# Introduction ilter Sheets are non standard components used in Oil & Natural gas Industry for filtration. The usual engineering practice is to extend the ever-current design is available with an increased factor of safety. Around the world, for environmental reasons, oil refineries equipped with a Filter Unit have to face the challenge of particulate emission reduction. The refinery would not be able to meet the tighter limits with its existing Filter Unit flue gas cleanup equipment. The 3 rd stage blowback filter option would enable industries to meet current particulate emission requirements and also get close to if not already meet particulate emission Author : M.E Design, D.Y.Patil college of engineering akurdi, pune . E-mail : shweta.naik19@gmail.com a number of years in advance of 2010 requirements. Existing tube sheet Filter assembly as shown in fig. 1 have less filtration capacity due to less number of filter tubes. Existing assembly model design is less advanced and flexible. We are going to increase the number of filter tube for increasing the filtration capacity.Fig. 2 shows proposed tube sheet assembly with increase number of tubes. The filtration capacity of proposed design can improve by using optimum pitch layout for filter candle. So to optimized the shape and weight of proposed filter sheet assembly considering various design constraints without affecting their functional characteristics. This entire unit is divided into seven different chambers. The central, hexagonal chamber has more filtration capacity than others. Each chamber is intented to filter a different gas allowing primary mixing of these gases. Inlet nozzles are provided to each chamber. Each inlet has flow control valve to control the flow of gas, thus enabling the control of percentile of each gas. Special filter candles, which remove flue gas particles as small as 2 micron, are proposed to be employed. The filter elements should be removed if the dirty filter P (differential pressure) is higher than the 0.7 bar as per operational guidelines. Fig- 4 shows the four pitch pattern. Among the four we select the 60 0 pitch pattern. The Design of proposed filter sheet are based on the following assumptions: i) The plate is flat, of uniform thickness, and of homogeneous isotropic material. ii) The thickness is not more than about one-quarter of the least transverse dimension, and the maximum deflection is not more than about one-half the thickness. Figure 4 : Pitch Pattern iii) All forces-loads and reactions are normal to the plane of the plate. iv) The plate is nowhere stressed beyond the elastic limit. For convenience in discussion, it will be assumed further that the plane of the plate is horizontal. # a) Manufacturing and Testing Manufacturing of the filter sheet is done by Casting and machining .In machining the holes are Drilled and Reamed, then applying the Heat treating process. In Gulf countries they preferred Gas cutting or Rolled plates. For testing of Filter sheet, Non-Destructive Ultrasonic Testing machine is used. In other words, NDT allows parts and material to be inspected and measured without damaging them. Non-Linear Analysis of filter sheet is done by applying the following different seven conditions, for the same we consider 1/6 th portion of the filter sheet as shown in fig. Figure 6 : Filter sheet assembly with different parts 1. To be analyzing given filter sheet for its self weight. 2. To be analyzing given filter sheet for differential pressure of 0.07MPa without self weight. 3. To be analyzing given filter sheet for differential pressure of 0.07MPa with self weight. 4. To be analyzing given filter sheet for hydro test with 2.5 times of given pressure of 0.07 MPa without self weight. 5. To be analyzing given filter sheet for hydro test with 2.5 times of given pressure of 0.07 MPa with self weight. 6. To be analyzing given filter sheet for back pressure of 0.07 MPa without self weight. 7. To be analyzing given filter sheet for back pressure of 0.07 MPa with self weight. Top support and base support are welded to the shell. Therefore these are act as a fixed support. c) Non-Linearity Nonlinear structural behavior arises from a number of causes, which can be grouped into these principal categories: Geometric Non-linearity, Material Non-linearity, Contact Non-linearity. Contact forms a distinctive and important subset to the category of changing-status nonlinearities. When two bodies comes in contact but Homoginity is lost, Contact Non-linear Analysis is there and force is transmitted from one body to other body. In this project we have different materials Stainless Steel (SS), Structural steel (SA) & Neoprene rubber. Neoprene rubber has material nonlinearity as shown in following graphs. There are five types of Contact Non-Linearity, these are- # Meshing of Filter Sheet Assembly # Mass Modeling In filter sheet assembly, filters are to be hanged on filter sheet. These filters are shown as a mass model. IV. # The mass model is modeled by using RBE3 (Rigid Body Element).Figures 11 show the # Experimental Validation For all new product lines, initial Design should follow SOC-306. All new product equipments shall be tested at 2.5 times the operating pressure using Hydro test. The Hydro test shall have slow built up of pressure, from base pressure to test pressure over a period of 120 min. The equipment shall be maintained at test pressure for 30 min. The pressure shall be gradually reduced to base pressure within a period of 45 min. After test, all components shall be subjected to NDT (Non Destructive Test), the following NDT shall be done-Visual Inspection-No surface irregularities must be present and Pre Dyed components should have no loss of dye due to leakage. Ultra Sonic Testing-Post Test, internal damage shall get amplified if any, and shall be recorded in an Ultra Sonic Test. The test performance of the assembly should be completely elastic, this shall be verified by checking the dimensions of product for any permanent yield. 2) The Mesh is satisfactorily fine enough to generate accurate results. 3) The boundary conditions were inspected. The maximum Stress in Filter sheet is 32 MPa, however nominal value if calculated is much lower, it satisfy FOS is 5. 4) Gasket plate shows peak pressure of 34 MPa.however it is observed to significant stress raiser due to vicinity of contact and relatively less thickness of the plate compared to the other components. 5) Material Non Linearity may not be modeled in future analysis as it will have negligible effect on accuracy and unnecessary increases solution time. V. # Design Optimization As we see there is chance for design optimization, we checked for two different optimizations, Shape optimization and Thickness optimization a) Shape Optimization For shape optimization we tried with increasing filter mounting holes. While increasing filter mounting holes we didn't violate minimum centre distance between two holes. We could increase holes from 21 to 28. For 28 holes we analyze the filter sheet assembly as shown in fig 13 with keeping same boundary conditions as were for 21 holes. We directly analyzed for the worst case. # Mesh Sensitivity Analysis Size of elements influences the convergence of the solution directly and hence it has to be chosen with care. If the size of elements is small, the final solution is expected to be more accurate. However, we have to remember that the use of elements of smaller size will also mean more computational time. As the number of elements increases, the size of each element must and consequently the accuracy of the model generally increases. Gasket plate having 12 mm thickness which is less as compared to others. The Gasket plate having contact on both sides Therefore there is not reliable stress concentration. Hence we should rely more on probe values as there is stress concentration. Currently inlet to central plate is not designed. If such a inlet is designed then its structural analysis is recommended in the future. In such analysis, we will have to reassess the performance of peripheral shell. 1![Fig. 1 : Existing filter sheet Fig. 2 : Proposed sheet Due to Coagulation in filter, the Internal pressure increases with time. Due to this internal pressure, the tube sheet in filter is deflected for some time it will break and the joint break. Ignition temp of Natural gas is around 300 0 C .The impurities which are present in it having temp near about 110 0 C. In Middle East Region, during operation due to high temp it gets ignited and Explosion of overall plant is there. To avoid this model of the tube sheet is require to improve. Finite element based modeling is the best way to improve model of tube sheet assembly. Analysis require for Validation of FEA results with tested (actual) results. After validation we have base for modeling and simulation of proposed assembly.The proposed filter unit contains seven chambers as shown in fig3.It has six circular sector filter sheets and one central hexagonal filter sheet. The thickness of the chamber wall depends upon Internal working pressure, factor of safety and Welding allowances. The filter sheets consist of holes in which filter candles are inserted. The capacity of filtration depends upon the number of candles used in filter sheet assembly. The central Hexagonal filter sheet has no input system so it is not a part of analysis.](image-2.png "Fig. 1 :") 3![Figure 3 : Proposed model of air filter unit](image-3.png "Figure 3 :") ![The refining industries require to design and analyze the filter assembly for achieving following properties:a) High mechanical strength for longer filter life b) Low pressure drop for less interruption of process flow. c) Clean ability by pulse jet or back flushing to reduce maintenance costs. d) Increased filtration area, particularly with pleated elements. e) Increased dirt-holding capacity. f) Low in weight & Low implementation cost.](image-4.png "") ![Fig 5 shows different parts.](image-5.png "") 5![Figure 5 : Section of Filter sheet](image-6.png "Figure 5 :") 7![Figure 7 : Neoprene Rubber > Biaxial Test Data](image-7.png "Figure 7 :") 8![Figure 8 : Meshed model of Filter sheet Solid 95 is a higher order version of the 3-D 8node solid element. It can tolerate irregular shapes without as much loss of accuracy. Solid 95 has plasticity, creep, stress stiffening, large deflection, and large strain capabilities. In this project work, the filter sheet assembly model is meshed with hexahedron elements as shown in figure. Mapped face Meshing is given to 21 holes in the filter sheet as well as Base support. Filter sheet assembly along with all the parts are meshed as shown in fig 8 with Hex-dominant and Aesize given to 15mm or 0.015m. The elements created are 28401 whereas number of nodes present are 126636. After meshing is done, solve this model for different seven conditions, different values for stress and](image-8.png "Figure 8 :") 9![Figure 9 : Five points where stress value is maximum](image-9.png "Figure 9 :") ![Filter tube sheetAssembly with considering the weight of the tubes. Weight of each tube is 45 kg.](image-10.png "") 11![Figure 11 : Filter sheet with Considering Point mass Figure 12 shows the four different point at which the Stress value is maximum near at the base support for the worst condition i.e. at Hydro test -without weight which is having maximum stress value among all the conditions considering the point mass.](image-11.png "Figure 11 :") 12![Figure 12 : Four points where stress value is maximum Analyzed the 1/6 th portion of Existing filter sheet having 21 holes for mesh size 15 mm. Following table shows Von mises stresses and Deformation value for without point mass and considering the mass of tubes(Each tube weight = 45 kg) for all seven conditions.](image-12.png "Figure 12 :") ![a) Hydro Test Condition Working fluid -Water with Anti Scaling Additives Test Pressure -2.5 x 0.07 MPa Leak Inspection -Sensors (LDR) on the top side of Filter Assembly. Remark-Simultaneous testing of all 7 chambers was done. Filter holes were plugged with caps of SA 204involved No leak observed on Top Side of Assembly, No visible damage observed after test and Plug Adhesion intact after test. According to Auditors Remark, 1) Code requirements have been met by the analysis.](image-13.png "") 13![Figure 13 : Proposed Filter sheet model Following are the results after solving proposed tube sheet having 28 holes for the worst condition with and without point mass with refined mesh size is taken as 15mm which shows that design is safe. Therefore shape can be optimized upto 28 holes. Max Equivalent stress = 4.2636 e7 Pa Max. Deformation = 0.00014293 m](image-14.png "Figure 13 :") 16![Figure 16 : Stress& Displacement Convergence For shape & thickness optimization, the Stress and Displacement Convergence is as shown in figure 16 for worst condition. As the no of element goes on increasing corresponding stress and displacement goes on increasing. The above graph of obtained for any general finite element analysis shows how the accuracy of the analysis increases with increasing element numbers.VII.](image-15.png "Figure 16 :") 19LOCKING PINSS 304Dia16x 75 lg6REMOVABLE8TOP SUPPORTSA 516 Gr.7040 thk4WELDED TO SHELL7WASHER(M16)SS 304M16 (spring)2STD6ALLEN BOLTSS 304Dia16x 60lg2STD5PACKING PLATESS 304L40 thk4REMOVABLE4FILTER SHEETSA 240 TYPE 304L40 thk1REMOVABLE3SQ.GASKETRUBBERSq. 8X81GLUID TO TUBE SHEET2GASKET PLATESS 304L12 thk1REMOVABLE1BASE SUPPORTSA 516 Gr.7050 thk1WELDED TO SHELLP.N.DESCRIPTIONMATLSIZEQTYREMARKS 2Mesh size =15 mm = 0.015 mS.NConditionsWithout Point MassWith Point MassVon Mises Stress (Pa) Deformation (m) Von Mises Stress(Pa) Deformation (m)1Self Weight7.2964 e52.2804 e-65.2877 e61.8405 e-52Differential1.6705 e75.1273 e-51.6705 e75.1273 e-5Pressure-Without wt3Differential1.5976 e74.8994 e-51.1419 e73.2932 e-5Pressure-With wt4Hydro test-4.1757 e70.000128144.1757 e70.00012814Without wt © 2013 Global Journals Inc. (US) "Thickness and Shape Optimization of Filter Sheet by Non-Linear Fea" "Thickness and Shape Optimization of Filter Sheet by Non-Linear Fea" Global Journals Inc. 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