Title Enhanced logical engineering suggestion for Stacking load
Name Admin Date 2022-05-03
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To enhance the stacking load; this is an engineering reviewing / suggestion in engineering view points on the basis of actual technical logical calculation without overkill investment.

 

a) Gists:

 1) The main reason why stacking load noted as an issue

 2) The current trend by big shipping companies

 3) Technical idea to back up

 

 

Materially:

1) please refer to this attached because containers stacked into the vessel collapsed.

++ quoted++

Recently, the World Shipping Council (WSC), which represents the major ocean container carriers, contacted the IICL advising that they had noticed a discrepancy between the ISO stacking strength standard and the IMO’s CSC Annex 1 stacking strength regulation. When the ISO standard stacking strength for containers was increased from 192,000 kg to 213,360 kg in 2005, the IMO CSC stacking strength was not changed and has remained at 192,000 kg.

Therefore a discrepancy exists in the governing publications which has raised a possible safety concern, how to prevent a container with an stacking strength below 213,360 kg being erroneously placed on the bottom of a stack with a gross mass over the bottom container of 213,360 kg.

The WSC and BIC have prepared a draft paper (attached) that they intend to submit to the IMO at the upcoming CCC 6 meeting in London during the week of 9 September requesting that the CCC Sub-Committee “consider the information provided and take action as appropriate” meaning that the co-signers are recommending that the IMO CCC Sub-Committee member country representatives approve an increase in the CSC’s stacking strength to 213,360 kg, and then recommend to the IMO’s Maritime Safety Committee their approval of the increase.

The BIMCO and ICHCA have already agreed to co-sponsor the paper. The WSC is asking that the IICL also consider co-sponsoring the paper in a show of unity on the part of the container industry for improving safety on ships.

The WSC and BIC noted that while the ISO standard was updated 13 years ago, there are still containers in existence with stacking strengths below 213,360 in existence. You may recall that after the MV Annabella accident in 2007 where a reduced stacking strength container was placed in the bottom position of a heavy stack resulting in an under-deck collapse of the stack, ISO standard 1496-1 was revised to establish a container decaling program to reflect containers with stacking capacity under 192,000 kg. Unfortunately there is a small percentage, estimated at 1 to 2% of the leased fleet that have stacking strengths between 192,000 kg and 213,360 kg which may have to be remarked, upgraded or retired when the new regulation is implemented.

The IICL’s Technology Committee has been reviewing this matter since the email was received from the WSC. While there is consensus on the need to support safety by increasing the CCC stacking strength, there remain differing views on how to effectively identify containers with stacking capacities between 192,000 kg and 213,360 kg.

The WSC and BIC realized that the reduced stacking capacity remarking/identification issue could be disruptive to the industry, so they did not address the effective date for remarking/identification in this paper, opting for it to be worked out among industry and governmental representative participants in an IMO working or correspondence group.

It is expected that the IMO’s CCC 6 will establish such a Working Group or Correspondence Group to address the changes that may be required by this stacking strength change if approved. The IICL intends to participate on the relevant group when it is established to propose efficient and nondisruptive methodologies to be adopted on the implementation.

++ Unquoted++


As  diagramed; according to the above letter, a container positioned on the 1st tier of M/V " Annabella" whose stacking load strength was  low (86,400 kgs ) in comparison with the current design (97,200 kgs). consequently, the 1st tier container couldn't be withstood the upper weight.

According to IMO/CSC regulation updated:

In case of 86,400 kgs container is shipped into hold of the vessel, a special note has to be indicated on CSC plate to avoid this kind of accident. then a captain of Vessel can recognize it, treating it as a special attention / plan to stow.



2) currently, big shipping companies such as NYK, MSC, etc are to make a big sized vessel with reportedly 10~12 tiers stacking onto under-decks by enhanced strength of vessels' bottom tank top plates as well as simultaneously MGW of the container has been up-graded as 30,480 kgs, 32,500 krs, 34,000 kgs and 35,000 kgs.

In this view; please refer to stacking load increased with allowable Stacking mass for 1.8g respectively:




In these connection; please refer to several CSC plates as per different clients:


 

This is for 86,400 kgs stacking load
 






ܡThis is for 97,200 kgs of stacking load.
 

ܡܡThis is for high stacking load, 109,700 kgs like NYK.

3) To avoid any possible problem under increasing high stacking load / tiers on the vessel and to take a technical idea / countermeasure by change design in advance; shipping companies / manufacturers are to act technical countermeasure logically / mechanically and theoretically as below:

Frankly, manufacturers don't like to increase the stacking load voluntarily unless clients require it because of cost involved.

However, a special focus to increase stacking load / higher stacking on the vessel by shipping companies like NYK, MSC, etc; they are to discuss with manufacturers technically to modify the spec.

Besides, to update the stacking load, clients have to request manufacturer to test the stacking load increased from time to time to know its actual strength even though there's NO modification of the design subjectively.

FYI,

General the rear / front corner posts designs ( by 97,200 kgs per post ) are as follows:

Rear corner post:




Front corner post:
 
 


¢High stacking load design by NYK is as follow:


 

AS shown by diagrams above on colored as red, a special reinforcements plates are to be applied by clients' request. of course, special cost is to be added.

cost calculation:

Rear:  Steel plate:(50mm x2301mmx 4 x 2x @7.85)÷1,000,000x0.9$=$6,5

Front: steel plate: (50mmx 2301 mm x4mm x 2x@7.85)÷1,000,000 x 0.9$=$6.5

in addition: paint, shot, welding & wage:$2 x2( rear / front)=$4

Total: about $17 per unit is to be added.

 

Besides:

As you know, the corner casting strength is also very important against increased MGW / stacking load with design modifications. in this connection, according to ISO 1161 updated; the wall thickness has to be modified as 11mm against 9 mm existed.

However, ISO standard is just recommendation, but not mandatory. consequently, corner casting manufacturers haven't taken action pursuant to the new ISO standard.

As far as client is to increase stacking load / MGW / high tiers onto the vessel, clients have to pay a special attention to check / test the quality of the corner castings frequently to avoid any of possible accident because as you may know well, the casting manufacturers are to apply poor steel scraps to save cost.

FYI, for ISO new standard for the corner casting:

 



The bottom thickness of the top corner castings ( at the front side ) is 11 mm

 

 In closing:

To match key points with clients' technical expectation to increase MGW / stacking load to carry more containers onto vessel without any of accident; any design change with cost adding has to be economical without overkill and both enhancing by corner posts design modification and corner casting strength improvement is naturally essential.







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