Portal cranes can be classified according to door frame structure, main beam structure, main beam structure, and usage form. [1] Door frame structure
Divided into gantry cranes and cantilever gantry cranes
portal crane
1. Full door crane: The main beam has no overhang, and the trolley operates within the main span;
2. Semi gantry crane: The height difference of the support legs can be determined according to the civil engineering requirements of the site of use.
Cantilever gantry crane
1. Double cantilever gantry crane: The most common structural form, with reasonable stress distribution and effective utilization of site area.
2. Single cantilever gantry crane: This structural form is often chosen due to site limitations. [1] Main beam form
1. Single main beam
The single main beam gantry crane has a simple structure, easy manufacturing and installation, and a small self weight. The main beam is mostly a skewed rail box frame structure. Compared with double girder gantry cranes, the overall stiffness is weaker. Therefore, when the lifting capacity Q is ≤ 50t and the span S is ≤ 35m, this form can be used. The single girder gantry crane has two types of gantry legs: L-shaped and C-shaped. The L-shaped design is easy to manufacture and install, with good stress conditions and relatively small weight. However, the space for lifting goods through the support legs is relatively small. The C-shaped legs are designed to be inclined or curved, with the aim of providing ample lateral space for goods to pass smoothly through the legs.
2. Double main beams
The double main beam gantry crane has strong bearing capacity, large span, good overall stability, and a variety of types. However, its own weight is larger than that of a single main beam gantry crane with the same lifting capacity, and the cost is also higher. According to the different structures of the main beam, it can be divided into two forms: box girder and truss. Box shaped structures are generally used. [1] Main beam structure
1. Truss beam
The structural form welded with angle steel or I-beam has the advantages of low cost, light weight, and good wind resistance. However, due to the large number of welding points and defects in the truss itself, the truss beam also has disadvantages such as large deflection, low stiffness, relatively low reliability, and the need for frequent detection of welding points. Suitable for venues with low safety requirements and small lifting capacity.
2. Box girder
Welding steel plates into a box structure has the characteristics of high safety and high rigidity. Generally used for gantry cranes with large and super large tonnage. As shown in the figure on the right, MGhz1200 has a lifting capacity of 1200 tons and is the largest gantry crane in China. The main beam adopts a box girder structure. Box girders also have disadvantages such as high cost, heavy weight, and poor wind resistance.
3. Honeycomb beam
Generally refers to an "isosceles triangular honeycomb beam", with a triangular main beam end face, honeycomb holes on both sides of the inclined belly, and chord members at the upper and lower parts. Honeycomb beams absorb the characteristics of truss beams and box beams, and have greater stiffness, smaller deflection, and higher reliability than truss beams. However, due to the use of steel plate welding, the weight and cost are slightly higher than those of truss beams. Suitable for fields or beam fields with frequent use or heavy lifting capacity. Due to the fact that this beam type is a patented product, there are relatively few manufacturers. [1] Usage form
1. Ordinary gantry crane

Rail gantry crane [1]
This type of crane is commonly used in box and truss structures, and has the widest range of applications. It can transport various packaged and bulk materials, with a lifting capacity of less than 100 tons and a span of 4 to 39 meters. The ordinary gantry crane with a grab bucket has a higher working level. Ordinary gantry cranes mainly refer to hook, grab bucket, electromagnetic, and hoist gantry cranes, as well as semi gantry cranes.
2. Hydroelectric power station gantry crane
It is mainly used for lifting and opening/closing gates, and can also be used for installation operations. The lifting capacity is 80-500 tons, with a small span of 8-16 meters; The lifting speed is relatively low, ranging from 1 to 5 meters per minute. Although this type of crane is not used frequently for lifting, once it is put into use, the workload can be very heavy, so it is necessary to raise the working level appropriately.
3. Shipbuilding gantry crane
Used for assembling ship hulls on slipways, there are always two crane trolleys: one has two main hooks and runs on the track of the flange on the bridge frame; The other one has a main hook and a secondary hook, which run on the track of the lower flange of the bridge to flip and lift large ship sections. The lifting capacity is generally 100-1500 tons; Spanning up to 185 meters; The lifting speed is 2-15 meters per minute, with a micro movement speed of 0.1-0.5 meters per minute.
4. Container gantry crane
Used for container terminals. The trailer unloads containers from the shore container carrier bridge onto the ship

Rail gantry crane [1]
After being transported to the yard or rear, it can be stacked by container gantry cranes or directly loaded onto trucks for transportation, which can accelerate the turnover of container transport bridges or other cranes. A storage yard that can stack containers with a height of 3-4 layers and a width of 6 rows, generally using tire type or rail type. Compared with container gantry cranes, container gantry cranes have larger spans and higher heights on both sides of the gantry. To meet the transportation needs of port terminals, this type of crane has a higher working level. The lifting speed is 8-10 meters per minute; The span is determined by the number of container rows that need to be crossed, with a maximum of about 60 meters corresponding to the lifting capacity of 20 foot, 30 foot, and 40 foot containers, which are approximately 20 tons, 25 tons, and 30 tons, respectively.
According to the industry standard GB/T14406, gantry cranes are mainly composed of the following components
1. Cylindrical wheel
2. Buffer
3. Block brake
4. Steel wire rope
5. Lifting hook
6. Driver's cab
7. Reducer
8. Casting pulleys
9. Casting drum
10. Electric motor
11. Electric control equipment [1]
Structural diagram of gantry crane (8 sheets) Edit the representation method in this paragraph
1、 Model standard
The gantry crane is characterized by four main elements: code, rated lifting capacity, span, and working level to indicate the model.
2、 Single girder gantry crane
Its symbols include: MDG、MDE、MDZ、MDN、MDP、MDS。
For example: MDN - single main beam single trolley grab hook gantry crane;
MDS - Three purpose gantry crane for single main beam trolley.
3、 Double beam gantry crane
Its symbols include: MG、ME、MZ、MC、MP、MS。
For example: MG - double beam single trolley hook gantry crane;
ME - Double beam double trolley hook gantry crane.
National Standard of the People's Republic of China GB/T14406-93 General Purpose Portal Crane
1. Main content and scope of use
This standard specifies the classification, technical requirements, testing methods, and inspection rules for general gantry cranes.
This standard is applicable to general gantry cranes (hereinafter referred to as cranes) for outdoor operations, whose lifting devices are hooks, grab buckets, or electric suction cups (lifting electromagnets), or two or three of them are used simultaneously.
The same and similar parts in dedicated gantry cranes can also be used as reference.
2. Reference standards
GB 191 Packaging, Storage and Transportation Symbols
GB 699 Technical Conditions for High Quality Carbon Structural Steel
GB 700 Carbon Structural Steel
GB 783 Maximum Lifting Capacity Series of Cranes
GB 985 Basic forms and dimensions of weld grooves for gas welding, manual arc welding, and gas shielded welding
GB 986 Basic forms and dimensions of submerged arc welding groove
GB 1102 Round Strand Wire Rope
GB 1348 Ductile Iron Castings
GB 1591 Low alloy structural steel
GB 3323 Classification of Radiographic Quality for Fusion Welded Butt Joints of Steel
GB 3811 Code for Design of Cranes
GB 4628 Bridge Crane Cylindrical Wheel
GB 4942.2 Degrees of Protection Provided by Enclosures for Low Voltage Electrical Appliances
GB 5905 Crane Test Specifications and Procedures
GB 5972 Code of practice for inspection and scrapping of steel wire ropes for lifting machinery
GB 6164 Crane Buffer
GB 6333 Electric Hydraulic Block Brake
GB 6334 DC Electromagnetic Block Brake
GB 6417 Classification and Explanation of Defects in Metal Melting Welds
GB 6974 Terminology for lifting machinery
GB 8918 High Quality Steel Wire Rope
GB 8923 Corrosion grades and rust removal grades of steel surfaces before painting
GB 9286 Cross cut Test for Paint Films of Colored and Clear Coatings
GB 10051 Crane Hook
GB 10095 Precision of involute cylindrical gears
GB 10183 Tolerances for Manufacturing and Rail Installation of Bridge and Portal Cranes
GB 11352 General Engineering Cast Carbon Steel Parts
GB/T14007 Technical conditions for driver's cab of general bridge and gantry cranes
ZBJ 19 010 Crane Reducer
ZBJ 19 011 Crane Base Reducer
ZBJ 80 006 Cast Pulley for Crane
ZBJ 80 007 Casting Drum for Crane
ZBK 26 008 YZR series winding rotor three-phase asynchronous motor technical specifications for lifting and metallurgical applications
ZBK 26 007 YZ series three-phase asynchronous motors for lifting and metallurgy - Technical specifications
JB 1152 Ultrasonic Testing for Butt Welding Seam of Boiler and Steel Pressure Vessel
JB 2299 Painting Colors and Safety Signs for Mining, Engineering, and Crane Transport Machinery Products
JB 2759 General Technical Conditions for Packaging of Mechanical and Electrical Products
JB 4315 Crane Electrical Control Equipment
3 Categories
3.1 Types of Types
3.1.1 According to the structural types of the main beam of the crane, it can be divided into single main beam gantry crane (see Figure 1) and double beam gantry crane (see Figure 2). There are three types of gantry structures: double cantilever, single cantilever, and no cantilever
1、 Selection of gantry crane
It complies with the relevant provisions of GB/T14406-1993 and GB5905-86 for general gantry cranes.
In general, when the lifting capacity is below 50t and the span is within 35m, without special usage requirements, a single main beam type should be selected. If the width of the door legs is required to be large, the working speed is high, or heavy or long items are frequently lifted, a double beam gantry crane should be selected.
2、 Span and cantilever length
The span of a gantry crane is an important factor affecting its own quality. In the selection process, while meeting the equipment usage conditions and complying with the span series standards, the span should be minimized as much as possible.
3、 Principles for determining wheelbase
(a) Can meet the stability requirements of the gantry along the direction of the crane track;
(b) The external dimensions of the goods should be able to smoothly pass through the leg flat steel frame;
(c) Pay attention to making the wheelbase B proportional to the span S, generally taking the wheelbase B=(1/4-1/6) S.
4、 Determination of spacing dimensions for gantry cranes [1] During operation, there should be a certain amount of space between the external dimensions of the gantry crane and the cargo and transportation vehicle passages in the yard to facilitate loading and unloading operations. When general transport vehicles are loaded and unloaded within the span, they should maintain a distance of at least 0.7m from the door legs. When the lifting device is not working, there should be a distance of at least 0.5m between it and the transport vehicle. When the goods pass through the door legs, there should be a distance of at least 0.5m.

Outline of gantry crane (8 sheets)
1、 Operating Procedures for Double Beam Bridge Crane
1. Before work
a. Inspect components such as brakes, hooks, wire ropes, and safety devices according to the requirements of the inspection card. If any abnormal phenomena are found, they should be eliminated first.
b. The operator must confirm that there is no one on the platform or track before closing the main power supply. When a lock or notice board is added to the power circuit breaker, the original relevant person should remove it before closing the main power supply.
2. At work
a. When lifting a heavy object for the first time in each shift (or when the load reaches its maximum weight), the object should be lowered again after being lifted 0.5 meters above the ground, and the brake performance should be checked to confirm reliability before proceeding with normal operations.
b. During the operation, the operator should sound the alarm for the following tasks according to regulations.
① Lifting and lowering heavy objects; When driving large and small cars.

Portal crane [1]
② When the crane passes through with unclear visibility, it should continuously sound the alarm bell;
③ When the crane approaches another heavy crane within the span.
④ When lifting heavy objects close to personnel.
c. The operation should be carried out according to the unified command signals.
d. When there is a sudden power outage during work, all controller handles should be placed in the "zero" position, and the crane should be checked for normal operation before resuming work.
e. During normal operation, it is strictly prohibited to use reverse braking to stop the crane and trolley; When changing the direction of movement of the vehicle, the handle must be placed in the "zero" position to completely stop the mechanism before driving in the opposite direction.
f. A crane with two hooks must operate separately when the main and auxiliary hooks are used and when their heights are close to each other to avoid collision.
g. A crane with two hooks is not allowed to lift two objects at the same time; Adjust the brake of the lifting mechanism when it is not working.
h. Do not use the limit position limiter to stop, and it is strictly prohibited to adjust the brake of the lifting mechanism under load.
i. Strictly implement the "Ten No Hanging" system:
① The command signal is unclear or chaotic, and the command is not suspended;
② Do not lift when exceeding the rated lifting capacity;
③ Unreasonable use of lifting equipment or failure to securely hang objects;
④ If there are people or other floating objects on the suspended object, do not lift it;
⑤ Failure to lift due to malfunction of the brake or other braking safety devices;
⑥ When lifting heavy objects directly for processing, do not lift them;
⑦ Slant pulling and hanging without lifting;
⑧ Explosive objects are not suspended;
⑨ Objects buried underground should not be pulled or suspended;
⑩ Objects with sharp edges and corners, not suspended without padding;
j. If any abnormality is found, stop the machine immediately, check the cause and promptly eliminate it.
3. After work
a. Raise the hook to a certain height, stop the large and small vehicles at the designated position, and place the controller handle in the "zero" position; Pull down the switch handle of the protective box and cut off the power supply.
b. Perform daily maintenance and upkeep.
c. Do a good job in handover work.
2、 Operating Procedures for Single Beam Bridge Crane
1. Before work
a. Before taking over the single beam bridge crane with a cab, the driver should inspect the hook, wire rope, safety device and other components according to the requirements of the inspection card. If any abnormal situation is found, it should be eliminated.
b. The single beam bridge crane operated on the ground should be inspected by a dedicated person per shift according to the requirements of the inspection card. Any abnormal situations found should be eliminated.
c. The operator must confirm that there is no one on the platform or track before closing the main power supply. When a lock or notice board is added to the power circuit breaker, the original relevant person should remove it before closing the main power supply.
2. At work
a. When lifting a heavy object for the first time in each shift (or when the load reaches its maximum weight), the object should be lowered again after being lifted 0.5 meters above the ground, and the brake performance should be checked to confirm reliability before proceeding with normal operations.
b. Strictly implement the "Ten No Hanging" system:
① The command signal is unclear or chaotic, and the command is not suspended;
② Do not lift when exceeding the rated lifting capacity;
③ Unreasonable use of lifting equipment or failure to securely hang objects;
④ If there are people or other floating objects on the suspended object, do not lift it;
⑤ Failure to lift due to malfunction of the brake or other braking safety devices;
⑥ When lifting heavy objects directly for processing, do not lift them;
⑦ Slant pulling and hanging without lifting;
⑧ Explosive objects are not suspended;
⑨ Objects buried underground are not suspended;
⑩ Objects with sharp edges and corners, not suspended without padding;
c. If any abnormality is found, immediately shut down the machine, cut off the power supply, check the cause and promptly eliminate it.
3. After work
a. Raise the hook to a certain height, park the cart at the designated position, and place the controller handle in the "zero" position; Pull down the knife switch and cut off the power supply.
b. Perform daily maintenance and upkeep.
c. Do a good job in handover work.
Longmen crane, also known as gantry crane, has a working level A: it reflects the working characteristics of the crane in terms of load state and utilization busyness.
The classification of work levels is determined by the utilization level U and load state Q of the crane. They are divided into eight levels, A1 to A8. Crane working level,
That is to say, the working level of metal structures is determined according to the lifting mechanism and divided into A1-A8 levels. If compared with the working types of cranes specified in China,
Generally equivalent to: A1-A4- light; A5-A6- medium; A7 Heavy, A8 Extra Heavy.
According to relevant national regulations, the registration of gantry cranes requires the following procedures:
Factory qualification certificate, manufacturing enterprise qualification certificate, installation personnel operation certificate, commencement notice, self inspection report.
1、 Lubrication
The working performance and service life of various mechanisms of a crane largely depend on lubrication.
When lubricating, the maintenance and lubrication of mechanical and electrical products should refer to their own instructions. Large vehicles such as traveling carts and overhead cranes should be lubricated once a week. When adding industrial gear oil (SY1172-80) 200 to the winch, the oil level should be checked regularly and replenished in a timely manner.
2、 Steel wire rope
Attention should be paid to the situation of wire rope breakage. If there are broken wires, broken strands or the wear reaches the scrap standard, new ropes should be replaced in a timely manner.
3、 Lifting equipment
Lifting equipment must be inspected regularly.
4、 Pulley system
The main inspection is to check the wear of the rope groove, whether the wheel rim is cracked, and whether the pulley is stuck on the shaft.
5、 Wheels
Regularly inspect the wheel rim and tread, and replace the wheel with a new one when the wear or cracking of the wheel rim reaches 10% thickness.
When the diameter difference between the two driving wheels on the tread exceeds D/600, or when there are serious scratches on the tread, it should be re polished.
6、 Brake system
Each class should be checked once.
The brake should act accurately and the pin shaft should not be stuck. The brake shoes should fit the brake wheels correctly, and the gap between the brake shoes should be equal when releasing the brake