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Loading & Lashing Requirements for 2 in 1 (Two in One) in a Containership

Containership Cargo handling operation involves numerous complexities. To accommodate all container as booked, prevent slot missing, and at the same time for a quick turn around terminal planners often consider loading 2 in 1. The term 2 in 1 operation means when two 20' units loaded in one 40' slots (cell) under the deck.

Before doing such a loading operation, the ship's planner should confirm that the terminal staff is aware of the vessel's lashing system. For such a loading under the deck, twist stackers, or equivalent lashing gear generally need. However, it also involves some associated risk of ship structural or cargo damages.

Explained below, two very typical kinds of damages may result from 2 in 1 loading operations if not planned and executed carefully. Firstly, as per the Cargo securing manual, some vessels will require to place sliding base cones at tank top for loading two 20' bottom containers in hold. When changing from 40' stowage to 2 x 20' stowage or vice versa, stevedores will have to go down inside the hold for inserting/removing sliding base cones as required. If sliding base cones are not inserted before loading 2 x 20’ containers, the stack will not be secure and may be liable to shift enroute.

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Alternatively, if sliding base cones are not removed before loading 40' containers (after discharging 2 x 20' containers), middle parts of bottom rails of the 40' containers will be bent / damaged by these base cones (“protrusions”).

container 2 in 1 loading
Container 2 in 1 loading

Secondly, damages may occur due to 20' containers not being appropriately set into the base cone. If a 40' cntr is loaded over a stow of 2 x 20' containers under-deck, this 40' cntr will be damaged if the 20' boxes below are not correctly set on the base cones and therefore protruding upwards. Whenever C/Off receives pre-stow plan from the terminal and notices the stowage change from 40' to 2 x 20' or vise versa; he has the responsibility of blowing the whistle to call cargo watch personnel and terminal's attention to the setting/removing base cones in the hold. Cargo holds where 2 in 1 operation are in progress, must be monitored by Cargo watch personnel and they must be familiar with the peculiarities of such operation and possible damages that may result.

Vessels' cargo securing manual and loading manual shall be consulted to obtain such information as to maximum tiers of 20' centers that may be loaded under-deck before capping by a 40' containers. Any other stipulated restrictions also must be complied with.

20 feet & 40 feet mixed loading
20 feet & 40 feet mixed loading

The abbreviation "FEU" is occasionally used for the "Forty-foot Equivalent Unit" and refers to a 40ft container. A 40ft container comprises 2 TEUs (Twenty-foot Equivalent Unit, 20ft container). Therefore: 1 FEU = 2 TEU.

Containers are rectangular box-shaped units of cargo. It is easy to stow them in classical block stowage both on and below deck. A ship-specific lashing manual approved by the classification society is a guide for ship officers to load and secure containers on deck. All boxes on deck are secured with twist locks and lashings that usually consist of steel rods and turnbuckles.

When containers are carried below deck, the containers are slotted into cell guides on a cellular container ship, or sit on the tanktop, joined together with stacking cones, in the holds of a dry cargo ship. Containers can easily be stowed in box-shaped holds; it is more difficult to carry them in the holds of a dry cargo ship fitted with side hopper tanks, in which case, buttresses may be fitted.

When carried within a cell guide framework, no further external support is generally required. When 20-foot containers are stowed below deck in 40-foot cell guides, it may be beneficial to overstow the 20-foot containers with a 40-foot container. The Cargo Securing Manual should be consulted before loading.

container cell guide
container cell guide

Containers carried on deck may be secured by twist locks alone, provided the stack is not more than two containers high. When containers are carried three high, twist locks alone may be sufficient depending on the weight of the boxes. The twist locks or cones resist the horizontal movement of a deck stow. The pull-out strength of the twist-lock prevents the lifting of containers in extreme seas. The limitation of a twist-lock only stow is often the racking strength of the vessels. For stows of more than three boxes high, lashing rods are fitted because they provide additional racking strength.

In the early days of containerization, lashings used to fit vertically to resist tipping. However, it soon became apparent that it is more effective to arrange the lashings diagonally so that the container and the lashings work together to resist racking forces. The usual arrangement is to fit one tier of lashings, placed diagonally within the width of the container, with the tops of the lashing rods placed in the bottom corner castings of the second-tier containers. It is called 'cross-lashing.' An alternative arrangement, with the lashing rods located outside of the width of the container, is called 'external lashing,' which is often used for high stacks and lashed from a two-tier lashing bridge.

(Further Reading: A masters guide to container securing by STANDARD P&I CLUB)

Related Information:

How to load maximum number 20 feet container on deck ?

What are the extra precaution should be taken prior loading a 45 feet container on deck ?

Our additional pages contain somewhat larger lists of resources where you can find useful informations

Container handling more info pages:

  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.
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  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 Company’s 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, it’s 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......

ShipsBusiness.com is merely an informational site about various aspects of ships operation,maintenance procedure, prevention of pollution and many safety guideline. The procedures explained here are only indicative, not exhaustive in nature and one must always be guided by practices of good seamanship.

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Oceangoing Cargo Ships Safety & Operational Matters