ABS测厚换标准.doc

GENERAL INFORMATION – GAUGING WASTAGE Gauging requirements are shown in Tables 2a, 3a and 4a. When gauging a drilling unit, wastage found is to be limited to the wastage allowances shown in Tables 2b, 3b and 4b. These allowances are only acceptable when local wastage is evident. “Local Wastage” is defined as average wastage of structure within two stiffener spacing and between frames/girders, i.e. “Panel” structure. However, where wastage is throughout a single structural bay, circumference, panel, etc., (hereinafter, called a “Global Wastage”), wastage allowances shown in Tables 2b, 3b and 4b are not sufficient and considered unacceptable. Typically, global wastage would be where wastage is found throughout one of the following areas: A single bay of a leg structure on a SEDU; A single girth of cylindrical leg shell plating on a SEDU; Entire length of either bottom, deck or shell plating of a preload tank on a SEDU; A leg-well structure (shell or internals) on a SEDU; Circumference of a diagonal / horizontal bracing on a CSDU; Circumference of a column on a CSDU; Bracing / column / hull intersection on a CSDU; Entire drill-floor substructure members on any MODU; Entire helicopter-deck structure on any MODU; A single belt gauged on any MODU. Above listing is just a sample of global wastage, but should give an idea as to what it means. Even if the wastage was less than “substantial corrosion”, this may be considered as excessive wastage and require renewal. Where the Owner decides not to renew excessive global wastage and requests to continue operations for extended period of time, the attending Surveyor is to recommend global strength analysis to be carried by the Owner, submitted to ABS engineering and accepted by ABS before the extension is accepted. Global wastage percentage of Special Application Structures on a MODU is to be less than 5%. Global wastage of 5% or over requires structure to be renewed. If global wastage was less than 5% but more than global su