How to Determine Working Radius and Lifting Height? Which Is Better for My Vessel – Knuckle Boom or Telescopic Boom?

When selecting a marine crane, vessel owners and shipyard engineers often face two key questions: how to determine the working radius and lifting height, and which boom type – Knuckle Boom ortelescopic boom – is more suitable for their vessel? Drawing on MAXTECH’s years of engineering experience, here are detailed answers to these questions.

I. Working Radius: How Far Can the Crane Reach?

Working radius is the horizontal distance from the crane’s slewing center to the hook center. It determines the area the crane can cover. A proper working radius should ensure that the crane can reach every corner of the vessel’s cargo stowage area and extend over the ship’s side for quayside loading/unloading or barge transfer operations.

Steps to determine working radius:

1. Measure the vessel’s main dimensions. Measure from the hatch center to the deck edge, add half the vessel’s beam, and then add the required outreach beyond the ship’s side.

2. Allow an operational margin. Typically, the maximum working radius should cover the farthest corner of each cargo hold, plus an additional 1–2 meters of margin to ensure safety during lifting.

3. Refer to experience from similar vessels. For example, a 3,500 DWT bulk carrier using a grab usually requires a working radius of 8–12 meters; for container vessels using deck spreaders, a working radius of 24–36 meters is common.

II. Lifting Height: How High Can the Crane Lift?

Lifting height consists of two parts: height above deck (from deck level to the hook’s highest position) and depth below deck (from deck level down to the bottom of the hold).

Steps to determine lifting height:

1. Calculate the height above deck. This depends on cargo stacking height, hatch cover clearance, and a safety margin. Container vessels generally require 15–20 meters; bulk carriers using grabs usually require 12–15 meters.

2. Calculate the depth below deck. Based on the depth of the cargo hold, typically between 10 and 15 meters.

3. Core principle: bigger is not always better. The actual goal should be the minimum lifting height sufficient to cover all operational areas. Excessively large working radius and lifting height increase crane weight, procurement costs, and challenges to vessel stability.

III. Knuckle Boom vs. Telescopic Boom – Which One to Choose?

The two boom types that dominate the current marine crane market – knuckle boom and telescopic boom – each have distinct characteristics and suitable applications.

1. Knuckle Boom Crane

Structural characteristics: Uses multiple articulated arms that can fold and extend like joints, enabling three-dimensional operation. When folded, the height is very low (typically only 2–3 meters), which helps maintain clear sightlines across the deck – ideal for vessels with limited deck space.

Working radius: Can reach up to 30 meters or more, with highly flexible luffing.

Operational flexibility: Can precisely position loads around obstacles (e.g., containers, superstructures) and in confined spaces – one of the knuckle boom’s greatest advantages.

Cost: The structure is relatively complex and requires high manufacturing precision, so the overall price is generally higher than that of a telescopic boom crane of comparable capacity.

Suitable vessel types and applications:

• Chemical tankers / oil tankers: dense piping on deck – the knuckle boom can fold to avoid pipelines and operate flexibly at narrow berths.

• Ro-Ro vessels: need to lift cargo between different deck heights; the knuckle boom’s articulated motion and luffing range meet this demand well.

• Yachts: extremely high demands on deck space and aesthetics.

• Multi-purpose vessels / general cargo vessels: cargo types vary widely, and lifting paths are rarely straight – the knuckle boom’s flexibility is a great advantage.

• Research vessels: numerous instruments and limited space.

2. Telescopic Boom Crane

Structural characteristics: Uses multi-section box-type telescopic booms. The boom extends in stages during operation and retracts when stowed. When retracted, the height is relatively high, usually around 5–8 meters.

Working radius: The maximum working radius is relatively fixed, typically between 20 and 36 meters.

Operation: Usually uses luffing cylinders to change the boom’s elevation angle, thereby changing the radius. Straight-line telescoping is more precise than knuckle booms. High lifting height is a notable advantage of telescopic booms.

Lifting capacity: Covers a wide tonnage range, typically 10–100 tons – much higher than knuckle boom cranes (most knuckle booms are in the 1–30 ton range).

Cost: Structure is relatively simpler, manufacturing requirements are lower, and both procurement and maintenance costs are lower.

Suitable vessel types and applications:

• Bulk carriers: grab operations require significant lifting height and stable straight-line lifting capability.

• Container vessels: require large working radius and lifting height.

• Heavy-lift vessels: require lifting capacities of 10–100 tons.

In addition, telescopic booms are particularly suitable for applications that require frequent changes in working radius. If most lifting operations on board follow straight-line paths and cargo loading/unloading points are relatively fixed, the straight-line telescoping operation of a telescopic boom is simpler and more efficient.

IV. Combination Boom: A Solution Combining the Advantages of Both

Beyond the two types above, a new boom type – the telescopic knuckle boom – is gaining increasing market favor. It essentially integrates a telescopic section at the end of a knuckle boom. When folded, the height is very low, while the telescopic section provides additional straight outreach capacity.

The advantages of this combination boom are clear: during operation, the crane can reach over obstacles and around various deck structures; when stowed, the foldable design takes up very little deck space.

MAXTECH’s 3-ton 12-meter telescopic knuckle boom marine crane is a typical example of this technical approach. This model is currently the company’s most popular marine crane solution, particularly suitable for vessel types with tight deck space but high demands on operational flexibility, such as yachts, research vessels, and multi-purpose workboats.

V. Comprehensive Selection Recommendations

In summary, when selecting a marine crane, we recommend following these principles:

1. First, identify the most demanding lifting scenario. Find the operational scenario that requires the greatest working radius and lifting height, and use it as the primary basis for selection. Aim to cover all operational areas, but do not blindly pursue extreme values.

2. Choose the boom type based on vessel type and primary cargo. Bulk carriers, container vessels, and heavy-lift vessels should prioritize telescopic booms; chemical tankers, Ro-Ro vessels, yachts, and research vessels should prioritize knuckle booms. When space is extremely limited and scenarios are complex, the telescopic knuckle boom is often the better solution.

3. Consider cost comprehensively. Not only the procurement cost, but also the impact on deck space utilization, operational efficiency, and vessel stability.

4. Prioritize products with international certifications. Comply with requirements such as IMO MSC.532(107), and choose equipment with ABS, BV, CCS, DNV, or other international classification society certifications to ensure safety and compliance.

As a leading Asian manufacturer of marine cranes and port equipment, MAXTECH offers a complete product line covering knuckle boom, telescopic boom, and telescopic knuckle boom cranes. We can provide tailored equipment selection recommendations and technical solutions based on the specific vessel type and operational needs.

About MAXTECH

MAXTECH is a well-known Chinese manufacturer of ship automation equipment, headquartered in Wuxi. The company specializes in the R&D, production, and sales of fully automatic mooring systems, marine and port cranes, and handling equipment. Its product portfolio includes vacuum suction pad automatic mooring systems, marine deck cranes, knuckle boom cranes, active heave compensation offshore cranes, container spreaders, grabs, hoppers, and more. MAXTECH holds multiple international certifications including ABS, BV, CCS, DNV, KR, and RS, and serves customers across the globe. Driven by technological innovation, MAXTECH is committed to providing advanced, efficient, and reliable ship and port automation solutions to customers worldwide.