Case Study on Industrial Gantry Crane Jitesh Kumar Singh, Surendra Kumar Dwivedi

Transcription

1 Case Study on Industrial Gantry Crane Jitesh Kumar Singh, Surendra Kumar Dwivedi Abstract The aim of this thesis is to study about gantry crane & its performance analysis & thereby suggesting some useful techniques to enhance its performance. Also this thesis focused on reduction of total weight of gantry crane so that a simpler design of industrial gantry crane can be fabricated with effectiveness. The aim of this thesis is also provide a significant reduction in power consumption, minimize total cost of gantry crane and to give useful suggestion for increasing performance of gantry crane. There are few strategies presented in the literature for this problem and these are open-ended, guaranteeing no more than a time asymptotic approach to the final desired state load at target. As will be seen, such strategies are unnecessarily imprecise. In this paper, wave based approaches will be presented, culminating in a definitive solution that, for all but the briefest manoeuvres, can stop the load dead, precisely at target. Index Terms Strategies, guaranteeing, asymptotic, imprecise, culminating, manoeuvres, etc. I. INTRODUCTION Gantry cranes are types of crane which lift objects by a hoist which is fitted in a trolley and can move horizontally on a rail or pair of rails fitted under a beam. An overhead travelling crane, also known as an overhead crane or as a suspended crane, has the ends of the supporting beam resting on wheels running on rails at high level, usually on the parallel side walls of a factory or similar large industrial building, so that the whole crane can move the length of the building while the hoist can be moved to and fro across the width of the building. A gantry crane or portal crane has a similar mechanism supported by uprights, usually with wheels at the foot of the uprights allowing the whole crane to traverse. Some portal cranes may have only a fixed gantry, particularly when they are lifting loads such as railway cargoes that are already easily moved beneath them. Overhead travelling cranes and gantry cranes are particularly suited to lifting very heavy objects and huge gantry cranes have been used for shipbuilding where the crane straddles the ship allowing massive objects like ships' engines to be lifted and moved over the ship. Gantry cranes have two upright supports which move along two ground based rails. The height of the portals depends on the maximum hook height. Gantry cranes are used in factories and in outdoor storage yards such as railway and shipping storage areas. 305

2 Specifications- Capacity - 25 Tons Onward Span Meter to 40 Meter Lift Meter to 20 meter Features -Each crane has a bridge which extends across the crane structure from rail to rail. Long travel is the direction of travel of the bridge along the rails. Cross travel is the movement of the crab from one side of the bridge to the other. The crab is the cross travel unit from which the hook is lowered and raised. The hook block is used for raising and lowering the hook. Buffer stops are fitted to absorb the impact from a collision at either end of the long travel. The earth wire connection takes any electrical leak to earth. The working load limit (WLL) can be found printed on the bridge. II. CONTROLS OF GANTRY CRANE Cabin Controls-Most modern cranes have joystick to control the movement of the hoist, the long travel and the cross travel movement and the rising and lowering of the hook. Remote Controls-Remote controls are usually worn on a belt around the waist. When using a remote control it is important to be in a position to review the load and the travel path. Remote controls can be either infra red or radio controlled. Both infra red and radio controlled remote controls have a limited range. lnfra red controls must be pointed towards the crane during operation or the crane will stop. Hoist Limit Switches-Limit switches prevent over-winding and over-lowering of the hook block. The upper limit prevents the hook block coming into contact with the rope drum and sheaves. Fuel Consumption Technique -The VYCON REGEN flywheel energy system can be installed on any RTG crane, either retrofitted or as an option in manufacturing, to create a hybrid power system. It works by capturing the regenerated energy from the hoist motor and making that energy available during the life cycle. III. SAFE OPERATIONS OF GANTRY CRANE Safe operation is a smooth operation. A void jumpy and jerky operation, flying starts quick reversal and sudden stops. Do not move a load over a busy work area without giving warning. Watch out for any unexpected movement or obstructions while a load is moving. Do not carry passengers or allow anyone to interfere with a load. Raising and Lowering-The driver must use the same control setting to lower the load as needed to raise the load. If the load needed No 3 setting to be smoothly raised then lower the load with No 3 setting. Do not use a lower setting to lower a load than was needed to raise the load. Some cranes have a creep lower speed for accurate 306

3 positioning while lowering loads. Some cranes have two hooks from the same crab. Do not change hooks while the first hook is still under load. Some operations use both hooks such as tipping hot metals ladles and skips. Starting and Stopping-Start all motion slowly and accelerate slowly, step by step, until the fastest speed is reached. Stop the crane slowly by returning the control to the OFF position step by step. Rapid acceleration can cause the contacts to arc and burn. Do not plug -Do NOT bring the load to a halt by plugging the controls. Plugging is continuously pushing and releasing the control button. This will run the motor too slowly to activate the cooling fan and can burn out the motor and overheat the contacts. PRE-CHECKS PRIOR TO TURNING ON THE MAIN SWITCH 1. Make sure there are no maintenance signs. 2. Make sure there is no obvious damage to the crane. 3. Check mains switch box for danger tags. 4. Check the main isolating switch for danger tags. 5. Check for any maintenance crew working on the crane. 6. Check that collector wires have not been blown or knocked off the insulators. They must not have ladders or any other gear resting on them. 7. Check spreaders (container loading gantry cranes) for: Hydraulic fluid level Oil leaks Damage to twist locks. 8. Check wires and anchorages for defects. PRE-CHECKS INSIDE THE CABIN AND WITH THE PENDANT CONTROL 1. Check the WLL (or SWL) stamped on the bridge of the crane. 2. Unlock emergency switch and switch power on. 3. Check control panel lights. (Cabin only) 4. Check for fire extinguisher. (Cabin only) 5. Make sure that you can identify each of the buttons on the pendant and that they operate freely without sticking. 6. Check that the pendant strainer wire is properly attached and that the pendant moves freely across the crane without undue force. 7. Drive and then stop the crane a few times in each direction to check the brakes for adjustment and operation of the crane for the job. 8. Test the operation of the working limit switches. 9. Where possible have a full view of the load and the general work area. 10. Make sure that the runways and the general work area are clear of obstructions. 11. If the load hook is fitted with a safety catch make sure it is working properly. 12. Make sure that the hoist rope is free of kinks or obvious broken wires. 13. Make sure that the rope passes easily through all the running sheaves. 14. Check for any obvious mechanical problems. 15. Make sure that the runways and the general work area are clear. Hoist motion-when the load is ready to hoist, start hoisting upward until the slack is taken out of the sling. Only continue to hoist if the load is in balance. The person who has slung the load must check the balance of the load for the operator of a cabin controlled crane. Hoist slowly until the load is clear of the floor and then increase speed smoothly until the load is at the required height. When lowering the load gradually reduce the speed as the load nears its target. Reduce to the lowest speed and then inch the load down. Follow the dogger s directions if you are driving a cabin controlled cranes. 307

4 IV. MAINTENANCE PROCEDURE Maintenance procedures vary according to the type of crane. Follow the specific maintenance safety procedures as laid down for your workplace. Before carrying out maintenance the main switch must be opened and tagged by every worker who will be working on the crane. This process isolates the crane from the power source while maintenance workers are on the crane. When all the tags have been removed from the main switch visually inspect the crane and call out to make doubly sure that there is no worker still on the crane before reactivating the power. Where there is more than one crane operating and one crane must be isolated for maintenance. For maintenance of a gantry crane uses the following methods- Remove the power to the crane by turning off the all motion isolation switch. Install temporary end stops on the main crane runway. Install a flashlight at the end stop on the other side of driver s cabin. Hang danger flags from the temporary end stop on one rail across the other rail. Where applicable a worker must sit in the driver cabin to observer. Cordon off the area beneath the crane and place men working above signs on each side. V. RULES TO FOLLOW WHEN SLINGING AND HANDLING A LOAD General handling-make sure that there is a suitable packing or lagging at all sharp edges of steel, beams and other hard materials. Use packing to prevent the sling from coming into contact with sharp edges. This will lengthen the life of the sling and prevent breaks. Make sure that packing or lagging is secure so that it will not fall out when the slings go slack. Before lifting a load make sure that it is not caught or trapped in some way. Machinery and plant with lifting lugs should be marked with the mass. Caution: Some lifting lugs are used for assembly and dismantling, not for lifting the entire unit. KNOWLEDGE OF THESE EIGHT HAND SIGNALS IS REQUIRED 308

5 VI. SAFETY PRECAUTIONS AND SUGGESTION Do not allow loads to come in contact with other objects. Make sure that the path of travels is free of obstruction before moving the load. Avoid sudden starts and stops. This prevents shock loading which can stress the system beyond its capacity. Do not lift load higher than necessary to avoid obstructions in its path. Take instructions only from the person designated to give signals. Make sure hoist rope or chain is free from twists, knots and kinks. Multiple part lines should not be twisted around each other. To ensure load is balanced and stable, make a preliminary lift of a few inches. Do not overload crane or hoist. Make sure the combined weight of the lifter and load does not exceed the rated load capacity of the crane or hoist. Lifters must only be used by trained operators. Test operation of moving lifter parts and controls at the beginning of each shift. VII. FUTURE SCOPE In coming times gantry crane developer are building new techniques to lift load upto tonnes with minimum energy consumption by replacing rail cars with rubber tyre. Scientists and engineers are working on how to reduce the material used in the gantry crane without hampering its basic features and its load carrying capacity. Computer based operation of gantry crane is also one of the major concentration of today s demand which will reduce incidents at ports and company. Now the world is on a verge of green house gas problems so europian countries are focusing on crane which can run on fuels which have too low impact on environment so they are developing cranes which can run on other fuels which has less or no impact on environment and they are naming it as green crane. [1] Bridge and gantry crane drivers guide REFERENCES [2] Overhead Crane Safety Lecture by Milton J. Shoup III (University of Rochester). [3] Crane modernization why & how by Peter M. Darly & Jimmy Liang. 309

6 [4] Diagnosing Bridge Crane Tracking Problems By Gary J. Davis, P.E [5] Stability of a Closed-Loop Control System - Applied to a Gantry Crane with Heavy Chains by Dominik sturzer. [6] A paper on fatigue damage and new design of gantry crane equalizer beam presented in INTERNATIONAL DESIGN CONFERENCE - DESIGN [7] Control of Gantry and Tower Cranes by Hanafy M. Omar. [8] The educational impact of a gantry crane project in an undergraduate controls class by Michael C Reynolds, Peter H. Meckl & Bin Yao. [9] Tensor Product Model Transformation-based Controller Design for Gantry Crane Control System An Application Approach by Fetah Kolonic, Alen Poljugan, Ivan Petrovic. [10] Design of an overhead crane by Takashi Yoshida, Stephen Ju, Matthew corley & chady attieh. [11] Modelling & vibration control of gantry crane by ZAIRULAZHA BIN ZAINAL. [12] Modelling & optimal control of tower crane motions BY Ali R. Golafshani. [13] Sensor less anti-swing control strategy for automatic gantry crane by MAHMUD IWAN SOLIHIN. [14] Vibrational control of a gantry crane system using inverse dynamic analysis by AZDIANA BINTI. MD. YUSOP & NOOR ASYIKIN BINTI SULAIMAN. 310