Integrity assessment of ammonia spherical storage tank

The integrity of the ammonia spherical tank (with a volume of 1800 m3 and the outer diameter of 15120 mm, nominal wall thickness 30 mm) was analyzed due to discovered cracks on the longitudinal and transverse but joints of the segments, of different lengths and depth. The calculation according to EN 13445-3: 2014 specifies the minimum required spherical shell wall thickness. The finite element method was used to analyze the cracks and determine the hoop stress value. The stress intensity factor for the analysed cracks was analytically determined, and the obtained values were compared with the critical value of the stress intensity factor to assess the integrity of the observed structure

Application of Fracture Mechanics Parameters to Spherical Storage Tank Integrity Assessment

Fracture mechanics parameters have been applied to assess pressure vessel integrity. The pressure vessel analysed here was the ammonia spherical tank (volume of 1800 m(3), outer diameter 15.12 m, thickness 30 mm) where different cracks in the longitudinal and transverse butt joints were found. The finite element method was used to calculate stress and strain state and to analyse cracks and their influence on spherical storage tank integrity. Toward this end, the stress intensity factors were analytically determined, and compared with the fracture toughness to find out the critical pressure using Failure Assessment Diagram (FAD) in combination with net stress vs. critical stress

Application of Fracture Mechanics Parameters to Spherical Storage Tank Integrity Assessment

Fracture mechanics parameters have been applied to assess pressure vessel integrity. The pressure vessel analysed here was the ammonia spherical tank (volume of 1800 m3, outer diameter 15.12 m, thickness 30 mm) where different cracks in the longitudinal and transverse butt joints were found. The finite element method was used to calculate stress and strain state and to analyse cracks and their influence on spherical storage tank integrity. Toward this end, the stress intensity factors were analytically determined, and compared with the fracture toughness to find out the critical pressure using Failure Assessment Diagram (FAD) in combination with net stress vs. critical stress

Integrity assessment of turbine flat cover pipe

The turbine flat cover pipe (dimension phi 219.1x12.7 mm, and material STPG-38) is tested and cracks are found. Determination of the required wall thickness for a pipe exposed to internal pressure is done according to EN 13480: 3-2012. An analytically determined stress intensity factor for the analysed crack is compared with the critical value of the stress intensity factor to assess the integrity of the analysed structure

Application of parameters of elastic-plastic fracture mechanics for integrity assessment of large spherical storage tanks

U radu se analizira integritet konstrukcije velikog sfernog rezervoara za skladištenje tečnog amonijaka koji je izložen dejstvu unutrašnjeg pritiska, koji je izrađen zavarivanjem segmenata gornjeg i donjeg dela polusfernog omotača sa gornjom i donjom kalotom, koji su takođe izvedeni zavarivanjem prethodno deformacijom oblikovanih limova, u čijim zavarenim spojevima je otkriveno 211 grešaka ispitivanjem metodama bez razaranja. Primenom parametara elasto-plastične mehanike loma propisan je postupak određivanja kritične dubine greške u zonama zavarenih spojeva konstrukcije. Određen je adekvatan postupak obrade (geometrijsko oblikovanje) strukture u lokalnoj uskoj zoni u okolini greške kojom se postiže bezbednost konstrukcije sa aspekta čvrstoće. Pokazano je da debljina omotača sfernog rezervoara u lokalnim zonama otkrivenih grešaka može biti i manja od minimalne propisane standardom EN 13445-3:2017, a da pritom integritet konstrukcije nije narušen. Eksperimentalno-numeričkim istraživanjem propisane su granične geometrijske karakteristike greške, odnosno propisana je procedura kojom su definisane dubine grešaka koje je moguće sanirati bez primene dodatnog materijala (bez navarivanja) i kojom se obezbeđuje bezbedan rad konstrukcije.The paper analyzes the construction integrity of a large spherical storage tank for liquid ammonia exposed to internal pressure. The spherical storage tank was made by welding the previously deformed segments of sheet metal. 211 welding defects were detected performing the ultrasonic testing on welding joints. The critical depth of defect in a small zone of welded joint of a structure is defined using the parameters of elastic-plastic fracture mechanics. Adequate process of machining of the structure in the local narrow zone of detected defect is determined which achieves structural safety from the aspect of strength. It has been shown that the thickness of the spherical reservoir shell in zones of detected defects may be less than the minimum specified by standard EN 13445-3: 2017, without compromising structural integrity. Experimental and numerical investigation prescribed the boundary geometric characteristics of the defect that can be repaired without the use of additional material (without welding) and ensuring the safe operation of the structure

Integrity assessment of turbine flat cover pipe

The turbine flat cover pipe (dimension phi 219.1x12.7 mm, and material STPG-38) is tested and cracks are found. Determination of the required wall thickness for a pipe exposed to internal pressure is done according to EN 13480: 3-2012. An analytically determined stress intensity factor for the analysed crack is compared with the critical value of the stress intensity factor to assess the integrity of the analysed structure

On Drazin inverse of operator matrices

AbstractIn this short paper, we offer (another) formula for the Drazin inverse of an operator matrix for which certain products of the entries vanish. We also give formula for the Drazin inverse of the sum of two operators under special conditions

Design Aspects of Hip Implant Made of Ti-6Al-4V Extra Low Interstitials Alloy

The main concerns in design of hip implants are fracture and fatigue related issues. In this paper, reverse engineering is used to redesign a hip implant produced by precision casting, using Ti6Al4V Extra Low Interstitials (ELI) alloy. As the most critical part, hip neck has been in the focus of this analysis, keeping in mind that the lower the thickness is, the higher the movement of joint may be, but affecting its structural integrity at the same time. Thus, 5 different models are created with different neck thickness and analyzed by using the Finite Element Method (FEM) for stress-strain calculation and extended FEM (XFEM) for fatigue crack growth

Influence of second-phase particles on fracture behavior of PLA and advanced PLA-X material

Most widespread materials in Additive Manufacturing are PLA (PolyLactic Acid) and ABS (Acrylonitrile Butadiene Styrene), which are dissimilar materials in terms of printing abilities and mechanical properties. PLA material originates from renewable resources making it better solution for environment in comparison with petroleum-based ABS material. Addition of second-phase particles to polymer matrix may have a substantial influence on mechanical properties of created material. Subject of this paper are natural PLA material and advanced PLA material with addition of second-phase particles (''PLA-X'') which has similar mechanical properties as ABS material, making it a perfect PLA based substitute. Tensile tests are conducted according to ISO 527-2 standard. Subject of this paper is the analysis of fracture behaviour of PLA and advanced PLA-X material, which ranges from brittle to formation of large craze zones before fracture. Analysis is conducted for five batches of both materials, with variation in printing parameters. The main focus of this research was to evaluate the influence of second-phase particles on fracture behaviour of PLA and advanced PLA-X material