Load Calculation for Trough Idler Rolls - MHEA · Idler Rolls Load Analysis •Cross-section...

1 Challenge the future

Load Calculation for Trough Idler Rolls

MSc. Xiangwei Liu

Delft University of Technology

--Stress Discontinuity Model

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Outline

Introduction

Methodology

Idler Rolls Load Analysis

Result

Conclusion

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Introduction Self-intro

• Born in Rizhao, China

• PhD at TU Delft (2012/09- )

• Research Topic Sustainable Design of Idlers for Large

-scale Belt Conveyor Systems

CSC Scholarship

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Introduction

• Belt conveyor

Background

[2]

[1]

[1] Workplace Health & Safety Policy and Legislation. Quebec. 2003

[2] DSMAC Group.

• Large-scale belt conveyor system Large capacity

High speed

Long distance

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Introduction

• Idlers

Background

[3]

[3] USA Mining, 2013.

[4] Saimh.co.za, “Idler Basics.”

[4]

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Introduction Challenge 1

• Stress profile on loaded conveyor belt

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Introduction Challenge 2

• Potential high cost of idler failure

[5] L. Nordell, 1995

[5]

• Unbalanced load distribution

• Large design margin

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Methodology

• Theoretical research • Coulomb earth pressure theory, Krause & Hettler, 1974

• Numerical modelling method, Wheeler, 2003

Literature Survey

• Experimental research • Trough conveyor, Grabner, 1993

• Garland conveyor, Geesmann, 2001

• Conclusion: 1. More precise theoretical method needed

2. No load analysis regarding varying roll lengths

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Methodology

• Stress Discontinuity Method

Stress Discontinuity model (SD model)

[6]

[6] W. Powrie, 2004

• Stress Field Analysis

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Idler Rolls Load Analysis

• Cross-section simplification

Analysis of Forces on Idler Rolls

[7] [7] C. A. Wheeler, 2004

• Three-dimensional forces

• Active and passive stress statuses

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Idler Rolls Load Analysis

Dividing bulk material into two zones

SD model

• Active stress status analysis

Stress field analysis in zone 1

2cos

cos sin

b

b

gz

gz

(1) [8]

[8] K. Terzaghi, 1943

Stress field analysis in zone 2

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Idler Rolls Load Analysis

SD analysis from zone 1 to zone 2

SD model

• Active stress status analysis

2 tan

2 1a i

OC OC e (2)

Calculating the stress on the belt

,

,tan

w a a

w a a w

gzK

gzK

(3)

where

2

2 tan

2

1

cos1 sin cos( )

1 sin cos( )a i

a i w

i

K e

(4)

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Idler Rolls Load Analysis

Obtain the normal and frictional force on the wing belt

section

SD model

• Active stress status analysis

2

2

, , 12

',

1 coscos tan sin

2 4 cosNG bulk a aw a

lF glK L

(5) Normal force

2

2

, , 12

',

1 coscos tan sin tan

2 4 cosNA bulk a a ww a

lF glK L

Frictional force (6)

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Idler Rolls Load Analysis

Same procedures with the active

Different directions and magnitudes of effective stress

SD model

• Passive stress status analysis

Obtain the normal and frictional force on the wing belt section

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Idler Rolls Load Analysis

The normal and axial force on the wing roll

Load distribution among rolls

(7) Normal force

Axial force (8)

(9)

, , , , , , ,cos

NG w NG bulk a NG bulk p G belt wF F F F

, , , , ,, ,sin

NA w NA bulk a NA bulk pG belt wF F F F

The normal and axial force on the centre roll

' '

, , ,2 cos 2 sin

NG c bulk belt NG w NA wF m m ga F F Normal force

Axial force , 0NA CF (10)

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Result

parameter value parameter value

material coal belt speed ( ) 5

capacity ( ) 6000 idler spacing (m) 3

density ( ) 850 belt width (m) 2

surcharge angle (°) 15 belt line load ( ) 53

wall friction angle (°) 20 gravity acceleration ( ) 9.81

internal friction angle (°) 30

Case Study

/t h

/m s

3/kg m

/kg m

2/m s

parameter Configuration for Result 1 Configuration for Result 2

trough angle (°) varying 35

centre roll length ( ) 0.75 varying

wing roll length ( ) 0.75 varying m

m

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Result Result 1

Result 1 Forces on wing and centre rolls with varying trough angle

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Result Result 2

Result 2 Forces on wing and centre rolls with varying roll length

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Conclusion

• The applicability of stress discontinuity method

Application

• Optimum idler design – varying roll length and/or trough angle is

potential success

• Basis for the physical modelling of idler

Conclusion

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Any questions?

Delft University of Technology

Section Transport Engineering and Logistics

Room: 34 B-3-330

T +31 (0) 15 278 6573

E X.LIU-4@tudelft.nl

Thank you!

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