2003-11-13
Folding hatch covers from MacGREGOR with special design features and sealing systems are specified for the innovative Diamond 53 class handymax bulk carriers building in China for overseas ownersResponding to cross-industry calls for safer and stronger bulk carriers, the Diamond 53 class was jointly developed by Danish naval architects Carl Bro and the Cardiff, Wales-based Graig shipping group, which have a joint venture design company in Shanghai.

The geared 53,000 dwt design was evolved after extensive discussions with charterers on operational requirements and consultation with DNV on structural and regulatory issues, the key considerations being:

• economical operation and maintenance
• loading flexibility and robustness
• safety and hull integrity
• environmental friendliness
• future IMO/IACS regulations for such tonnage.

Numerous structural and operational merits are cited for the resulting wide-hatch design which features a complete double hull in the cargo holds forming a second barrier against accidental water ingress and substantially strengthening the hull. A cargo capacity of 64,000m³ is provided in five holds served by four 36 tonnes-capacity cranes.

Major operational cost savings, with significantly enhanced safety and environmental protection, have attracted orders from leading operators for Diamond 53 bulkers to be built in Chinese yards.

Cargo handling efficiency and security are enhanced by MacGREGOR high-stowing end-folding hatch covers, each set comprising 2+2 panels arranged fore and aft of the holds to yield the following clear openings: 19.2m long x 20.8m wide (No 1 hatch) and 21.6m long x 22.4m wide (Nos. 2-5 hatches). The weathertight covers are operated by external hydraulic cylinders and manually cleated.

A double-skin steel construction facilitates cleaning of the covers, and their top and skirt plates are specified with scantlings that are greater than the minimum. Hatch cover loadings and corrosion allowances are in accordance with the future UR S21 Revision 3 and IMO revised Load Line Protocol of 1988.

A number of distinctive design features benefit the installation, operation and reliability of the covers, notably:

• replaceable longitudinal stoppers/guides easing installation and compensating for wear
• end-hinge links compensating for hogging/sagging and keeping the meeting joint tight
• double row sealing securing tightness in the hinge joints
• double row sealing, based on MacGREGOR Omega seal, enhancing tightness in the meeting joints
• a new generation MacGREGOR FlexSeal which can cope with even larger hatch movements than before; long-lasting tightness is associated with the solid FlexSeal configuration, along with minimal compression set, no water absorption, corrosion prevention and a wide operating range
• easily-installed non-sliding MacGREGOR FlexiPads adapting to misalignments and deflections.

For further information, please contact:
Mr Torbj¶rn Dahl, Senior Naval Architect, MacGREGOR (FIN) Oy
Hallimestarinkatu 6, FIN-20780 Kaarina, Finland
Tel: +358 2 4121 313 Fax: +358 2 4121 508
e-mail: torbjorn.dahl@macgregor-group.com