Engineering for Hazardous Seas: Dual-Hook Marine Cranes Pass Factory Testing for Southeast Asian FSO Duty

Offshore lifting operations in hazardous oil and gas zones demand equipment capable of handling both heavy supply transfers and rapid deck movements under volatile sea conditions. Addressing these operational requirements, two custom-built 15T22M stiff boom marine cranes recently cleared comprehensive Factory Acceptance Testing (FAT) in China before deployment to Southeast Asia.

Ordered by a Malaysian offshore service contractor, the explosion-proof deck cranes are designated for installation on a Floating Storage and Offloading (FSO) vessel. The equipment will support offshore support vessel (OSV) supply transfers, deck repositioning, and personnel hoisting in operational environments subject to significant wave action.

Operating on an FSO platform presents distinct engineering hurdles. Space constraints on deck, strict hazardous area electrical classifications, and dynamic forces caused by wave heights reaching 3 meters require high structural margin and versatile lifting capabilities.

To resolve the dual challenge of lifting heavy equipment while maintaining fast cycle times for smaller loads, a dual-hook arrangement was integrated into the stiff boom design:

• Primary Lifting Mechanism: A main hook rated at 15 tonnes Safe Working Load (SWL) across a 22-meter operational radius, engineered to handle heavy machinery and rated for 1-tonne personnel transfer.
• Secondary Handling Unit: An auxiliary hook providing 3.5 tonnes SWL at an extended 23-meter reach, designed for lighter cargo and rapid maneuvering, also configured for 1-tonne personnel lifting.

This setup enables vessel crew to adapt to varying payload weights without reconfiguring the primary crane structure, improving handling efficiency during offshore supply operations.

During the FAT phase, technical representatives from the Malaysian contractor conducted an on-site audit of the completed units. The inspection prioritized critical load-bearing components, including structural weld passes, slewing ring assemblies, pin connections, wire ropes, hydraulic power units (HPUs), and flameproof electrical enclosures.

Technical discussions between field engineers centered on evaluating crane behavior during ship pitch and roll motions. Verification steps covered emergency failsafe braking response times during power interruption, system pressure stability under peak hydraulic loads, dynamic amplification factor calculations, and moment limiter cutoff logic.

Physical performance testing took place under the joint supervision of American Bureau of Shipping (ABS) surveyors and client engineers to confirm compliance with API Spec 2C rules and class society specifications.

The testing protocol encompassed two key phases:

• Static Overload Verification: The primary hook held a 1.25x SWL proof load for a 15-minute duration, validating hydraulic circuit integrity, structural yield resistance, and mechanical brake holding capacity.
• Dynamic Motion Cycles: Full-capacity operational tests were run through complete slewing, luffing, and hoisting movements to evaluate thermal dissipation, safety interlock behavior, and overall motion control.

Following initial testing success across all criteria, ABS issued the Certificate for Lifting Appliances, verifying full compliance with API Spec 2C standard requirements. The units cleared final physical nameplate and material traceability documentation checks before FAT sign-off, clearing the way for offshore transport.

This project highlights the growing importance of flexible, certified deck equipment engineered to meet stringent offshore safety protocols without extending production timelines.

OUCO manufactures custom deck machinery, stiff boom cranes, and offshore handling equipment designed to meet major classification standards, including ABS, API Spec 2C, CCS, DNV, and BV. To learn more about customized marine cranes or discuss engineering requirements for upcoming offshore projects, contact us today.