BANGLADESH POWER DEVELOPMENT BOARD TENDER ... - BPDB

C; when surf aces are wet or exposed to rain, or strong wind; or when weldersare exposed to inclement weather conditions.Surfaces to be welded shall be free from loose or thick scale, slag, rust, moisture,grease and other foreign material that will prevent proper welding or produceobjectionable fumes. Welding shall be principally carried out in workshops. Wherenecessary the Board may approve site welding, subject to the satisfactoryprovision of effective protection and safeguards for welding works by theContractor.(6) Welding ProcedureDetails of the proposed welding procedure, manufacturer, classification on, codetype and size of electrodes to be used shall be submitted to the Board forapproval. When necessary, welding tests shall include specimen weld detailsrepresentative of the actual construction which shall be welded in a mannersimulating to most unfavourable conditions liable to occur in the particularapplication. All costs of the tests shall be borne by the Contractor. All welds shallbe finished full and made with correct number of runs. Slag and other inclusionsshall be cleaned from all welds.Notwithstanding the approval of welding schedule and procedure by the Board,the Contractor shall bear full responsibility for correct welding and for minimisingthe distortion in the finished structure.a. Preparation of Base MetalSurface and edges to be welded shall be smooth, uniform, and free from fins,tears, cracks, and other discontinuities, which will adversely affect the quality orstrength of the weld. In the preparation of the fusion faces, shearing shall belimited to metal thickness not greater than 8 mm. All fusion faces shall be preparedby machining shall be limited to metal shall be prepared by machining orflame cutting, or where approved, by special oxygen cutting apparatus. Fusionfaces, angle of level, root radius, and the like shall be properly prepared to givethe approved weld forms. The parts to be jointed by fillet welds shall be broughtin-to contact as close as practicable. The gap between parts shall normally notexceed 4.8 mm (3/16 in.). A butting parts to be joined by butt welds shall becarefully aligned and the correct gap and alignment maintained during thewelding operation.b. Butt Welded JointEnds of the welds shall have full throat thickness by means of runoff tab.Additional metal remaining after the removal of the tab shall be removed bymachining, or by other approved means. Ends and surfaces of the welds shall besmoothly finished. All main butt welds shall have complete penetration and,except on tubes or partial penetration Joint, shall be welded from both sides. Theback of the first run shall be suitably gouged out.c. Intermittent WeldsIntermittent welds shall not be permitted without the approval of the Board.Ghorasal 200 MW to 300 MW Gas Turbine Peaking Power Plant Project (Vol-2 of 3)197