
throttling valve before stopping the pump.
Bypass Lines
If a system check valve is used due to high dis
charge head, it may be necessary to vent trapped
air from the top of the pump during the priming
process. This may be accomplished by installing a
bypass line from the top of the pump, back to the
source of liquid. The end of the bypass line must be
submerged. The line must be large enough to pre
vent clogging, but not so large as to affect pump
discharge capacity.

OM-06788
10 SERIES
OPERATION PAGE C - 1
OPERATION - SECTION C
Review all SAFETY information in Section A.
Follow the instructions on all tags, labels and
decals attached to the pump.
This pump is designed to pump most
non‐volatile, non‐flammable liquids
containing specified entrained solids.
Do not attempt to pump volatile, corro
sive, or flammable liquids which may
damage the pump or endanger person
nel as a result of pump failure.
Never tamper with the governor to gain
more power. The governor establishes
safe operating limits that should not be
exceeded. The maximum continuous
operating speed for this pump is 3600
RPM.
PRIMING
Install the pump and piping as described in IN
STALLATION. Make sure that the piping connec
tions are tight, and that the pump is securely
mounted. Check that the pump is properly lubri
cated (see LUBRICATION in MAINTENANCE
AND REPAIR).
This pump is self‐priming, but the pump should
never be operated unless there is liquid in the
pump casing.
Never operate this pump unless there is
liquid in the pump casing. The pump will
not prime when dry. Extended operation of
a dry pump will destroy the seal assembly.
Add liquid to the pump casing when:
1. The pump is being put into service for the
first time.
2. The pump has not been used for a consider
able length of time.
3. The liquid in the pump casing has evapo
rated.
Once the pump casing has been filled, the pump
will prime and reprime as necessary.
After filling the pump casing, reinstall
and tighten the fill plug. Do not attempt
to operate the pump unless all connect
ing piping is securely installed. Other
wise, liquid in the pump forced out un
der pressure could cause injury to per
sonnel.
To fill the pump, remove the pump casing fill cover
or fill plug in the top of the casing, and add clean
liquid until the casing is filled. Replace the fill cover
or fill plug before operating the pump.
STARTING
Consult the operations manual furnished with the
engine.
OPERATION
Pump speed and operating condition
points must be within the continuous per
formance range shown on the curve (see
Section E, Page 1).

OM-06788 10 SERIES
OPERATIONPAGE C - 2
Lines With a Bypass
Close the discharge throttling valve (if so
equipped) so that the pump will not have to prime
against the weight of the liquid in the discharge
line. Air from the suction line will be discharged
through the bypass line back to the wet well during
the priming cycle. When the pump is fully primed
and liquid is flowing steadily from the bypass line,
open the discharge throttling valve. Liquid will then
continue to circulate through the bypass line while
the pump is in operation.
Lines Without a Bypass
Open all valves in the discharge line and start the
engine. Priming is indicated by a positive reading
on the discharge pressure gauge or by a quieter
operation. The pump may not prime immediately
because the suction line must first fill with liquid. If
the pump fails to prime within five minutes, stop it
and check the suction line for leaks.
After the pump has been primed, partially close the
discharge line throttling valve in order to fill the line
slowly and guard against excessive shock pres
sure which could damage pipe ends, gaskets,
sprinkler heads, and any other fixtures connected
to the line. When the discharge line is completely
filled, adjust the throttling valve to the required flow
rate.
Leakage
No leakage should be visible at pump mating sur
faces, or at pump connections or fittings. Keep all
line connections and fittings tight to maintain maxi
mum pump efficiency.
Liquid Temperature And Overheating
The maximum liquid temperature for this pump is
110_F (43_C). Do not apply it at a higher operating
temperature.
Overheating can occur if operated with the valves
in the suction or discharge lines closed. Operating
against closed valves could bring the liquid to a
boil, build pressure, and cause the pump to rup
ture or explode. If overheating occurs, stop the
pump and allow it to cool before servicing it. Refill
the pump casing with cool liquid.
Do not remove plates, covers, gauges,
pipe plugs, or fittings from an over
heated pump. Vapor pressure within the
pump can cause parts being disen
gaged to be ejected with great force. Al
low the pump to cool before servicing.
Strainer Check
If a suction strainer has been shipped with the
pump or installed by the user, check the strainer
regularly, and clean it as necessary. The strainer
should also be checked if pump flow rate begins to
drop. If a vacuum suction gauge has been in
stalled, monitor and record the readings regularly
to detect strainer blockage.
Never introduce air or steam pressure into the
pump casing or piping to remove a blockage. This
could result in personal injury or damage to the
equipment. If backflushing is absolutely neces
sary, liquid pressure must be limited to 50% of the
maximum permissible operating pressure shown
on the pump performance curve (see Section E,
Page 1). If the pump is fitted with a Gorman‐Rupp
double grease lubricated seal, the maximum in
coming pressure must be reduced to 10 p.s.i.
Pump Vacuum Check
With the pump inoperative, install a vacuum gauge
in the system, using pipe dope on the threads.
Block the suction line and start the pump. At oper
ating speed the pump should pull a vacuum of 20
inches (508 mm) or more of mercury. If it does not,
check for air leaks in the seal, gasket, or discharge
valve.
Open the suction line, and read the vacuum gauge
with the pump primed and at operation speed.
Shut off the pump. The vacuum gauge reading will
immediately drop proportionate to static suction
lift, and should then stabilize. If the vacuum reading
falls off rapidly after stabilization, an air leak exists.
Before checking for the source of the leak, check
the point of installation of the vacuum gauge.

OM-06788
10 SERIES
OPERATION PAGE C - 3
STOPPING
Never halt the flow of liquid suddenly. If the liquid
being pumped is stopped abruptly, damaging
shock waves can be transmitted to the pump and
piping system. Close all connecting valves slowly.
On engine driven pumps, reduce the throttle
speed slowly and allow the engine to idle briefly be
fore stopping.
If the application involves a high discharge
head, gradually close the discharge
throttling valve before stopping the pump.
After stopping the pump, remove the positive bat
tery cable to ensure that the pump will remain inop
erative.
Cold Weather Preservation
In below freezing conditions, drain the pump to
prevent damage from freezing. Also, clean out any
solids by flushing with a hose. Operate the pump
for approximately one minute; this will remove any
remaining liquid that could freeze the pump rotat
ing parts. If the pump will be idle for more than a
few hours, or if it has been pumping liquids con
taining a large amount of solids, drain the pump,
and flush it thoroughly with clean water. To prevent
large solids from clogging the drain port and pre
venting the pump from completely draining, insert
a rod or stiff wire in the drain port, and agitate the
liquid during the draining process. Clean out any
remaining solids by flushing with a hose.

TROUBLE POSSIBLE CAUSE PROBABLE REMEDY
PUMP FAILS TO
PRIME
Strainer clogged. Check strainer and clean if neces
sary.
Suction lift or discharge head too high. Check piping installation and install
bypass line if needed. See INSTAL
LATION.
Leaking or worn seal or pump gasket. Check pump vacuum. Replace
leaking or worn seal or gasket.
Lining of suction hose collapsed. Replace suction hose.
Air leak in suction line. Correct leak.
Suction check valve or foot valve
clogged or binding.
Clean valve.
Not enough liquid in casing. Add liquid to casing. See PRIMING.
Suction check valve contaminated or
damaged.
Clean or replace check valve.
OM-0678810 SERIES
TROUBLESHOOTING PAGE D - 1
TROUBLESHOOTING - SECTION D
Review all SAFETY information in Section A.
Before attempting to open or service the
pump:
1. Familiarize yourself with this manual.
2. Shut down the engine and take pre
cautions to ensure that the pump will
remain inoperative.
3. Allow the pump to completely cool if
overheated.
4. Check the temperature before open
ing any covers, plates, or plugs.
5. Close the suction and discharge
valves.
6. Vent the pump slowly and cautiously.
7. Drain the pump.

TROUBLE POSSIBLE CAUSE PROBABLE REMEDY
PUMP STOPS OR
FAILS TO DELIVER
RATED FLOW OR
PRESSURE
PUMP REQUIRES
TOO MUCH
POWER
PUMP CLOGS
FREQUENTLY
Free impeller of debris.Impeller clogged.
Discharge head too low.
Dilute if possible.Liquid solution too thick.
Adjust discharge valve.
Open discharge valve fully to in
crease flow rate, and run engine at
maximum governed speed.
Discharge flow too slow.
EXCESSIVE NOISE Cavitation in pump. Reduce suction lift and/or friction
losses in suction line. Record vac
uum and pressure gauge readings
and consult local representative or
factory.
Secure mounting hardware.Pump or drive not securely mounted.
Locate and eliminate source of air
bubble.
Pumping entrained air.
Strainer clogged. Check strainer and clean if neces
sary.
Suction check valve or foot valve
clogged or binding.
Clean valve.
Leaking or worn seal or pump gasket. Check pump vacuum. Replace
leaking or worn seal or gasket.
Pump speed too slow. Check engine output; consult en
gine operation manual.
Pump speed too high. Check engine output.
Suction lift or discharge head too high. Check piping installation and install
bypass line if needed. See INSTAL
LATION.
Discharge line clogged or restricted;
hose kinked.
Check discharge lines; straighten
hose.
Impeller clogged or dam
aged.
Clean out debris; replace damaged
parts.
Air leak in suction line. Correct leak.
Lining of suction hose collapsed. Replace suction hose.
Suction intake not submerged at
proper level or sump too small.
Check installation and correct
submergence as needed.
Impeller or other wearing parts worn
or damaged.
Replace worn or damaged parts.
Check that impeller is properly
centered and rotates freely.
OM-06788 10 SERIES
TROUBLESHOOTINGPAGE D - 2

OM-0678810 SERIES
TROUBLESHOOTING PAGE D - 3
PREVENTIVE MAINTENANCE
Since pump applications are seldom identical, and
pump wear is directly affected by such things as
the abrasive qualities, pressure and temperature
of the liquid being pumped, this section is intended
only to provide general recommendations and
practices for preventive maintenance. Regardless
of the application however, following a routine pre
ventive maintenance schedule will help assure
trouble‐free performance and long life from your
Gorman‐Rupp pump. For specific questions con
cerning your application, contact your Gorman‐
Rupp distributor or the Gorman‐Rupp Company.
Record keeping is an essential component of a
good preventive maintenance program. Changes
in suction and discharge gauge readings (if so
equipped) between regularly scheduled inspec
tions can indicate problems that can be corrected
before system damage or catastrophic failure oc
curs. The appearance of wearing parts should also
be documented at each inspection for comparison
as well. Also, if records indicate that a certain part
(such as the seal) fails at approximately the same
duty cycle, the part can be checked and replaced
before failure occurs, reducing unscheduled down
time.
For new applications, a first inspection of wearing
parts at 250 hours will give insight into the wear rate
for your particular application. Subsequent inspec
tions should be performed at the intervals shown
on the chart below. Critical applications should be
inspected more frequently.
General Condition (Temperature, Unusual
Noises or Vibrations, Cracks, Leaks,
Loose Hardware, Etc.) I
Pump Performance (Gauges, Speed, Flow) I
Bearing Lubrication I R
Seal Lubrication (And Packing Adjustment,
If So Equipped) I R
V‐Belts (If So Equipped) I
Air Release Valve Plunger Rod (If So Equipped) I C
Front Impeller Clearance (Wear Plate) I
Rear Impeller Clearance (Seal Plate) I
Check Valve I
Pressure Relief Valve (If So Equipped) C
Pump and Driver Alignment I
Shaft Deflection I
Bearings I
Bearing Housing I
Piping I
Driver Lubrication - See Mfgr's Literature
Legend:
I = Inspect, Clean, Adjust, Repair or Replace as Necessary
C = Clean
R = Replace
* Service interval based on an intermittent duty cycle equal to approximately 4000 hours annually.
Adjust schedule as required for lower or higher duty cycles or extreme operating conditions.
Preventive Maintenance Schedule
Item Daily Weekly Monthly Semi‐
Annually
Annually
Service Interval*

10 SERIES OM-06788
MAINTENANCE & REPAIR PAGE E - 1
PUMP MAINTENANCE AND REPAIR ‐ SECTION E
MAINTENANCE AND REPAIR OF THE WEARING PARTS OF THE PUMP WILL MAINTAIN PEAK
OPERATING PERFORMANCE.
STANDARD PERFORMANCE FOR PUMP MODEL 12D-1B20 FT4
Based on 70_F (21_C) clear water at sea level
with minimum suction lift. Since pump installations
are seldom identical, your performance may be dif
ferent due to such factors as viscosity, specific
gravity, elevation, temperature, and impeller trim.
If your pump serial number is followed by an “N”,
your pump is NOT a standard production model.
Contact the Gorman‐Rupp Company to verify per
formance or part numbers.
Never tamper with the governor to gain
more power. The governor establishes
safe operating limits that should not be
exceeded. The maximum continuous
operating speed for this pump is 3600
RPM.

10 SERIESOM-06788
MAINTENANCE & REPAIRPAGE E - 2
ILLUSTRATION
PARTSPAGE
Figure 1. Pump Model 12D-1B20 FT4