ship handling

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Container Stowage Plan affecting hull strength & stability of ship

Particular attention must be paid to the hydrodynamic design of container ships which operate at high cruising speeds. The tall, heavy deck loads cause problems with righting capacity. In order to ensure adequate stability, most all-container ships thus have to carry special solid or liquid ballast and/or be broader amidships.

The capsize risk of the vessels can be kept within acceptable limits by high values of the roll moment of inertia. Large ballast capacities and high power pumps are absolutely essential, both for trimming the ships and for offsetting longitudinal bending moments. Shipbuilders can tailor characteristics by selecting appropriate ratios between length, beam, molded depth, draft and other dimensions.

Carrying containers

The deadweight and hold capacity of container ships may also be stated in metric tons and cubic meters. The number of available slots for 20' or 40' containers, however, is more meaningful. TEU means "Twenty foot Equivalent Unit", while FEU means "Forty foot Equivalent Unit".

Standard loading conditions

Loading conditions to be examined for the purpose of assessing whether the stability criteria are met. For a cargo ship the standard loading conditions are as follows
  1. Ship in the fully loaded departure condition with cargo homogeneously distributed throughout all the cargo spaces and with full stores and fuel.
  2. Ship in the fully loaded arrival condition with cargo homogeneously distributed throughout all the cargo spaces and with 10% stores and fuel.
  3. Ship in ballast in the departure condition without cargo but with full stores and fuel.
  4. Ship in ballast in the arrival condition without cargo and with 10% stores and fuel remaining.

Stress Stability

The Master is responsible for making sure that at all loading conditions the ship satisfies the permissible Stress/Stability criteria. The Chief Officer is responsible for making the Stability/Stress/Trim calculations and for reporting the results to the Master.

Stability & Stress Calculations

The Chief Officer must review the pre-stowage plan . He must also review the final stowage plan presented to him by Stevedores latest before completion of loading/discharging operations. The actual values of Stability/Stress/Stack-weights are to be compared with the permissible values during the voyage (on departure/during voyage/on arrival) and must be reported to the Master in writing (Printout). This report must also include details for: The Master must satisfy himself that the above figures are within the permissible limits. If not, and no further improvement can be achieved by means of ballasting, the Master must demand from the Stevedores to arrange cargo changes. The Master must seek clarification in case the read draught is not in line with the calculated draught due to undeclared weights.

Stability calculations to obtain the GM and bending moments must be made for all sailing and arrival conditions and also for the worst possible condition to be experienced during the passage. The GM (fluid) must always be above the IMO minimum GM for that condition and the bending moments, shearing forces and torsional moments are within the required limits.

Copies of Stability calculations are to be signed by the Master and filed as appropriate. The Chief Officer shall calculate the shipís stability condition and print out to get Masterís signature every three days if sailing period is longer than the three days.

Trimming Tanks Free Surface

The free surface effect of trimming tanks and other ballast tanks in use must be taken into consideration when planning the loading/discharging operations. Wherever possible, ballast tanks must either be empty or fully pressed up.

Bridge Copy Of Stability Calculation

A copy of the stability calculations must be posted on the bridge and all deck and engine room officers made aware of the stability situation.

Departure Stability

A copy of the departure stability condition for each port is to be filed onboard. The Management Office may request a copy to be forwarded to the Office.

Effect Of Strong Winds

Masters and officers must bear in mind the effects of strong winds and/or ice accretion on high sided vessels, especially with seven or eight tiers of containers on deck.

Flume Tanks(Passive Roll Stabilisation Tanks)

Flume stabilisation tanks must be emptied or pressed up (in the case of FW) on arrival in port. If the flume tanks are to be used on passage, the final GM must be calculated having due allowance for flume tank contents and free surface effect.

Stack Weight Limitation

The Master must ensure that all Deck Officers are familiar with the contents of the Cargo Securing Manual, in particular the stack weight limitations for tank top, hatch covers and deck loading. When the final cargo distribution file is received, the Chief Officer must check and approve the stack weights on the loading computer to ensure they are in within safe limits. The Officer of the Watch must monitor compliance with the approved loading plan for which stack weights must be taken into account.

Layering Of Containers By Weight

Whenever possible and especially with deck containers, all efforts are to be made to layer the containers with the heaviest ones on the lower tiers. This assists in stability and reduces the strain on lashings.

Stability Computers

The Chief Officer is responsible for running, at quarterly intervals, a test condition and the results are to be compared with the published data approved by Class. A printout of the results is to be maintained on board for verification purposes. Whenever the vessel is empty the CO to make a draught survey calculation to identify the vessel light weights and compare the same with the light ship calculation from the shipyard newbuiliding

When considering acceptability of a container cargo stowage plan, the following factors/guidelines concerning hull strength & stability shall be taken into account:

Draft, Trim and Heel

IMO Intact Stability Criterion

Corrected GoM

Severe Wind and Rolling criterion

Visibility from Bridge

Propeller immersion

Shearing forces, Bending moments and Torsional moment

Other factors affecting Hull Strength and Stability as necessary

Container handling more info pages:

  1. Containership advantages

  2. Containership cargo stowage and planning

  3. Procedures and guidelines for dangerous cargo handling

  4. How to avoid irregular stowage of containers ?

  5. Measures against lashing failure

  6. Reefer container stowage guideline

  7. Care of Reefer container during sea passage

  8. Container ships procedures for securing for sea

  9. Deployment and monitoring of moorings and safety of crew

  10. Cargo securing procedure for container ship

Confirmation and record of securing

The following checklists shall be used to confirm the securing condition:

Cargo ships preparation for sailing

Checklist for Navigation in Heavy weather

Checklist for Departure

How to maintain Water tightness, Seaworthiness, Fire integrity and Security of ship ?

Securing your vessel for sea passage - when to check and what to check

Confirming stability & hull strength prior sailing

Collecting Information and Data for Passage Planning

Various Cargo handling

2 in 1 container operation in cargo hold

How to load 45 feet containers

Container damage in ''2 in 1'' cargo Operation

Containership operation detail procedure

  1. Definition of various containers in containership
    The exterior dimensions of all containers conforming to ISO standards are 20 feet long x 8 feet wide x 8 feet 6 inches high or 9 feet 6 inches high for high cube containers. Some of the most commonly used types are:Read more......

  2. Dimensions of various containers
  3. Containers are standardized cargo units. They are manufactured in a large variety of sizes and types, each designed to meet specific cargo and transportation requirements. Their length is usually 20 or 40 feet, although longer containers are used, principally in the US trade; these containers are 45, 48 and 53 feet long.
    Read more......

  4. Containership advantages : In principle they are boxes or containers within a box. These boxes or containers have dimensions of 2.60 x 2.45 m with lengths of 6.10, 9.15 and 12.20 m. Containers are made in steel, aluminium or GRP. They are also of refrigerated design, thus advantageous for long voyages between Australia or New Zealand and the UK. Read more......

  5. Containership cargo stowage and planning : When considering acceptability of a container cargo stowage plan, the following procedures / guidelines concerning cargo stowage shall be taken into account: Stacking Weights Restrictions, Lashing strength calculation, Dangerous goods stowage and segregation, Reefer Container Stowage , Out of Gauge Container Stowage , ....Read more......

  6. DG cargo handling - IMDG code guideline :The general provisions for segregation between the various classes of dangerous goods are shown in "Segregation table" (IMDG Code Chapter In addition to the general provisions, there may be a need to segregate a particular substance, material or article from other goods which could contribute to its hazard. Read more......

  7. How to avoid irregular stowage of containers ? Stowage plan must be checked for any irregular stowage like those mentioned here : Stacking Weights, Lashing Strength, Special Container Stowage, Over-stow of Containers, Dangerous Cargo Stowage & Segregation, 20 or 40 or 45 feet Compulsory Stowage Locations, Hatch Cover Clearance (High cube containers Under Deck ), Out of Gauge Container Stowage etc.Read more......

  8. Measures against lashing failure : Lashing strength of deck cargo shall be ascertained by using the appropriate lashing strength calculation software where provided. All resulting values for lashing strength must be within the tolerance limits prescribed by vessels classification society.Read more......

  9. Reefer container stowage guideline : Reefer containers proposed for stowage must be accompanied by a reefer manifest. This reefer manifest should contain information regarding Container No., Stow position, Commodity, Temperature and Ventilation status. Read more......

  10. Care of Reefer container during sea passage :Reefer containers require special care after they are loaded on board ship. These containers need to be supplied with power, monitored closely for proper function and repaired as required in case of malfunction. Read more......

  11. Container ships procedures for securing for sea :All movable items on deck, inside accommodation and in E/R spaces, including under-deck passages and steering flat are firmly secured. Any unsecured items, in heavy weather, risk not only being damaged themselves, but could also pose a danger to vessel safety by violent contact with sensitive equipment or fittings.Read more......

  12. Deployment and monitoring of moorings and safety of crew :The Companyís Risk Assessment procedure shall be utilized to ensure that during all anticipated mooring arrangements and equipment use, the safety of crew is ensured. Read more......

  13. Cargo securing procedure for container ship :Securing equipment will vary depending on the type of ship but is likely to include; Twistlocks Lashing bars Turnbuckles Extension hooks Stacking cones (single and double) Twist Stackers Lashing D rings Shoes/Sockets for base twistlocks ...Read more......

  14. Containership operation -Check items upon completion of repair works : As the nature of container ship operation, itís tread to be lack of stability, due to Top Heavy Load, the Master shall always take special attention for her stability. Also the Master should remind factors to cause reducing stability more such as Alternating course with Big angle of Rudder, Towing by tugs at the scene of Berthing / Un-berthing, etc. Read more......

  15. Containership operation -Cargo ventilation requirement : Cargo holds of container ships are fitted with two basic types of ventilation systems, namely natural and mechanical. Mechanical ventilation could be of either the supply or the exhaust type. Read more......

  16. Containership operation -How to avoid wet damage ? :Water entered into vessel cargo holds may cause wet damage to the cargo inside containers especially stowed on the bottom, unless the bilge water is drained in a proper and swift manner. Read more......

Other info pages !

Ships Charterparties Related terms & guideline
Stevedores injury How to prevent injury onboard
Environmental issues How to prevent marine pollution
Cargo & Ballast Handling Safety Guideline
Reefer cargo handling Troubleshoot and countermeasures
DG cargo handling Procedures & Guidelines
Safety in engine room Standard procedures
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