Design and Analysis of Reactor Dish Vessel

Transcription

1 IJIRST International Journal for Innovative Research in Science & Technology Volume 3 Issue 11 April 2017 ISSN (online): Design and Analysis of Reactor Dish Vessel Aniket D. Patil PG Student Department of Mechanical(CAD-CAM) Engineering Annasaheb Dange College of Engineering & Technology, Ashta Manoj M. Jadhav Assistant Professor Department of Mechanical Engineering Annasaheb Dange College of Engineering & Technology, Ashta Abstract This paper presents design and analysis of reactor dish vessel. In chemical processes due reaction of different chemicals high pressure and temperature is developed in the vessel. The pressure vessel has to withstand forces developed due this pressure and temperature. Major consideration in design of a pressure vessel is safety because of potential impact of accidents. The paper is focused on analysis of vessel for safe working under working condition. The material is selected from the pressure vessel design manual. Allowable working stresses are taken from the same according to this the parameters of vessel are changes to sustain this pressure and temperature. Reactor dish vessel must be designed with material compatible with many process reactions. This also must be designed to sustain at high temperature and pressure generated during reaction. The vessel is designed in such a way that the pressure generated inside should not cause any deformation in body of shell. Also the nozzle location and support effects on the stress development in particular area. Keywords: Reactor Dish Vessel, Design Manual, Process Reaction, Deformation, Nozzle Location I. INTRODUCTION A Pressure Vessel is closed container to hold gasses & liquids at pressure substantially different than ambient pressure, the pressure differential is dangerous and many fatal accidents have occurred in the history of pressure vessel development and operation [1]. Consequently, pressure vessel design, manufacture, and operation are regulated by engineering authorities backed by legislation. For these reasons, the definition of a pressure vessel varies from country to country, but involves parameters such as maximum safe operating pressure and temperature. The possible risks of a given failure and its consequent are balanced against the effort required for its prevention; the resulting design should achieve an adequate standard of safety at minimum cost. Pressure vessels are containers for the containment of pressure either internal or external. This pressure comes from an external source or by the application of heat from a direct or indirect source or any combination of them. II. PROBLEM STATEMENT The vessel may fail due many reasons such as failure of joints, excess nozzle deformation, cracks produced due temperature variation The failure may also due to wrong selection of material, stress concentration. The previous study is based only on stress due to pressure they have not considered effect of temperature. Hence there is a need to consider effect of temperature also. While analyzing the vessel temperature effect has to be considered in combination with pressure. III. METHODOLOGY Design of pressure vessel is carried with reference from joshi s process equipment design book and material selection is done on the basis of ASME standards. The modeling and analysis is carried out in Ansys. IV. DESIGN PRESSURE Pressure for which vessel is designed is called design pressure. The pressure is given by the company for the vessel. Hence according to this pressure further calculations are done. Maximum allowable working pressure for a vessel is permissible pressure at the top of the vessel in its normal operating position at a specific temperature. This pressure based on calculation for every element of the vessel using nominal thickness exclusive of corrosion allowance. It is the base for establishing the set pressure of any pressure relieving devices protecting the vessel. V. DESIGN TEMPERATURE Design temperature is the temperature which generated in pressure vessel due to reaction and it is considered in calculation. There may be two values for a vessel for temperature one is maximum and another is minimum. Design temperature for vessel under external pressure should not be exceeding the maximum temperature. All rights reserved by 148

2 VI. CORROSION ALLOWANCES Corrosion occurring over the time is catered by corrosion allowance; this value depends on the corrosiveness of the fluid inside and working time of vessel. The corrosion allowance of 1.5 mm is given for the parts. VII. DESIGN OF SHELL In designing of the shell it required to consider circumferential or longitudinal stress. Selection of the type of stress depends on the thickness and radius of the shell as per the criteria. When the thickness does not exceed half of the inside radius or pressure does not exceed of allowable stress then circumferential stress has to be considered. If thickness does not exceed half of the inside radius or pressure does not exceed 1.25 of allowable stress then longitudinal stress has to be applied. In given case value of pressure is less than times of yield strength. Circumferential stress criteria Checking for 0.385SE S = 138 Mpa E = SE = > 138 Hence following formula can be applied t = t = 5.33 But according to ASME minimum thickness should be 18 mm. Hence t = 18 mm PR SE 0.6 P VIII. ELLIPSOIDAL HEAD DESIGN The required thickness of a dished head of semi ellipsoidal form, is determined by PD t = SE 0.2 P t = 5.33 But according to ASME minimum thickness should be 18 mm. IX. NOZZLE AND REINFORCEMENT Opening in vessels is mostly provided in circular or elliptical shape. For elliptical shape it is necessary to provide reinforcing to avoid excessive distortion. The flow rate and standard pipe section available has to be considered while designing the nozzle. Diameter of the nozzle is 450 mm, given by company. Nozzle thickness is calculated by following formula trn = 0.37 mm But as per ASME code minimum thickness should be 6 mm. trn = 6 mm Corrosion allowance = 3 mm. Hence trn = 9 mm trn = Pi Di 2δ J Pi dip = internal diameter of reinforcement pad dop= Outer diameter of reinforcement pad t = thickness of reinforcement pad dip = di + 2tn dip = x 9 dip = 468 mm dop = Ar + dip tp dop = dop = mm for outlet nozzle dip = x 9 X. DESIGN OF REINFORCEMENT PAD All rights reserved by 149

3 dip = 568 mm dop = dop = mm Nozzle length (N L)= 1.5 x diameter N L=1.5 x 450 N L= 675 mm XI. SIMULATION The vessel is analyzed for stresses and forces acting on it at different points and magnitude at same point. Optimization is carried out according the results obtained from the iterations. First iteration is carried out with boundary conditions Wind load, Pressure and Gravity. Fig. 1: boundary conditions Wind load, Pressure and Gravity. Fig. 2: Maximum stress with boundary conditions Wind load, Pressure and Gravity. From the above analysis it is observed that maximum stress generated is Mpa. This value of stress is much higher than the allowable stress 138 Mpa. Hence it is required to increase the width of the vessel wall. Width of the vessel is increased by 2 mm every iteration and different values of stress are obtained as in following table. All rights reserved by 150

4 Table 1 Result for different thickness Thickness (mm) Shell Dome Skirt Stress Deformation Combinations of values are made for each part to obtain better optimization. Initial 12 mm thickness is kept same for dome, shell and skirt. Numbers of combinations are made to get results. It is found that value of stress is become mpa for thickness of 18 mm for dome and 18 mm for skirt. After this point the values again goes on increasing. Hence these values are taken for further analysis. Result of this analysis is depicted below. Fig. 3: Stress analysis at thickness of Lower Dome 18mm and skirt 18mm Fig. 4: Stress analysis at thickness of Lower Dome 18mm and skirt 18mm All rights reserved by 151

5 In the above analysis value of stress obtained is Mpa and deformation 4.12 mm. This stress value is less than the allowable stress hence now the vessel is safe for stress. Location of maximum stress is at the junction of outlet nozzle and lower dome. XII. EXPERIMENTAL RESULTS Deformation observed in experimental testing on site is 3.9 mm and no damage occurred to the vessel. Hence it can be considered as the vessel is safe under actual working condition. XIII. CONCLUSION Table 2 Results from experimental and FEA Analysis Result (mm) Sr. No. Validation Error % Experiment FEA 1 Deformation Ultrasonic Testing No Crack Detected The above table shows a comparison between FEA & experimental result, from experimental testing the maximum deformation is 3.9 mm FEA Error Calculation % Error Calculation = EXP FEA X = X = 5.64 % Manufactured tested values are within 10% of FEA calculations hence our FEA results are reliable. EXP REFERENCES [1] V. V. Mahajani, Joshi s Process Equipment Design, fifth edition Trinity Press [2] Chinna Rosaiah Unnava, Ch. Siva Ramakrishna, Design and Analysis of Spherical Shell with Radial Nozzle in Pressure Vessels IJAERS Vol. III Issue I Oct.-Dec, 2013/ [3] Viraj H. Barge, Dr. Prof. S.S.Gawade, Thermal-Structural Analysis &Optimization of Pressure Vessel Using Finite Element Analysis IJAERS Vol. II Issue IV July-Sept., 2013/ [4] B.S.Thakkar, Design of Pressure Vessel Using ASME Code, Section VIII, Division 1 E-ISSN IJAERS/Vol. I/ Issue II/January-March, 2012/ [5] Apurva R. Pendbhaje, Rajkumar Patil, Design & analysis of the Pressure Vessel, IJIRTS, VOLUME 2 ISSN: [6] W. F. English Fatigue Design Criterion for Pressure Vessel Alloys, 236 Vol. 100, MAY [7] Jaroslav Mackerle, Finite elements in the analysis of pressure vessels and piping, an addendum: A bibliography ( ), Elsevier International Journal of Pressure Vessels and Piping 82 (2005) All rights reserved by 152