什麼是門式起重機?

到底什麼是門式起重機?

一個 portal crane (也稱為港口門式旋臂起重機) is a rail-mounted, full-circle rotating jib crane exclusively designed for port and waterfront operations. It features a prominent portal base (four-leg portal frame) that spans over shore railway tracks or truck passages, allowing land transport vehicles to pass directly beneath the crane without hindrance.

Different from gantry cranes (which move horizontally with a straight girder) and container gantry cranes, the most typical feature of a portal crane is its rotational jib mechanism. Its upper lifting structure can rotate 360 自由度, matching the loading and unloading needs of docked ships. It is mainly used for lifting bulk cargo, general groceries, and small containers between ships and shore terminals, and is the most classic and widely used crane in inland and coastal ports.

Core Components of a Portal Crane

The complete structure of a portal crane is divided into a lower portal traveling mechanism and an upper rotating lifting mechanism. Each core component undertakes independent and collaborative work to ensure efficient and safe cargo handling:

• ◆ Portal Base & 行走機構: The lower four-legged rigid portal frame is the main support of the whole crane. Installed on ground rails along the dock, it can drive the entire crane to move back and forth along the wharf. The hollow portal space underneath reserves a passage for trucks and trains, realizing uninterrupted logistics operations.
• ◆ Rotating Platform & Slewing Mechanism: Mounted on the portal base, this structure supports the full rotation of the upper jib and lifting system. It can flexibly adjust the working angle to align with different ship cargo holds, solving the positioning problem of ship-borne cargo.
• ◆ Luffing & Jib System: The telescopic and luffing jib is the working arm of the crane. It can adjust the working radius (forward and backward pitching) to cover different cargo areas on the ship deck and shore, realizing precise cargo picking and placing.
• ◆ Hoist Lifting Mechanism: Composed of steel wires, pulleys and a lifting motor, it undertakes vertical lifting and lowering of various cargoes, supporting frequent and high-intensity lifting work.
• ◆ Cab & Safety Protection System: The independent operating cab provides a full-view working perspective for operators. 配備過載限制器, luffing limit switches, wind alarm devices and emergency stop systems, it effectively avoids operational risks in port outdoor environments.

How Does a Portal Crane Work?

Portal cranes rely on three core collaborative actions to complete ship-shore cargo loading and unloading, with a highly mature and efficient working flow. 第一的, according to the berthing position of the ship and the distribution of cargo, the crane travels along the dock rails to lock the optimal working position. 第二, the upper platform rotates and the jib luffs to adjust the working radius, aiming the lifting hook at the target cargo on the ship.

最後, the hoist system lifts the cargo stably, and the rotary and luffing structures cooperate to transfer the cargo from the ship deck to the shore transport vehicle, or complete reverse loading work. The combination of walking, 旋轉, luffing and lifting enables the portal crane to cover fan-shaped and rectangular working areas along the wharf, perfectly adapting to the irregular cargo distribution of docked ships.

Common Types of Portal Cranes

Portal cranes are mainly classified by structural form and working performance, and the mainstream types in the market are as follows:

1. Fixed Portal Cranes

This type of crane is fixed on the dock foundation without a traveling function. It has a simple structure, low cost and stable performance, and is suitable for small fixed terminals, single cargo berths and inland river shallow-water docks with fixed working ranges.

2. Mobile Rail-Mounted Portal Cranes

The most widely used standard portal crane. It can move freely along the dock rails, with a large adjustable working range and strong flexibility. It is suitable for medium and large ports with frequent ship berthing and diverse cargo types, and can handle bulk cargo, groceries and light container goods efficiently.

3. Single-Jib & Double-Jib Portal Cranes

Single-jib portal cranes are lightweight and flexible, suitable for small-tonnage cargo handling. Double-jib models have higher lifting efficiency and larger load capacity, which can realize alternate operation of double hooks, and are mostly used for large coastal ports with high cargo throughput.

Key Industrial Applications

As special port-specific lifting equipment, portal cranes are highly targeted in application scenarios, focusing on waterfront ship-shore handling operations:

• ◆ Coastal & Inland River Ports: The core application scenario, responsible for loading and unloading bulk cargo such as coal, 礦石, sand and grain, as well as general groceries, steel products and mechanical parts.
• ◆ Small Container Terminals: Suitable for handling small and medium-sized containers and scattered container goods in regional ports and temporary berths.
• ◆ 船舶修理 & 造船廠: Used for lifting ship accessories, hull parts and maintenance equipment, assisting in ship berthing maintenance and minor assembly work.
• ◆ Dock Freight Yards: Cooperating with shore transport vehicles to complete cargo stacking, transfer and temporary storage operations on the wharf.

Core Advantages of Portal Cranes

• ◆ Professional Ship-Shore Matching: The 360° rotation and luffing design perfectly adapts to the irregular working range of ship decks, which is irreplaceable for dock cargo handling.
• ◆ High Site Utilization: The overhead portal design realizes the separation of upper lifting operation and lower ground transportation, without occupying dock passage space.
• ◆ 環境適應力強: Designed with wind resistance, rain resistance and seawater corrosion resistance, it can work stably in outdoor waterfront environments for a long time.
• ◆ 靈活 & 高效營運: Multiple movement modes cooperate efficiently, with fast cargo handling speed, suitable for long-term and high-frequency port operations.
• ◆ 維修方便 & 使用壽命長: The mechanical structure is sturdy and durable, with low failure rate, and daily maintenance is simple and convenient, reducing port operation costs.

FAQ About Portal Cranes

Q1: What is the biggest difference between a portal crane and a gantry crane?

A1: This is the most confusing point for most people. Portal cranes are rotating jib cranes for port ship-shore handling, with 360° rotary and luffing functions, specially for dock ship cargo. Gantry cranes are straight-beam linear moving cranes, mainly used for factory workshops, yard stacking and inland cargo handling, without large-range rotation function. Their working principles, structures and application scenarios are completely different.

Q2: What is the usual lifting tonnage of a portal crane?

A2: Conventional portal cranes for general port use have a lifting capacity of 5 噸至 50 噸, which meets the handling needs of most bulk cargo and groceries. Customized large-tonnage models for heavy port operations can reach 80–100 tons, used for super-heavy equipment and large steel component handling.

第三季度: Can portal cranes be used indoors?

A3: Rarely. Portal cranes are large-scale outdoor professional port equipment with tall fuselage, large rotating working range and wind-resistant and corrosion-resistant structural design, which is completely tailored for open-air dock environments. Indoor workshops mostly use overhead cranes and small gantry cranes instead of portal cranes.

第四季度: What are the main working limitations of portal cranes?

A4: Portal cranes are only suitable for waterfront ship-berthing scenarios and cannot be used for inland large-area yard stacking. 此外, they need to stop working in extreme weather such as strong winds above level 6, heavy rain and typhoons to prevent equipment tilting and cargo falling accidents.

Q5: How to maintain a portal crane regularly?

A5: Daily maintenance includes checking the tightness of steel wires, the flexibility of rotation and luffing mechanisms, and the sensitivity of safety limit devices. Regular anti-corrosion treatment is required for the steel structure to resist seawater erosion. Professional overall inspection and lubrication of transmission parts shall be carried out every 6 months to ensure stable operation.

Q6: Why are portal cranes still widely used despite container cranes?

A6: Container cranes are only suitable for standard container handling, while portal cranes have stronger versatility. They can handle bulk cargo, groceries, steel and special-shaped goods that container cranes cannot adapt to, and are the essential core equipment for mixed cargo ports and inland river terminals.

最後的想法

As a professional and classic port machinery, portal cranes occupy an irreplaceable position in waterfront cargo handling. Its unique rotary luffing structure and ship-shore matching working mode make it the preferred equipment for bulk and general cargo transportation in various ports around the world. Understanding its structural characteristics and application scenarios can help us better recognize the efficient operation logic of modern port logistics systems.