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Coke tower in service and a comprehensive assessment of the safety inspection


There increased the amount of seam, wrong side, angular degrees, etc.) caused by geometric stress concentration resulting from continuous use to describe the stress concentration factor. For buried defects (weld consider the impact of increased volume): Kt = 1 +3 (E + b) / 2a +05 the coke tower (1 / 2) degree of weld edges E and the wrong side of b max were measured 3.0mm and 10.5mm, Minimum thickness of the tower measured 26.7mm, calculate K1 = 226. Evenly distributed along the cross-section tensile stress: 1 = 220MPa (take the measured maximum); bending stress of equivalent stress: friends = 03) assessment of welding residual stress cracks in weld areas must be considered when welding residual stress in the calculation of crack stress intensity factor and crack opening displacement, the residual stress with the tensile stress when the value back to said coke drum (1 / 2) despite 20 years of natural aging (has been running for 28 years), as somewhat safe, according to CVDA a dr = 1984 take readers, cut no = ar (ar = 0.2, = 205Mpa), calculated: = 41MPa. 4) the total tensile stress a = dl + a2 + a3, a1 = 220MPa, friends = 0,mbt chaussures paris, q = 41MPa, then a = 261MPa5) the total tensile strain because the dl + power> d. (L +62 = 220MPa,abercrombie paris, as = 205MPa), take the Ministry of Aviation Industry 621 1987, Beijing Institute of Aeronautics and measured the maximum strain value of coke tower (e = 1900 ~) for brittle fracture assessment calculations. 6.3 Fracture Assessment 1) calculate the crack size to allow for e Asahi> 1 (e = 1900 ~, = 1541 ~),abercrombie pas cher, application of COD method, determined by the formula allows the crack size dm = chaos /, Ke) where a- one allows the crack size, rnna No. 4 Deng Xiaoming et al: In-service safety inspection and coke tower comprehensive assessment of e = 1900, uE (total tensile strain, take the maximum strain value measured coke tower) = 1541UE (yield strain) = 0. 06mm (H Ⅱ fracture toughness values) results: = 0.06 / Ji X (1900-I-1541) × 10 = 5.55mm2) fracture assessment when a <, then the assessment of the defect is allowed to keep, by the coke tower (tower l / 2) defect assessment computation shows that ultrasound detected all the 78 defects allowed to keep. 7 7.1 tower fatigue assessment base metal and weld parts of the fatigue fracture from the coke drum temperature field, strain field and stress field testing elastic-plastic finite element results can be seen, coke drum temperature, stress is very complex, axial, circumferential, radial exist in temperature, thermal stress and mechanical stress such as intertwined. Alternating temperature and stress the role of the tower's base metal and weld to withstand the high temperature low cycle fatigue, thermal fatigue and mechanical fatigue and the interaction of the wall change. As the local stress exceeds the material yield limit, so each time the loop by the time damage. According to the research unit of the domestic trials and Ministry of Aviation Industry 621 1987, Beijing Institute of Aeronautics and coke tower measured maximum strain value (measured maximum strain e = 1900 ~, it Aet = 2e = 380o ~) calculation of the base metal and weld parts number of cycles Nf fracture and fatigue fracture life (183 cycles per year basis), the calculation results, the shortest life span to meet the equipment running to the next test period (December 2002) requirements. Wrapped 3 tower base metal and weld parts of the malaria workers weld rupture life calculations 7.2 crack fatigue growth defects due to parts of the seam weld joints are also subject to alternating loads part of the role, and the fracture toughness of the weld than base metal. Weld thermal stress due to geometric discontinuities than the base material is high, so easy to weld cracks. Another coke drum during the manufacturing process, welding joints that inevitably exist in incomplete penetration, slag, not melting units, linear defects such as cracks, defects extended to allow control of these values ​​is the assurance of safety, with the stress intensity factor range below AK--da/dN crack fatigue growth curve analysis. J stems from the ultrasonic inspection found 78 deficiencies in the equipment selection lO at greater risk of fatigue crack propagation life defects calculated by the crack growth rate: da / ckN = C (AK) = 2.18X10X (△ K) ( AK units of MPa √ m) 1. f: (2 a / 2 a = (2 a) / 21z points after that: NI_n, - two LUtomJ where △ a stress amplitude, △ d == 220MPa according to AE's recommendation, the number of cycles N as 2O-fold safety factor, and once per 48 hours cycle operating conditions The calculations shown in Table 4 seen from the table, ultrasonic testing
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