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7/23/2019 Couplings - A basic introduction to different types of couplings
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Couplings
Presented By : Mohsin Murtaza
GTE NP Machinery
7/23/2019 Couplings - A basic introduction to different types of couplings
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Couplings
A coupling is a device that is used to connect two axially oriented
shafts for power transmission.
Its purpose is to transmit torque or rotary motion without slip and at
the same time compensate for angular, parallel and axial
misalignment.
Supplementary functions may include providing for or restrictingaxial movement of connected shafts, minimizing or eliminating the
conduction of heat, torsional dampening and torsional tuning of
system.
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Couplings
Distance Between Shaft nds !
"he distance from the face of one shaft to the face of the next shaft.
Distance Between #lange #aces !
It is the distance from the flange face of one hu$ to the flange face of other
hu$. It is also called Spacer gap length.
%ea& "orque 'ating!
(orresponds to a factor of safety of ).)* with respect to the component+s
material yield strength, using a com$ination of speed, angular misalignment,
and axial displacement.
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Couplings
'ated Speed!
"he maximum speed at which the coupling is capa$le of transmitting the
continuousrated torque while simultaneously su$-ected to the rated angularmisalignment and the couplingrated axial displacement.
ighspeed (oupling!
A coupling that is designed to operate at speeds a$ove )/00 revolutions per
minute 1rpm2.
"ransmitted Axial #orce!
"he axial force transmitted through the coupling from one shaft to the other3
it is a function of the resistance to deflection of the flexi$le elements or
sliding friction of gear teeth.
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Flexible
The most common for motors, pumps,compressors, fans and blowers
Rigid
Most common in large steam turbine -generator units and in small machines.
Types of couplings
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A flexible-element coupling obtains its flexibility from the flexing
of thin discs or diaphragms.
These couplings offer the extra advantages of providing for or
restricting axial movement of the connected shafts; minimizing oreliminating the conduction of heat electricity or sound; torsional
dampening; and torsional tuning of a system.
Flexible couplings can be mechanically flexing or material flexing.
Flexible Couplings
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Transmit po!er
Allo! limited misalignment
Allo! axial movement of shafts
"inimize torsional vibration
Flexible Couplings
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"echanically Flexible#lastomeric
Flexible $iaphragm %r $is&
Types %f Flexible Couplings
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'ear Coupling
Chain Coupling'rid Coupling
%ldham Coupling
(niversal )oint
"echanically Flexible
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Capable of transmitting proportionately high
tor*ues at either lo! or high speeds.
They are compact and consist of t!o identical hubs!ith external gear teeth and a sleeve or sleeves !ith
matching internal gear teeth.
These can be of spacer type or spindle type.
+ubrication of these couplings can be of ,'rease lubricated , up to // rpm
Combined oil and grease , // to /// rpm
%il lubricated , /// rpm or more
'ear Coupling
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Consist of t!o hubs having sproc&et teeth !hich are
connected by a strand of single roller double roller
or silent chain.
These are used for proportionately high tor*ue atlo! speeds.
These couplings are mostly grease lubricated.
0on metallic chains are used for light duty drives.
Chain Coupling
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They consist of t!o flanged hubs !ith special
grooves or slots cut axially on the outside. The
flanges are 1oined by interlacing a metallic grid.
These are used for proportionately high tor*ue atmoderate speeds.
These couplings can be oil or grease lubricated.
A cover must be installed to retain lubricant and
prevent dust grit etc to entercoupling
'rid Coupling
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0o +ubrication Re*uired
+ight!eight And #xcellent 2alance
Characteristics3igh Temperature #nvironment (se
%nly +imited Axial "isalignment
Components 4ery $elicateAl!ays A 5re-stretch 6pecification
Flexible $iaphragm
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Flexible $isc Coupling
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#lastomeric couplings are available in a large
number of variations.
These are generally classified into t!o main groups. Elastomer in shear.
Elastomer in compression.
+ight to medium duty and moderate speed services.
These are usually maintenance free but regular
inspection of elastomer is recommended.
#lastomer Couplings
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(sually has a rubber urethane teflon or nylon
flexible element.
4ery soft torsionally.
6peed limited due to distortion of elastomeric
element.
#lastomeric element sub1ect to chemical
deterioration and heat build up due to flexing.
#lastomer Couplings
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02R - 2(0A
(rethane
3ytrel
2ronze
Teflon
0ylon
Flexible #lements "aterials
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02R 7 2(0A
Most commonly used elementmaterial for all general applications -
Pumps, gear box, etc.
Flexible #lements "aterials
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(rethane
Greater torque capacity than rubber Good abrasion / wear resistance
Better resistance to enironmental
conditions such as o!one, ultraiolet and
some oils or chemicals agents."hould not be used in cyclic or start/stop
applications
#imited to $%&'f
Flexible #lements "aterials
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3ytrel
igher torque capacity than ru$$er andurethane
Best chemical resistance, compared to
urethane and maximum temperature of 4*05#.
Angular misalignment less than urethane andru$$er. )645 compare to ) 5
As urethane, should not $e use in frequent
start6stop applications or regular shoc&s and
vi$rations
Flexible #lements "aterials
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2ronze
7ot elastomeric, $ut an option for high temperatures,such as 8*0 5#
(ould $e used in salt6marine applications
9nly used in slow speeds, generally $elow 4*0 rpm,
since it+s a metaltometal contact which increases wear
Flexible #lements "aterials
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A rigid coupling is one in !hich no
compensation is made to accommodate
for shaft misalignments.
Rigid Coupling
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Cost effective solution
4ery rigid transmission characteristics
2ac&lash free6uitable for positioning tas&s and reversing drives.
+arge tor*ues can be transferred in small space.
$o not permit any torsional radial or angular
misalignment.
Rigid Coupling
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Flanged Coupling
6plit muff Coupling
Friction Coupling
Rigid Coupling
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A &ey is used to fix the coupling hu$ to the shaft,
and then $oth hu$s are $olted together.
It is the simplest of all couplings.
Shafts must $e perfectly aligned when they areconnected $y flange coupling.
6leeve or muff Coupling
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A key is used to fix the coupling and the shaft and the
two halves of the coupling are bolted together.
The split muff facilitates easy installation and removal
of shaft key.
6plit muff Coupling
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Friction Coupling
(lutch Disengaged (lutch ngaged
Driver
%late A
#riction :aterial
Driven Shaft
StationaryDriver ShaftIn motion
Driver Shaft
In motion
Driven Shaft
In motion
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Fluid Coupling
( fluid coupling transmits power through fluid.
)here is no direct mechanical lin* between the input
and the output shafts.
)he impeller +pump of the coupling forces fluid
through the turbine, which forces the turbine to turn.
)he pump is connected to the input shaft and
turbine is splined to the output shaft.
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Fluid Coupling
5arts ,
; 8mpeller
; 6tator
; Turbine
; Cover
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Fluid Coupling
; 6oft starting on load
; 'ood mechanical shoc& absorption.
; 3igh starting tor*ue for starting heavy machines.
; Reduce the re*uired motor starting tor*ue.; "inimize electrical po!er factor and save electrical
energy.
; 2alance loads on multiple drive systems.
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6traight 2ore 6liding Clearance
9:ey!ay
6traight 2ore 8nterference Fit9:ey!ay
6plined 6haft 9:+oc&nut
Tapered 2ore 9:ey!ayeyless Taper 2ore
Coupling 3ub
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There are several different mounting methods
available to ensure that the coupling hub remains
tightly secured to the shaft.
Fretting occurs !hen a hub becomes loose on the
shaft. 8f not corrected the hub &ey!ay or &ey !ill
fail.
The hub can be shrunk onto the shaft by heating the
hub
The hub can be hydraulically expanded to fit up on
the taper
6pline shaft !ith very slight interference </.///= in>
Coupling 3ubs
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There can be many factors contributing to!ards
failure of a coupling.
8mproper or poor machining.$efective material and material !ith inade*uate
strength .
8mproper product design.
+ac& of lubrication film. 8mproper assembly and operation of coupling.
#xcessive misalignment
6afety in operation and service.
Causes of coupling failures
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5roper selection of a coupling is the first step ofgood maintenance.
Type of driver and driven e*uipment.
Torsional characteristics.
"inimum and maximum tor*ue.
0ormal and maximum rotating speed.
6haft sizes.
6pan or distance bet!een shaft ends.
Thermal gro!th.
+ateral loading lateral vibration and inherent balance.
#*uipment position <horizontal vertical or inclined>
Ambient conditions <$ry 9et Corrosion $ust etc>
2earing locations.
Cost < Capital installation and maintenance>
Available space and expected life
Coupling 6election
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