Gantry and Overhead Cranes

Gantry and overhead cranes travel on fixed rails and lift within one working area of a drilling unit. The Category covers BOP and riser gantries on floating rigs, pipe deck gantries, engine room and pump room bridge cranes, and workshop monorails with electric chain or wire rope hoists. Runway geometry and the vessel motions a crane was designed for decide reuse more than its nominal capacity.

Operating principle

A bridge girder, or a pair of girders, spans the working area on end carriages that run along runway rails. A trolley carrying the hoist runs across the girder. On a gantry the girder stands on legs that run on deck-level rails. On an overhead crane it runs on elevated runway beams. A monorail is a single beam with a hoist trolley under it.

On a floating rig the crane must hold position against heel, trim and roll. Some travel drives use rack and pinion instead of wheel friction for that reason, and storm locks pin the crane to the runway for transit.

Configurations

Type	Typical duty	What sets it apart
BOP gantry	Moves the stack between setback and well centre	Tandem hoists, synchronised control, creep speed
Riser gantry	Picks riser joints from the riser hold	High cycle count, motion-rated design
Pipe deck gantry	Moves tubulars and bundles	Long travel, often outdoor exposure
Engine room bridge crane	Engine, generator and pump overhauls	Low headroom, light duty
Workshop monorail	Small loads on a fixed path	Often a standard chain hoist

Key specifications

Parameter	Why it matters	Typical classes or units
SWL per hoist and combined	Tandem lifts need a combined rating	t (short tons)
Span and rail gauge	Must match your runway exactly	m (ft)
Lift height and hook approach	Decide what the hook can reach	m (ft)
Duty classification	Shows how hard it was designed to work	ISO 4301-1 classes A1 to A8, FEM 1.001
Design motions	Heel, trim and acceleration it can operate in	degrees, m/s²
Hazardous-area rating	Electrics on a BOP deck may sit in a zone	Zone 1 or 2, gas group, T class

Standards and certification

EN 15011 covers design of bridge and gantry cranes, and ISO 4301-1 or FEM 1.001 classifies their duty. Neither covers vessel motion. On a classed unit, DNV-ST-0378, the ABS Guide for Certification of Lifting Appliances or equivalent class rules add design loads for heel, trim and accelerations, plus the stowed condition at sea. A crane built for a shore workshop needs a design check against those loads before class will accept it offshore.

In service, LOLER, NORSOK R-003 or your flag state's rules set thorough examinations, usually at least every 12 months.

Failure modes and inspection

Runway and wheels. Check rail alignment and rail head wear, wheel flange and tread wear, and signs of crabbing. Measure tooth wear on any rack and pinion drive.
Structure. Run magnetic particle inspection at leg-to-girder and end carriage connections, where roll-induced side loads concentrate.
Storm locks, end stops and buffers. Look for bent pins, cracked brackets and worn latch faces.
Hoists. Assess wire rope against ISO 4309 or gauge load chain for wear and stretch. Check drum grooves, sheaves, hook throat opening and every brake, including any secondary drum brake.
Electrics. Check collector rails or festoon cables for corrosion, and read the drive fault log.
Function tests. Prove limits, anti-collision, overload protection, hoist synchronisation and emergency lowering.

Documentation

Design calculations stating the vessel motion criteria
Class certificate or certificate of conformity
Last proof load test and thorough examination reports
Rope or chain certificates
Electrical drawings, drive parameter backup and software version
Spare parts list and modification history

Integration and compatibility

A BOP or riser gantry is designed around one vessel's runway, rail section, end stop positions and handling sequence. Check its interlocks with the BOP carrier, moonpool doors and any other crane sharing the runway. Match the travel and hoist drives to your switchboard voltage and frequency. Older drives may need replacing simply because spares are gone.

Refurbishment and recertification

Typical work covers new wheels and rails, re-roping or new chain, brake overhaul, a drive retrofit and a proof load test with class attendance. A used BOP or riser gantry fits best on a sister vessel with an identical runway. Engine room and workshop cranes are more interchangeable, and Konecranes, which also owns the Demag brand, is a common maker. For equipment that moves loads across the moonpool, see moonpool trolleys and carts.

FAQ

Frequently asked questions

Can a used BOP gantry crane be fitted to a different drillship?

Only if the runway, span, rail section, lift height and handling sequence match, which usually means a sister vessel. On any other rig, engineering must check the structure, rails and interlocks, and the crane needs class approval for the new installation and a proof load test.

Can an onshore overhead crane be used on a floating rig?

Only after a design check against the vessel's heel, trim and accelerations. Shore cranes built to EN 15011 assume a level, still runway. Class rules for offshore lifting appliances add motion loads, storm locks and a stowed condition, and the crane may need structural or brake changes to pass.

Why do gantry cranes on floating rigs need storm locks?

Storm locks pin the crane to its runway so vessel roll and pitch cannot drive it along the rails. Travel brakes alone may not hold a heavy gantry at large heel angles. Check that locks, end stops and buffers are intact and that the crane parks in its designed stowed position.

What does the duty class of an overhead crane tell me?

The duty class shows how many cycles and how heavy a load spectrum the crane was designed for. ISO 4301-1 uses classes A1 to A8, and FEM 1.001 uses a similar scheme. A light-duty engine room crane put to daily production use will wear its hoist and structure out early.

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