Offshore Crane

Offshore Crane Folding Arm Tilt Cylinder

A knuckle-boom crane folds its arm at a joint — the tilt cylinder controls this joint angle. Push to extend the forearm outward (8,454 KN), pull to fold it back (3,589 KN). The dual-direction force allows the crane to extend over the vessel side for cargo operations, then fold compactly for storm stowage.

≤580mmBore

≤5,170mmStroke

8,454 KNPush

3,589 KNPull

Technical Specifications

Parameter	Specification
Product Name	Offshore Crane Folding Arm Tilt Cylinder
Features	Adjust horizontal angle of the crane forearm (knuckle joint)
Bore Diameter	Up to 580 mm
Rod Diameter	Up to 400 mm
Stroke	Up to 5,170 mm
Thrust Force	Maximum 8,454 KN (push)
Pulling Force	Maximum 3,589 KN (pull)
Working Pressure	Up to 32 MPa
Application	Offshore Crane (Knuckle Boom)

How the Folding Arm Tilt Cylinder Works on a Knuckle-Boom Crane

Offshore Crane Folding Arm Tilt Cylinder

A knuckle-boom (folding) offshore crane has two boom sections connected by a knuckle joint. The main boom is raised and lowered by the main boom luffing cylinder (#17). The forearm (jib) is folded or extended by the tilt cylinder. When the forearm is extended, the crane reaches maximum radius — ideal for loading from supply vessels alongside the platform. When folded, the entire crane occupies minimum deck space — essential for storm survival stowage.

The tilt cylinder requires significant force in both directions. The push stroke (8,454 KN) extends the forearm against the weight of the jib, hook block, and suspended load. The pull stroke (3,589 KN) folds the forearm back — overcoming the moment arm of the extended jib weight and any wind loading pushing the jib outward. Browse the offshore hydraulic cylinder range for the main boom luffing cylinder (#17) and A-type mast cylinder (#19).

Why Dual-Direction Force Matters for Knuckle-Boom Cranes

Unlike the main boom luffing cylinder (#17) which primarily pushes, the folding arm tilt cylinder must produce near-maximum force in both push and pull directions. The reasons are specific to the knuckle-boom geometry:

⚙️ Push (extending): 8,454 KN — the jib weight creates a moment that resists extension as the jib moves from folded (nearly vertical) to extended (nearly horizontal). The maximum push force occurs near the fully extended position where the jib's weight moment arm is longest.
Pull (folding): 3,589 KN — although gravity assists the folding motion, the cylinder must overcome wind forces on the jib (which can be substantial on a 30+ metre crane boom in open ocean) and control the folding speed to prevent the jib from slamming into the main boom.
Dynamic loads from vessel motion — during cargo operations, vessel roll accelerates the jib laterally, creating dynamic forces that add to the static push/pull requirement. The cylinder must handle these combined loads without seal failure or structural yielding.

Folding Arm Tilt Cylinder OEM & ODM

Provide the crane model, jib weight, knuckle joint geometry, maximum SWL at each radius, and classification requirement. Korea Ever-Power delivers the tilt cylinder with FEA report, hydrostatic and functional test certificates, and classification documentation (DNV, LR, ABS, BV).

Korea Ever-Power crane hydraulic cylinder workshop

Offshore crane hydraulic cylinder configurations

FAQ

What is a knuckle-boom crane?

A knuckle-boom crane has a folding arm (jib) connected to the main boom by a knuckle joint. This allows the crane to fold compactly for stowage and extend for maximum reach. The tilt cylinder controls the knuckle joint angle.

How does the tilt cylinder work with the main boom luffing cylinder?

The main boom luffing cylinder (#17) sets the overall boom elevation. The tilt cylinder adjusts the forearm angle independently. Together, they provide the operator with two-axis control of the hook position — height (luffing) and reach (tilting).

Can the same cylinder be used on different crane models?

Each crane model has a specific knuckle joint geometry, jib weight, and SWL rating. The tilt cylinder is engineered for the specific crane. However, Korea Ever-Power can supply cylinders across a wide range of offshore crane sizes and manufacturers.

What surface treatments are available?

Ceramic spraying (HVOF), laser cladding, and hard chrome. The choice depends on the operating environment and maintenance schedule. Laser cladding is recommended for splash-zone installations on offshore cranes.

Can the tilt cylinder be ordered together with the main boom luffing cylinder?

Yes — Korea Ever-Power supplies complete offshore crane cylinder sets (main boom luffing + folding arm tilt) as a coordinated package. Browse the offshore hydraulic cylinder range.

What Our Customers Say

★★★★★Apr 2026

"The tilt cylinders on our 150-tonne knuckle-boom crane handle the dual-direction loading perfectly. The push-to-pull force ratio matches our crane manufacturer's specification exactly."

M. de Groot — Crane Technical Lead, Netherlands

★★★★★Jan 2026

"We ordered both main boom luffing (#17) and folding arm tilt (#18) cylinders for the same crane. Single supplier, single documentation package, single delivery. The LR surveyor approved the complete set in one visit."

Eng. J. Park — Project Engineer, South Korean offshore EPC

★★★★☆Aug 2025

"Good quality tilt cylinders. The 400 mm rod surface finish is excellent (Ra 0.2). One observation: the retraction port sizing could be slightly larger for faster folding speed on our high-cycle crane (60+ lifts per day)."

R. Johansson — Maintenance Superintendent, Swedish platform

★★★★★May 2025

"Emergency replacement for a leaking tilt cylinder. Korea Ever-Power reverse-engineered from our measurements in 6 weeks. The crane was back to full operation before the next maintenance window."

H. Al-Sabah — Equipment Manager, Kuwaiti offshore operator

★★★★★Jan 2025

"Consistent quality across multiple orders. We now specify Korea Ever-Power for all knuckle-boom crane cylinders on our FPSO fleet."

C. Ferreira — Fleet Engineering, Brazilian offshore company