GORMAN-RUPP PUMPS GMS1 1/2 User manual

OM-07468-05
September 1, 2022
GORMAN‐RUPP PUMPS
www.grpumps.com
2022 Gorman‐Rupp Pumps Printed in U.S.A.
INSTALLATION, OPERATION,
AND MAINTENANCE MANUAL
ROTARY GEAR PUMP
MODELS
GMS SERIES PUMPS
GMS1 1/2GH3-B /S2

Register your new
Gorman‐Rupp pump online at
www.grpumps.com
Valid serial number and e‐mail address required.
RECORD YOUR PUMP MODEL AND SERIAL NUMBER
Please record your pump model and serial number in the
spaces provided below. Your Gorman‐Rupp distributor
needs this information when you require parts or service.
Pump Model:
Serial Number:

TABLE OF CONTENTS
i
INTRODUCTION PAGE I - 1...................................................
SAFETY - SECTION A PAGE A - 1............................................
INSTALLATION - SECTION B PAGE B - 1.....................................
PUMP MODEL DESIGNATION PAGE B-1..................................................
PREINSTALLATION INSPECTION PAGE B-2................................................
STORAGE PAGE B-2....................................................................
Flushing PAGE B-2..................................................................
PUMP INSTALLATION PAGE B-3..........................................................
Lifting PAGE B-3.....................................................................
Positioning The Pump PAGE B-3......................................................
Mounting PAGE B-3.................................................................
Piping PAGE B-3....................................................................
Strainers PAGE B-4..................................................................
Gauges PAGE B-4...................................................................
Sealing PAGE B-4...................................................................
Valves PAGE B-4....................................................................
Barrier Liquids for Optional Double Lipseal PAGE B-4....................................
ALIGNMENT PAGE B-4..................................................................
Coupled Drives PAGE B-4............................................................
V‐Belt Drives PAGE B-5...............................................................
V‐BELT TENSIONING PAGE B-5..........................................................
General Rules of Tensioning PAGE B-5.................................................
Tension Measurement PAGE B-6......................................................
ELECTRICAL CONNECTIONS PAGE B-7...................................................
OPERATION - SECTION C PAGE C - 1.......................................
PUMP OPERATION PAGE C-1............................................................
PRE‐OPERATION PAGE C-1..............................................................
Before Starting The Pump PAGE C-1...................................................
Checking Pump Rotation PAGE C-1...................................................
STARTING PAGE C-1....................................................................
OPERATION PAGE C-2..................................................................
Liquid Temperature PAGE C-2.........................................................
Overheating PAGE C-2...............................................................
Checking Gauges PAGE C-2..........................................................
Strainer Check PAGE C-2.............................................................
Leakage PAGE C-2..................................................................
PRESSURE RELIEF VALVE ADJUSTMENT PAGE C-3........................................
Cracking Pressure PAGE C-3.........................................................
Complete By‐Pass Pressure PAGE C-3.................................................
STOPPING PAGE C-3....................................................................
TROUBLESHOOTING - SECTION D PAGE D - 1...............................
TROUBLESHOOTING WITH GAUGES PAGE D-1............................................
TROUBLESHOOTING CHART PAGE D-2...................................................
PREVENTIVE MAINTENANCE PAGE D-3...................................................

TABLE OF CONTENTS
(continued)
ii
PUMP MAINTENANCE AND REPAIR - SECTION E PAGE E - 1.................
PARTS KEY:
Typical GMS D, G, J And N Pump Models PAGE E-3.....................................
Typical GMS R Pump Model PAGE E-5.................................................
PUMP DISASSEMBLY PAGE E-6..........................................................
Preparing for Disassembly PAGE E-7..................................................
Pressure Relief Valve (10) PAGE E-7...................................................
Foot Bracket Kit (08) PAGE E-7........................................................
Head/Idler Kit (01/02) PAGE E-7.......................................................
Gland Removal (04N) PAGE E-7.......................................................
Backhead Removal (06) PAGE E-8....................................................
Rotor/Shaft Removal (03) PAGE E-8...................................................
Seal Removal (05) PAGE E-8..........................................................
Housing Assembly (04) PAGE E-8.....................................................
PUMP REASSEMBLY PAGE E-8..........................................................
Cleaning and Inspection PAGE E-8....................................................
Bushing Preparation PAGE E-9........................................................
Housing Assembly (04) PAGE E-9.....................................................
Backhead Kit (06) PAGE E-9..........................................................
Rotor/Shaft Assembly (03) PAGE E-9..................................................
Head/Idler Kit (01/02) PAGE E-10......................................................
Seal Installation (05) PAGE E-10.......................................................
Gland Installation (04N) PAGE E-10....................................................
Foot Bracket Kit (08) PAGE E-10.......................................................
SETTING END CLEARANCE PAGE E-10...................................................
RELIEF VALVE DISASSEMBLY PAGE E-11.................................................
RELIEF VALVE REASSEMBLY PAGE E-12..................................................
Relief Valve (10) Installation PAGE E-13................................................
SEAL APPENDIX - SECTION F PAGE F-1.....................................
Standard Friction Drive And Optional 60A And 61J Mech. Seals PAGE F-1......................
Lip Seal Option 65A PAGE F-3............................................................
Positive Drive (Option 60D) Seal PAGE F-5..................................................
Standard Packing Seal (Option 65) PAGE F-7...............................................
O‐RING APPENDIX - SECTION G PAGE G-1..................................
JACKETED HEAD/BACKHEAD APPENDIX - SECTION H ………………….PAGE H-1
Inlet and Outlet Location …… .PAGE H-1...................................................

OM-04386GMS SERIES
PAGE I-1INTRODUCTION
INTRODUCTION
Thank You for purchasing a Gorman‐Rupp Rotary
Gear Pump. This manual is designed to help you
achieve the best performance and longest life from
your Gorman‐Rupp Rotary Gear pump. Read this
manual carefully to learn how to safely install, op
erate and repair your pump. Failure to do so could
result in personal injury or damage to the pump.
This manual will alert personnel to known proce
dures which require special attention, to those
which could damage equipment, and to those
which could be dangerous to personnel. However,
this manual cannot possibly provide detailed in
structions and precautions for each specific ap
plication or for every situation that might occur dur
ing maintenance of the unit. Therefore, it is the re
sponsibility of the owner, installer and/or mainte
nance personnel to ensure that applications and/
or maintenance procedures not addressed in this
manual are performed only after establishing that
neither personal safety nor pump integrity are
compromised by such applications or procedures.
In addition to this manual, a separate Parts List is
shipped with the pump. Refer to the Parts List when
ordering parts. If your pump is furnished with a
drive unit, refer to the drive unit manufacturer's in
stallation and operation instructions in the litera
ture accompanying the pump.
These pumps can transfer a wide range of light,
medium, and heavy viscosity liquids, depending
on design and components. Some models are
not recommended for use with water; others
when fitted with specific options, may be used
with water; consult the factory.
If there are any questions regarding the pump or
drive unit which are not covered in this manual or
in other literature accompanying this unit, please
contact your Gorman‐Rupp distributor or the Gor
man‐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]
WARRANTY INFORMATION
The warranty provided with your pump is part of
Gorman‐Rupp's support program for customers
who operate and maintain their equipment as de
scribed in this and the other accompanying litera
ture. Please note that should the equipment be
abused or modified to change its performance be
yond the original factory specifications, the war
ranty will become void and any claim will be de
nied.
The following are used to alert personnel to proce
dures which require special attention, 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 de
scribe the requirements and the possible
damage which could result from failure to
follow the procedure.
NOTE
Instructions to aid in installation, operation, and
maintenance or which clarify a procedure.

GMS SERIESOM-04386
PAGE I-2 INTRODUCTION
RECORDING MODEL AND
SERIAL NUMBERS
Please record the pump model and serial number
in the spaces provided below. Your Gorman‐Rupp
distributor needs this information when you require
parts or service.
Pump Model:
Serial Number:

OM-07468-05GMS SERIES
SAFETY PAGE A-1
SAFETY - SECTION A
This information is specific to Gorman‐Rupp GMS
Series Rotary Gear Pumps. It applies throughout
this manual and any manual or literature ac
companying the pump.
In addition to this manual, see the separate litera
ture covering the drive unit used to operate this
pump.
Pumps and related equipment must be in
stalled and operated according to all na
tional, local and industry standards.
This manual will alert personnel to
known procedures which require spe
cial attention, to those which could
damage equipment, and to those which
could be dangerous to personnel. How
ever, this manual cannot possibly pro
vide detailed instructions and precau
tions for each specific application or for
every situation that might occur during
maintenance of the unit. Therefore, it is
the responsibility of the owner, installer
and/or maintenance personnel to en
sure that applications and/or mainte
nance procedures not addressed in this
manual are performed only after estab
lishing that neither personal safety nor
pump integrity are compromised by
such applications or procedures.
Before attempting to install, operate, or
service this pump, familiarize yourself
with this manual, and with all other liter
ature shipped with the pump. Unfamil
iarity with all aspects of pump operation
covered in this manual could lead to de
struction of equipment, injury, or death.
The standard version of this pump is de
signed to handle a wide range of light,
medium, and heavy viscosity liquid, de
pending on design and components,
and a range of temperatures when fitted
with different seals. Do not apply at
higher temperatures than the seal will
handle. Do not attempt to pump liquids
which may damage the pump or endan
ger personnel as a result of pump fail
ure; consult the factory for chemical
compatibility.
If the pump and motor are furnished
mounted on a base, make certain that all
lifting devices have adequate capacity.
If chains or cables are used in lifting,
make certain that they are positioned so
as not to damage components, and so
that the load will be balanced.
After the pump has been installed, make
certain that the pump and all piping or
hose connections are secure before op
eration. Loose connections can result in
damage to the equipment and serious
injury to personnel.
Never operate the pump without a pres
sure relief valve installed on the pump
or in the discharge piping. Make certain
that pump‐mounted pressure relief

GMS SERIESOM-07468-05
PAGE A-2 SAFETY
valves are installed with their adjusting
ends toward the suction port. If bi‐rota
tional operation is required, a pressure
relief device must be provided for both
directions of flow. Operation without a
pressure relief valve or with an improp
erly installed relief valve could cause
the pump to explode, resulting in seri
ous injury or death to personnel.
Before attempting to open or service the
pump:
1. Familiarize yourself with this man
ual.
2. Lock out incoming power to the
drive unit to ensure that the pump
will remain inoperative.
3. Allow the pump to completely cool
if overheated.
4. Close the discharge and suction
valve (if used).
An overheated pump can cause severe
burns and injury. If overheating occurs:
1. Stop the pump immediately.
2. Allow the pump to completely cool.
3. Refer to the instructions in this
manual before restarting the
pump.
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 completely cool before
servicing.
Do not operate this pump without
guards in place over the rotating parts.
Exposed rotating parts can catch cloth
ing, fingers or tools, causing severe in
jury to personnel.
This pump may be used to handle liq
uids which may cause serious illness or
injury through direct exposure or
emitted fumes. Wear protective cloth
ing, such as rubber gloves, face mask
and rubber apron, as necessary, before
disconnecting or servicing the pump or
piping.

GHC SERIES OM-07468-05
PAGE B-1INSTALLATION
INSTALLATION - SECTION B
Review all SAFETY information in Section A.
Pumps and related equipment must be in
stalled and operated according to all na
tional, local and industry standards.
Since pump installations are seldom identical, this
section is intended only to summarize general rec
ommendations and practices required to inspect,
position, and arrange the pump and piping. If there
are any questions concerning your specific instal
lation, contact your Gorman‐Rupp distributor or
the Gorman‐Rupp Company.
Most of the information applies to a flooded suction
installation where liquid is supplied under pres
sure.
If the pump is positioned above the liquid in a static
lift installation, information such as mounting, pip
ing configuration and priming must be tailored to
specific conditions.
These pumps are not recommended for
use with water. Some models, when fitted
with specific options, may be used with wa
ter; consult the factory.
PUMP MODEL DESIGNATION
Following is a description of the model numbering
system for Gorman‐Rupp rotary gear pumps.
Rotary gear pump model numbers include design
style, port size, hydraulic size and construction
code.
Typical Pump Model
GHS 1 1/2 GF 32
Design
Style
Port
Size
Hydraulic
Size
Construction
Code
Design Style: Gorman‐Rupp rotary gear pumps
are available in five basic designs:
GMC - Medium Duty - Compact
GMS - Medium Duty
GHC - Heavy Duty - Compact
GHS - Heavy Duty
GHA - Abrasive Duty
Port Size: Gorman‐Rupp rotary gear pumps are
available in port sizes from 1 to 6 inches, depend
ing on the design style. Consult your Gorman‐
Rupp distributor or the factory for additional sizes.
Hydraulic Size: The first letter in the hydraulic size
is a rotor diameter code. The second letter indi
cates tooth length.
Construction Code: Construction Codes for Gor
man‐Rupp rotary gear pumps are as follows:
Code Description
3 Iron w/Mechanical Seal(s)
4 Iron w/Packing or Lip Seal(s)
9 316 SST w/Mechanical Seal(s)
10 316 SST w/Packing or Lip Seal(s)
32 Steel w/Mechanical Seal(s)
38 Steel w/Packing or Lip Seal(s)
Theoretical Displacement: Table B‐1 indicates
theoretical displacement values for each hydraulic
size.
NOTE
Actual capacities and recommended shaft speeds
vary according to application. Consult your Gor
man‐Rupp distributor or the factory for addtional in
formation.

GMS SERIES
OM-07468-05
PAGE B-2 INSTALLATION
Table B‐1. Theoretical Displacement
Hydraulic
Size
Theoretical Displacement
Per Revolution
Gallons Centimeters3
DC 0.00568 21.486
DE 0.00704 26.646
GC 0.00967 36.619
GF 0.01405 53.186
GH 0.01915 72.479
GJ 0.02317 87.700
JG 0.03579 135.49
JJ 0.05159 195.28
JL 0.07078 267.94
JP 0.10078 381.48
NK 0.10665 403.71
NM 0.14173 536.51
NP 0.17681 669.31
RM 0.24030 909.65
RP 0.29979 1134.8
RR 0.35927 1360.0
RS 0.41876 1585.1
SR 0.65752 2489.0
SU 1.10240 4173.2
TU 1.91280 7240.7
PREINSTALLATION INSPECTION
The pump assembly was inspected and tested be
fore shipment from the factory. Before installation,
check for damage which may have occurred dur
ing shipment. Check as follows:
a. Inspect the pump assembly for cracks, dents,
damaged threads, and other obvious dam
age.
b. Check for loose attaching hardware. Since
gaskets tend to shrink after drying, check for
loose hardware at the mating surfaces.
c. Carefully read all tags, decals, and markings
on the pump assembly, and perform all duties
indicated.
STORAGE
Due to the extreme close machining toler
ances within rotary gear pumps, proper
storage before installation is essential to
prevent damage to the pump.
If the pump will not be immediately installed, follow
these procedures or damage to the pump will oc
cur.
a. Do not flush the pump. Ensure that the port
plugs shipped with the pump remain in place
until piping is installed to help prevent dust or
other foreign objects from entering the pump.
b. Pumps that will not be installed for an ex
tended period should be stored indoors if
possible. The factory‐installed port plugs will
not ensure protection from excessive humid
ity, splash water or rain. In very humid or wet
conditions, install air‐tight plugs in the ports
and fill the pump completely with a lubricating
preservative liquid that is compatible with the
liquid to be pumped.
c. Pumps stored outdoors must be fully pre
served as described above, completely cov
ered with plastic or other water‐tight material,
and the covering anchored to ensure that it
will not be blown off.
Flushing
Clean piping is essential because of close‐
tolerance moving parts in this pump. Flush
all dirt, grit, weld beads or scale from the
suction piping before installing the pump.
Damage to the pump because of debris in
the suction line is not covered by the pump
warranty.
The pump may have been tested using a petro
leum‐based preservative, or a preservative may
have been used for long‐term storage of the pump.
If flushing is required, do not do so until just before
installation; the test oil protects close‐tolerance
pump parts from corrosion.
Most cleaning solvents are toxic and
flammable. Use them only in a well ven
tilated area free from flame, sparks, and
excessive heat. Read and follow all pre
cautions printed on solvent containers.

GHC SERIES OM-07468-05
PAGE B-3INSTALLATION
To flush the pump, use an approved solvent com
patible with the liquid being pumped. Make cer
tain that the solvent will not attack pump com
ponents, particularly seals and gaskets.
PUMP INSTALLATION
Pump dimensions are shown in the separate
Pump Specification Bulletin.
Never operate the pump without a pres
sure relief valve installed on the pump
or in the discharge piping. Make certain
that pump‐mounted pressure relief
valves are installed with their adjusting
ends toward the suction port. If bi‐rota
tional operation is required, a pressure
relief device must be provided for both
directions of flow. Operation without a
pressure relief valve or with an improp
erly installed relief valve could cause
the pump to explode, resulting in seri
ous injury or death to personnel.
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.
Positioning The Pump
Locate the pump as close as possible to the liquid
being pumped. Locating the pump below the liq
uid source will help self‐priming and reduce the
possibility of cavitation.
Mounting
The pump may be shipped alone, mounted on a
base, or with pump and motor mounted on a base.
Install the pump and motor on a base before
mounting the base on a foundation.
Mount the base on a foundation that will provide
permanent, rigid support for the pump, and will be
heavy enough to absorb any vibration, strain or
shock.
Piping
Before establishing suction and discharge lines,
determine pump port positions and rotation. Fig
ure B‐1 shows typical port positions for the stan
dard 90housing; if you have selected a 180
housing port option, your port positions will be dif
ferent.
Begin piping layout at the pump, and work toward
the source of supply and the point of discharge.
Either hose or rigid pipe may be used to make con
nections. If rigid piping is used, install expansion
joints to protect the pump from vibration and ther
mal expansion in the piping. Do not use expansion
joints or flexible connectors to adjust misaligned
piping.
Housing Position Std. 90 Pump
(3-12 O'clock) Head Mounted Relief Valve
STD.
OPT.
Rotation Clockwise
Drive End
Rotation Counter‐clockwise
01A
D
SS
Front End
S
D
D
D
S
Figure B‐1. Typical Port Positions & Rotation
The discharge and suction lines must be inde
pendently supported to avoid vibration and strain
on the pump. For maximum pumping capacity,
keep the lines as short and straight as possible. El

GMS SERIES
OM-07468-05
PAGE B-4 INSTALLATION
bows and fittings used in the lines increase friction
losses; minimize their use. Reducers used in suc
tion lines should be the eccentric type installed
with the flat part uppermost to avoid creating air
pockets.
Before tightening a connection or flange, align it
exactly with the pump port. Never pull a pipe line
into place by tightening the flange bolts and/or
couplings.
Strainers
Because of the close‐tolerance moving parts of
this pump, it is recommended that a strainer be in
stalled in the suction line. The strainer should be
large enough to prevent excessive vacuum, and
capable of operating under high vacuum without
collapsing. The net open area of the strainer
screen depends on liquid viscosity and desired
flow rate; in any case, the sum of the area of all the
holes in the screen should be three to five times the
area of the suction pipe.
Gauges
To monitor operation and assist in troubleshooting,
a vacuum gauge and a pressure gauge should be
installed on the pump.
Sealing
Even a slight leak will affect priming, head, and ca
pacity, especially in a suction lift application. Seal
all piping joints, valves and gauges with pipe dope
or teflon tape. The sealing material should be com
patible with the liquid being pumped.
Valves
To avoid air pockets, install piping valves with the
stem horizontal.
To prevent leakage during shutdown, install a shut
off valve in the discharge line, particularly on a
flooded suction application. Shutoff valves are not
recommended for suction lines.
It is not recommended that a foot valve be installed
at the end of the suction line. If desired to install a
foot valve, consult the factory.
When handling very hot or cold liquids, install a
pressure relief valve in any part of the system that
can be valved off or isolated; this will protect piping
against damage from liquid thermal expansion or
contraction from temperature changes during
shutdown.
Barrier Liquids for Optional Double Lipseal
In general, a barrier liquid is always recommended
for these seals. This requirement may be satisfied
by a simple oiler, or it may become more compli
cated based on the application. The following bar
rier liquid guidelines are offered for maximum per
formance;
1. Select a clean, lubricating liquid that is
compatible with the pumped product
and with the pump construction (iron or
316 SST).
2. Depending upon pump shaft speed, a
pressurized barrier liquid may not be re
quired. Consult the factory for your spe
cific application.
ALIGNMENT
Make certain that power to the drive unit
is disconnected before attempting to
connect the pump drive; otherwise, per
sonal injury may result.
NOTE
See ROTATION in Section C before mounting the
pump on the base.
Coupled Drives
When using couplings, the axis of the power
source must be aligned to the axis of the pump
shaft in both the horizontal and vertical planes.
Most couplings require a specific gap or clearance
between the driving and the driven shafts. Refer to
the coupling manufacturer's service literature.
Align spider insert type couplings by using calipers
to measure the dimensions on the circumference
of the outer ends of the coupling hub every 90.

GHC SERIES OM-07468-05
PAGE B-5INSTALLATION
The coupling is in alignment when the hub ends
are the same distance apart at all points (see Fig
ure B‐2).
Figure B‐2. Spider‐type Couplings
Align non‐spider type couplings by using a feeler
gauge or taper gauge between the coupling halves
every 90. The coupling is in alignment when the
hubs are the same distance apart at all points (see
Figure B‐3).
Figure B‐3.Aligning Non‐Spider Type Coupling
Check parallel adjustment by laying a straightedge
across both coupling rims at the top, bottom, and
side. When the straightedge rests evenly on both
halves of the coupling, the coupling is in horizontal
parallel alignment. If the coupling is misaligned,
use a feeler gauge between the coupling and the
straightedge to measure the amount of misalign
ment.
V‐Belt Drives
GMS style pumps will require an external
bearing support when using V‐belt drives.
When using V‐belt drives, the power source and
the pump must be parallel. Use a straightedge
along the sides of the pulleys to ensure that they
are properly aligned (see Figure B‐4). In drive sys
tems using two or more belts, make certain that the
belts are a matched set; unmatched sets will cause
accelerated belt wear.
MISALIGNED:
SHAFTS
NOT PARALLEL
MISALIGNED:
SHAFTS
NOT IN LINE
ALIGNED: SHAFTS
PARALLEL AND
SHEAVES IN LINE
Figure B‐4. V‐belt Alignment
Tighten the belts in accordance with the belt man
ufacturer's instructions. If the belts are too loose
they will slip; if they are too tight, there will be ex
cessive power loss and possible bearing failure.
Select pulleys to match the proper speed ratio;
overspeeding the pump may damage both pump
and power source.
Do not operate this pump without
guards in place over the rotating parts.
Exposed rotating parts can catch cloth
ing, fingers or tools, causing severe in
jury to personnel.
V‐BELT TENSIONING
General Rules of Tensioning
For new v‐belts, check the tension after 5, 20 and
50 hours of operation and re‐tension as required
(see the following procedure for measuring belt
tension). Thereafter, check and re‐tension if re
quired monthly or at 500 hour intervals, whichever
comes first.

GMS SERIES
OM-07468-05
PAGE B-6 INSTALLATION
Ideal v‐belt tension is the lowest tension at which
the belt will not slip under peak load conditions. Do
not over‐tension v‐belts. Over‐tensioning will short
en both v‐belt and bearing life. Under‐tensioning
will cause belt slippage. Always keep belts free
from dirt, grease, oil and other foreign material
which may cause slippage.
Tension Measurement
Correct v‐belt tension can be achieved using a v‐
belt tension tester and Table B‐2 or B‐3. Use the
tables to find the v‐belt size (cross‐section), the
smallest sheave diameter, the belt type for your ap
plication. The corresponding deflection force re
quired for new or used belts is shown opposite the
RPM range of the pump.
Belt Span
Deflection
Figure B‐5. Belt Tension Measurement
The ratio of deflection to belt span is 1:64 for both
ASA and metric units. Therefore, a belt with a span
of 64 inches would require a deflection of 1 inch at
the force shown on the Tables for your particular
application.
For example, if the span as measured in Figure B‐5
is 32 inches (813 mm), the v‐belt cross‐section is C,
the smallest sheave diameter is 8 inches, the pump
speed is 1250 RPM, and the belts are uncogged
Yy‐T type, then 11.5 lbs. of force on the tensioner
should show 1/2‐inch (12,7 mm) of deflection.
A tension tester is available as an option from Gor
man‐Rupp (P/N 29513-001). Other tension test
ers are available from your local belt/sheave dis
tributor, and work on a similar principal.
To use the Gorman‐Rupp tensioner, measure the
belt span as shown in Figure B‐5. Position the bot
tom of the large O‐ring on the span scale of the ten
sioner at the measured belt span. Set the small O‐
ring on the deflection force scale to zero.
Place the tension tester squarely on the belt at the
center of the belt span. Apply force on the plunger,
perpendicular to the belt span, until the bottom of
the large O‐ring is even with the top of the next belt,
or with the bottom of a straight edge laid across the
sheaves.
Read the force applied from the bottom of the small
O‐ring on the deflection force scale. Compare this
force with the value shown in Table B‐2 or B‐3 and
adjust the tension accordingly. Note that the ten
sion for new belts is higher than that for used
belts to allow for expected belt stretching. Do not
over‐tension used belts to the higher deflection
forces shown for new belts.

GHC SERIES OM-07468-05
PAGE B-7INSTALLATION
Cross
Section
Smallest
Sheave
Diameter
Range
R.P.M.
Range
Used
Belt
New
Belt
Used
Belt
New
Belt
Belt Deflection Force
Uncogged
Hy‐T Belts &
Uncogged
Hy‐T Torque
Team
Cogged
Torque‐Flex
& Machined
Edge torque
Team Belts
A,AX
3.0 ‐ 3.6 1000‐2500
2501‐4000
3.7
2.8
5.5
4.2
4.1
3.4
6.1
5.0
3.8 ‐ 4.8 1000‐2500
2501‐4000
4.5
3.8
6.8
5.7
5.0
4.3 7.4
6.4
5.0 ‐ 7.0 1000‐2500
2501‐4000
5.4
4.7
8.0
7.0
5.7
5.1
9.4
7.4
B,BX
3.4 ‐ 4.2 860‐2500
2501‐4000
4.9
4.2
7.2
6.2
4.4 ‐ 5.6 860‐2500
2501‐4000
5.3
4.5
7.9
6.7
7.1
7.1
10.5
9.1
5.8 ‐ 8.6 860‐2500
2501‐4000
6.3
6.0
9.4
8.9
8.5
7.3
12.6
10.9
C,CX
7.0 ‐ 9.0 500‐1740
1741‐3000
11.5
9.4
17.0
13.8
14.7
11.9
21.8
17.5
9.5 ‐ 16.0 500‐1740
1741‐3000
14.1
12.5
21.0
18.5
15.9
14.6
23.5
21.6
D
12.0 ‐ 16.0 200‐850
851‐1500
11.5
9.4
17.0
13.8
14.7
11.9
21.8
17.5
18.0 ‐ 20.0 200‐850
851‐1500
30.4
25.6
45.2
38.0
3V,
3VX
2.2 ‐ 2.4 1000‐2500
2501‐4000
3.3
2.9
4.9
4.3
2.65 ‐ 3.65 1000‐2500
2501‐4000
3.6
3.0
5.1
4.4
4.2
3.8
6.2
5.6
4.12 ‐ 6.90 1000‐2500
2501‐4000
4.9
4.4
7.3
6.6
5.3
4.9
7.9
7.3
5V,
5VX
4.4 ‐ 6.7
500‐1749
1750‐3000
3001‐4000
10.2
8.8
5.6
15.2
13.2
8.5
7.1 ‐ 10.9 500‐1740
1741‐3000
12.7
11.2
18.9
16.7
14.8
13.7
22.1
20.1
11.8 ‐ 16.0 500‐1740
1741‐3000
15.5
14.6
23.4
21.8
17.1
16.8
25.5
25.0
8V
12.5 ‐ 17.0 200‐850
851‐1500
33.0
26.8
49.3
39.9
200‐850
851‐1500
39.6
35.3
59.2
52.7
18.0 ‐ 22.4
Cross
Section
Smallest
Sheave
Diameter
Range
R.P.M.
Range
Used
Belt
New
Belt
Used
Belt
New
Belt
Belt Deflection Force
Uncogged
Hy‐T Belts &
Uncogged
Hy‐T Torque
Team
Cogged
Torque‐Flex
& Machined
Edge torque
Team Belts
A,AX
75 ‐ 90 1000‐2500
2501‐4000
1.7
1.3
2.5
1.9
1.9
1.5
2.8
2.3
91 ‐ 120 1000‐2500
2501‐4000
2.0
1.7
3.1
2.6
2.3
2.0 3.4
2.9
125 ‐ 175 1000‐2500
2501‐4000
2.4
2.1
3.6
3.2
2.6
2.3
4.3
3.4
B,BX
85 ‐ 105 860‐2500
2501‐4000
2.2
1.9
3.3
2.8
106 ‐ 140 860‐2500
2501‐4000
2.4
2.0
3.6
3.0
3.2
3.2
4.8
4.1
141 ‐ 220 860‐2500
2501‐4000
2.9
2.7
4.3
4.0
3.9
3.3
5.7
4.9
C,CX
175 ‐ 230 500‐1740
1741‐3000
5.2
4.3
7.7
6.3
6.7
5.4
9.9
7.9
231 ‐ 400 500‐1740
1741‐3000
6.4
5.7
9.5
8.4
7.2
6.6
10.7
9.8
D
305 ‐ 400 200‐850
851‐1500
11.3
9.6
16.8
14.2
401 ‐ 510 200‐850
851‐1500
13.8
11.6
20.5
17.2
3V,
3VX
55 ‐ 60 1000‐2500
2501‐4000
1.5
1.3
2.2
2.0
61 ‐ 90 1000‐2500
2501‐4000
1.6
1.4
2.3
2.0
1.9
1.7
2.8
2.5
91 ‐ 175 1000‐2500
2501‐4000
2.2
2.0
3.3
3.0
2.4
2.2
3.6
3.3
5V,
5VX
110 ‐ 170
500‐1749
1750‐3000
3001‐4000
4.6
4.0
2.5
6.9
6.0
3.9
171 ‐ 1275 500‐1740
1741‐3000
5.8
5.1
8.6
7.6
6.7
6.2
10.0
9.1
276 ‐ 400 500‐1740
1741‐3000
7.0
6.6
10.6
9.9
7.8
7.6
11.6
11.3
8V
315 ‐ 430 200‐850
851‐1500
15.0
12.2
22.4
18.1
200‐850
851‐1500
18.0
16.0
26.8
23.9
431 ‐ 570
Table B‐2. Sheave Diameter (In.)
Deflection Force (Lbs.)
Table B‐3. Sheave Diameter (Mm.)
Deflection Force (Kg.)
ELECTRICAL CONNECTIONS
Before connecting an electric motor to incoming
power, check that the electrical service available
matches the pump motor requirements stamped
on the motor nameplate.
The electrical power used to operate
this pump is high enough to cause inju
ry or death. Obtain the services of a qu

GMS SERIES
OM-07468-05
PAGE B-8 INSTALLATION
alified electrician to make all electrical
connections.
Do not install and operate a non‐explo
sion proof motor in an explosive atmo
sphere. Install, connect, and operate
the motor in accordance with The Na
tional Electrical Code and all local
codes. If there is a conflict between the
instructions in the manual accompany
ing the unit and The National Electrical
Code or the applicable local code, The
National or local code shall take prece
dence.

GMS SERIES OM-07468-05
PAGE C-1OPERATION
OPERATION - SECTION C
Review all SAFETY information in Section A.
Follow the instructions on all tags, labels and
decals attached to the pump.
PUMP OPERATION
Pressure relief valves are designed to
operate as safety devices and should
never be used to regulate liquid flow.
Otherwise, the pump or piping may ex
plode and cause personal injury or
death.
PRE‐OPERATION
Make certain that all instructions in INSTALLA
TION, Section B have been carried out.
The standard version of the pump is de
signed to handle a wide range of light, me
dium, and heavy viscosity liquids, depend
ing on design and components. Do not in
stall the pump in a service with higher liquid
temperatures than what it was designed;
otherwise, pump components and opera
tion may be affected. For temperature
range consult The Gorman‐Rupp Compa
ny.
Before Starting The Pump
Never operate the pump against a
closed suction or discharge valve. The
pump will overheat, and may rupture or
explode, causing personal injury or
death.
Open all valves in the suction and discharge lines,
and close all drain valves.
Consult the drive manufacturer's operating manu
al before attempting to start the drive.
In a suction lift, fill the pump housing with liquid to
seal clearances and to lubricate.
Checking Pump Rotation
Correct rotation of your pump is shown on the
pump serial plate or direction arrow plate.
In applications with a single direction of
flow and a single pump‐mounted pressure
relief valve, make certain that the drive unit
turns the pump in the correct direction of
rotation. Otherwise, the pump‐mounted
pressure relief valve will not function.
Follow the drive unit manufacturer's instructions,
jog the pump motor briefly, and check rotation.
If a 3‐phase motor is being used and rotation is in
correct, have a qualified electrician interchange
any two of the 3‐phase wires to change the direc
tion of rotation. If a 1‐phase motor is being used
and rotation is incorrect, consult the motor man
ufacturer's literature.
STARTING
Start the drive unit as indicated in the manufactur
er's instructions and observe the suction and dis
charge gauges. If the pump does not deliver liquid
within one minute, stop the drive unit. Do not oper
ate the pump more than one minute without liquid
in it; dry operation will damage or destroy the
pump.
Although this pump is self‐priming, never
operate it dry. Dry operation could cause

OM-07468-05 GMS SERIES
PAGE C-2 OPERATION
galling, seizing, damage to the seal or ex
cessive wear of rotating parts.
Review the previous steps outlined in PRE‐OP
ERATION and review TROUBLESHOOTING,
Section D. If everything appears normal, add liquid
to the pump housing to assist priming and start the
driver again.
If the pump does not deliver liquid within two min
utes, stop the pump; it may be necessary to vent
the discharge line until liquid begins to flow.
If the pump still does not deliver after consulting
TROUBLESHOOTING and venting the discharge
line, contact your local Gorman‐Rupp Rotary Gear
Distributor or the factory.
OPERATION
NOTE
If the pump malfunctions or does not meet operat
ing specifications, refer to TROUBLESHOOTING
- Section D.
A change in operating noise when liquid first enters
the pump is normal. After the pump is fully opera
tional, monitor it for any unusual noises or vibra
tion; if either occurs, shut the pump down immedi
ately.
Liquid Temperature
Do not install the pump in a service with higher liq
uid temperatures than what it was designed. Intro
ducing hot liquid into a cold pump will expand
parts unevenly, causing excessive wear, pump fail
ure, and operation may be affected. This thermal
shock can be reduced by gradually heating the liq
uid being introduced into the pump. If it is not pos
sible to heat the liquid, use heat tape and/or insula
tion to heat the pump.
High temperature bushings as well as optional
jackets which may be used to heat or cool the
pump are available options for many models.
Overheating
Overheating can occur if the pump is operated with
valves in the suction or discharge lines closed. Op
erating against closed valves could bring the liquid
to a boil, build pressure, and cause the pump to
rupture or explode. If overheating occurs, stop the
pump and allow it to completely cool before servic
ing.
Do not remove plates, covers, gauges,
pipe plugs or fittings from an overheated
pump. Vapor pressure within the pump
can cause parts being disengaged to be
ejected with great force. Allow the pump to
completely cool before cooling.
Checking Gauges
Monitor vacuum and pressure gauge readings to
ensure that the pump is operating within normal
range and delivering full flow.
Strainer Check
If a strainer has been installed in the suction line,
monitor vacuum gauge readings to detect block
age. Check the strainer if flow rate begins to drop.
Never introduce air or steam pressure
into the pump housing to remove a
blockage. This could result in personal
injury or damage to the equipment. If
backflushing is absolutely necessary,
limit liquid pressure input to 50% of the
maximum permissible operating pres
sure shown in the pump performance
data.
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 efficiency.
If your pump is equipped with a packing seal, the
packing is lubricated by the liquid being pumped.
Some leakage around the packing seal is normal.

GMS SERIES OM-07468-05
PAGE C-3OPERATION
Packing pumps must leak slightly to cool and lu
bricate the shaft and to allow the shaft to turn freely.
Wait until the pump has run long enough to reach
its normal operating temperature to adjust the
gland nuts. Adjust the nuts only tight enough to re
duce excessive leakage.
PRESSURE RELIEF VALVE
ADJUSTMENT
Some pumps are not provided with a pressure re
lief valve. A pressure relief valve must be installed
on the pump or in the discharge piping to ensure
safe operation. Otherwise, the pump may be dam
aged and personnel injured.
If operating at high temperatures, allow the
pump to completely cool before attempt
ing any adjustments.
Cracking Pressure
Cracking pressure is the pressure at which the
pressure relief valve first begins to open and by
pass fluid. The nominal cracking pressure of the re
lief valve provided with this pump is set at the facto
ry and is indicated on the tag attached to the relief
valve.
If the nominal cracking pressure set at the factory
must be changed, see Table E‐2 and instructions in
Section E ‐ MAINTENANCE AND REPAIR.
Complete By‐pass Pressure
Complete by‐pass pressure is the maximum pres
sure the pump will see when all the pumped fluid is
being by‐passed through the pressure relief valve.
This pressure will vary depending on the cracking
pressure setting, liquid viscosity, and pump speed
(pump capacity).
To determine the complete by‐pass pressure, refer
to the pump performance chart or consult the fac
tory.
Do not remove the adjusting screw jam
nut; with the jam nut removed the relief
valve spring(s) can be compressed too
far for the valve to open. If the valve
does not open, excessive pressure can
develop, causing damage to the pump
and possible injury to personnel.
STOPPING
If the pump will be out of service for an extended
length of time, particularly when handling non‐lu
bricating liquids, drain the system and flush the
pump and piping with an oil‐based preservative to
protect close‐tolerance pump parts.
When handling liquids that solidify when at rest
(tar, glue, etc.), flush the pump and piping with an
approved solvent compatible with the pump com
ponents and the liquids being pumped.

GMS SERIES OM-07468-05
PAGE D-1TROUBLESHOOTING
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. Allow the pump to completely cool if
overheated.
3. Check the temperature before open
ing any covers, plates, or plugs.
4. Close the suction and discharge
valves.
5. Drain the pump.
TROUBLESHOOTING WITH GAUGES
Most pump or system malfunctions can be detected by installing vacuum suction and discharge pressure
gauges. Read the gauges and refer to the following information for interpretation of the gauge readings. For
additional troubleshooting procedures, see the TROUBLESHOOTING CHART.
Vacuum Gauges
HIGH READING
Suction valve closed, suction line blocked,
foot valve jammed, strainer blocked.
Liquid too viscous.
Lift too high.
Suction line undersized.
LOW READING
Air leak in suction line.
End of suction line not submerged.
Pump parts worn or defective.
Pump needs priming.
ERRATIC READING
Liquid overheated, vaporizing.
Liquid entering intermittently, suction air leak,
end of suction line not submerged.
Vibration from cavitation, misalignment, dam‐
aged parts.
Pressure Gauges
HIGH READING
Liquid too viscous.
Discharge line undersized or too long.
Discharge valve partially closed.
Strainer blocked.
Relief valve pressure set too high.
Thermal changes in liquid.
LOW READING
Relief valve pressure set too low.
Internal valve not seating properly.
Pump bypass partially open.
End clearance too great.
Pump parts worn or defective.
ERRATIC READING
Cavitation.
Liquid entering intermittently, suction air leak,
End of suction line not submerged.
Drive misalignment causing vibration.