This design scheme is aimed at the systematic design of 32/5t double-girder bridge crane, covering the detailed calculation and selection from the overall structure to each key component. As the core equipment of modern industrial material handling, the design of double-girder bridge crane needs to consider the carrying capacity, operation stability, operation safety and long-term reliability. The following will comprehensively explain the seven aspects of design purpose and requirements, overall structural design, lifting mechanism design, operating mechanism design, bridge structure design, electrical control system and safety protection system, and provide a complete set of 32/5t double-girder bridge crane design scheme.
32/5t double-girder bridge crane is a heavy-duty material handling equipment widely used in industrial plants, warehouses, power stations and other places. Its design needs to meet strict industry standards and technical specifications. The main purpose of this design is to develop a double-girder bridge crane with a working level of A5 (heavy duty system), a span that can be adjusted according to actual needs (usually in the range of 7.5-35 meters), and suitable for ambient temperatures of -25℃ to +40℃.
Design goals include: main lifting rated load of 32 tons, auxiliary lifting rated load of 5 tons; main lifting height of 12 meters, auxiliary lifting height of 13 meters (adjustable according to user needs); main lifting speed of 7.5m/min, auxiliary lifting speed of 19.7m/min. The crane adopts a double main beam structure to ensure smooth operation, and is equipped with two independent lifting mechanisms. The main hook can be hung with an electromagnetic suction cup or a hook, and the auxiliary hook can also be equipped with different picking devices according to needs. The design working level is A5, which complies with JB/T3695-1994 and other crane industry standards.
The design needs to meet the following basic requirements:
Functional requirements: realize vertical lifting and horizontal movement of heavy objects, the main hook and auxiliary hook work in coordination, the main hook is used for heavy loads, and the auxiliary hook is used for auxiliary lifting or lighter loads.
The key parameters that need to be considered during the design process include: crane deadweight (about 42-48 tons at A5/A6 working level), motor power (42KW for main hoisting and 17KW for auxiliary hoisting), maximum wheel pressure (affecting track foundation design), running speed (about 70-90m/min for large trolley and 28-32m/min for small trolley) and power supply requirements (usually three-phase AC 380V, 50Hz). These parameters not only affect the performance of the crane, but also relate to its compatibility with the site of use, and need to be clearly determined at the beginning of the design.
The 32/5t double-beam bridge crane adopts the traditional double-girder structure, which is composed of the bridge, trolley running mechanism, lifting trolley and electrical control system. This structural form has the advantages of high rigidity, stable operation and strong load-bearing capacity, and is particularly suitable for working conditions with medium spans and heavy-duty working systems. In terms of overall layout, two box-type main beams are arranged in parallel, and the two ends are connected by end beams to form a stable bridge structure. Walkways and guardrails are laid on the bridge for easy inspection and maintenance. The lifting trolley runs on the main beam track, and the main and auxiliary lifting mechanisms and trolley running mechanisms are arranged on the trolley to form a three-dimensional material handling system.
The determination of the main parameters is the basis of the design. According to user needs and standard specifications, the main technical parameters of this machine are determined as follows: the rated lifting capacity is 32t for the main hook and 5t for the auxiliary hook; the span can be selected within the range of 16-31.5m according to the actual needs of the plant, and the design is based on the base span of 22.5m; the lifting height is 12m for the main hook and 13m for the auxiliary hook (which can be adjusted to 16m according to user needs); the working level is A5 (the main lifting mechanism can reach A6); the ambient working temperature is -25℃~+40℃. These parameters will serve as the basis for the subsequent design and calculation of various components, and the actual working conditions and standard specifications of the user need to be considered comprehensively.
In terms of structural form selection, this design adopts a box-type double-beam structure rather than a truss structure, mainly based on the following considerations: the manufacturing process of the box-type beam is mature and convenient for mass production; the internal space can be used to arrange the operating mechanism and electrical equipment; it has good torsional stiffness and overall stability; it is easy to use automatic welding technology to ensure welding quality. The main beam and the end beam are connected by high-strength bolts (flange connection), which is convenient for transportation and on-site installation, while ensuring the integrity of the structure. This structural form has been widely used in medium and heavy industrial cranes, and the technology is mature and reliable.
The overall layout design needs to consider the reasonable configuration of each functional module. The two main beams are arranged symmetrically, and the center distance is determined according to the trolley gauge; the walkway is set on the outside of the main beam, with a width of about 1m and equipped with a protective railing with a height of ≥1050mm; the driver’s cab is suspended under one side of the main beam, located at the end or mid-span of the crane, which is determined according to the user’s process flow; the electrical control cabinet is arranged on the other side of the walkway for easy maintenance and heat dissipation. QU70 or QU80 crane-specific steel rails are laid on the upper flange of the main beam as the trolley running track, which is fixed by a pressure plate to ensure the smooth operation of the trolley. This layout ensures that the functional areas are clearly divided and the maintenance channels are unobstructed, while also considering the balance and aesthetics of the overall structure.
Material selection has an important impact on the performance and economy of the crane. The main beam and end beam are mainly welded with Q235B or Q345B steel plates. Q345B material has higher yield strength, which can reduce the deadweight of the structure but has a slightly higher cost. Small and medium-sized parts use high-quality carbon structural steel such as 45 steel or 40Cr. The steel wire rope uses high-strength steel wire ropes such as 6×37+FC-1770 or 6×36SW+IWRC-1960. The wheels are made of ZG340-640 cast steel and are heat-treated, with a tread hardness of 300-380HB. Material selection not only considers strength requirements, but also welding performance, wear resistance, and environmental adaptability to ensure reliable operation under various working conditions.
The hoisting mechanism is the core component of the 32/5t double-beam bridge crane, which is directly related to the performance and safety and reliability of the whole machine. This design adopts a dual-mechanism independent layout scheme. The main hoisting mechanism (32t) and the auxiliary hoisting mechanism (5t) are respectively equipped with their own drive system, wire rope winding system and object picking device, which can work alone or in coordination. The main hoisting mechanism adopts the YZR280S-10 winding rotor motor with a power of 42KW; the auxiliary hoisting mechanism adopts the YZR180L-6 motor with a power of 17KW, both of which are equipped with corresponding brakes and reducers. This configuration method not only ensures the demand for large-tonnage hoisting of the main hook, but also realizes the function of light-load and fast operation through the auxiliary hook, thereby improving work efficiency.
The transmission scheme design adopts the typical “motor-coupling-brake-reducer-drum” layout. The main hoisting mechanism adopts a closed transmission. The motor is connected to the high-speed shaft of the reducer through a gear coupling, and the low-speed shaft of the reducer drives the drum to rotate through the drum coupling; the auxiliary hoisting mechanism adopts a similar arrangement, but the structure is more compact. In terms of pulley block design, the main hoisting adopts a double pulley block (ratio m=4), which not only ensures that the wire rope deflection angle does not exceed the specified value (usually ≤4°), but also improves the carrying capacity of the hoisting mechanism; the auxiliary hoisting adopts a single pulley block with a ratio of m=2 to achieve a higher hoisting speed. This transmission scheme has a compact structure, high efficiency, and is easy to maintain and repair. It is a typical configuration of the hoisting mechanism of a bridge crane.
Wire rope selection calculation is a key link in the design of the hoisting mechanism. The selection of wire rope is directly related to the safety of the lifting operation, and it needs to be accurately calculated based on the maximum working tension and safety factor. The maximum working tension S_max of the main hoisting mechanism wire rope is calculated as follows: Smax=Q/(m·η), where Q is the rated lifting weight (including the weight of the hook group, 32t+0.5t=32500kg), m is the pulley group ratio (4), and η is the pulley group efficiency (take 0.97). Considering the safety factor n≥5.6 (A5 working level), it is calculated that the minimum breaking tension of the main hoisting wire rope should be no less than 32500×9.8/(4×0.97)×5.6≈460kN, and 6×36SW+IWRC-1960 wire rope with a diameter of 20mm is selected. The auxiliary hoisting mechanism is calculated in the same way, and 6×37+FC-1770 wire rope with a diameter of 14mm is selected. The end of the wire rope is fixed to the drum by a pressure plate, and the number of pressure plates is not less than 3 to ensure reliable fixation.
The drum design needs to consider factors such as rope capacity, diameter ratio and wall thickness. The diameter of the main hoisting drum is D≥h·d (h is the ratio of the drum diameter to the wire rope diameter, which is 20; d is the wire rope diameter of 20mm), so D≥400mm, and D=500mm is actually taken. The drum length L is determined according to the total length of the wire rope and the number of winding layers: the working length of the wire rope Lw=H·m=12×4=48m (H is the lifting height); the drum groove pitch p=22mm, winding 3 layers, after calculation L≈1500mm. The drum wall thickness δ=0.02D+10=20mm, the material is HT200 gray cast iron or Q345B steel plate rolled and welded. One end of the drum is connected to the output shaft of the reducer through a flange, and the other end is supported on the rotating shaft. An anti-rope skipping device is set inside to prevent the wire rope from being tangled. The design method of the auxiliary hoisting drum is the same, but because the lifting height is larger (13m) and the ratio is smaller (2), the diameter is finally determined to be 400mm and the length is 1200mm.
The selection of motors and reducers needs to comprehensively consider the lifting power, speed requirements and load characteristics. The power calculation of the main lifting mechanism motor: P=(Q·v)/(6120·η)=(32500×7.5)/(6120×0.85)≈47kW, the YZR280S-10 motor is selected, the rated power is 42kW, the temporary load rate is 40%, and the applicability is confirmed by thermal verification and overload verification. The reducer is ZQ500-III-3CA type, the transmission ratio i=31.5, the input speed is 571r/min, the output speed is 18.1r/min, the actual lifting speed v=(πDn)/(mi)=(3.14×0.5×18.1)/(4×31.5)≈7.2m/min, which meets the design requirement of 7.5m/min. The auxiliary lifting mechanism is calculated in the same way. The motor is YZR180L-6 (17kW, 955r/min), the reducer is ZQ350-V-3Z (transmission ratio 23.34), and the actual lifting speed is about 19.7m/min. The brake is YWZ series hydraulic push rod brake, the main lifting is YWZ-400/90 (braking torque 1600N·m), and the auxiliary lifting is YWZ-300/90 (braking torque 630N·m), ensuring reliable braking of 1.25 times the rated load.
The trolley running mechanism is a key component that drives the lifting trolley to move along the main beam track. Its design directly affects the positioning accuracy and running stability of the crane. The trolley running mechanism of the 32/5t double-beam bridge crane adopts centralized drive or separate drive mode. This design uses a separate drive solution, that is, the driving wheels on both sides are driven by an independent drive device, which improves the running reliability and deviation correction ability. The trolley running speed is designed to be 28-32m/min (adjustable), and the YZR series wound rotor motor is used with a worm gear reducer to ensure smooth starting and braking. The trolley frame adopts a box-type welded structure, with the lifting mechanism and trolley running mechanism arranged on the top, and connected to the main beam track through the wheel group below to form a stable running system.
The choice of drive mode is the primary decision in the design of the trolley running mechanism. Although the traditional centralized drive method has a lower cost, it has problems such as long drive shaft, large torsional deformation, and poor synchronization of wheels on both sides. This design adopts a separate drive mode, and the drive devices on both sides are independently but synchronously controlled, which has the following advantages: simplified transmission structure, eliminating the long transmission shaft; the drive devices on both sides are backup for each other, and limited operation can still be achieved when one side fails; easy installation and maintenance; both sides can be synchronized through electrical control to avoid the trolley “running off”. Each set of drive devices includes an electric motor (YZR160M2-6 type, 5.8KW), a brake (YWZ-200/25 type), a vertical reducer (ZSC600 type, i=22.4) and a wheel group, which are connected by an elastic pin coupling. This arrangement has become the mainstream in modern bridge cranes, especially suitable for trolleys with large tonnage and wide track gauges.
The wheel and track design needs to comprehensively consider wheel pressure, contact strength and running resistance. The trolley adopts a four-wheel structure, two of which are active wheels (driving side) and two are driven wheels. The wheel diameter is selected according to the maximum wheel pressure: the maximum wheel pressure P_max≈(Q+G)/4=(320+60)×9.8/4≈930kN is calculated (Q is the rated load, G is the weight of the trolley), and the wheel with a diameter of DC=350mm is selected, the material is ZG340-640, and the tread quenching hardness is 300-380HB. The track uses QU70 crane special rails with a rail top hardness of 280HB, which matches the wheel hardness to reduce wear. The wheel bearing uses spherical roller bearings (such as 22320 type), which can automatically align to adapt to installation errors and main beam deflection deformation. The running resistance calculation includes friction resistance (bearing friction + rolling friction) and ramp resistance. The total resistance W≈(Q+G)(2f+μd)/D=(320+60)×9.8×(0.05+0.3×0.12)/0.35≈8.2kN, which is used to check whether the motor power is sufficient.
The calculation of motor power needs to be based on the running resistance and speed requirements. The motor power of the trolley running mechanism is calculated as follows: P=(W·v)/(6120·η)=(8.2×30)/(6120×0.85)≈0.047kW. Considering the starting inertia load (usually 1.5-2 times the static load), the actual required power is about 4.7kW. The YZR160M2-6 motor is selected with a rated power of 5.8kW and a speed of 930r/min, leaving an appropriate margin. The reducer transmission ratio i=(n·πD)/(v)=(930×3.14×0.35)/30≈34. The ZSC600 vertical reducer is selected with a nominal transmission ratio of 22.4. The total transmission ratio of 33.6 is achieved through an open gear pair (transmission ratio 1.5), which is close to the design value. The actual running speed v=(πDn)/i=(3.14×0.35×930)/33.6≈30.4m/min, which meets the design requirements. The brake uses the YWZ-200/25 hydraulic push rod brake with a braking torque of 200N·m to ensure that the trolley can stop reliably on the slope.
The trolley frame structure is designed as a welded box-type structure, which must have sufficient strength and rigidity. The trolley frame consists of two longitudinal beams and several cross beams. The longitudinal beams adopt a box-type section (height of about 500mm, width of about 300mm), and the cross beams are I-beams or box beams. The design load considers the following working conditions: lifting dynamic load coefficient φ_2=1.1-1.3 (A5 working level); running impact coefficient φ4=1.1-1.2; eccentric load condition (one side is fully loaded and the other side is unloaded). Finite element analysis verifies the strength and stiffness of the trolley frame under maximum load: maximum stress σ_max≤[σ]=170MPa (Q345B material); maximum deflection f≤L/1000 (L is the longitudinal beam span). The motor seat, reducer seat, reel support and other installation parts on the trolley frame need to be partially strengthened; guardrails and maintenance platforms are set on the top for easy maintenance. The connection between the trolley frame and the wheel group adopts an articulated balance beam structure to ensure uniform contact between the four wheels and avoid uneven wheel pressure caused by uneven tracks.
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