Transfer Lift		Splash Zone
Subsea Heave Compensation		Overload Protection

Cranemaster on the splash zone
Cranemaster lifting spool through the splash zone

Cranemaster Subsea
Cranemaster used to install a submerged turret loading buoy (STLTM).

Cranemaster Applications

Under the trade name Cranemaster™, Ernst-B. Johansen AS is the world leader in the design and manufacture of passive heave compensators for splash zone and subsea lifts as well as hydraulic shock absorbers for offshore cranes. The following sections describes Cranemaster's standard applications.

Transfer Lifts

A typical example of a transfer lift occurs when a load needs to be lifted from a supply vessel by the crane mounted on a semi submersible rig. The problem encountered in this lifting situation is the dynamic load felt by the crane due to the vessels motion in the waves in relation to the rig. Peak loads and the possibility of re-contact with the load being lifted may represent a safety threat. Cranemaster will absorb these peak loads - taking up the energy over a longer period of time.
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Cranemaster absorbing peak loads
The Cranemaster is a well proven and extremely cost efficient system designed to reduce the dynamic loads and thereby increasing the lifting capacity of offshore cranes. Based on the original crane specifications installing a Cranemaster may double and in some cases even triple the offshore lifting capacity.

Ernst–B. Johansen A.S is certified by Lloyds and DnV to calculate temporary enhanced load charts for offshore cranes incorporating Cranemasters. These enhanced load charts are valid for up to 6 months and can be permanently certified by performing a dynamic test.

Cranemasters for offshore cranes can be permanently installed on the crane boom, on the whip line complete with swivel, hook and wire connections or on the main hoist complete with shackles, slings and hook. The standard Cranemaster range is from SWL 2 to 500 tons, or they can be custom made to fit your requirements.

Splash Zone

The splash zone introduces a unique set of problems easily solved by including a Cranemaster unit in an offshore lift. When items with large surface areas, typically GRP covers, are lowered through the splash zone, the dynamic forces due to the movement of the vessel, waves, slamming, drag and added mass will all expose the crane as well as the load being lifted to severe loads.
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For these lifts, the Cranemaster will normally be adjusted so that the piston rod initially extends to about 2/3 of full length when in air, and retracts to about 1/3 when submerged. As the piston rod is extended the Cranemaster will be free to cycle, instantly responding to its surroundings and catching slack wire when lifting through the splash zone. When the load is fully submerged the Cranemaster will act as a passive heave compensator and reduce the vertical displacement and thus landing speed when installing the covers subsea.

Since active heave compensators are not effective when lifting through the splash zone, including a Cranemaster unit in your lifting system may substantially increase your weather window, reduce costs and increase safety.

Subsea Heave Compensation

Cranemaster is the ideal tool to increase the weather window for subsea installations. When working mainly as a subsea heave compensator, the unit will be adjusted to cycle around 1/3 to ½ of full stroke - leaving the load in a more stable state as the Cranemaster absorbs motion and vibrations transmitted by the wire.
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Since the load being installed will be exposed to less dynamic motion it will be possible to control the vertical displacement and landing speed, and thereby providing a safer installation.

In addition to acting as a passive heave compensator, the unit can also be adjusted to reduce or avoid resonance.

With rental Cranemasters ranging from SWL 25 to 400 tones and strokes from 1000 to 4300mm, we can adjust our product to meet a wide range of lifting situations down to water depths of 3000 meters. For further flexibility we can also use Cranemasters in parallel to increase the load capacity, or in series to increase the stroke.

Overload protection

The Cranemaster offers a perfect solution for protecting the crane from overload both during installation, but also when retrieving objects from the seabed. The unit will in these cases normally be adjusted to initially be at zero stroke. When retrieving subsea structures the Cranemaster will be able to take up the vessels motion topside and protect the crane from overload. The unit uses its spring force provided by the preset Nitrogen pressure to ensure a controlled retrieval of the subsea equipment from its installed position.
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When the crane starts lifting, the increased tension in the crane wire will make Cranemaster extend until the tension of the crane wire exceeds the force necessary for pulling the object out of the seabed. Then in turn Cranemaster will ensure a controlled retraction, catching up slack wire and acting as a passive heave compensator as the object is lifted towards the surface.

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