A feeder container ship series on order in Germany features MacGREGOR hatch covers with a partial box design, offering improved construction, maintenance, and operational characteristics

Six 2,478 TEU container carriers ordered by Islamic Republic of Iran Shipping Lines (IRISL) will be equipped with MacGREGOR hatch covers featuring a partial box-girder design - which offers advantage during construction, maintenance, and operations. Access to the holds of the 33,900 dwt ships will be arranged by weathertight lift-away covers serving the 10 hatches, each complete outfit totalling 29 panels.

MacGREGOR developed the partial box design to make optimum use of steel materials used in lift-away hatch covers with longitudinal joints. In this type of cover the joint beam area is heavily loaded when a ship heels, but when the ship is upright all beams are loaded equally. This means that the joint beam contains steel material which is effectively redundant for part of the time. The partial box-design enables loads incurred when the ship is upright to be transmitted to the same areas as in a heeled situation - and hence the usage of material is optimised.

Another advantage is the high quality of painting that can be achieved underneath the cover, accessed through closed top plate stiffeners. This area can be blasted much more effectively compared with the usual angle-bar stiffeners. The dirt-collecting surfaces formed by angle-bar stiffeners are also avoided by the smooth-surface partial box construction. These dirt-collecting surfaces can be difficult to see, let alone clean and without cleaning can be a source of corrosion.

The ships have been ordered by the Tehran-based owner from the Aker MTW (four ships) and Kvaerner Warnow Werft (two ships) yards in Germany for delivery in 2003/2004 (see separate press release). Both yards are members of Norway's Aker Kvaerner Yards group. Efficient container handling (as well as removal and replacement of the hatch cover panels) will be executed by three MacGREGOR electro-hydraulic GL-2 wire-luffing deck cranes.