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Tham khảo tài liệu 'machinery components maintenance and repair episode 1 part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Process Machinery Piping 165 Text continued from page 157 All bolt torque values are based on the use of new nuts ASTM A194 GR 2H and new bolts ASTM A193 GR 87 of proper design acceptable quality and approved materials of construction as well as metallurgy. It is also required that two hardened steel washers be used under the head of each nut and that a non-metallic-based lubricant i.e. oil and graphite be used on the nuts bolts and washers. The flanges are assumed to be in good condition and in compliance with ASME B16.5 specifications. Special attention should be given to seating surface finish and flatness. Only torque wrenches that have been calibrated should be used. The proper bolt tightening pattern must be followed see Figure 4.6 for proper bolting pattern with the desired ultimate torque value arrived at in a minimum of three equal increments. All bolts in the flange should then be checked in consecutive order in a counterclockwise direction. The contact dimensions listed are taken from the inside diameter ID and outside diameter OD of the windings which are different from the ASME ring gasket dimensions. No provisions have been made in these tables to account for vibration effects on the bolts. These tables are based on ambient conditions without compensation for elevated temperatures. If conditions different from these exist we suggest that further analysis be performed to determine the appropriate torque values. Gasket Installation In a flanged connection all components must be correct to achieve a seal. The most common cause of leaky gasketed joints is improper installation procedures. 4-Bolt Flange 8-Bolt Flange 16-Bolt Flange Figure 4-6. Installation sequence for 4- 8- and 16-bolt flanges. 166 Machinery Component Maintenance and Repair Bolting Procedures Place the gasket on the flange surface to be sealed Bring the opposing flange into contact with the gasket Clean the bolts and lubricate them with a quality lubricant such as an oil and graphite .
