Arjstme 01 101

Advanced Research Journals of Science and Technology

ADVANCED RESEARCH JOURNALS OF SCIENCE AND TECHNOLOGY

(ARJST)

FAILURE ANALYSIS OF COMPOSITE PRESSURE VESSELS

2349-1845

G Nagendra Krishna1, A.SwarnaKumari2, 1 Research Scholar, Department of Mechanical Engineering,University college of Engineering, JNTUK,Kakinada,AP,India.

2 Professor , Department of Mechanical Engineering, University college of Engineering, JNTUK,Kakinada,AP,India.

Abstract Light weight composite pressure vessels can be used in space applications. Composite pressure vessels need number of layers to achieve required thickness and also to achieve required strength to bear the pressure of gases/liquids.

The aim of the project is to provide composite pressure vessel with sufficient strength using different layer orientations. data collection will be done to prepare design and to select suitable materials.

Structural calculations will be done to find the stress and strains values theoretically.

3D modeling will be done according to the allowable standards.

Structural and thermal analysis will be conducted on pressure vessel using different layer orientations and the above analysis will be done on traditional material for comparison.

Results and discussion will be done to determine conclusion.

*Corresponding Author: G Nagendra Krishna, Research Scholar, Department Of Mechanical Engineering, University college of Engineering, JNTUK,Kakinada,AP,India.

Published: July 04, 2014 Review Type: peer reviewed Volume: I, Issue : I Citation: G Nagendra Krishna,Research Scholar (2014) FAILURE ANALYSIS OF COMPOSITE PRESSURE VESSELS

INTRODUCTION Pressure vessel: A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.

Pressure vessels can theoretically be almost any shape, but shapes made of sections of spheres, cylinders, and cones are usually employed. A common design is a cylinder with end caps called heads. Head shapes are frequently either hemispherical or dished (torispherical).

More complicated shapes have historically been much harder to analyze for safe operation and are usually far more difficult to construct.

Theoretically, a spherical pressure vessel has approximately twice the strength of a cylindrical pressure vessel with the same wall thickness.[1] However, a spherical shape is difficult to manufacture, and therefore more expensive, so most pressure vessels are cylindrical with 2:1 semi-elliptical heads or end caps on each end. Smaller pressure vessels are assembled from a pipe and two

covers. For cylindrical vessels with a diameter up to 600 mm, it is possible to use seamless pipe for the shell, thus avoiding many inspection and testing issues. A disadvantage of these vessels is that greater breadths are more expensive, so that for example the most economic shape of a 1,000 litres (35 cu ft), 250 bars (3,600 psi) pressure vessel might be a breadth of 914.4 millimetres (36 in) and a width of 1,701.8 millimetres (67 in) including the 2:1 semi-elliptical domed end caps.

Types of pressure vessels: When a container is pressurized then pressure is exerted against the walls of the vessels. Pressure is always normal to the surface regardless of the shape. Pressure vessel is a container that has pressure different from the atmospheric pressure. There are many types of pressure vessel they are; thin walled, thick walled, strong tanks, transportable containers, propane bottles and gas cylinders.

Pressure vessel is a container that holds liquid, vapor or gas at different pressure other than atmospheric pressure at the same elevation. Generally, a pressure vessel is considered to be thin-walled if its radius is larger than 5 times its wall thickness. Under this condition, the stress in the wall may be considered uniform. Thin wall pressure vessels are in fairly common use. Under this condition, the stress in the wall may be considered uniform. The stress in thin walled vessel varies from a maximum value at the inside surface to a minimum value at the outside surface of the vessel. Storage tanks are a category of thin walled pressure vessel.

Thin wall pressure vessels (TWPV) are widely used in industry for storage and transportation of liquids and gases when configured as tanks. They also appear as components of aerospace and marine vehicles such as rocket and balloon skins and submarine hulls.

There are mainly two types: • Cylindrical pressure vessels. • Spherical pressure vessels.

1

Advanced Research Journals of Science and Technology

The walls of an ideal thin-wall pressure vessel act as a membrane (that is, they are unaffected by bending stresses over most of their extent). A sphere is the optimal geometry for a closed pressure vessel in the sense of being the most structurally efficient shape. A cylindrical vessel is somewhat less efficient for two reasons: (1) the wall stresses vary with direction, (2) closure by end caps can alter significantly the ideal membrane state, requiring additional local reinforcements. However the cylindrical shape may be more convenient to fabricate and transport.

COMPOSITE PRESSURE VESSEL: Lightweight composite pressure vessels can be used for space applications. Composite pressure vessels need liners because composite materials cannot prevent a gas leak. Generally, the role of a liner is the barrier of a gas leak as well as load sharing. This liner is called load sharing liner. The load sharing liner was mostly made by a metallic material. The composite pressure vessel with the metallic liner was mainly reported for the load sharing liner. The non-load sharing liner was reported by a limited number of papers.

manufacture. Shell-type pressure components such as pressure vessel and heat exchanger shells and heads of different geometric configurations resist pressure primarily by membrane action. Cylindrical shells are used in nuclear, fossil and petrochemical industries .

HEAD: All pressure vessel shells must be closed at the ends by heads (or another shell section). Heads are typically curved rather than flat. Curved configurations are stronger and allow the heads to be thinner, lighter, and less expensive than flat heads. Heads can also be used inside a vessel. These “intermediate heads” separate sections of the pressure vessel to permit different design conditions in each section. Heads are usually categorized by their shapes. Ellipsoidal, hemispherical, torispherical, conical, toriconical and flat are the common types of heads. The below images shows the types of heads used in pressure vessel.

PRESSURE VESSEL DESIGN: Tower (Column): Tall vertical towers are constructed in a wide range of shell diameters and heights. Towers can be relatively small in diameter and very tall (e.g., a 4 ft. diameter and 200 ft.tall distillation column), or very large in diameter and moderately tall (e.g., a 30 ft. diameter and 150 ft. tall pipestill tower). The shell sections of a tall tower may be constructed of different materials, thicknesses, and diameters. This is because temperature and phase changes of the process fluid which are the factors that affect the corrosiveness of the process fluid, vary along the tower’s length .

Reactor: Reactor vessel with a cylindrical shell. The process fluid undergoes a chemical reaction inside a reactor. This reaction is normally facilitated by the presence of catalyst which is held in one or more catalyst beds.

Spherical Tank: Spherical tanks are usually used for gas storage under high pressure.

COMPONENTS OF PRESSURE VESSELS: SHELL: The shell is the primary component that contains the pressure. Pressure vessel shells are welded together to form a structure that has a common rotational axis. Most pressure vessel shells are cylindrical, spherical and conical in shape.

Most of the shells are generated by the revolution of a plane curve. The term shell is applied to bodies bounded by two curved surfaces, where the distance between the surfaces is small in comparison with other body dimensions .The vessel geometries can be broadly divided into plate- and shell-type configurations. The shell-type construction is the preferred form because it requires less thickness (as can be demonstrated analytically) and therefore less material is required for its

Nozzle: A nozzle is a cylindrical component that penetrates the shell or heads of a pressure vessel. The nozzle ends are usually flanged to allow for the necessary connections and to permit easy disassembly for maintenance or access. Nozzles are used for the following applications: • Attach piping for flow into or out of the vessel.

• Attach instrument connections, (e.g., level gauges, thermo wells, or pressure gauges).

• Provide access to the vessel interior at man ways.

• Provide for direct attachment of other equipment items, (e.g., a heat exchanger or mixer).

Nozzles are also sometimes extended into the vessel interior for some applications, such as for inlet flow distribution or to permit the entry of thermo wells.

SUPPORT: The type of support that is used depends primarily on the size and orientation of the pressure vessel. In all cases, the pressure vessel support must be adequate for the applied weight, wind, and earthquake loads. Calculated base loads are used to design of anchorage and foundation for the pressure vessels. Typical kinds of supports are as follow: a) Skirt: Tall, vertical, cylindrical pressure vessels (e.g., the tower and reactor shown in Figure ‎ 1-4 and Figure ‎ 1-5respectively) are typically supported by skirts. A 2

Advanced Research Journals of Science and Technology

support skirt is a cylindrical shell section that is welded either to the lower portion of the vessel shell or to the bottom head (for cylindrical vessels). Skirts for spherical vessels are welded to the vessel near the mid-plane of the shell. The skirt is normally long enough to provide enough flexibility so that radial thermal expansion of the shell does not cause high thermal stresses at its junction with the skirt . b) Leg: Small vertical drums are typically supported on legs that are welded to the lower portion of the shell. The maximum ratio of support leg length to drum diameter is typically 2:1. The number of legs needed depends on the drum size and the loads to be carried. Support legs are also typically used for spherical pressurized storage vessels. The support legs for small vertical drums and spherical pressurized storage vessels may be made from structural steel columns or pipe sections, whichever provides a more efficient design. Cross bracing between the legs, is typically used to help absorb wind or earthquake loads. c) Saddle:

INTRODUCTION TO ANSYS ANSYS is general-purpose finite element analysis (FEA) software package. Finite Element Analysis is a numerical method of deconstructing a complex system into very small pieces (of user-designated size) called elements.

The software implements equations that govern the behaviour of these elements and solves them all; creating a comprehensive explanation of how the system acts as a whole. These results then can be presented in tabulated, or graphical forms. This type of analysis is typically used for the design and optimization of a system far too complex to analyze by hand. Systems that may fit into this category are too complex due to their geometry, scale, or governing equations.

ANSYS is the standard FEA teaching tool within the Mechanical Engineering Department at many colleges. ANSYS is also used in Civil and Electrical Engineering, as well as the Physics and Chemistry departments.

STRUCTURAL ANALYSIS OF PRESSURE VESSEL USING HIGH CARBON STEEL

Horizontal drums are typically supported at two locations by saddle supports. A saddle support spreads the weight load over a large area of the shell to prevent an excessive local stress in the shell at the support points. The width of the saddle, among other design details, is determined by the specific size and design conditions of the pressure vessel. One saddle support is normally fixed or anchored to its foundation. The other support is normally free to permit unrestrained longitudinal thermal expansion of the drum.

MODELING OF PRESSURE VESSEL

The above image is the imported model

The above image shows the vessel without stands

The above image shows von-misses stress

The above image shows the complete vessel

3

Advanced Research Journals of Science and Technology

MODAL ANALYSIS

The above image shows von-misses stress

The above image shows frequency mode1

STRUCTURAL ANALYSIS OF PRESSURE VESSEL USING FIVE LAYER WITH E-GLASS EPOXY

THERMAL ANALYSIS

The above image shows the pressure vessel with five layers

The above image shows the nodal temperature

The above image shows von-misses stress The above image shows the thermal gradient

STRUCTURAL ANALYSIS OF PRESSURE VESSEL USING THREE LAYER WITH E-GLASS EPOXY

RESULTS TABLE material

Stress

Displacement

Mode1

Mode2

Mode3

Mode4

Mode5

High carbon steel

653.1

10.22

0.4079

0.408

0.794

0.868

0.3753

E-glass 3 layers

1031.8

41.87

0.1513

0.149

0.1349

0.1445

0.1351

E-glass 5 layers

661.5

35.82

0.1393

0.148

0.1314

0.1448

0.3730

4

Advanced Research Journals of Science and Technology

CONCLUSION

BIBLIOGRAPHY

This project work is done on failure analysis of composite pressure vessel to predict the failures after manufacturing pressure vessel with composites.

1. HectorEstrada, Stanley S. Smeltzer, III[1]

In first step data was collected to understand methodology and for further investigation of composite failure.

Composite design calculation s are done for the preparation of pressure vessel model using 3 layers and 5 layers.

3D model was prepared to conduct analysis in ansys.

Static and thermal analysis was conducted on pressure vessel using regular material carbon steel and E-glass epoxy (FRP- fiber rein forced polymer).

2. Cheol-Won Kong, Jong-Hoon Yoon, Young-Soon Jang and Yeong-Mooo Yi[2] 3. Douglas W. Eisberg, C. Peter Darby[3] 4. RAO YARRAPRAGADA K.S.S1, R.KRISHNA MOHAN2, B.VIJAY KIRAN3[4] 5. David Heckman [5] AUTHOR

Static and modal analysis is carried out to find structural characteristics like stress, displacement and mode shapes us to natural frequency.

Thermal analysis was carried out to find flex and gradient rates for subzero (-20) and high temperature (270c move for gases).

As per the analysis E- glass having less stress and displacement for 5 layered object but having low factor of safety.

G Nagendra Krishna, Research Scholar, Department of Mechanical Engineering, University college of Engineering, JNTUK, Kakinada,AP,India.

Static analysis was conducted by increasing thickness up to 10 mm with 5 layers with 45 of angular variation in layers.

As per the analysis results of modified thickness pressure vessel with E- glass epoxy 10 thick along with 5 layers is the best option.

By using E – glass we can decrease up to 68% of weight even after increasing thickness.

A.SwarnaKumari, Professor , Department of Mechanical Engineering, University college of Engineering, JNTUK, Kakinada,AP,India.

5