Project Background & Customer Requirements

In response to the harsh operating conditions of offshore applications, we undertake customized offshore lifting equipment orders for the overseas offshore engineering sector by virtue of our in-house design team.

The core customer requirements are as follows:

Adapt to the severe offshore environment with high salt spray and 85% relative humidity;
Achieve a lifting capacity of 35 tonnes at a radius of 12 metres and 20 tonnes at a radius of 20 metres;
Be capable of underwater operation;
Ensure stability during dynamic offshore operations;
Feature a constant tension control mode and be pre-configured with an interface for a wave compensation system;
Comply with ABS certification standards and be suitable for installation on offshore platforms and special-purpose vessels.

Design Requirements

1. Standards: ABS Guide for Certification of Lifting Appliances

2. Service Life: The offshore crane is designed for a service life of 20 years.

3. Applications:

Lifting operations between vessels and quays within sheltered waters
Lifting operations on ship decks
Ship-to-ship lifting operations
Deepwater and underwater lifting: deduction of the weight of underwater wire ropes and the dynamic amplification factor (DAF) caused by hydrodynamic forces, with consideration of load buoyancy
Deepwater lifting under active heave compensation conditions, i.e., AHC lifting

4. Environmental Conditions

Design temperature: −10 °C
Ambient temperature: −20 °C ~ +45 °C
Wind conditions: in accordance with ABS requirements
Atmospheric environment: high salinity
Humidity: 85% relative humidity

Customized Solution

We strictly comply with the design and manufacturing standards of ABS Classification Society to provide a custom-designed 35-ton offshore knuckle boom crane, fully matched to your operational requirements. All core specifications and configurations are tailored to the actual application needs of your project:

35T offshore knuckle boom crane is undergoing load testing at the shipyard

35T Offshore Knuckle Boom Crane is performing load testing at the dock.

Technical Parameters

Slewing Angle	＜350°	Slewing System & Foundation (DAF+SFI)	2.0	Deck Structure Load	-
Slewing Speed	0～0.7 rpm	Luffing Time	100 sec for raising/ lowering	Dynamic Overturning Moment	9500 kN·m
Dynamic Amplification Factor (DAF)	1.4	Outer diameter of foundation	2800 mm	Dynamic Vertical Force	1200 kN
Additional Safety Factor (SFI)	1.4	Wall thickness of foundation	20 mm	Dynamic Horizontal Force	185 kN

Winch Parameters

Item	Main Winch	Auxiliary Winch
Safe Working Load (SWL)	35 tons @ 12 m, 20 tons @ 20 m	5 tons (including 1.5 tons personnel-carrying capacity)
Rope reeving ratio	1	1
Operating radius	min. 5.0 m / max. 20 m	min. 5.2 m / max. 22 m
Main hoisting speed (rated)	0～20 m/min at 35 tons 0～50 m/min at light load	0～60 m/min at full load
Rope capacity of drum	2000 m	110 m
Hook travel	1700 m	100 m
Heel / Trim condition	5°/2°	5°/2°
Wire rope diameter	44 mm	19 mm
Rated load of outer layer rope	35 tons	5 tons
Wire rope	galvanized, anti-rotational type	galvanized, anti-rotational type

Remarks

All above operating speeds are calculated based on the average volumetric efficiency of our hydraulic component suppliers. A speed deviation within the range of +10% ～ -5% is acceptable and shall be taken into account.

Offshore Knuckle Boom Crane Winch

The Offshore Crane Hook Underwater Operation

Water Depth(m)	Remaining Hook Lifting Capacity (Submerged: tons)	Estimated Lowering Capacity (Dry: tons)
0	35	35
500	30	33
1000	25	28
1500	21	24
1700	17	19

Note: Hydrodynamic factors are not considered in this table.

Control System of the offshore knuckle boom crane

Operator's Cabin
Located on the right-hand side when looking from the crane machinery room toward the boom tip Accessible via a ladder mounted on the foundation Lockable access door with ventilation Mounted on shock absorbers Material: low carbon steel – Q355B Sandblasted to SA 2.5 grade Topcoat color: yellow Rubber mat laid on cabin floor	Air conditioning unit Internal lighting 1 earthed power socket (230V) Fire extinguisher, 2kg CO₂ type Windows Front window Two side windows (one each side) All windows made of tempered safety glass Two upper side windows openable for ventilation Front window equipped with wiper and washer system
Control Levers
Main control valves	English operation manual and nameplates Dynamic load radius diagram
Spring-return control levers (Note: All functions feature infinitely variable speed control from zero to full speed.)	Hoisting/lowering Folding boom luffing up / down Main boom luffing up / down Slewing right/left
Control Modes	Normal mode and Constant tension mode

Offshore Knuckle Boom Crane Cabin

Safety System Of the Knuckle Boom Crane

Control System
Load limiting system
*All main hydraulic circuits are protected against over-pressure by relief valves set to values corresponding to the knuckle boom crane's* capacities**
Overload protection	Emergency stop
Drive System
Electric motors Thermistor protection Hydraulic power unit	Hydraulic oil high-temperature alarm/shutdown Hydraulic oil low-level alarm/shutdown
Slewing Mechanism
Load holding valve to maintain position in case of hydraulic pressure drop	Fail-safe multi-disc brake
Slewing Bearing
Renowned and industry-approved manufacturer	High-strength steel bolts and nuts
Slewing Gear
Integrated assembly with brake, motor, and load control valve	Internal pinion drive
Luffing Mechanism
Load holding valve: locks movement in case of hydraulic pressure drop	Luffing cylinders are designed to automatically decelerate before end positions
Hoisting Mechanism – Main Winch
Manual Overload Protection System (MOPS) and Automatic Overload Protection System (AOPS) Load holding valve: locks movement in case of hydraulic pressure drop Fail-safe multi-disc brake: spring-applied, hydraulically released	Minimum 5 full rope turns retained on drum when fully paid out Upper and lower limit switches for hook Wire Rope Sheaves -- Fixed wire rope sheave brackets -- Grease nipples

Hydraulic System Configuration of the offshore crane

Hydraulic System
Open-loop circuit
Hydraulic Oil Tank
Integrated design with the crane Inspection and cleaning openings Drain valve Full-flow return oil filter;		pressure and return filters for pilot, supply and other sensitive circuits Sight glass with temperature indicator Oil level switch for low oil level alarm and very low level shutdown Temperature sensor for cooler control and automatic overheat shutdown
Hydraulic Piping
Hard pipes		Low carbon steel, painted;Pipe fittings: galvanized low carbon steel; Exposed fittings painted and protected against corrosion with Denso Tape or Tectyl. Hard pipes and fittings comply with ISO 8434-1 (DIN 2353).
Hoses		High-quality rubber, UV and salt spray resistant; Steel wire braid construction to specified hydraulic pressure rating; Hoses comply with EN 856 (SAE R13/12) / EN 857 (SAE R2T).
Hose fittings		Galvanized low carbon steel; Exposed fittings painted and protected against corrosion with Denso Tape or Tectyl; Hose fittings made of carbon steel with Tuff Coat hard coating.
System Cleanliness
All components thoroughly cleaned before installation		Cleanliness class: NAS 8

Electrical Arrangement of the knuckle boom offshore crane

Power Supply System
Slip ring assembly for power transmission to rotating parts of the crane
Electric Motors (suitable for applicable hazardous areas)
Duty class: S1 – 100% continuous duty Power supply: main 690V/60Hz / 3-phase; control and lighting 230V/60Hz / single-phase Power rating: -- Main motors: 2×250kW -- Emergency motor: 50kW	Protection class: IP54 Insulation class: F Temperature rise class: F Anti-condensation heating device for shutdown Squirrel cage rotor Self-cooled (fan-cooled)
Motor Starters
Protection class: IP54 Starting method: star-delta starting	Safety door (main isolator switch) -- Start button: green -- Stop button: red -- Emergency push-pull button: red
Indicator lights
Power indicator: white	Running indicator: green
Floodlights
(Qty: 3 sets)	Crane boom equipped with 1 pendent-type 400W marine floodlight in marine enclosure.
Aircraft Warning Light
(Qty: 1 set)	1 aircraft warning light installed on top of the main winch, in marine enclosure.

Offshore Knuckle Boom Crane Motor

Offshore Knuckle Boom Crane Electrical and Hydraulic System

Surface Treatment

External Surface Treatment
Foundation, crane machinery room, and crane's boom	External surfaces sandblasted to Sa 2.5 1st primer: Interzinc 52, DFT 75μm 2nd intermediate coat: Intergard 345, DFT 125μm 3rd topcoat: Interthane 990, DFT 60μm Topcoat color: RAL1003 yellow
Internal Treatment
Foundation and machinery room	External surfaces sandblasted to Sa 2.5 1 coat Interzinc 52 primer, DFT 40μm 2nd coat Intergard 345, DFT 75μm
Oil tank (integrated in machinery room)	External surfaces sandblasted to Sa 2.5 1 coat Interzinc 52 primer, DFT 40μm
Boom	No treatment applied due to fully enclosed steel box structure

Lubrication

Lubrication: All lubrication points piped to nearby access positions and labeled

Offshore Crane: Fully lubricated prior to initial operating hours

Recommended Oils and Greases

System	Fluid / Grease Type
Hydraulic system oil	ISO VG 168 (VI 95), SAE 20W-20
Pump drive gearbox	SAE 90 with EP additives
Transmission gearbox	ISO VG 150 (VI 95)
Disc brake	ISO VG 32, SAE 10W
Open gears	Molybdenum disulfide based grease
Bearings	Molybdenum disulfide based grease
Wire rope	Molybdenum disulfide based grease

Scope of Supply

1. Crane Structure

Foundation as independent unit:

--- For foundation with diameter ＞2250 mm and height ＞2150 mm, internal stiffeners for transportation provided

Crane machinery room as independent unit
Main boom as independent unit
Folding boom as independent unit
Main winch as independent unit
Wire rope as independent unit (optional)
Loose parts, ladders, platforms, etc.
Hydraulic cylinders as independent unit

2. Special Tools: Grease gun

offshore knuckle boom crane is undergoing assembly and testing prior to delivery

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ABS Certified 35T Offshore Knuckle Boom Crane