A ship sailing in a seaway has six degrees of motion: surge, sway, heave, roll, pitch and yaw. The boat itself bends and twists as the waves pass by. The hatch cover moves relative to the hatch opening and the container stack moves as the gap in the lashing device is occupied. Only the lashing system can resist these movements and try to keep the shipping container on board.

The lashing system is tested in inclement weather and failures can result in the loss of shipping containers. In fact, the increasing number of containers falling into the water has caused concern across the maritime industry. Cargo claims rise and floating containers pose a threat to navigation. Captains need to understand the pros and cons of container securing systems. The captain must know what steps can be taken to prevent the loss of the container.

The vessel needs to be suitable for receiving containers and its lashing equipment is in good condition. Lashing areas need to be safe places for crew and stevedores to work.

Here's our guide on container securing systems, why lashings fail, and how to minimise damage.

Container ship cargo securing devices include portable securing devices and fixed securing devices. Fixing accessories are stacking cones, foundations, deck foundations, lashing plates, lashing eyes, lashing pots, D-rings. Fixtures are integrated in the hull structure or mounted on double bottoms or hatch covers. Loose fittings are twist locks, stackers, bridge fittings, tension/pressure elements, wrenches, lashing rods and turnbuckles.

An open turnbuckle combined with a multi-knob rod is used to secure shipping containers of different heights with one rod length. For quick adjustment and secure connection, the turnbuckle is equipped with a sliding nut. A 50 ton breaking load system (rod diameter 26 mm) is used almost exclusively.

Periodic inspection and maintenance of the ship's cargo securing arrangements must be carried out. These will include routine visual inspection of in-use components, lubrication of fixtures, repair of damaged fixtures, and separation and rejection of damaged/unusable fixtures.

An appropriate number of portable fixtures should be kept on board at all times. Generally, the number of securing devices required on board is determined by the figures provided in the ship's cargo securing manual (maximum capacity loading). Alternatively, if the ship operator requires a smaller number of cargo securing devices to be kept on board, that number should be maintained.

In this case, the factor considered is usually the quantity of goods transported in a given trade. However, in any case, cargo that cannot be secured in accordance with the Cargo Securing Manual due to insufficient securing devices shall not be carried.

Various lashing devices that are common onboard containerships are explained below:

Twist lock 

A mechanical locking device for the corners of a container. Traditional twist locks are manually locked and unlocked by means of a lever. A twist-lock base that rotates a movable part about a vertical axis to lock the device and container to a hatch or to another container. Reverse action effect unlocked.

The semi-automatic twist lock is automatically locked and manually unlocked by the lever. The fully automatic lock is placed in the lower corner of the dock container. They automatically lock when the container is placed on top and automatically unlock when the container is lifted.

The D-ring is the lashing point in the shape of the letter D. They can be welded to the deck of a boat and used as lashing points to secure cars, trailers and various cargoes with chains and mesh lashings. We offer MBL 4 ton (carlashing), 20 ton, 36 ton, 50 ton and 67 ton D-rings.

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