Electric Overhead Travelling (EOT) Crane is one of the essential industrial equipment for material handling job. Indecent years little attention has been paid to the optimal design heavy electric overhead travelling bridges. The motive might be, but not limited to the availability of prevailing FEM, DIN, ISO, CMAA, BS, Chinese and now CEN standards for the design of cranes. Most of the crane manufacture has standardized the single dimensioned box section for multiple spans and duties of crane bridges for manufacturing simplicity.
LIST OF TABLES Table No. | Table Description | Page No. | 1 Different cross section formula 2 Dimension for ramshorn hooks
LIST OF FIGURES
Figure No. Figure Description Page No.
1.1.1 Overhead crane
1.3.1 Standard crane
1.4.1 Free standing crane
1.5.1 Gear box
1.5.2 Electric brake motor
1.5.3 Rope guide
1.5.4 Load limiter
1.5.5 Low headroom trolley
1.6.1(A) Top Running Bridge Cranes
1.6.1(B) Under Running Bridge Crane
1.7.1 Top running vs. under running
1.9 Double girder crane hoist
1.9.1 Chain hoist
1.9.2 Wire rope hoist
3.1.1 Drawing of 160 ton hook, nut &
Lock plate
3.2.1 CAD model of 160 ton hook
3.3.1 Different views of crane hook
3.3.2 Bending of a beam with larger
Initial curvature
3.4.1 Modified cross section
3.5.1 Circular cross section
3.5.2 Rectangular cross section
3.5.3 Triangular cross section
3.5.4 Trapezoidal cross section
3.6.1 Ramshorn hook with different dimensions
3.6.2 Load test on ramshorn hooks
LIST OF SYMBOLS
C= Bad diameter
P= Load applied on ton d = Diameter of hook
W = Crane hook caries a load y = Distance form the natural axis h = Link radius m = Banding moment about the centrodial axis σt = Direct tensile stress
Rn = Radius of curvature of the neutral axis
Ae = Area of section σb =Bending stress yi = Distance of the neutral axis to the inside fiber yo= Distance of the neutral axis to the outside fiber
LIST OF ABRIVATIONS
TABLE OF CONTENTS
TITLE PAGE I
CERTIFICATE II
ACKNOWLEDGEMENT III
ABSTRACT IV
LIST OF TABLES V
LIST OF FIGURES VI
LIST OF SYMBOLS VII
CHAPTER 1 INTRODUCTION 1.1 Introduction of crane 1.2Range of crane 01 1.3Standard crane 02 1.4Free standing crane 03 1.5Main parts of crane 04 1.5.1 Gear box 1.5.2 Electric brake motor 1.5.3 Rope guide 1.5.4 Load limiter 1.5.5 Low headroom trolley 1.6Different types of crane 05 1.7 Top running VS. Under running 1.8 Prevents the problem encounter with cranes 1.9 Types of electric hoist 1.9.1 Chain hoist 1.9.2 Wire rope hoist
CHAPTER 2 LITERATURE REVIEW
CHAPTER 3 WORK DONE 3.1 Drawing of 160 ton hook, nut & lock plate 3.2 CAD model of 160 ton hook 3.3 Different views of the crane hook and
Calculation
3.4 Modified section
3.5 Stress cross section
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CHAPTER-1 INTRODUCTION ABOUT PROJECT 1.1 INTRODUCTION OF CRANE
Overhead cranes raise, shift, and lower loads with a projected, swinging arm or a hoisting apparatus supported on an overhead track. There are many different types of products. Overhead cranes or bridge cranes attach a horizontal load-carrying beam to wall columns (overhung).
Overhead cranes differ in terms of product specifications, features, and applications. Performance specifications to consider include load capacity, vertical available lifting height, and horizontal available span. Overhead cranes with wheels are designed for load transport and positioning. Typically, these machines are equipped with a brake or stabilizing outriggers. Overhead cranes that provide motorized motion move loads with a motor instead of manual pulling. With some applications, an industrial pendant is used to enable an operator to actuate lift or trolley travel. There are many different sizes of overhead cranes.
Fig.1.1.1 Overhead Cranes[1]
Many overhead crane models exist, all offering unique advantages according to the application. The single girder over lungcrane is possibly one of the most popular. Also available are double girder cranes and under slung cranes. Electrically motor driven end carriages and hoist provide effortless accuracy when lifting and positioning heavy components and plant in machine shops, factories, warehouses, loading bays, etc.
Multi-functional controls are usually housed in a single control box. Operational control can be via suspended pendant, alternatively static pendant; remote or automatic controls can be fitted. There are a number of safety devices i.e. limit switches, warning lights, horns and anti-collision units, available to guarantee operator and pedestrian safety.
1.2 RANGE OF CRANE * Standard Cranes 4 - 4000 * Heavy Duty Cranes 5 - 5000 * Double and Single girder cranes * Hand operated cranes * Jib Cranes * Crane Kits
1.3STANDARDCRANE
Fig. 1.3.1 Standard crane[2] * Externally mounted motors allow for better ventilation and ease of access during maintenance, giving faster turnaround times. * Reduced scheduled maintenance and emergency downtime * Hoist independently load tested to 125% and certified by tests undertaken in the workshop * Easily adjustable over-raise and over-lower limit-switches allow swift changes on-site * Primary braking operates directly on the gearbox for maximum safety - secondary braking optional. * Fail-safe braking system incorporating a manual-release mechanism for emergency lowering in the event of a power failure. * Low voltage control system is an additional factor in operator safety * High quality structural assembly ensures compliance with BS466 (ISO4301) and BS2573. * End carriages fabricated from rolled steel with internal diaphragms for high torsional resistance. * Travel wheels made from spheroidal graphite cast iron with a high tensile strength and a high resistance to impact loads. * Graphite material castings within the wheel material act as a lubricant, reducing wear of the wheels and track. * Live axle drive system and precise speed control on all motors allows for smooth and accurate movement. * Rapid access to spare parts * Crane configuration selected to meet needs of application including Single girder, Double girder, Underslung, Goliath and Semi-Goliath.
1.4 FREE STANDING CRANE * Free standing cranes are usually supplied in standard sizes, but if the application requires it specific cranes can be designed to your needs. * Bespoke applications include wide spans and long down shops /lengths. * The versatility of the system means that if you have pillars or other obstacles the crane system can be designed to take account of these.
Fig. 1.4.1free standing crane[3]
1.5 MAIN PARTS OF CRANE
1.5.1 GEAR BOX
The 2 or 3-stage planet art gear reduces the speed of the electric motor to the RPM necessary for the drum.All gears of the planetary gear are made of heat-treated high quality steel.
Fig. 1.5.1 Gear box[4]
1.5.2. ELECTRIC BRAKE MOTOR
Three-phase asynchronous 1 or 2-speed motor with cone rotor and integrated cone brake driven by a coil spring.
The brake release is due to the sliding of the rotor after switching-on of the power supply.
Fig. 1.5.2 Electric brake motor[4] 1.5.3 ROPE GUIDE
The rope guide basically consists of two parts: a guide ring and a pressure spring that properly guide the rope on the drum grooves.
Fig. 1.5.3 Rope guide[4] The guide ting maintains the rope in position during the inkling, preventing it coming-off the groove and, when the load oscillates, is guided by a fixed bar and runs on bearings.
1.5.4 LOAD LIMITER
All "M" series hoists with 2 and 4 rope falls are equipped with a load limiter with 3 reaction thresholds. The load limiter consists of an electric-mechanical system with pre-set springs acting on two microswitches stop all movements, exception made for the lowering of the load. The first threshold activates a warning, the 2nd stops the function.
Fig .1.5.4 Load limiter[4]
1.5.5 LOW HEADROOM TROLLY
Low headroom trolleys are equipped with 2 travel units, consisting of planetary gears with double speed brake motors directly flanged to the wheels the wheels, therefore without external teeth
Fig.1.5.5Low headroom trolley[4]
1.6DIFFERENT TYPES OF CRANE
1.6.1 Top Running Bridge Cranes and Under Running (Under Hung) Bridge Cranes.
A.Top Running Bridge Cranes * Single Girder Bridge Crane * Up to 10 Ton Capacity * Up to 120 Feet Span * Double Girder Bridge Crane * Up to 300 Ton Capacity * Up to 200 Feet Span
B.Under Running (Under Hung) Bridge Cranes * Single Girder Bridge Crane * Up to 10 Ton Capacity * Up to 200 Feet Span (Multi-Runway Cranes) * Double Girder Bridge Crane * Up to 15 Ton Capacity * Up to 200 Feet Span (Multi-Runway Cranes)
Fig.1.6.1(a) Top running Bridge crane[5]
Fig. 1.6.1(b) Under Running Bridge Crane[6] * Overhead Bridge Cranes can be divided into two groups: 1. Top Running Bridge Cranes, and 2. Under Running Bridge Cranes (sometimes called under hung). * A Bridge Crane system consists of three major components. 1. the Bridge Crane, which traverses across the runway 2. the hoist & trolley, which traverses across the bridge and lifts up and down 3. the runway, which is tied to the building structure.
1.7 Top Running vs. Under Running
1.7.1 Top Running vs. Under Running is primarily determined by two factors: 1. Capacity - Although under running can be up to 25 ton capacity, the practical limit is more like 15 tons and the economic sweet spot is 1 to 7.5 ton range. 2. Support Structure - Under running can be suspended directly from the overhead steel (for lighter cranes). Top running cranes will require a bracket off the building support steel (up to 10 tons capacity) or independent columns for heavier capacities.
Fig. 1.7.1 Top running VS. Under running * The top running configuration is best used in cases where the end user has issues with headroom. The most space efficient configuration is the double girder, top running crane system. When headroom is not an issue a top or under running configuration can be used with either the double or single girder bridge crane.
1.8 Prevent the problems encounter with cranes: * Crane Travels Too Far Before Stopping.
If crane coasts more than a few feet, then it is likely that it uses electric motor brakes and that, like most cranes, the brake pads haven't been replaced (they require replacing or adjusting every 3 months). * Use a mechanical braking system thatnever needs adjusting or replacing. This provides a gentle, consistent coasting stop that does not vary over time. For cranes that travel over 100 FPM or require quick stopping, considering the soft-stop feature of a variable speed inverter. * Bearings wearing out too soon.
Use a minimum of 2 bearings per wheel. All of bearings are Class "D" which means they are designed with a minimum life expectancy of 10,000 hours of actual motor on-time. This is double the Class "C" rating - bearings for Class “C” cranes have a minimum life expectancy of 5,000 hours. Class "D" bearings are also sealed-for-life and never need lubricating. * Contactor problems.
Contactors, rated for 20,000,000 stop / start cycles if used in conjunction with inverters or electronic soft start features, should never need replacing under normal operating conditions. * Broken Push Button Pendant or Cable.
NAI pendants are ergonomically designed to be easily held in one hand, and are constructed of a durable thermoplastic material. The pendant cable has 2 steel wires built into the cable jacket for permanent strain relief. * Parts Availability Problems.
Components-bearings, contactors, gearboxes, motors and electrical systems-are designed to industry standards, and most are readily available throughout the U.S. All motor name plates and gearbox name plates are clearly labeled with the original manufacturing information. And virtually every spare part for the crane (excluding the hoist) is in stock here at North American and can be shipped immediately. * Brakes wearing out or not working properly.
Mechanical braking system on the trolley and bridge eliminates the need to adjust brakes on a regular basis (typically every 3 months). There are no brake pads to change or adjust with our mechanical brakes. This will reduce overall maintenance and extend the life of the wheel gears and pinions.
1.9 Main types of electric hoists:
A hoist is a device used for lifting or lowering a load by means of a drum or lift-wheel around which rope or chain wraps. Cranes and Hoists are somewhat interchangeable terminology since the actual lifting mechanism of a crane is commonly referred to as a hoist. Hoists may be integral to a crane or mounted in affixed position, permanently or temporarily. When a hoist is mounted to a trolley on a fixed monorail, two directions of load motion areavailable: forward or reverse, up or down. When the hoist is mounted on a crane, three directions of loadmotion are available: right or left, forward or reverse, up or down. Figure below shows a rope hoist for double girder crane application.
Fig-1.9 Double Girder Crane Hoist[6]
Hoist Lifting Media
There are two basic hoist lifting media - Wire Rope Hoist which is very durable and will provide long term,reliable usage and the other type of hoist is the Chain Hoist.For a given rated load, wire rope is of lighter weight per running foot but is limited to drum diameters farlarge than the lift wheel over which chain may function. Therefore a high-performance chain hoist may beof significantly smaller physical size than a wire rope hoist rated at the same working load. High speedlifting (60 Ft. /min +) requires wire rope over a drum because chain over a pocket wheel generates fatigue inducing resonance for long lifts.
1.9.1 Chain hoists
Fig. 1.9.1chain hoist[7] * Lift by pulling the chain through sprockets and depositing the chain into a chain container * Are more common for applications below 7.5 tons * Require less maintenance * Are less expensive * Provide true vertical lift at no extra cost 1.9.2 Wire rope hoists
Fig. 1.9.2wire rope hoist[8] * Lift by wrapping cable around a grooved drum * Dominate the market at 10 tons and above * Offer very fast lifting speeds * Offer a wide array of options * Can be rated H-5 (severe duty)
Both chain and wire rope hoists are rated H-4 (heavy duty) or H-3 (moderate duty). Duty ratings are a better indicator of hoist durability than hoist type (chain or wire rope). Both types use similar motors, brakes and controls. The main difference between electric chain hoists and wire rope hoists is in the design of the lifting mechanism.
Be sure to request an H-4 rating on either your chain or wire rope hoist to ensure long life and low maintenance.
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CHAPTER-2 LITERATURE REVIEW
Optimization of crane Box Bridge is a complex nonlinear problem for which a simple computational procedure has been suggested. The worksheet with solver can take more than thousand variables and very small to large scale nonlinear optimization can be performed. The results seem to be encouraging and the optimized girders are lighter than the cranes manufactured and supplied in the prevailing market. Additionally the designed spreadsheet does not cross any limit and therefore robust design can be approached. Computational work sheet as well as numerical optimizer calculates optimum parameters in millimeters and most of the time thicknesses are not in whole number. Such problem can be solved by rounding up to a nearest whole number or introducing the integer constraint in the solver which could bring about fractional rise in the weight of the crane. In crane design environment this methodology might help to save precious design time, without incurring high computational cost. The Numerical optimizer has been assessed for simple unstiffened box beam to girders with stiffener and variety of load cases and it has been established that computation time may increase to a moderate level. The APDL created for girder needs only parameter, loads and spans initialization. Later no further assistance is required for the complete model construction in FE software. The optimization is to be triggered of by another batch command which inputs design constraints and design variable limits to FE optimizer. The computational worksheet has not been considered for fatigue and weld design optimization for the plate girder which has been intentionally left for the sake of simplicity. These cases can be incorporated in the spread sheet in future.[12]
Bridge girder is an important structural member whose fatigue life decides the life of an EOT crane. In this paper, the fatigue life of bridge girder of a working EOT crane is calculated based on Palmgren& Miner’s rule for the important decision of replacing or maintaining the girder. The variable loadings coming on the bridge girder at the exact loading points of a working crane and stress spectrums by reservoir counting method are presented. A working crane of class of duty 4 as per BIS “M8” commissioned in 1983 is selected for this. The fatigue life considering probabilistic survival of 97.5% comes out to be 25.68 years. It is suggested that the bridge girder has lived its fatigue life and needs replacement.The fatigue life of the crane girder under consideration is found to be 26.31 years.[13]
Considering probabilistic survival of 97.5%, the fatigue life comes to 25.68 years. It may be interesting to note here, that the subject crane was commissioned in the year of 1983, already it has rendered the service of 25 years, and hence the management has started thinking of replacing the entire crane/girders. EOT crane’s bridge girder fatigue life calculation is made available in the form of MS-Excel program based on Palmgren-Miner rule considering the structural construction detail Tables of Euro code 3 and IS: 1024. It is possible to calculate the stress spectrum of the bridge girder for each and every point of loadings along with variable loadings, considering the effects of acceleration and deceleration of trolley movement. Using reservoir cycle counting method, stress spectrum of variable loadings is calculated. The program developed can be useful to predict preventive maintenance of EOT cranes, and or in taking the larger decision of replacing parts or whole of the bridge girder and also to predict the fatigue life of the girder of a newly commissioned EOT crane.[]
Control and protection Devices Play a Great Role in the Working of the Electrical Equipment’s. The protection of EOT Cranes from Free-Fall/ Breakdown of due to Over-Speed needs a Protection and control devices to minimize the accidents and avoid damage to Human life and Equipment. In the Existing System Hydraulic-Operated Caliper Brake unit is used for Protection due to Breakdown and Free-Fall of Crane. The Present system is Operator Dependent and time delayed. Adequate alarm and Isolation from Power Circuit are not available. It is not been Integrated with the Existing Process Automation System. The main Objective of the Current Project is to utilize the Flexible Operation of Counter and Sensor for Control and Protection of Crane from failure. Programmable Counter ProvidesInformation about the Initial and Final set Values of Speed through Sensor. It sets the Alarm during fault Condition. In addition the most Important things is that it sends Signals to the Caliper Brake unit and VVVF drive unit to take Necessary Actions and These things are Operator Independent and fully Automated.
From the above set-up and arrangement we can ensure control and protection of crane from possible failure this increases reliability of the system because of operator independent and additional Caliper brake, drive and power circuit can be disconnected immediately after the fault within fraction of seconds . Above all this is the most economical in Cost wise flexible for multiple operations.[15]
Main Component of Overhead Crane is Girder Beam which transfers load to structural member. In Present Practice, industries overdesign girder beam which turns costly solution. So, our aim is to reduce weight of girder which has direct effect on cost of girder and also performance Optimization is done for fatigue (life) point of view. In this paper FE analysis of girder beam is carried out for the specific load condition i.e. turning operation. Here, we done a mathematical design calculation crane component, and thrust forces are used in FE analysis. Here, we used ANSYS WORK BENCH V12.1.Software for the FE analysis of the girder beam. Through this analysis we get the result in terms of stresses and deformation and this result are within the allowable limits.[14] David c. wycoff (1974) has explained that to control the braking system for apparatusdriven by single and polyphase alternating current induction motors. The system prevent destructive and dangerous overspeeding when the nature of the driven load is such that it can furnish sufficient torque to overdrive apparatus in any one of several potential modes. Acapacitor selected according to this invention is permanently connected across the motor winding such as to cause the drive motor to automatically develop retarding torque in the absence of power supplied there to sufficient to restrict the overdrive speed to a value not appreciably exceeding the normal operating speed the system also incorporates drive motor specifically designed with a predetermined value of starting torque appreciably less than that conventionally applied to similar apparatus for the specific purpose of limiting.[] Thomas Karl McNeil (1975) invented a system for detection of fault along an electric overhead travelling crane runway has a transducer detecting axial movement of a crane wheel drive shaft connected to a vibration analyzer. As the crane is moved along the runway, the analyzer provides a signal indicative of axial vibration to a calibrated recorder to produce a graphical record which is correlated with the location of supporting column and rail joints.[] John b. Shaw (1975) invented an arrangement for one or more tiltable drums that may be used in conjunction with cranes or other hoisting devices to overcome fleet angle limitation and controls the points of cross-over and reversal of the winding of the running line due to feet angle limitations of the line when the load bearing blocks are brought near their high limit.[] A Team (2007) Improved electric lift actuator for use on variety of lift system, includes various improvement that enable a universal design with interchangeable parts across several load ranges. The universal design further enable additional features and functionality (e.g., improved load cell location, improved operator sensing and electrical signal/air channel in operator pendant, improved reliability and reduced cost for operator force sensing, etc.) In addition the universal design is incorporated with a rotational drive assembly wherein the load sensing and wire rope slack sensing, as well as cable limits may be achieved using improved components and techniques such as non-contact sensors, etc. many of the improvements described are believed to reduce cost and improved performance and expand the capacity and reliability of the actuator in addition to making the actuator a common design across several applications and load ranges.[] Travelling cranes of the hand operated type were in use in the 1880’s. About this time complicated designs of powered motion were offered by English and American builders, involving a driving shaft along the runway and multiple clutches for transferring the power of the driving shaft to the hoist, trolley or bridge motions. Study of crane hook for trapezoidal cross section finite element analysis santosh Shaun , in this paper CAE is used to shorten the development FEM concept is used in the locking system of the crane hook stress factor is distributed uniformly. Damage factor the database is used to identify the load conditions that were Fatal to those damaged crane-hooks. Some of the feature points are selected on the crane-hook design; the Deformation of a damaged crane-hook can be then obtained based on the feature points detected by means Of the image processing. The critical load condition of the damaged crane-hook is calculated by comparing the obtained actual deformation and the simulated deformation values in the database. On the basis of these calculated load conditions, the critical load condition for the crane-hook is estimated as a statistical Distribution based on the Bayesian approach.[11]
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CHAPTER-3WORK DONE
3.1 Drawing of 160 ton hook, nut & lock plate
Fig. 3.1.1 Drawing of 160 ton hook, nut & lock plate
3.2 design of 160 ton hook
Fig. 3.2.1 CAD model of 160 ton hook
3.3 different views of the crane hook and calculation
Fig. 3.3.1 Different views of the crane hook
* The inner side is called intrados and the outer side is called the extrado. * According to force diagram of the hook intrado experiences more tensile force than the extrado. * Hook bed diameter is given by the formula c=μPcm * Where P is the load applied in tone c is the bed diameter * μ is a constant varying from 3.8 to 7.6 * Considering μ = 4.24 c = 30cm =300mm * Throat of the hook is taken 0.75c =225mm * d= 3.2P+C/10 =256.2mm * Using safety factor 6 * W=6x50000 =300,000 N * A crane hook is treated as a curved beam * Straight beam theory and shallow beam bending theory is not applied to the crane hook. Bending theory of beam with larger curvature is applied here
Fig 3.3.2 Bending of a beam with larger initial curvature
* In a beam with larger curvature neutral surface is displaced from the passing through the centroid towards the centre of curvature.
* The stress distribution in the curved beam due to moment is found by balancing the internalresisting moment to the externally applied moment
* And we get the following result σ=MyAe(Rn-y)………..(1) * By simplifying putting value of Rn we can obtain the following equation σ=MAR1-R2yh2(R-y)…………(2) [ Where h_ is called link radius and the value is given by the formula h2=RAy2R+ydA ]…………(3) * If σ is +ve then stress is tensile if σ is –ve then the stress is negative * The value of y is taken as –ve if it is on the opposite of the neutral axis
Table no. 1 different cross section formula Cross Section | Value of link radius | Rectangular | h2=2.3R3Dlog2R+D2R-D-R2 | Circular | h2=d216+18×d416R2 | Trapezoidal | h2=R3A2.3B2B1-B2R2DlogR2R!-B1-B2-R2 | Triangular | h2=R3A×BD2.3R2logR2R1-D-R2 |
3.4 modified section D=3.2p+c10 =256.2 mm R=0.75d=192.1 r=18d=32.05
Fig3.4.1Modifiedcrosssection
3.5Stress Calculation
Circular cross section * D=d=256.2 * A=51526.1 mm2 * R=c+d/2= 428 * h2=4280.89 * σ=WA+MAR1-R2yh2R-yFig.3.5.1 Circular cross section * Considering M ≈W×R We can have * σ=WA2-R2yh2R-y * σ =-368.7 for y =d/2
Rectangular Cross section * D= 256.2 mm * A=51562.1mm2 * B=120.4 * h2=2.3R3Dlog2R+D2R-D-R2 * h2=5626 * σ=12.50 for y=d/2Fig.3.5.2.Rectangular cross section
Triangular cross section * D=256.2 mm * B=402.5 * A=51552mm2 * h2=R3A×BD2.3R2logR2R1-D-R2 * Considering M ≈W×R We can have * σ=17.97Fig.3.5.3 Triangular cross section
Trapezoidal cross section * B1=300 * B2=102.4 * h2=R3A2.3B2B1-B2R2DlogR2R!-B1-B2-R2 * Considering M ≈W×R We can have * σ=16.35
Fig.3.5.4 Trapezoidal cross section
3.6 Ramshorn hook * All the ramshorn hooks shall, before testing, be normalized by heating uniformly in a furnace until the whole of the material has attained a temperature between 880°C and 910°C. It shall then be withdrawn from the furnace and allowed to cool in still air.
Fig. 3.6.1Ramshorn hook with different dimensions
Table no.2 Dimension for ramshorn hook[9]
PROOF LOADING
Each completed ramshorn hook shall, after heat treatment, besubjected to a vertical proof load specified in Table 1. If the vertical proof load test is applied in accordance with Fig 1A, an additional test of half the proof load specified for the vertical loading shall be applied horizontally as indicated in Fig 1B Prior to the application of proof loading, each hook shall bear a centre punch mark at position a from which scribed lines shall be trammelled to position b After removal of the load, the hook shall be re-scribed with the trammel unaltered, and the difference between the scribed lines shall be the amount of permanent set. The permanent set shall in no case exceed 0 25 percent of the distance ab.Theramshorn hook shall then be thoroughly examined by a competent person and shall be accepted as complying with this standard only if found free from flaw or defect.
Fig. 3.6.2 Load test on ramshorn hooks
THRUST BEARINGS FOR RAMSHORN HOOKS
B-1. Up to 125 tones capacity, standard single thrust ball bearings may be obtained. With the majority of ball thrust bearings, it is generally found necessary to locate the bearings on spigots or recesses on the hook nut and crosshead.
B-2. For hooks above 125 tones capacity, tapered roller or special thrust ball bearings are recommended. The bearing manufacturer should be consulted for suitable sizes.
B-3. When mounting single thrust ball bearings, care should be taken that the race does not take excessive horizontal load due to clearance between the ramshorn hook shank and the bore of the crosshead.
RECOMMENDATIONS FOR THE USE OF RAMSHORN HOOKS
D-1. The ramshorn hooks covered by this standard should not be upgraded for use with slings at included angles less than 90°, as the capacity of the hook is also governed by the permissible stress in the shank. ( Advantage cannot therefore be taken of the increased body strength when the included sling angles are less than 90°. )
D-2. Ramshorn hooks should not be used with sling legs at excessive angles, since the stress in the body of the hook will increase at a greater rate than that in the sling leg. (Tables of angular loading on slings will not therefore be equally applicable to the loading on the ramshorn hooks. )
D-3. For heavy and bulky loads, it is preferable to use a lifting beam suspended from the hook by two pairs of links at fixed centers, the centers of the link pins on the beam being slightly greater than the centersof the bed diameters of the hook.
D-4. An appropriate included angle between the link plates would be of the order of 30°. With so small an included angle, the stress reduction factor for the hook body is less than one-half.
D-5. To avoid the danger of overloading individual link plates and their associated link pins, due to the possible tilting of the beam and the consequent out-of-balance effect, link plate assemblies should be designed with an ample margin of safety.
D-6. When using lifting beams, their length can be arranged to take varying centers of slings to suit the loads and ensure true balancing. True balancing is essential in order that the hook may rotate freely under load when required.
D-7. When lifting bulky loads where the centre of gravity is not central between the points of slinging, it is desirable to adjust the length of theslings so that the centre of gravity of the load is immediately below the centre line of the hook.
D-8. In order to reduce the effort required to rotate the hook when loaded, it is recommended that the hook be carried on a ball or roller thrust bearing (see Appendix B ).
D-9. When sling angles approach the limiting included angle for which the hook is designed, it is necessary to take care that neither of the two horns is subjected to a load exceeding one-half of the safe working load of the hook, since the stress reduction factor would then be nearly unity, and any out-of-balance effect could overload one of the horns. When lifting loads just within the capacity of the hook, extreme care is needed in this respect.
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CHAPTER 4 FUTURE WORK
Hook will be analyzed for stress and deformation using analysis software and material might be changed if standard material available.
For increase load lifting capacity Hook, material used for hook, weight of load carried out by crane, weight of crane can be considerd.
[10]http://en.m.wikipedia.org/wiki/overhead_crane
[11] Takuma Nishimura, Takao Muromaki, KazuyukiHanahara, Yukio Tada, Shigeyuki Kuroda and Tadahisa Fukui; “Damage Factor Estimation of Crane-Hook (A Database Approach with Image, Knowledge and Simulation)” 4th International Workshop on Reliable Engineering
Computing (REC 2010)
[12]http://www.ijirset.com/upload/2013/december/57a_optimization.pdf
[13]http://www.grouppofrattura.it/osc/index.php/icf/icf12/paper/viewfile/1543/9080
[14]http://www.ejournalaessangli.in/asseejournals/mech68.pdf
[15]http://ijiset.com/v1s6/ijiset_v1_i6_41.pdf
[16]www.naicranes.com
[17]RajendraParmanik“Design Of Hoisting Arrangement Of E.O.T. Crane”Posted on July 26,2008 by http://rparmanik.wordpress.com/about-me-rajendra-parmanik/
[18] R. Uddanwadiker, "Stress Analysis of Crane Hook and Validation by Photo-Elasticity," Engineering, Vol. 3 No. 9, 2011, pp. 935-941
[19]http://www.codecogs.com/reference/engineering/materials/curved_beams.php(updatedlast on 2011-10-17 08:12:34
[20] R.S.Khurmi,“Strength of materials” 23rd Edition (2009) ,Chapter 33
