For global shipping and maritime operations, efficiency and reliability in cargo handling are paramount. Marine cranes, also known as ship cranes or deck cranes, play a vital role in loading and unloading various goods on vessels. This blog will explore the different types of marine cranes, their core functions, key components, and essential usage considerations, providing valuable insights for maritime professionals and industry stakeholders.

What is a Marine Crane?

A marine crane, also referred to as a ship crane or deck crane, is a type of crane primarily installed on ships for loading and unloading various cargoes. It is one of the most essential deck machinery for production operations on vessels. Marine cranes are characterized by their compact structure, aesthetic appearance, safety, reliability, energy efficiency, and excellent handling performance.

Their boom configurations include straight booms, telescopic booms, and knuckle booms, while power source controls encompass manual, electric, and electro-hydraulic types. As specialized cranes operating in maritime environments, they are crucial for tasks such as cargo transfer between ships, offshore supply, deployment and recovery of underwater equipment, and other vital missions.

Types of Marine Cranes

Several types of cranes are employed on ships, each designed for specific applications and vessel types:

• Offshore Crane: Built for harsh offshore conditions, used on platforms and vessels for heavy lifting, construction, and supply.https://www.zehuacranes.com/Heavy-duty-offshore-crane-for-marine-operations.html

• Marine Knuckle Boom Crane: Features an articulated boom (like a finger knuckle) offering flexibility and precise load placement in confined spaces.https://www.zehuacranes.com/Marine-knuckle-boom-crane-loading-cargo.html

• Marine Telescopic Crane: Equipped with a boom that extends and retracts, ideal for applications requiring variable reach.https://www.zehuacranes.com/Marine-Telescopic-Crane-for-Ships.html

• Marine Straight Boom Crane: A traditional crane with a fixed-length, straight boom, commonly used for general cargo handling.https://www.zehuacranes.com/Marine-Stiff-Boom-Crane-lifting-heavy-cargo.html

• Marine Hatch Cover Crane: Specifically designed for handling ship hatch covers.https://www.zehuacranes.com/Marine-Hatch-Cover-Gantry-Crane.html

• Marine Cargo Crane: A general term for cranes used primarily for loading and unloading cargo on various vessels like bulk carriers and multi-purpose ships.https://www.zehuacranes.com/Heavy-duty-marine-deck-crane-for-cargo-handling.html

Core Functions and Roles of Various Marine Cranes

Different marine cranes serve distinct purposes based on their design:

• Offshore Cranes handle complex lifting operations involving equipment and supplies for offshore platforms.

• Knuckle Boom Cranes excel in precision tasks, such as handling cargo in tight spots or deploying/recovering smaller boats and equipment.

• Telescopic Cranes provide versatility in reach, making them suitable for various cargo handling duties where space is a constraint.

• Straight Boom Cranes offer robust and reliable service for standard cargo lifting operations.

• Hatch Cover Cranes streamline the process of opening and closing hatch covers, improving operational efficiency.

• Cargo Cranes are the workhorses on cargo ships, directly facilitating the transfer of goods between ship and shore or between vessels.

Components and Structure of a Marine Crane

The structure primarily includes a derrick system and the crane itself.

Derrick System:
A traditional shipboard lifting device, the derrick system consists of a derrick boom, a mast (or samson post), rigging, and a winch. While involving complex ropes and somewhat cumbersome operation, its simple structure, ease of manufacture, and low cost have led to its widespread use.

• Single Derrick Operation: Uses a single boom. The boom lifts the cargo and is then swung outboard or over the hatch using guys (ropes). This method is less efficient and more labor-intensive.

• Double Derrick Operation: Utilizes two booms—one positioned over the hatch, the other swung outboard. Their cargo wires are connected to a single hook. By alternately heaving and slacking these wires, cargo is moved between ship and shore. This method offers higher efficiency and reduced labor compared to single derrick operation.

Improved Derrick Systems:
Modernized versions have been developed:

• Double Span Derrick System: An enhanced single derrick system using only cargo wires and two separate sets of span wires (topping lifts). Operated by one cargo winch and two span winches, it provides convenient operation and high efficiency.

• Ebel Derrick System: An improved double derrick system incorporating cargo, span, and guy winches. It allows quick positioning of the boom and enables point lifting and lowering within the working radius, significantly boosting efficiency—a major step towards fully automated cargo handling.

Modern Marine Crane Structure:
Modern cranes, commonly found on bulk carriers, container ships, tankers, and multi-purpose vessels, are sophisticated machines. Unlike land-based cranes, they operate on unstable platforms (ships), enduring tilt, roll, harsh environments, saltwater corrosion, and various dynamic forces during transit.

• Structural Components: The load-bearing structure includes a base column welded to the ship's hull, a tower (slewing platform) housing machinery and the operator's cab, and a boom (often a box-girder truss structure) that supports the load.

• Mechanisms:

• Hoisting Mechanism: Uses a motor and gearbox to drive a winch drum, winding/unwinding wire rope to raise/lower the hook.

• Luffing Mechanism: Uses a motor and gearbox to adjust the boom's angle, changing the hook's radius.

• Slewing Mechanism: Uses a motor and gearbox to drive a pinion engaging with a slewing ring gear, rotating the tower and boom.

• Each mechanism typically has a fail-safe brake. Coordinated operation of these three systems positions the load accurately.

• Control Systems:

• Electrical System: Includes control components in panels and operator inputs (buttons, levers) in the cab.

• Hydraulic System: Comprises pumps, motors, valves, pipes, and fittings to control and drive the mechanisms (common in electro-hydraulic cranes).

• Auxiliary Equipment: Includes access ways, ventilation, etc.

Precautions for Using Marine Cranes

1. Pre-Operation Check: Ensure ship's list and trim are within limits (typically ≤5° list, ≤2° trim). Operate within safe wind speeds (usually ≤20 m/s, wind pressure ≤250 Pa).

2. Fluid & Temperature: Confirm proper hydraulic oil level and temperature. Ensure ambient temperature is within the crane's operational range.

3. Wire Rope & Winch: Inspect wire rope for good condition. Ensure winch and sheaves function correctly.

4. Post-Operation Securing: Lock the boom and hook securely after use.

5. Leak Check: Inspect pumps, motors, and hydraulic lines for leaks.

6. Operator Competence & Safety: Operators must be trained in controls and emergency procedures. Unauthorized personnel must stay clear of the operating area and crane working radius.

7. Regular Maintenance: Conduct regular inspections of wire ropes, hooks, and hydraulic oil. Ensure key parts are lubricated. Perform annual crane inspections as required.

Key Inspection Points for Marine Cranes

1. Certification Validity: Verify that the crane has undergone required initial, periodic, and special surveys after damage/repair.

2. Safety Devices: Check load indicators and limit switches for proper function. Never exceed the Safe Working Load (SWL).

3. Wear and Corrosion:

• Check metal structures/fixed parts for significant deformation/cracks.

• Inspect wires for excessive wear/corrosion.

• Check brake linings and gear teeth for significant wear/cracks.

• Replacement/Repair is mandatory if: Metal structure corrosion exceeds 10% original size, or cracks/deformation exist. Detachable part corrosion exceeds 10% (or 6% for pins), or cracks exist. Wire rope has excessive wear/corrosion or 5% broken wires within 10x diameter length. Brake linings are worn exposing rivets. Gears are damaged or cracked.

• Hydraulic & Mechanical Parts: Inspect hydraulic lines for leaks. Check slewing mechanisms and bearings for proper condition.

Required Certificates for Marine Cranes

According to the Technical Rules for Statutory Survey of Lifting Appliances 1999:

• For International Voyages: Certificate of Test and Examination for Lifting Appliances; Register of Cranes and Lifting Appliances; Certificate of Test and Examination for Double Derrick; Certificate of Test and Examination for Wire Ropes; Certificate of Test and Examination for Loose Gear.

• For Non-International Voyages: Certificate of Test and Examination for Lifting Appliances.









Regulations for Survey of Marine Cranes


According to the Technical Rules for Statutory Survey of Lifting Appliances 1999:

• Scope: Lifting appliances on Chinese-flagged ships and offshore installations must undergo statutory survey.

• Initial & Repair Survey: Lifting appliances and loose gear require verification testing and thorough examination before initial use and after any repair/replacement affecting strength.

• Incident Reporting: Major accidents or defects must be reported by the Master or Owner promptly for subsequent survey.

• Regular Checks: Loose gear and wire ropes should be inspected by crew before each use (except if inspected within last 3 months). Ropes with broken wires require monthly checks.

• Survey Types for Certification: Initial Survey, Annual Survey, and Renewal Survey (every 4 years).

• Marking:

• Loose Gear: Certified items must be stamped by the testing authority with SWL (kN), Test Date, ID Number, and Tester's Mark (some exceptions for small items).

• Lifting Appliances: After initial/repair survey, the derrick/boom must be stamped near its root with SWL (kN), Test Date, Boom angle/radius during test, and Surveyor's Mark.

By understanding these aspects of marine cranes—from types and functions to operation, inspection, and certification—ship operators and maritime professionals can ensure safer, more efficient, and compliant cargo handling operations at sea.

HENAN ZEHUA HEAVY INDUSTRY EQUIPMENT CO., LTD  
Email: sale@zehuacranes.com

Website: [https://www.zehuacranes.com/]

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