Economic Design of EOT Crane(FINAL)

A Seminar II Report On

“Economic Design of EOT Cranes”

Submitted In Partial Fulfillment of the Requirement For The Award of Degree of Master of Engineering In Mechanical –Design Engineering Pune University Submitted By

Ashutosh kumar Under The Guidance of

Prof. P.B.Deshmane

Department of Mechanical Engineering Alard College of Engineering, Marunje, Pune

Pune University, Pune 2012-13 i   

Certificate This is to certify that Mr. Ashutosh kumar has successfully completed his seminar-II on “Economic Design of EOT Cranes” for the partial fulfillment of the Master’s Degree in the Mechanical- Design Engineering as prescribed by the Pune University, Pune during academic year 2012-13

Prof. P.B.Deshmane

Prof. V.M.Junnarkar

(Guide)

(P.G.Co-Ordinator)

Prof. V.M.Junnarkar (H.O.D Mechanical)

Dr.T.R.Sontakke (Principal ACEM)

ii   

ACKNOWLEDGEMENT

I wish to express my gratitude to number of people ,without whose constant guidance and encouragement this seminar would not have been possible. I express my sincere thanks to my seminar guide Prof. P.D.Deshmane for his continuous guidance and for providing me help as and when required.

I am also thankful for the wholehearted support and the encouragement given by Prof. V.M.Junnarkar, (H.O.D, Department of Mechanical Engineering).

Finally, I wish to thank my friends and all those who gave me valuable inputs directly or indirectly in making this seminar a success.

Thanking all of you once again….

Ashutosh Kumar

iii   

INDEX

SR.

Name of Topic

Page Number

Title Sheet Certificate Abstract Index List of Figures

i

List of Tables

ii

Introduction

1

1.1 Types of Electric overhead cranes

1

1.2 Basic crane components

2

2.

Literature Review

5

3.

Design Details

8

3.1 Conventional details of the Crane Girder and

8

1.

modern design of crane girder 3.2

Girder’s Plate Details

10

4.

Boundary condition for Girder Design

15

5.

Analysis of cases

19

6.

Conclusions

23

References

24

iv   

LIST OF FIGURE

Figure No 1.1 

Title of Figure Top Running Girder Crane

2.1 

Girder section

2.2 

Girder Details

LIST OF TABLE Title of table

Table No  3.1 

Girder’s Plate Details

3.2 

Plate sectional Properties

3.3 

Buckling Safety factor

3.4 

Buckling Coefficient for the Partial Panel (Without stiffener)

3.5 

Buckling Coefficient for the Partial Panel (With stiffener)

4.1 

Compressive stress

4.2 

Fatigue stress

5.1 

Input Data Table

5.2 

Girder Section

5.3 

Result Table

 

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CHAPTER 1 INTRODUCTION

Cranes are industrial machines that are mainly used for materials movements in Construction sites, production halls, assembly lines, storage areas, power stations and similar places. Their design features vary widely according to their major operational specifications such as: type of motion of the crane structure, weight and type of the load, location of the crane, geometric features, operating regimes and environmental conditions

1.1 TYPES OF ELECTRIC OVERHEAD CRANES There are various types of overhead cranes with many being highly specialized, but the great majority of installations fall into one of three categories: a) Top running single girder bridge cranes, b) Top running double girder bridge cranes and c) Under-running single girder bridge cranes. Electric Overhead Traveling (EOT) Cranes come in various types: 1) Single girder cranes - The crane consists of a single bridge girder supported on two end trucks. It has a trolley hoist mechanism that runs on the bottom flange of the bridge girder. 2) Double Girder Bridge Cranes - The crane consists of two bridge girders supported on two end trucks. The trolley runs on rails on the top of the bridge girders.

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3) Gantry Cranes - These cranes are essentially the same as the regular overhead cranes except that the bridge for carrying the trolley or trolleys is rigidly supported on two or more legs running on fixed rails or other runway. These “legs” eliminate the supporting runway and column system and connect to end trucks which run on a rail either embedded in, or laid on top of, the floor. 4) Monorail - For some applications such as production assembly line or service line, only a trolley hoist is required. The hoisting mechanism is similar to a single girder crane with a difference that the crane doesn’t have a movable bridge and the hoisting trolley runs on a fixed girder. Monorail beams are usually I-beams (tapered beam flanges).

1.2 BASIC CRANE COMPONENTS To help the reader better understand names and expressions used throughout this course, find below is a diagram of basic crane components

Fig 1.1 Top Running Girder Crane

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1) Bridge - The main traveling structure of the crane which spans the width of the bay and travels in a direction parallel to the runway. The bridge consists of two end trucks and one or two bridge girders depending on the equipment type. The bridge also supports the trolley and hoisting mechanism for up and down lifting of load. 2) End trucks - Located on either side of the bridge, the end trucks house the wheels on which the entire crane travels. It is an assembly consisting of structural members, wheels, bearings, axles, etc., which supports the bridge girder(s) or the trolley cross member(s). 3) Bridge Girder(s) - The principal horizontal beam of the crane bridge which supports the trolley and is supported by the end trucks. 4) Runway - The rails, beams, brackets and framework on which the crane operates. 5) Runway Rail - The rail supported by the runway beams on which the crane travels. 6) Hoist - The hoist mechanism is a unit consisting of a motor drive, coupling, brakes, gearing, drum, ropes, and load block designed to raise, hold and lower the maximum rated load. Hoist mechanism is mounted to the trolley. 7) Trolley - The unit carrying the hoisting mechanism which travels on the bridge rails in a direction at right angles to the crane runway. Trolley frame is the basic structure of the trolley on which are mounted the hoisting and traversing mechanisms. 8) Bumper (Buffer) - An energy absorbing device for reducing impact when a moving crane or trolley reaches the end of its permitted travel, or when two moving cranes or

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trolleys come into contact. This device may be attached to the bridge, trolley or runway stop. The escalating price of structural material and energy is a global problem consequently optimal consumption of the both cannot be considered redundant. Overhead crane, which is a synonym for material handling in the industrial environment, utilizes structural steel for its girder and energy (mostly electrical) for its operation. Light girder for overhead cranes not only save material cost but also trim down energy expenditure because of subsequent employment of low powered drive units. The general procedure for design of EOT crane girders is accomplished through guidance stipulated in the prevailing codes and standards. Thus optimal design in such case is not the one which just exhibit stress criteria offered in structural design methods but the one which follows the limits restrained by the aforementioned codes and safety rules. Shape optimization of closed box type section was studied by Gibczynska et al.. Regarding optimal design of simple symmetrical welded box beam Farkas J & Jarmai K incorporated bending stress, shear stress and buckling constraints while kept cost, mass and deflection as objective function. Megson, T H.G. Hallak , parametrically and numerically analyzed load bearing diaphragms girder at single support point. Narayanan, in his two consecutive papers examined strength capacity of webs with cut-outs and rectangular holes and emphasized on prediction of stress in such cases.. Recently little literature is found which chiefly reviews crane box beam optimization except for Tadeusz Niezgodzin´skia, Tomasz Kubiakb who considered buckling problem of web sheets in box girders of overhead cranes due to welding of the backing strips.

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CHAPTER 2 LITERATURE REVIEW Fig-2.1 & 2.2 shows the basic components of Crane girder. It’s construction can be any of the below mentioned: (1) Beam profile Section (2) Built-up profile Section (3) Box Section

Fig - 2.1

Fig - 2.2

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Our topic is related to box girder sections. Usually for span (Girder length) more than 12 meters and load more than 10t box profile is selected because of having better sectional property with lower weight. In case of Box girders it is very important to define the sectional parameters in terms of dimension. Poor selection will not lead to optimum design. There are certain instructions about the section parameters as per IS-807-2006 listed below: a) l/h shall not exceed 25, b) l/b shall not exceed 60, c) b/c shall not exceed 60. Where, l=Span of the crane in mm; h=Depth of the Girder; b=Width of the Girder; c=Thickness of the top cover plate. Once the Girder proportion is considered then we get some boundary to work in as to design and optimize any girder we need to follow certain norms as well. Henceforth we will be considering IS: 807-2006 &IS: 800-1984 as the guiding source. These standards only define some boundary in which we have to design the structure. Basically IS: 807 & IS: 800 are the Indian standard which is used in our country by all crane manufacturers who design as per these Norms. As mentioned earlier the box girder is the welded structure with the help of four plates- top plate, bottom plate and two web plates inside the top and bottom, thus forming a box structure. These plates are welded to each other. There are some more parts which keeps the

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Economic Design of EOT Cranes  

structure balanced and stable. These are diaphragm plates, Angular stiffeners and backing strips for web (not shown in figure). Rail on which crane trolley runs can be either welded on the top of the web above top plate (as shown) or can be placed on the girder top at the center of the top flange. These two positions are not only the locations where the rail can be placed as it also depends on the design and dimensional requirement of the Crane. Rails used in the crane girders can either be flat bar type or can be profile rails as used in railway. This selection depends on the wheel selected for crane trolley and also sometimes as per customer requirement.

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CHAPTER 3 DESIGN DETAILS 3.1 CONVENTIONAL DETAILS OF THE CRANE GIRDER AND MODERN DESIGN OF THE CRANE GIRDER (a) Conventional Design of the Crane Girder (Rail on Center Construction) In such crane, Wheel load which is coming from trolley is directly applied on top flange, which results in buckling of top flange in addition to stresses coming on it. In order to avoid buckling we have to provide full diaphragm & short diaphragm throughout length of girder. This not only helps in eliminating the buckling of top flange but also helps in reducing the bending stresses coming in the rail. In addition to these angular stiffeners are also added to web plates to avoid its buckling. Thus the girder structure weight consists of Rail, Top & Bottom flanges, web plates, backing strips, Short diaphragm & Long diaphragm. (b) Modern Design of the Crane Girder (Rail on web) In such crane, Wheel load which is coming from trolley is directly applied on web, which results in load transmission through it. The web plates are then subjected to buckling also but due to addition of angular stiffener the buckling effects are nullified. Rail being on web has another one important advantage that the rail is not subjected to bending stress. So here in this type of girder design Short diaphragms are not required as the rails bending is taken care by web and the top flange is also not subjected to buckling loads. Thus the girder structure weight consists of Rail, Top & Bottom flanges, web plates, backing strips& Long diaphragm.

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(c) Findings of above study Girder manufactured as per the conventional design style is heavy as compared to the Girder manufactured as per the Modern design way. Out of the whole crane structure weight Girder Keeps the maximum share for small span cranes, but for long span cranes girder weights are the major decisive for cranes weight. It is always preferable to have lower crane weight from both customer and vendor point of view. Thus in order to reduce the crane weight the girder’s weight must be minimized. As the weight of girder increases  The loading on End carriage increases which results in heavier end carriage.  Once the structural weight rises up the mechanical component sizing also goes up which results in the increase in cost of the mechanical components for the same usage and hence the crane pricing goes up.  It results in selection of heavier electrical components like motor, drive etc. Heavier electrical requires higher electrical input which again increases the cost of the electrical energy consumption on daily basis.  Higher crane weight needs the gantry girder much heavier so here the customer also faces. His workshop columns and gantry needs to be heavier if the crane weight has increased.  Ultimately daily manufacturing cost goes up.

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3.2 GIRDER’S PLATE DETAILS Depending on the dimensional availability of the plates in the market some standard sizing has been used as the regular practice now days. FLANGE WEB

Thickness (t) mm

(F)mm

(W)mm 6

8

10

12

16

20

200

410

F,W

F,W

F,W

F,W

F,W

F

300

490

F,W

F,W

F,W

F,W

F,W

F

410

610

F,W

F,W

F,W

F,W

F,W

F

490

740

F,W

F,W

F,W

F,W

F,W

F

610

860

F,W

F,W

F,W

F,W

F,W

F

740

980

F,W

F,W

F,W

F,W

F,W

F

860

1230

F,W

F,W

F,W

F,W

F,W

F

980

1480

F,W

F,W

F,W

F,W

F,W

F

1230

1780

F,W

F,W

F,W

F,W

F,W

F

1980

W

W

W

W

W

2180

W

W

W

W

W

2380

W

W

W

W

W

NA

NA

TABLE-3.1 Table 3.1 shows the preferred dimensions of Flanges and Web plates with various thickness combinations. Usually rectangular Box sections with flanges more than 1230mm width and 20mm thickness are not preferred as it reduces structural stability with same construction. Same is applicable for web plates also. But in case of web plates the total depth can be up to 2380mm with 16mm thickness. These dimensions cannot be considered as the bounding figures.

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Span Flange

Web

Flange

web

(l)

(b)

(h)

thk(c)

thk

m

mm

mm

mm

mm

Ixx(cm4)

Iyy(cm4)

Zxx

Zyy

wt/mtr

(cm3)

(cm3)

(kg/m)

10

200

410

6

6

17276.2

5148.8

818.8

514.9

57.5

15

200

610

6

6

45466.2

7270.2

1462

727.1

76.4

20

300

860

6

6

131102.8

24102.7

3007

1606.9

109.3

25

410

1230

8

8

499472.8

85576.1

8017.3

4174.5

206

30

490

1230

10

8

624835.8

127378.5

9997.4

5199.2

231.5

35

490

1480

10

8

976171.6

149283.1

13015.7

6093.2

262.9

40

610

1780

12

10

2115299

348965.8

23451.3

11441.5

394.4

45

740

1980

16

12

3911066

696908.6

38877.4

18835.4

559

50

740

2180

16

12

4926967

756388.3

44547.7

20443

596.6

55

860

2380

16

16

7544746

1475129

62560.1

34305.4

813.9

60

980

2480

18

16

9571243

2043057

76083.1

41695.1

900

TABLE-3.2 Table 3.2 shows the chart which shows the plate dimensions of a girder for different spans. In order to optimize the Girder Section web plate plays important role. As per Table-3.2 it is clear that for the same flange dimension but different web dimension the sectional properties increases much faster as compared to the increase in the weight. Web Plate selection and design: Web plates are not only selected as per the dimensions mentioned above but also checked for buckling stresses. In case of box girder there are two important internal elements also as mentioned earlier-Diaphragm and Horizontal stiffeners.

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Role of Diaphragm:- Diaphragm not only support the structure internally but also is a relevant support for web plates. It divides the web plates in different part known as panels. IS-800 clearly specifies it. This panel is detailed by two dimensions-a & b. a – Length of the panel. b – Depth of the panel. Buckling of this panel is checked as per the formula mentioned below:

Where, σe – Buckling Stress; t1- Thickness of the panel; b1- Depth of the panel; ν – Poisson’s ratio; E- Modulus of Elasticity. Absolute value of maximum compressive stress(σ1) & Shear stress (τ):

σ1ki – Local ideal buckling stress calculated as below: σ1ki = σe . k (kg/cm2) or (N/mm2) S - Service factor (From Table-3.3) K – Local Buckling Coefficient (From Table-3.4 & 3.5)

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Loading Condition

Safety Factor for Buckling Safety Factor for Buckling of the of the whole plane.

partial plane surrounded by stiffeners.

I

1.71 + 0.180 (ϕ -1)

1.5 + 0.075 (ϕ -1)

II

1.50 + 0.125 (ϕ -1)

1.35 + 0.05 (ϕ -1)

III

1.35 + 0.075 (ϕ -1)

1.25 + 0.025 (ϕ -1)

TABLE-3.3 Buckling Coefficient for the Partial Panel (Without stiffener)

TABLE-3.4 Table-3.4 shows the panel which is nothing but the web plate section which is dimensioned as a & b. From the above table we can select the Buckling coefficient K. This Chart is applicable to only unstiffened web.

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Table 3.5 is applicable to the webs which are subjected to both vertical as well as horizontal stiffener. In this the panel formed due to vertical diaphragm is further subdivided into small sub panels with the help of angular stiffener. Buckling Coefficient for the Partial Panel (With stiffener)

TABLE-3.5

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CHAPTER 4 BOUNDARY CONDITION FOR GIRDER DESIGN Crane girder design is guided by various design norms like-IS: 807, FEM, CMAA, EN etc. We have following conditions to be satisfied in order to get the girder on the safer side: (a) Static stresses to be within limit. (b) Fatigue Stresses to be within limit. (c) Horizontal & vertical deflections to be within limit. (d) Horizontal & Vertical vibrations to be within limit.

(a) Static Stress Check: In this check we are checking the stress ratio of the structure due to static loading which arises on account of self weight and lifted capacity. The allowable value is well defined in design norms. Basically tensile stress ratio and compressive stress ratio is checked in this case. The allowable value of tensile stress and compressive stress for steel plates as per IS: 807 are given as below: Tensile stress value: σt σt = 0.66*Syt*Duty factor (As per IS-807) Where, Syt-Yield Stress of selected material (N/mm2) Duty Factor- 1 (For class-I), 0.95 (For Class-II), 0.9 (For class-III),0.85 (For Class-IV) Compressive stress value: σc Allowable compressive stress value is considered from following two conditions (As per IS: 807) (1)Allowable compressive stress is to be considered 1235 Kg/cm2 if the ratio b/c is equal to or less than 38

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(2)When the ratio exceeds 38 then the allowable compressive stress value is considered from the table below: b/c

σc (kg/cm2)

40

1145

44

990

48

870

52

770

56

690

60

625

TABLE-4.1 (b) Fatigue stress check In this we check the fatigue stress occurring in the structure and compare it directly to the corresponding fatigue stress value as guided by design Norms. The allowable value of fatigue stress for different load cycles are given below which is purely as per IS:807. fatigue stress depending on stress cycles (Kg/cm2) stress category

10000-20000

100000-500000

500000-2000000

over 2000000

A

2760

2210

1660

1660

B

2280

1720

1170

1030

C

1930

1450

960

830

D

1660

1170

690

620

E

1170

830

480

410

F

1170

960

760

620

TABLE-4.2

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Stress category –C is applicable to crane girders so the fatigue stresses can be cross checked for different hoisting cycles for different stress values tabulated above.

(c ) Horizontal & Vertical deflection Check: In this we check the girder’s deflection in both direction –Horizontal and vertical. For vertical deflection there is general guidance as per IS:807 which speaks that the vertical deflection must be limited by ratio of span/900. The vertical deflection should involve the live load deflection only and no impact should be considered. For horizontal deflection there are no such guidelines so we generally restrict it by the same ratio as mentioned above. (d) Horizontal and Vertical vibrations This is one of the important check which must be done at least for long span crane. Unfortunately there is no guideline in IS:807 for this but we follow ISO standard for this checking. Formulae used for checking the vertical as well as horizontal vibrations are given below:-

Where, fV= Vertical natural frequency E= Modulus of Elasticity (N/mm2) Iy= Vertical Moment of Inertia S= Span of the crane Mc=Crab Mass Mg= Girder mass

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Above mentioned formula is given in ISO-22896. We use this formulae to check girders vibration. For Horizontal Vibration the calculation procedure is shown below:

Where, Fh= Horizontal natural frequency E= Modulus of Elasticity (N/mm2) Iz= Horizontal Moment of Inertia Kmg= Typical value considered as 0.4857 Mc=Crab Mass Mg= Girder mass The allowable values of vertical frequency and Horizontal frequency are considered as 2 and 1.7 respectively as per ISO standard

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CHAPTER 5 ANALYSIS OF CASES Case-1 When the rail is placed on the top of the girder and the rail center is matching to the web center Case-2 When the rail is placed on the top of the girder and the rail center is matching to the top flange center 2.1 Basic Inputs: PARAMETERS

Case-1

Case-2

Total payload

500000 kg

500000 kg

Design Standard

IS-807

IS-807

Crane Duty class

II

II

Bridge travelling speed

40 m/min

40 m/min

Span

37900 mm

37900 mm

Trolley Rail gauge

8500 mm

8500 mm

Trolley Wheelbase

5600 mm

5600 mm

Trolley approach at end 1

1000 mm

1000 mm

Trolley approach at end 2

1000 mm

1000 mm

Trolley Wheel diameter

900 mm

900 mm

Trolley Wheel width

170 mm

170 mm

Trolley Wheel flange height

20 mm

20 mm

Trolley Traversing speed

20 m/min

20 m/min

Trolley weight

160000 kg

160000 kg

TABLE-5.1 Input Data Table

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Above chart shows the basic input which is required to decide the girder section. 5.2 Girder Section

Parameters

Case-1

Case-2

H

3480

3480

T1

12

18

T3

12

10

BL

1750

1750

T2

40

40

B

1750

1750

T4

40

32

F1

75

200

F2

75

125

F3

75

125

F4

75

50

RAIL

A-150

A-150

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NOTE: Rail is intentionally not shown in the girder section. For case-1 the rail will be on the web top and for Cae-2 the rail will be on the girder top at the centre of the top flange. The material of the girder confirms IS-2062 with yield strength 250 N/mm2. Based on the above data the following results are tabulated below: Parameters

Case-1 (Rail on centre)

Case-2 (Rail on web)

Component

Ratio

Condition

Ratio

Condition

Stresses

0.82