UNIT-2 (Counts….)

COUPLINGS

The element which is used to join two shafts is known as “Couplings”.

Classification of couplings:-

Rigid Coupling:

It is used to connect two shafts which are perfectly aligned.

Flexible Coupling:

It is used to connect two shafts which are having both lateral and angular misalignment.

DESIGN PROCEDURE FOR SLEEVE OR MUFF COUPLING

1. Design for Shaft: (Calculating the diameter of the shaft)

Toque

1) Design for SleeveAssume D = 2d + 13

L = 3.5dCheck for shear stress in muff using

If induced shear stress in the muff is less than the given permissible shear stress, then the Design is safe.2) Design for Key

From PSG DB select the Gib- headed key and corresponding value of‘d’ choose the width(b) and thickness (h) of the key. Length of the key (l) = L/2Check for Shearing and Crushing

……………… (For

Shearing)Where w = thickness of key= h

If the induced shear stress and Crushing stresses are less than the permissible stresses, then design is safe.

DESIGN PROCEDURE FOR SPLIT MUFF COUPLING

1) Design for Shaft: (Calculating the diameter of the shaft)

Toque

2) Design for SleeveAssume D = 2d + 13

L = 3.5dCheck for shear stress in muff using

If induced shear stress in the muff is less than the given permissible shear stress, then the Design is safe.3) Design for Key

From PSG DB select the Gib- headed key and corresponding value of‘d’ choose the width(b) and thickness (h) of the key.

Length of the key (l) = L/2

Check for Shearing and Crushing

…… (For Shearing)

Where w = thickness of key= h

… (For

Crushing)If the induced shear stress and Crushing stresses are less than

the permissible stresses, then design is safe.4) Design for Bolts

By this above the diameter of the bolt is found.

Where = Co efficient of Friction (Generally taken as 0.3)

N = Number of Bolts

DESIGN PROCEDURE FOR PROTECTED FLANGE COUPLING

1. Design for Shaft: (Calculating the diameter of the shaft)

Toque

1) Dimensions of the flange CouplingsOuter diameter of hub, D = 2d Length of hub, L = 1.5dPitch Circle Diameter of the bolts, D1 = 3dOuter diameter of flange D2 = 4dThickness of the Flange tf = 0.5dThickness of the protective Circumference Flange tp= 0.5d

Then Check for shear stress in hub using

If induced shear stress in the muff is less than the given permissible shear stress, then the Design is safe.2) Design for Key

From PSG DB select the Gib- headed key and corresponding value of‘d’ choose the width(b) and thickness (h) of the key.

Length of the key (l) = L

Check for Shearing and Crushing

………… (For Shearing)

Where w = thickness of key= h

……… (For Crushing)

If the induced shear stress and Crushing stresses are less than the permissible stresses, then design is safe.

3) Design of Flange

Where induced shear stress in flange is found and compared with given permissible Shear stress.4) Design for Bolts

By this above the diameter of the bolt (db) is found.Where n = Number of Bolts

Check for Crushing

Where is found and checked.