The standard 40ft containers (FEU) are stowed in cell guides without any lashing devices. If there is also a certain number of 20ft units (TEU) available at all time, the creation of a hold with 20ft guides may be considered. In most cases, 40ft cell guides are installed exclusively and TEUs are stowed in the 40ft bays. This, however, needs securing job.
There are basically 3 systems to stow TEUs into 40ft cell guides:
1. Side support stowage system.
The containers are connected with double stacking cones in a transverse direction. At the longitudinal bulkhead, you have either a fixable installed guide rail or foundations for buttresses that take up the load. This is the most conventional system. The containers can be loaded/removed only tier wise.
2. Stowage with anti-rack spacers.
The containers are connected longitudinally with so called “anti racking spacers”, thus creating out of two 20ft containers one 40ft-unit. This system avoids side supporting, that means a 20ft stack can neighbour a 40ft stack and there are no foundations or rails in the longitudinal bulkhead. The disadvantage is that the containers have to be loaded/ removed also tier wise.
3. Mixed stowage
The third system becomes more and more popular with regard to the a.m. disadvantages: the mixed stowage. Starting from the tank top you can stow from one to four tiers 20ft containers (secured only by single stacking cones) and top them up with at least on FEU. This system allows stack wise loading/discharge. The only disadvantage is that the stackweight of the TEUs is reduced a bit to about 60 ton.
The new size containers make another problem. Most easily they can be stowed on deck installing additional foundations on hatch covers.