couplings - a basic introduction to different types of couplings

7/23/2019 Couplings - A basic introduction to different types of couplings

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Couplings

Presented By : Mohsin Murtaza

GTE NP Machinery



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.



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.



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.



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



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



Transmit po!er

Allo! limited misalignment

Allo! axial movement of shafts

"inimize torsional vibration

Flexible Couplings



"echanically Flexible#lastomeric

Flexible $iaphragm %r $is&

Types %f Flexible Couplings



'ear Coupling

Chain Coupling'rid Coupling

%ldham Coupling

(niversal )oint

"echanically Flexible



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



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



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



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



Flexible $isc Coupling



#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



(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



02R - 2(0A

(rethane

3ytrel

2ronze

Teflon

0ylon

Flexible #lements "aterials



02R 7 2(0A

Most commonly used elementmaterial for all general applications -

Pumps, gear box, etc.




(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




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




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




A rigid coupling is one in !hich no

compensation is made to accommodate

for shaft misalignments.

Rigid Coupling



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



Flanged Coupling

6plit muff Coupling

Friction Coupling

Rigid Coupling



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



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



Friction Coupling

(lutch Disengaged (lutch ngaged

Driver

%late A

#riction :aterial

Driven Shaft

StationaryDriver ShaftIn motion

Driver Shaft

In motion

Driven Shaft

In motion



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.



Fluid Coupling

5arts ,

; 8mpeller

; 6tator

; Turbine

; Cover



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.



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



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



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



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



THANK

YOU

couplings - a basic introduction to different types of couplings

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