Bridge crane, diploma project

Contents

1. Introduction of ______________________________________________________

2. Analytical overview of ____________________________________________

3. Research Section ________________________________________

4. Design Section _________________________________________

4.1. Calculation of load lifting mechanism ______________________________

4.2. Calculation of crane movement mechanisms ________________________

4.3. Calculation of steel structure of bridge crane ____________________

4.6. Electrical part _________________________________________

5. Process Section _________________________________________

6. Safety and health ______________________________

7. Economic section __________________________________________

8. Conclusion of the ____________________________________________________

9. List of literature _____________________________________________

1. Introduction

Lifting and transportation machines and mechanisms are the main means of mechanization and automation of loading and unloading operations in all sectors of industry and agriculture.

Due to the intensification of technological processes, the share of time for lifting operations has increased significantly. The dramatic increase in labor productivity that is urgently needed during the transition of the economy to new conditions of development and management can be achieved by mechanizing and automating lifting and installation operations that are less automated than technological ones.

Lifting and transportation machines (PTM) are very metal-intensive, and therefore require a large amount of material and labor costs, so it is necessary to create small metal-intensive, perfect, reliable and rational structures. Engineering and technological workers are engaged not only in narrowly specialized organizations and enterprises, but also in various industries.

Lifting and transportation equipment is an integral part of almost any mechanization scheme of any production process, in each branch of the economy. Therefore, lifting and transportation machines are of exceptional methodological interest as a design object in the training of engineers and mechanical engineers of a wide profile.

The ultimate goal of design, development, implementation and application of lifting and transportation machines is elimination of manual loading and unloading operations and elimination of heavy labor during basic and auxiliary operations.

Analytical Overview

Bridge cranes are called cranes in which the lifting mechanism is located on a trolley moving along a movable span structure - a bridge, and the bridge moves along rails located on crane beams resting on the consoles of columns of a building or columns of a special rack. Bridge cranes are used in almost all areas of human industrial activity. Installation diagrams of bridge cranes allow their use both in closed rooms and in open areas under any environmental conditions. This fact contributes to the fact that they are widely used in warehouses, factories of various profiles and customs terminals.

Their disadvantage is that they are tied to a building or trestle and cannot work without a path raised above the surface being served; positive in their design is that they use the building height of the building.

Classification of bridge cranes

1. Radial crane

Radial crane rotating relative to one of its supports has span length equal to radius R of annular working platform, which it serves. Axle of axle rotation is fixed on support mounted in central part of working platform and attached to building ceiling. The trolley is designed to service the area of the ring that is less than the area of ​ ​ the ring with a radius R, taking into account the distances that the trolley cannot approach the running driving trolley moving along the ring rail to the support.

2. Chord crane.

The chord crane, as well as the radial crane, moves along one ring rail. Running wheels are secured on running bogies arranged asymmetrically relative to bridge beams. The bridge trolley is designed to service a smaller area of ​ ​ the ring at the same radius R as that of a radial crane.

3. Rotary crane

Rotary bridge crane has crane bridge length equal to 2R of circular rail diameter. The trolley, moving along the beams of the bridge, serves a larger area than a radial crane, since it can lift loads in the center of the working platform. In this crane, the running bogies move in opposite directions when the bridge is turned relative to the center of the circumference of the ring rail. Running wheels, as in other cranes, have axes oriented along the radius of the annular platform .

4. Ring crane

Ring crane moves along two ring rails with radius R min and R max. Span of crane bridge L = R max - R min. To ensure movement of wheels of outer and inner running bogies without sliding, running outer and inner wheels are made with different diameters or rotation frequency proportional to radii R min and R max .

5. Magnetic cranes

Magnetic cranes are designed for lifting and transportation of ferromagnetic materials (scrap, chips, sheet and profile rolled stock, molds for steel casting, etc.) These cranes are equipped with load electromagnets suspended on hook suspension or cross-arm (on flexible or rigid suspension) located in longitudinal or transverse direction relative to bridge. The lifting capacity of magnetic cranes is from 5 to 40 tons, the lifting speed is 1420 m/min. The most common are steel structures with sheet single-stage main beams and auxiliary trusses, as well as two-block box structures with high fatigue resistance. The magnetic crane consists of a bridge with a movement mechanism, one or two trolleys with a lifting and movement mechanism, lifting magnets and a cab suspended from the steel structure of the bridge. The mechanisms of movement of these cranes and their trolleys have no difference compared to the mechanisms of general-purpose bridge cranes. Recently, mechanisms for moving cranes with a divided drive on each side of the bridge have become increasingly widespread.

6. Single-beam bridge cranes

Single-beam crane is used with small volumes of cargo flow both in the open air (at temperatures from -40 to + 40 С) and in closed rooms. The universal design of the bridge crane contributes to its wide application in the industrial sphere, as well as in the lifting and transportation of goods weighing from 1 to 10 tons .

Depending on the type of drive, single-beam bridge cranes with a manual and electric drive are distinguished. In manual overhead bridge cranes (GOST 707580 and GOST 741380), suspended chain hoists are used as lifting mechanisms. single-beam support bridge crane consists of bridge made in the form of I-beam resting on two end beams, manual movement mechanism driven by chain, and manual trolley with chain drive. The lifting capacity of these cranes is up to 5 tons, the span is up to 11.4 m. Single-beam bridge cranes with electric drive are divided into support and suspended. Lifting capacity of support cranes up to 5 tons, span up to 25.5 m. Lifting capacity of single-beam overhead bridge cranes up to 5 tons, span up to 34.8 m. Cranes with lifting capacity up to 5 tons are equipped with electric steels controlled from the floor. On larger cranes, conventional mechanisms for lifting bridge cranes of the supporting structure are installed and controlled with a fixed or movable cabin. Speed of cranes driven from the floor does not exceed 0.53 m/s; the speed of movement of cranes controlled from the cockpit reaches 1 m/s. As a load-bearing beam of single-beam cranes of suspended structure, as a rule, I-beams are used. In necessary cases, the bearing beam is reinforced with a vertical springel structure and a horizontal truss. Beams are suspended from running carriages, which move along crane I-beam guides. Half of the support carriages are driven. Connection of load-bearing beams of adjacent spans is performed by means of special locks preventing transfer of trolley to adjacent flight at open lock. Overhead bridge cranes are considerably lighter than support bridge cranes of the same lifting capacity. In addition, they allow you to use almost the entire useful area of ​ ​ the production room.

7. Double-beam bridge cranes

The double-beam crane is used in construction, repair work, as well as in the metallurgical and engineering industries, that is, in industries where it is necessary to lift and move heavy loads with large volumes of cargo flow.

Depending on the type of drive, two-beam bridge cranes with a manual and electric drive are distinguished. Bridge cranes come with box-shaped, continuous main beams, with lattice main and auxiliary beams. The most common bridge cranes with box-shaped main beams. Such a crane is a structure consisting of a beam or truss bridge resting on transverse end beams in which running wheels driven by the crane movement mechanism are fixed. The bridge moves along crane tracks (along the workshop) laid on crane beams resting on the columns of the building. The bridge movement mechanism consists of an electric motor and a reduction gear installed in the middle of the span, and a long shaft connecting the reduction gear with running wheels. For heavy-duty cranes, individual drives of running wheels are used. Freight trolley with hoisting winch located on it and trolley movement mechanism moves along rails laid along crane bridge. In order that the crane load hook does not have transverse movement during lifting and lowering, an equalizing unit is used, and the load rope is stored with two ends from opposite ends of the drum. The control of the bridge cranes is carried out from the crane operator's cab, located in most cases at the edge of the bridge. Slow-moving cranes can have control from the floor.

With a lifting capacity of bridge cranes of 15 tons and above, two lifting winches are used - the main and auxiliary ones for lifting light loads at a higher speed.

The crane is supplied with electricity through the main trolleys located along the crane beam. For their maintenance on the crane bridge there is a platform. Crane lattice bridges are manufactured by manual welding, and solid-wall automatic or semi-automatic welding. The trolley is a structure consisting of a welded frame, one or two lifting mechanisms, a moving mechanism. Movement mechanisms, as a rule, are made according to a scheme with a slow-moving shaft. Electric power is transferred to the engines of the bridge cranes mechanisms in two ways: with the help of a flexible suspension cable on coil supports (cable suspension) or by trolls stretched along the crane track and along the crane bridge, and current collectors fixed on the bridge and on the freight trolley. Trolley mechanisms are powered by special trolley bus bars or flexible cable. Lifting capacity of bridge double-beam cranes of general purpose Q = 5... 500 t.

In addition, depending on the installation diagram of the bridge cranes, you can distinguish: overhead crane and support crane. The overhead crane during installation is attached to the lower supports of the crane track, and the support crane is mounted on metal structures, which, in turn, are attached to the walls of the building.

Bridge cranes are usually made with a lifting hook, less often with a single-rope or two-rope grapher, with a magnetic plate and with a stacking device. Lifting mechanism of grab bridge cranes consists of two winches operating both together and separately.

The above differences mainly relate to the design of general-purpose bridge cranes. There are also various structures of special-purpose bridge cranes.

Currently, bridge cranes with a carrying capacity of up to 500 tons and spans of up to 40-50 m are being manufactured. The speed of working movements: lifting the cargo - up to 60 m/min, moving the trolley - 10-50 m/min and moving the bridge - 40-150 m/min. Height of lifting of bridge cranes is determined by height of location of crane tracks above serviced platform and rope capacity of drum.

Skew limiters

The rules of Gosgortekhnadzor provide for the equipment of goat cranes and bridge reloaders with limiters on the spit. When cranes, especially cranes of large spans, which include gantry cranes and bridge reloaders, travel of one crane support relative to another support and, therefore, skew of crane span structure occurs. There are many reasons for the movement of skewed cranes. The main ones are mounting skew of the running wheels in the horizontal gear of the speed relative to the longitudinal axis of the crane, inequality of the forces of distortions to the movement of the crane supports, asymmetry in the distribution of the crane masses relative to the longitudinal axis (in the direction of the crane movement), inequality of the stiffness coefficients of the characteristics of the drive engines and random slips of the drive crane wheels.

The formation of the crane skew goes through two stages: the free skew stage, when the span is turned within the free gap between the rail heads and the flanges of the running wheels; elastic skewing stage, when after contact of at least two wheels with rail heads the increase due to running of supports occurs due to elastic deformation of span and crane supports. In small-span cranes, is elastic skew small compared to the limit free skew? in cranes with large spans, the main type of skew is elastic.

The movement of the crane with a skew is accompanied by a number of negative phenomena: increased wear of the running wheels, an increased level of loads on the steel structure of the crane and crane rails, and in some cases by wedging the crane or pulling the wheels off the rails. Normal operation of cranes of large spans is impossible if in the crane structure and its control system there are no means for stabilizing movement during skewing or for periodic alignment of the crane after the formation of a critical race of supports. Skew limiters perform emergency automatic stop of the crane at unacceptable skew, they are installed on gantry cranes and bridge reloaders of any spans. In addition, systems for visual control of skew and systems for automatic stabilization of cross-over movement of the crane are installed on cranes of large spans (more than 100 m).

Skew in skew limiters or in systems of stabilisation of non-cross motion is measured in two ways: measurement of difference of paths passed by two crane supports, and measurement of elastic deformation of span or crane supports.

The first method is more preferable, since there is an unambiguous relationship between the skew of the span and the race of the supports. The difference between the tracks passed by the crane supports is determined by measuring the turning angles of the two idle wheels of the opposite crane supports (or special measuring rollers) or by measuring the distances passed by the crane supports from the stops installed at the end of the rail track. In the latter case, a discrete path measurement method is used.

For this purpose benchmarks are installed along rail track on both sides of crane at equal distances from each other, and pulse displacement sensors are installed on crane running trolleys. Skew is determined by difference of pulses received from two sides of crane. Skew limiters prevent operation of the crane with dangerous races of supports, but do not eliminate this race. It is possible to reduce the running of the supports to a minimum only with the use of an automatic stabilization system for the non-intersecting rectilinear movement of the crane, which is used on the goat cranes of large Spans and bridge overloaders.

Electrical part

4.4.1. Drive selection and control system solution

Increasing the requirements for mass-use crane drives poses the task of significantly improving their technical and technological parameters without significantly increasing the cost and complication of operation. The main directions of solving this problem are the use of semiconductor equipment in traditional systems in order to increase switching stability of contactor control equipment and implement more rational modes of regulation and braking of electric drives with dynamic braking of self-excitation. Where an uncontrolled diode bridge is used. Electric drive with TSA series magnetic controllers is selected for this lifting mechanism. Magnetic controllers (control units) of the TSA series are used when controlling asynchronous motors with a phase rotor with resistors in the rotor circuit. TSA controllers have AC control circuits. This electric drive with dynamic braking, self-excitation having rigid characteristics in descent mode. This electric drive is also used in movement mechanisms. One of the disadvantages of this drive is stepwise speed control.

4.4.2. Description of operation of typical diagram of TSA magnetic controller

For the lifting mechanism, an electric drive with magnetic controllers of the TSA series is used.

Typical TSA type magnetic controller circuit provides automatic acceleration, reversal, braking and stepwise speed control. When using TSA-type magnetic controllers for controlling asynchronous motors, the characteristics of the electric drive are similar to those of the Ks-type controller.

The TCA type controller has four lifting and lowering positions that allow for an appropriate number of mechanical characteristics.

At the extreme positions of the engine rotor, only a small limiting resistance remains and the engine operates at a lifting speed or lowering of the load close to the nominal. In addition to the reversing K1 and KT2 and the linear KM2, a contactor KM1 is provided in the circuit, which provides a single-phase braking characteristic when lowering weights. The stages of resistors in the rotor circuit are output using KM4KM7 acceleration contactors and KM3 anti-switch contactor. When lifting at the first position, lifting is performed at low speed; at the third, the first acceleration stage of the electric motor is performed. The last two stages of start-up are carried out automatically under the control of relays KT1 and KT2. At the positions, speed is controlled in the modes of anti-switch at the first and second positions and single-phase braking at the third position, when all stages of resistors are withdrawn, descent is carried out at the highest speed. In order to avoid lifting at the anti-switch braking positions, the engine is switched on only at the third single-phase braking position when the lifting is excluded during the forward course of the command controller. The single-phase braking circuit is assembled when KM1 and KT2 contactors are switched on in the stator circuit and KM4 acceleration contactors in the rotor circuit. To prevent simultaneous actuation of single-phase braking contactors KM1 and anti-actuation of KM3, as well as direction contactors are mechanically balanced in pairs. In order to avoid an unacceptably high speed in the third position, it is possible to immediately enable the first or second descent position by pressing the pedal SA. In the circuit with the help of contactor KM8, it is provided to turn on the electromagnetic brake YA to ensure mechanical braking until complete stop. The controller enables the SQ1 and SQ2 position switches.

Maximum and zero protection are displayed on the protective panel. The blocking relay KT1 plays a significant role. Through its closing contacts, coils of contactors switching the resistance of the rotor circuit are turned on, which contributes to the main start of the drive when the command controller is abruptly shifted from the zero position to the 4 position. The coil of the contactor KM8 is also switched on through the closing contacts KT1, so that the coil of the electromagnetic brake YA is powered only after turning on one of the contactors in the circuit of the stator KT1, KT "or KM1.

In addition, the KM8 relay provides additional electric braking of the engine shaft when the command controller is set to the zero position. Duration of braking is determined by time delay of RB relay.

Process Section

5.1 Causes of mechanism failures and organization of PTM repair

Damages and faults occur as a result of violation of maintenance, operation and safety instructions, overloads during operation, untimely adjustment of brakes and insufficient lubrication. Result: wear increases, clearances increase, dynamic loads increase, parts fail.

The most frequent malfunctions are: wear of shafts, bushings, axles, gears, bearings, poor brake balancing, improper assembly of gears, loosening of attachments, finger failure in the UVP, oil leakage.

Failure of shafts is caused by cracks or fractures, twisting, bending, wear of necks, trunnions, key slots, splines. All this occurs when loads are exceeded. Risks and balls of either insufficient or poor lubrication. Necks and trunnions change shape during wear: round to oval. Sliding bearings in the rope-block system wear out due to poor lubrication, incorrect installation, as a result of which cracks and fractures appear on the rings, fits are disturbed, separators are broken.

The presence of periodic knocking, strong uniform noise, heating of bearings in the reduction gears is due to the incorrect assembly of gears with nicks on the wheels, the loose and eccentric fit of the wheels on the shafts. Noise is caused by poor lubrication, incorrect installation of bearings and pinching of rolling bodies. Weakening of gear box attachment units degrades operating conditions of all mechanisms. The reducer vibrates during operation, shaft integrity is disturbed, bolt and hinge connections are loosened, motor legs are broken. Misalignment resulting from insufficient alignment results in premature failure of shafts, bearings and couplings.

Poor balancing of the brake pulley leads to additional loads on the shafts and bearings of the reduction gears, which causes vibration of the mechanism during rotation. When the brake pulley is worn, ovality and taper occur, the surfaces of the shoe are loosely adjacent to the pulley, the braking moment is not realized. Distortion can occur due to improper installation of the brake on the frame or due to manufacturing defects. It is dangerous to slip, that is, the brake does not hold the load, this is caused by incorrect adjustment, large production of shoes, incorrect installation in relation to the pulley and salting of the braking surface.

Rubbing of ropes occurs due to improper storage, that is, during operation, the ropes touch each other and the metal structure, especially when twisting the rope. Twisting takes place at single stock, long length of hook suspension, at high stiffness of rope, at rigid fixation of rope end in wedge bushing. Rubbing occurs when the rope leaves the stream of the unit. This happens if the fence bent away or the rope is poorly tensioned (obliquely) in relation to the block, as well as when the rope falls off the drum. Rope breaks occur due to natural wear, lack of lubrication, overload during operation, mechanical or corrosive damages, poor-quality rope fixation. When the bearing is wedged, the rope slides along the unit, streams and flanges are generated. In the steel structure, dents and bends are formed, unloading, installation, in case of incorrect installation in the transport position. The steel structure must be painted, otherwise it quickly corrodes.

Economic section

From the results of the study of ways to reduce the metal consumption of the trolley, it can be concluded that a trolley with a lightweight frame and a hinged reduction gear of the lifting mechanism can be recommended for industrial production at present.

The advantages of the new trolley are:

high accuracy of adjusting units of the lifting mechanism, eliminating the assembly by hot mounting;

simplicity of design of drum shaft connection to reduction gear box;

reduced dimensions and weight of the structure (specific metal capacity of the trolley in question is reduced by 46%, thermal capacity coefficient is increased by 6%).

In this part of the diploma project, the economic effect of introducing a small metal-intensive trolley design into production was calculated.

7.2. Conclusion

In accordance with production calculations, it can be concluded that the launch into production of a trolley with a lightweight frame and a mounted reduction gear will not only reduce metal consumption by 46% and assembly labor, but there will also be an integral economic effect in the amount of 23498.9 rubles. from the production and operation of one trolley.

The price of a small metal-intensive trolley will be 41413.4 rubles, while the price of an existing analogue is 65,000 rubles, and as a result, operating costs will decrease from 1,6138.7 rubles to 1,1495.3 rubles.

These results confirm the need for industrial development of the trolley.