ONLINE CALCULATORS TOWING & SEAFASTENING
CARGO SEA FASTENING CALCULATION WHILE TRANSPORTATION ON BARGE
WHAT IS SEAFASTENING?
Sea fastening is fastening cargo while transportation in sea. When moving cargo by sea it must be secured such that any movement which can damage cargo or ship must be avoided. Any major movement of cargo might result in stability problem which will jeopardize vessel,cargo and crew onboard.
Different cargoes will have different type of securing arrangement based on shape,size and carrier vessel.
NORMAL CARGO SEAFASTENING
CONTAINER SEAFASTENING
Sea fastening of containers in container ship is done by stacking the containers in vertical guide rails or by stowing them in stacks or blocks, the containers being connected together and fixed to parts of the vessel. The containers themselves are in the stack secured directly to the deck by bottom stackers or bottom twistlocks. Within the stacks, are located intermediate stackers or twistlocks, bridge fittings or linkage plate. Bottom stackers are “no locking” devices, which hold the container in position.
PIPE TRANSPORTATION SEAFASTENING
Pipes are transported by barges in pipe laying location where pipe laying vessel will be laying these pipes. Pipes are stacked onto each other and secured by stanchions and wire ropes. Padeyes are weldel on top of these stanchions and wire with shackles are wrapped around these pipes.
Sea fastening of Pipes
JACKET SEAFASTENING
Jackets are normally transported by barges for yard transfer or launching. These jackets are fastened on barge
TOPSIDE SEAFASTENING
TYPICAL SUPPORTS FOR SEAFASTENING
SEAFASTENING STANCHION OR BRACES
PLATE TYPE STANCHION FOR SEAFASTENING
SEAFASTENING LASHING STRAP
SEAFASTENING LASHING PADEYES
SEAFASTENING TAUT WIRE
SEAFASTENING DOG PLATE
SEAFASTENING GRILLAGE
SEAFASTENING PULLING LUGS DESIGN
WHAT IS STOWAGE PLAN DURING SEAFASTENING
SEAFASTENING LOADS DURING TRANSPORTATION
If neither a motions study nor model tests are performed, then for standard configurations and subject
to satisfactory marine procedures, the following motion criteria may be acceptable.
a. Roll and pitch axes shall be assumed to pass through the centre of floatation.
b. Heave shall be assumed to be parallel to the global vertical axis. Therefore the component of heave parallel to the deck at the roll or pitch angles shown above is additive to the forces caused by the static gravity component and by the roll or pitch acceleration.
c. Phasing shall be assumed to combine, as separate loadcases, the most severe combinations of
d. For Cases 7 and 8, the departure shall be limited to a maximum of Beaufort Force 5, with an improving forecast for the following 48 hours. The voyage duration including contingencies,should not be greater than 24 hours.
e. For Cases 9 and 10, the criteria stated is given as general guidance for short duration barge towages and vessel transports. The actual criteria should be agreed with the GL Noble Denton office concerned, taking into account the nature of the vessel or barge and cargo, the voyage route, the weather conditions which may be encountered, the shelter available and the weather forecasting services to be utilised.
f. For Case 11, the design loading in each direction shall be taken as the most onerous due to:
g. The additional heel or trim caused by the design wind should be considered. For most transports, it is permissible to omit the effects of direct wind load when computing the forces on the cargo (see Section 8.3). If the total effect of the wind on the cargo due to direct loading and wind heel are more than 10% of the loads from the default motion criteria, then they shall be
added.
Use below online calculator and change values in box to get motion loads as per NDI criteria.
b. Heave shall be assumed to be parallel to the global vertical axis. Therefore the component of heave parallel to the deck at the roll or pitch angles shown above is additive to the forces caused by the static gravity component and by the roll or pitch acceleration.
c. Phasing shall be assumed to combine, as separate loadcases, the most severe combinations of
- roll + heave
- pitch + heave
d. For Cases 7 and 8, the departure shall be limited to a maximum of Beaufort Force 5, with an improving forecast for the following 48 hours. The voyage duration including contingencies,should not be greater than 24 hours.
e. For Cases 9 and 10, the criteria stated is given as general guidance for short duration barge towages and vessel transports. The actual criteria should be agreed with the GL Noble Denton office concerned, taking into account the nature of the vessel or barge and cargo, the voyage route, the weather conditions which may be encountered, the shelter available and the weather forecasting services to be utilised.
f. For Case 11, the design loading in each direction shall be taken as the most onerous due to:
- 0.1g static load parallel to the deck, or
- the static inclination caused by the design wind, or
- the most severe inclination in the one-compartment damage condition.
g. The additional heel or trim caused by the design wind should be considered. For most transports, it is permissible to omit the effects of direct wind load when computing the forces on the cargo (see Section 8.3). If the total effect of the wind on the cargo due to direct loading and wind heel are more than 10% of the loads from the default motion criteria, then they shall be
added.
Use below online calculator and change values in box to get motion loads as per NDI criteria.
Click to set custom HTML
SEA FASTENING DESIGN
In this context, seafastenings include any grillage, dunnage, cribbing or other supporting structure, roll,pitch and uplift stops, and the connections to the barge or vessel.
- Seafastenings shall be designed to withstand the global loadings.
- Seafastenings shall be designed to accept deflections of the barge or vessel in a seaway, principally due to longitudinal bending.
- Where longitudinal bending is a consideration, suitable seafastening designs include Chocks which allow some movement between the barge and cargo.Pitch stops at one point only along the cargo, with other points free to slide or deflect longitudinally.Vertical supports at only 2 positions longitudinally.An integrated structure of barge-seafastenings-cargo, capable of resisting the loads induced by bending and shear.
- For towed objects such as FPSOs, which may have permanently installed modules with piping or other connections between them, there should be adequate flexibility in the connections to avoid overstress. It should be noted that the transport wave bending condition may be more severe than the operating condition. In long modules carried as cargo, internal pipework should be similarly considered.
- Grillage and seafastening design is frequently influenced by the load-out method. Cargoes lifted onto the transport barge or vessel, or floated over a submersible barge or vessel, are frequently supported by timber cribbing or dunnage to distribute the loads and allow for minor undulations in the deck plating. Cargoes loaded by skidding normally remain on, and are seafastened to, the skidways. Cargoes loaded out by trailers normally need a grillage structure higher than the minimum trailer eight. The grillage or cribbing height must allow for any projections below the cargo support line.
- Welded steel seafastenings are preferred, but for smaller cargoes, typically of less than 100 tonnes,chain, wire or webbing lashings with suitable tensioning devices may be acceptable. Chain binders,ratchets or turnbuckles shall be tensioned before departure to spread the load between the seafastenings and secured so that they cannot become slack. Lashings should be inspected regularly and after bad weather to ensure that tension is maintained. Wire lashings are not recommended for unmanned transportations.
Plan view of Cargo Sea fastening
|
Profile view of Cargo Sea fastening
|
SEA FASTENING SLING CHECK
Horizontal forces and uplift forces are taken by the slings, and the downward heave force is taken by the barge.
If configuration of slings are symmetrical in all quarters,so most loaded slings can be selected for MBL check. As in shown above arrangement,sling 7 and 8 are most loaded slings.
Basic geometry of barge and sling shall be used to determine angle between barge plane and sling,between roll direction and sling and pitch direction and sling. Further loads acting on any single sling can be calculated by equilibrium equations.
Load acting on any particular sling shall be less than corresponding MBL.
If configuration of slings are symmetrical in all quarters,so most loaded slings can be selected for MBL check. As in shown above arrangement,sling 7 and 8 are most loaded slings.
Basic geometry of barge and sling shall be used to determine angle between barge plane and sling,between roll direction and sling and pitch direction and sling. Further loads acting on any single sling can be calculated by equilibrium equations.
Load acting on any particular sling shall be less than corresponding MBL.
SEA FASTENING PADEYES CHECK
Click to set custom HTML
GRILLAGE AND SEAFASTENING DESIGN DURING TRANSPORTATION AND MATING
Strength of Grillage Members during Load-Out, Transportation and Float-over operations shall be verified.
Sea fastening members shall withstand loads during transportations and perform under deck Strength check of transportation vessel during Load-out, Transportation & Float Over Process.
Design Basic of Grillage and seafastening
Structural Analysis during Load out operation, during Transportation and Float over Operations shall be done for structure verification.
Load Out Operations
Load out FEM analysis shall be performed to check the structural integrity of both grillage designs and under hull deck strength.
Transportation Analysis
Transportation Analysis shall be based on the results of Stability and motion Analysis during Transportation. Motion Data shall be used for Acceleration and member forces on Sea fastening member . Among Motion load cases, maximum system load cases on each roll and pitch cases shall be applied on sea fastening members and skid beam area.
Float-Over Operations Analysis
Float over Analysis shall be checked for grillage members and Hull structure to have adequate strength against the loads from Jack unit during Float Over operation. Max Vertical and lateral load shall be taken from Mating Load Analysis.due to the structural strength, Limit of Max Vertical and Lateral load during Float-Over operations can be defined based on the strength limitation of structures.
