Annex 11 – Strength of Cargo Hatch Cover Securing Arrangements for Double-Side Skin Bulk Carriers

 The strength of securing devices shall comply with the following requirements:

• .1 Panel hatch covers shall be secured by appropriate devices (bolts, wedges or similar) suitably spaced alongside the coamings and between cover elements. The arrangement and spacing shall be determined with due attention to the weathertight effectiveness, depending upon the type and the size of the hatch cover, as well as on the stiffness of the cover edges between the securing devices.

• .2 The net sectional area of each securing device shall not be less than:

  A

  =

  1.4 a/f (cm2)

  where:

  a	=	spacing between securing devices not to be taken less than 2 m
  f	=	(σY / 235)e
  σY	=	specified minimum upper yield stress in N/mm2 of the steel used for fabrication, shall not be taken greater than 70% of the ultimate tensile strength
  e	=	0.75 for σY > 235
  	=	1.0 for σY ≤ 235

  Rods or bolts should have a net diameter not less than 19 mm for hatchways exceeding 5 m² in area.

• .3 Between cover and coaming and at cross-joints, a packing line pressure sufficient to obtain weathertightness shall be maintained by the securing devices. For packing line pressures exceeding 5 N/mm, the cross section area shall be increased in direct proportion. The packing line pressure shall be specified.

• .4 The cover edge stiffness shall be sufficient to maintain adequate sealing pressure between securing devices. The moment of inertia, I, of edge elements shall not be less than:

  I

  =

  6 p a4 (cm4)

  where:

  p	=	packing line pressure in N/mm, minimum 5 N/mm
  a	=	spacing in metres of securing devices.

• .5 Securing devices shall be of reliable construction and securely attached to the hatchway coamings, decks or covers. Individual securing devices on each cover shall have approximately the same stiffness characteristics.

• .6 Where rod cleats are fitted, resilient washers or cushions shall be incorporated.

• .7 Where hydraulic cleating is adopted, a positive means shall be provided to ensure that it remains mechanically locked in the closed position in the event of failure of the hydraulic system.

  2.1 Nos.1 and 2 hatch covers shall be effectively secured, by means of stoppers, against the transverse forces arising from a pressure of 175 kN/m².

  2.2 No.2 hatch covers should be effectively secured, by means of stoppers, against the longitudinal forces acting on the forward end arising from a pressure of 175 kN/m².

  2.3 No.1 hatch cover should be effectively secured, by means of stoppers, against the longitudinal forces acting on the forward end arising from a pressure of 230 kN/m². This pressure may be reduced to 175 kN/m² if a forecastle is fitted.

  2.4 The equivalent stress in stoppers and their supporting structures and calculated in the throat of the stopper welds is not to exceed the allowable value of 0.8 σ_Y.

 Where stoppers or securing devices are fitted to comply with this annex, they shall be manufactured of materials, including welding electrodes, to the satisfaction of the Administration.