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For the purpose of storing fluids under low pressure, storage tanks are used. For construction of storage tank, composite materials are widely used because of their various advantageous properties when compared to metals such as stainless steel. Fiber reinforced plastics is a type of composite material that is widely used for this purpose. FRP material has high corrosion resistance, less weight and high strength. The main aim of this research is to optimize the design of a vertical cylindrical fiber reinforced plastic storage tank by varying the thickness of the cylindrical shell.
Analysis is done using ANSYS 19 software and the results of the FRP storage tank is compared to similar storage tank which is made of stainless steel. In this research, storage tank is designed for storing chemical liquids.
During operation, Storage tanks are subjected to internal pressure and high internal stresses are developed in them. The safety aspect is important due to build-up of high stresses in the Storage tank.
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Therefore, stress analysis is essential for the safe working and performance evaluation of such Storage tanks.
The composite with glass fiber as reinforcement and resin as a matrix is known as Fiber reinforced plastics. Reinforced plastics have properties quite different from those of metallic materials of constructions. In FRP, the thickness is not the measure of strength but the amount of glass present per kg. counts. Hence, for plastics we consider higher factor of safety.
Fiberglass reinforced Plastic (FRP) made with Epoxy Vinyl Ester Resins provides process engineers with a reliable, cost effective construction material that can be employed in numerous applications that are corrosive to stainless steel, and at a much lower cost than high alloy clad steel.
Although some other materials may be cost competitive with FRP, their use typically results in higher life cycle costs due to maintenance.
In 2012,V. Rishab Kanth, V. Balakrishna Murthy , A. V. Ratna Prasad studied separate analysis is done on various models of FRP composite (i.e.) cylindrical model with single and different volumes. Cylindrical shell model is also considered under analysis.[9]
In 2014,Subhash N. Khetre, P. T. Nitnaware, Arun Meshram worked on the composite pressure vessel structure and various orientations of shells which are symmetric were designed. [2].
In 2015,Lakshmi Nair, Yezhil Arasu, Indu V S. worked on laminated pressure vessel design. The main aim is to determine the laminate configuration of vessel. Composite pressure vessel is subjected to progressive failure analysis .[3].
In 2016,M.A. Mujeeb Iqbal1, Mohd.Hasham Ali, Mohammed Fareed worked on filament wound GFRP pressure vessel and analysis is carried out for different orientations in winding. Burst pressure for the vessel is determined by applying a suitable failure criterion.[10].
M. Priyashagadevan, K. A. Kalaiarasi,(2017) worked on comparision between FRP and steel bars reinforced in columns. This study was conducted experimentally to investigate the physical and mechanical properties of the GFRP.[8].
J. Ganesh , K. Sonu Kumar , B. Anil Kumar.(2018) worked on design and analysis of composite pressure vessel. In this research, a graphical analysis is presented to find the Fiber orientation.[4].
In this research, the design specifications of stainless steel storage tank are defined in table.
| Parameter | Value |
|---|---|
| Type | Shell cylindrical, Top cone 15°, Flat bottom |
| Design Temperature | Less than 90°C |
| Design Pressure | Hydrostatic pressure, tank weight |
| Specific Gravity | 1.839 |
| Tank Dimension | 3000mm x 4000mm |
| Tank Thickness | 17.85 mm |
In this research, modeling of the stainless steel tank having above specifications is done using CREO software. Analysis of the model is done using ANSYS software for determining the different stresses induced in the tank.
Step 1: First I considered that the tank is made up of 4 courses each of diameter 3000mm and the thickness varying from bottom to top. Height of each course is 1000mm.
Step 2: Calculation of thickness of shell for various courses.
Thickness of shell =∑[ Number of layers(n) x Mass of reinforcement / unit area (m) x Thickness of fiber (mm per kg/𝒎^𝟐 of glass) ]
Thickness of fiber is taken as :
For 450 CSM = 2.5 mm per kg/𝑚^2 of glass
For 800 WR = 1.6 mm per kg/𝑚^2 of glass
UZCSM x mCSM x nCSM + UZWR x mWR x nWR ≥ Limiting load
Capacity (Q)
UZ = Design unit loading (N/mm per kg/ 𝑚^2 of glass )
The load limited allowable unit loading UL = U/K
The maximum allowable strain is ɛd = 0.2%
The strain limited allowable unit loading US = XZ x ɛd
If (i) US< UL , then UZ = US (ii) UL< US , then UZ = UL
For CSM , U = 200 N/mm per kg/𝑚^2 of glass
For WR , U = 250 N/mm per kg/𝑚^2 of glass
Hydrostatic pressure at tank bottom, N/ 𝑚^2
For variable height, N/mm
Consider laminate construction, as one of the two options :
For Laminate No. 1,
n= number of layers of 450 CSM
n= number of layers of 800 WR
19.11n ≥ Q (Eq. 1)
For Laminate No. 2,
n = number of layers of 450 CSM
n-1 = number of layers of 800 WR
19.11n ≥ Q + 11.61 (Eq. 2)
Both the layers are laid alternately in such a way that the outer most layer is of 450CSM
Step 3: Calculation of base thickness and top thickness.
Base thickness is equal to the maximum thickness of the shell at bottom =20.435 mm. Consider knuckle reinforcement at the base corner. This thickness is half of the base thickness ≈ 10 mm. Therefore, total thickness at base = 20.435+10=30.435 mm. Top thickness should be able to take the load of personnel and minor structural load. Consider laminate thickness as 16mm (i.e.) 7 CSM + 6 WR.
Step 4: Analysis of fiber reinforced plastic storage tank according to the above specification.
The FRP tank exhibits a maximum deformation of 0.96385 mm and an equivalent elastic strain of 0.00096218. The strength-to-weight ratio of the FRP tank (672.582 Pa/N) surpasses that of stainless steel (180.125 Pa/N), indicating its superior efficiency in construction.
The maximum allowable strain for the laminate is 1.3ɛd . The maximum strain obtained from the analysis is 0.00095968 mm/mm which is less than the maximum allowable strain. The strength to weight ratio for fiber reinforced plastic storage tank is 672.582 𝑃𝑎/𝑁 and strength to weight ratio for stainless steel storage tank is 180.125 𝑃𝑎/𝑁 . Hence, strength/weight for FRP tank is more than that stainless steel which makes it more effective for construction. Fiber reinforced plastic storage tank has low installation cost as compared to stainless steel tank. It requires less maintenance and inspection can be done easily. Transportation is much easier as compared to stainless steel tank due to less weight.
Optimization in FRP Storage Tank Design. (2024, Feb 22). Retrieved from https://studymoose.com/document/optimization-in-frp-storage-tank-design
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