Lifts in air
Lifts in air, either during loading or offloading of barges or supply vessels. Cranemaster can help to reduce the dynamic amplification factor (DAF) in all lift situation, which will protect the crane and the lifted structure. Cranemaster will in many situations also reduce the contact force during landing, and thereby protect the structure.
- Protection of crane and lifted payload through shock absorption at lift-off.
- Enabling crane to maintain its lifting capacity at increased wave heights.
- Revised load chart with improved capabilities, approved by DNV-GL.
- Ship stability – prevention of heeling during landing of heavy loads.
- Cranemaster will in many situations also reduce the contact force during landing, and thereby protect the structure.
Due to the low drag in air, Cranemaster will not reduce landing speed, as it will during subsea operations.
OFFLOADING FROM A SUPPLY VESSEL OR BARGE
Simulation of a lift-off situation from a barge. The crane is sitting on a fixed platform, but the principles are the same also if the crane is mounted on a moving vessel.
Manifold weight: 50T • Significant wave height (Hs): 2.0m • Wave period (Tz): 8sec. • Hoisting speed: 0.3 m/s.
Without Cranemaster: Significant snap load during lift-off, in this case around 85T. This corresponds to a DAF of 1.7.
With Cranemaster: Snap load is avoided, and the DAF is reduced to around 1.1.
For cranes with a slow lifting speed, there may be a risk of re-contact between the structure and the barge. Some Cranemaster units can be equipped with a quick-lift system which will pull in the Cranemaster piston and thereby avoiding the re-contact.
LOADING STRUCTURE (LANDING) ON A SUPPLY VESSEL OR BARGE
Simulation of landing a 50T structure on a supply vessel. When a structure is landed or a supply vessel or a barge, Cranemaster will normally reduce the initial contact force. In addition, for cranes with a low lifting/lowering speed, Cranemaster will also efficiently reduce the potential snap load after landing, caused by slack wire followed by a re-lift.
Lifting speed: 0.1m/s • Significant wave height (Hs): 2.5m • Wave period (Tz): 10sec
Without Cranemaster: DAF in crane wire = 1.8 Max. landing force = 130T
With Cranemaster: DAF in crane wire = approx. 1.1 Max. landing force = 60T
LANDING ON A FIXED PLATFORM
Simulation of landing a 50T structure on a fixed platform. If a crane vessel lands a structure on a fixed platform, there is risk of re-lift after the initial landing, particularly for slow lowering speeds. This re-lift may create a significant snap load.
Lifting speed: 0.1m/s • Significant wave height (Hs): 2.5m • Wave period (Tz): 9sec
Without Cranemaster: DAF in crane wire = 1.6
With Cranemaster: DAF in crane wire = approx. 1.1
PLATFORM CRANES – IMPROVING LOAD CHART
For cranes mounted on fixed or semi-fixed platforms, Cranemaster can be used to improve the weather windows for lifts from a supply vessel. The main effect given by using Cranemaster during the lifting operation in transfer lifts is to enable the crane to maintain its lifting capacity at increasing wave height. This is possible through an improved and formally approved Load Chart for the crane. An offshore crane will typically be able to keep its full onboard capacity up to a wave height (Hs) of around 2.0-2.5 meters. For higher waves its capacity will be significantly improved compared to the original load chart as seen in the example below.
Green bars shows original crane capacity (load chart) for a specific radius as function of the significant wave height. Blue bars show the resulting capacity using a Cranemaster unit.
A technical description of how this works can be found in our Introduction Guide for dynamic Load Chart with Cranemaster. The revised load chart approved by a classification body (typically DNV) will be prepared by Cranemaster prior to the lift.
REDUCING DAF ON LOAD
For stiff cranes, the dynamic amplification factor (DAF) resulting from wave induced movements, may be very high even for small wave heights. With a Cranemaster unit mounted, the DAF is typically reduced to 1.3 or below for sea states up to Hs = 2.0-2.5 m. Please contact us for preliminary calculations.
Cranemaster CM1-100T-1000-A protecting crane and load: