June 2014: Safe practice for ships carrying timber deck cargoes - loop lashing
A number of global incidents have occurred when best practice methods have not been used to secure cargoes. These have resulted in injuries and the loss of cargo overboard. Any lashing practice must be able to overcome the transverse forces generated by the ship's rolling movement. If the cargo is poorly lashed and the cargo moves during the voyage, it can cause a ship to lose stability. At present, the most common practice for securing timber deck cargoes to a ship is top-over lashing.
Top-over lashing is a frictional lashing practice that applies vertical pressure that increases the friction force between the outer stows of deck cargo and the ship’s deck or hatch-cover. Top-over lashing as the sole securing practice for timber deck cargoes is sufficient only when the friction is very large or the expected transverse acceleration is very small. This practice is not recommended other than for vessels trading in restricted sea areas, inland or sheltered waterways.
Engineering analysis shows that loop lashing is superior to top-over lashing for security and safety when transporting timber deck cargoes throughout a sea voyage.
As a consequence of this, the International Maritime Organization (IMO) has discussed and reviewed its Code of Safe Practice for Ships carrying timber deck cargo. In 2011, the IMO revised regulation 5.4.1 in the Code of Safe Practice for Ships carrying timber deck cargo to include loop lashing as an optional practice to top-over lashing for securing timber deck cargoes.
MNZ recommends loop lashing as the safest and most secure practice for ships carrying timber deck cargoes throughout a voyage. Loop lashings are passed over the top-of-stow in opposing pairs to provide horizontal elements that best prevent the timber deck cargoes racking when considering all conditions at sea.
Loop lashing practices
To secure the timber deck cargoes by loop lashing, the lashing is drawn from the base of one side of the cargo, up and fitted across the top of cargo to a securing point at the top of the stanchion. Alternatively, the lower part of the lashing may be fastened to a securing point on top of the hatch-cover or deck underneath the cargo.
The ‘loop’ is then completed by rigging a second lashing in the opposing direction, so that the two lashings form one structure.
There are three practices of loop lashing that can be used to secure timber deck cargoes. These are:
- hatch-cover fixed
Any of the above loop lashing practices can be used to achieve the best safe practice for transporting timber deck cargoes on a voyage. The ship’s fittings may determine the loop lashing practice selected.
This is the fastest securing practice. Less securing material and time is involved to secure the timber deck cargoes than with traditional chain and wiggle wire top-over lashing.
This version requires hog lashing to be placed in addition and separately to the opposing pairs of loop lashing.
This version is fixed in a similar manner to hatch-cover fixed.
Safe practice tips
- Crane operators and ship operators should check, as a matter of good practice, before cargo handling commences, that all crane components are in good condition and there is no sign of damage or excessive wear to crane blocks
- Ship operators should take note of the crane manufacturer’s recommendations for modifications to crane blocks and undertake remedial action as they see fit. IHI suggest either an additional bolt, or additional plate is used to reinforce the cargo block.
- Competent persons and ship operators should ensure that if, after consideration of the manufacturer’s recommendations, modifications to crane blocks are carried out (either permanent or temporary modifications or any repairs), that this work is appropriately certified. Standards for testing, inspection and examination of cranes on ships are covered by Maritime Rules Part 49: Ships’ Lifting Appliances. In undertaking any testing, inspections, repairs or modifications of ships’ cranes, the requirements of Part 49 must be adhered to
- Crane operators should ensure that they adhere to the crane manufacturer’s specified operating parameters and loading limits at all times, and be aware of the potential for failure caused by incorrect lifting.
- Chapters 5 & 6. (2011). In Code of Safe Practice For Ships Carrying Timber Deck Cargoes. IMO.
Original source content - Safety Bulletin Issue 29, June 2014: Safe practice for ships carrying timber deck cargoes – loop lashing.
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