1

In practice we must cater for various torque

conditions.

Time

Transient torques

Time

Cyclic torques

Peak Torques – Cyclic Stresses

H P Coupling – Membrane Design

2

Steady Stress

Cyclic

Str

ess

Safe working stress

Material Failure

MEAN TORQUE

(MAX)

SPEED

(MAX) (MAX) AXIAL

DEFLECTION

Angular

Deflection

plus

Cyclic Torque

ANGULAR LIMIT Rated

Operating

Point

> 2

Goodman Diagram

H P Coupling – Membrane Design

3

Potential for

failure at the

Edge of

Washer

H P Coupling - Fatigue Failure Mode

Clamping

Washer Area

4

Fatigue crack propagation area

H P Coupling - Fatigue Failure Mode

5 Washer Radius

Lif

e

Optimum Radius

Maximum

Life

Washer Radius

H P Coupling – Profiled Washers

Life Enhanced by Profiled Washers

6

H P Coupling - Bolting System Design

Hub

Stripper Bolt

Drive Bolt

Membrane

Overload Sleeve

Lock Nut

Spacer Washer

Guard Ring Spacer

7

Hubs High Alloy steel

Spacer High Alloy steel

Guard Ring High Alloy steel

Membranes AISI 301 Stainless steel

Drive Bolts High Alloy steel (Forged & plated)

Nuts High Alloy steel

Sleeves High Alloy steel

Overload Collars High Alloy steel (Monel Option)

Stripper Bolts High Alloy steel (Forged & plated)

Excluding stripper bolts and membranes all parts are

phosphate and oil protected

H P Coupling – Materials

8

Factors Affecting Performance

Rotor- dynamic behavior / natural vibration

frequencies (coupling & machine) Lateral

Axial

Torsional

High speeds - dynamic balance is critical

- windage effects

Shaft interface requirements/assembly

Peak torque - short circuit effects

Electrical insulation and other features

H P Coupling – Engineering Considerations

9

Machinery Natural Vibrations

SYSTEM LATERAL VIBRATION

BEARING

DRIVER COUPLING DRIVEN MACHINE

MASS MASS

BEARING BEARING BEARING

H P Coupling – Engineering Considerations

10

Coupling Natural Vibrations

MEMBRANES PIVOT MEMBRANES PIVOT

COUPLING WHIRLING

SPACER BENDS

H P Coupling – Engineering Considerations

11

SYSTEM AXIAL VIBRATIONS

Ka

MEMBRANES

SPACER Mass

Ka

MEMBRANES

Machinery Axial Vibrations

H P Coupling – Engineering Considerations

12

Machinery Natural

Torsional Vibrations

Node

SYSTEM TORSIONAL

VIBRATIONS

H P Coupling – Engineering Considerations

13

Electrical short circuits

High start and re-acceleration effects

5 + times normal torque for 100,000 cycles

Changes in torsional stiffness needed

No yield and/or no fracture, no shaft hub slip

H P Coupling – Engineering Considerations

Peak Torques

14

Contributors To Unbalance

Balance tolerance limits

Balance fixture/mandrel unbalance

Balance machine error

Balancing set up eccentricity

Pilot clearances & eccentricities

Hardware unbalance (match weight bolts)

Effect of keyways

Shaft run-out

Fit of hub on shaft

H P Coupling – Balancing Considerations

15

Dynamic Balance to API 671

Formula proportional to Weight

Speed

At 10,000rpm eccentricity of mass < .001 mm

Repeatability is critical

Dynamic balancing techniques are critical

H P Coupling – Balancing Considerations

16

Dynamic Balance to API 671 There are 3 options dependent on Weight & Speed

0

1

2

3

4

5

6

7

0 5000 10000 15000 20000

Speed in RPM

Ec

ce

ntr

icit

y i

n 0

,00

1 m

m

ISO 1940 G=0,63

API 671 [4W/N]

In practice 5000 rpm is the critical

speed, where formula 2 takes over,

and for couplings weighing less

than 5.7Kg formula 3 takes

precedent

1. U = 6350 W/N g mm

(4 W/N)

2. U = 1.25 W g mm

3. U = 7.2 g mm

H P Coupling – Balancing Considerations

17

Factory Assembled Membrane Packs

Balance to G0.66 (API 671 limits)

Spigotted Design

High Alloy materials

Profiled Spacer Washers

O/Load Collars

Tight controls on manufacturing process

Improves balance retention and reliability

Can operate up to very high speeds

To retain balance Integrity and repeatability

Light weight and high torque & speed

capability

High reliability

Over torque protection with Spark resistant

option

Ensure reliable and high integrity product

Feature Benefit

H P Coupling - Features & Benefits