Load Calculation for Trough Idler Rolls - MHEA · Idler Rolls Load Analysis •Cross-section simplification Analysis of Forces on Idler Rolls [7] [7] C. A. Wheeler, 2004 •Three-dimensional

1 Challenge the future

Load Calculation for Trough Idler Rolls

MSc. Xiangwei Liu

Delft University of Technology

--Stress Discontinuity Model

BULK 2014 CONFERENCE


Outline

Introduction

Methodology

Idler Rolls Load Analysis

Result

Conclusion



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



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



Introduction

• Idlers

Background

[3]

[3] USA Mining, 2013.

[4] Saimh.co.za, “Idler Basics.”

[4]


javascript:win('idlers-04.htm')


Introduction Challenge 1

• Stress profile on loaded conveyor belt



Introduction Challenge 2

• Potential high cost of idler failure

[5] L. Nordell, 1995

[5]

• Unbalanced load distribution

• Large design margin



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



Methodology

• Stress Discontinuity Method

Stress Discontinuity model (SD model)

[6]

[6] W. Powrie, 2004

• Stress Field Analysis




• Cross-section simplification

Analysis of Forces on Idler Rolls

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

• Three-dimensional forces

• Active and passive stress statuses




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




SD analysis from zone 1 to zone 2

SD model


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)




Obtain the normal and frictional force on the wing belt

section

SD model


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)




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




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)



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



Result Result 1

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



Result Result 2

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



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



Any questions?

Delft University of Technology

Section Transport Engineering and Logistics

Room: 34 B-3-330

T +31 (0) 15 278 6573

E [email protected]

Thank you!


mailto:[email protected]



Documents

Load Calculation for Trough Idler Rolls - MHEA · Idler Rolls Load Analysis •Cross-section simplification Analysis of Forces on Idler Rolls [7] [7] C. A. Wheeler, 2004 •Three-dimensional