BS ISO 13799:2020 pdf free.Ships and marine technology一Ship’s mooring and towing fittings一Recessed bitts [casting type).
BS ISO 13799 1 Scope This document specifies the types, nominal sizes, dimensions and materials, as well as construction, manufacturing and marking requirements, for casting type recessed bitts to meet normal towing  requirements. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IM0 Circular MSC/Circ.1175, Guidance on shipboard towing and mooring equipment.Depending on the size and strength of the material, recessed bitts shall be classified as belonging to one  of the following six types: a) Type 75: nominal size 850, casting material having a yield point of not less than 235 N/mm2;  b) Type 110: nominal size 850, casting material having a yield point of not less than 350 N/mm2; c Type 135: nominal size 850, casting material having a yield point of not less than 430 N/mm2; d) Type 100: nominal size 920, casting material having a yield point of not less than 235 N/mm2; e) Type 150: nominal size 920, casting material having a yield point of not less than 350 N/ mm2; f) Type 180: nominal size 920, casting material having a yield point of not less than 430 N/mm2. The recessed bitts shall be clearly marked with their SWL by weld bead or equivalent. The SWL shall be expressed in tonnes (symbol ‘t’) and be placed so that it is not obscured during operation of the fitting.The strength of the recessed bitts was evaluated by finite element model analysis and determined based on the following design criteria.Loading The recessed bitts shall be designed to withstand the loads imposed by the towing ropes.The recessed bitts shall be designed to withstand the following load case.They shall be designed to withstand the combined load produced by P imposed at the below positions,see Figure A.1.BS ISO 13799 pdf download.