**1. Introduction**

The structural engineers faced many challenges to safely and durably design and build the budget-consuming projects. The loadings may damage the piping structures or disturb their normal operations whenever their magnitudes reach the strength limits of the structure material [1].

Mostly the structural engineers performed three-dimensional (3D) finiteelement analyses to investigate the behavior of buried pipe subject to strike-slip fault movement in dry sand and, more realistically, in partially saturated sand [2].

Some literature presents specific methods and algorithms for evaluating potential damage zones of pipe joints that can be used to make decisions to ensure the safety of use of hazardous production systems that also concern human life in the gas-oil sector during the draft and detailed design and later use stages [3].

Design analysis engineers recommend to specify mechanical closure and fatigue conditions considering stress and amplitude depending on swage parameter and material for using swaged fittings to joining in structural engineering and mechanical handling [4].

In some load cases, to obtain more realistic results from design analysis for structural systems, it is necessary to determine or to define suitable fastener stiffness values in their connections [5].

It is necessary to propose an analytical or numerical useful method for the practicing engineers in the rational design of pipe connections in detail designing and structural analysis [6].

The most critically part of a piping is they are connections, each other or to equipment. Piping solutions using non-welded connections and cold bent piping offer significant value through reductions in fabrication and commissioning time, while improving workplace safety. The benefits of non-welded piping technology are ranging from reduced preparation and inspection time to a safer work environment [7].

Different methods are used to join the tubes. One of them is rotary swaging, in them the rotation energy changed to thermal friction energy and the fitting is swaged on the pipe with approximately 100% sealing [8].

The swaging as a joining method is used today in most crucial industries including the military, automotive, and medical. Within the military industry, swaging is used to form items such as gun barrels and anti-tank rocket tips. Fittings are also swaged into cable. Countless auto parts and systems, such as distress alert brake cables, steering components, and powertrains, are produced by rolling. In the medical sector; subcutaneous needles, catheter tape assemblies and optical parts and assemblies are the first to come to mind as products produced by rolling the same. In the energy sector; heater elements, heat conductive materials and zirconium profiles can be listed (items that the renewable energy industry relies upon), can be expertly machined using swaging machines. In aerospace; by swaging, the aerospace industry is assured of high-quality control rods, wire rope cable assemblies, and fluid transfer tubing [9].

It is useful for swaging tube and pipe made from the manufacturing industry's most common material (steel) and it's also suitable for stainless steels, aluminum, titanium alloys.

Also, swaged pipe in pipe construction has been increasingly used for offshore pipeline system. The end connection, produced by plastering and rolling, is transmitted to the outer tube by a cold deformation process and then connected to the inner tube. The twin welded piping system provides excellent thermal insulation [7].

In any case, literature studies have shown how important fasteners are to structural design engineers. Piping designs are generally calculated with 16 bar and below, and such connections are designed as removable flange or screw connections. In screw connections in such systems, rubber or metal plastered intermediate element between the screw and the nut provides both the connection and the sealing [10].

Connections in pipe systems operating under high pressure are produced using rubber or metal unions produced using the swaging method. Such connections are designed and tested at 1.5 times the working pressure and at burst pressure. Piping systems used in aerospace are produced from either stainless steel or mostly aluminum alloy pipes. In addition to rubber plastic piping, and also their tightness is tested by performing tests such as vibration tests under conditions far above operating conditions [11].

Although there is not much in this field (ring swaging pipe connection), design and analysis studies have been carried out [12].

### *How Impact the Design of Aluminum Swaging Circle Fitting on the Sealing for Piping… DOI: http://dx.doi.org/10.5772/intechopen.99938*

As can be seen in the swaging type A in **Figure 1**, both the direct connection of the two pipes and the connection of the fittings with the pipe can be done with the design of the swaging circle fitting (Sleeve), which is one of the main inspection elements of the study. The pipes to be connected can also be of different materials; however, different swaging parameters have to be determined in this case. These connections, as in welded connections, are expected to be made to withstand more pressures than the pipe itself. The design of the sealed swaging circle fitting pipe significantly affects the mechanical strength and tightness of the joint. As can be seen in **Figure 1**, the area to be compacted is designed as inclined and undulated in the axial direction; this prevents it from being pulled in the axial direction. Likewise, the swaging circle fitting creates an obstacle to the tangential rotation of the pipe in the fitting with waves in the circumferential direction. In addition, two internal circumferential grooves have been designed to provide greater sealing by placing an O-Ring in the ring.

In **Figure 1**, a cut-out view of the A-type fitting is given. Compression is applied in two steps by pressing the first pipe from the right and then the pipe from the left towards the center in a radial direction, so that the plastering circle counts the plastic displacements. Pipes and the middle part of the fitting exposed to pressure load does not exceed elastic loading. When pipes are of different materials, different swaging parameters must be applied from right and left.

In **Figure 2**, there is a cross-sectional view of the B type. The swaging fitting is axially and radially pressured to the first pipe from the right and then from the left to the second pipe, resulting in plastic deformation. Pipes and middle part of c fitting exposed to pressure load does not exceed elastic loading. When pipes are of different materials, different swaging parameters must be applied from right and left.

In **Figure 3**, there is a cut view of the Type C. The swaged fitting tube piece is clamped radially to the first tube from the right and then from the left to the second tube simultaneously with two pressure booster wedge rings. In the meantime, sealing is tried to be achieved by creating plastic deformation. Pipes and middle part of circle form fitting exposed to pressure load does not exceed elastic loading. When pipes are of different materials, different swaging parameters from right and left and different riser fitting designs must be applied.

In this study, the swaging circle fitting that will work without leakage under high or low pressures is tightened with each of the three different methods shown under the previous introducing, and the ability to join 2 aluminum alloy pipes is modeled and analyzed by analytical and numerical methods. Different types (Types A, B, and C) designs of aluminum alloy swaged strap fastener were designed in 3D

#### **Figure 1.**

*A type swaging circle fitting; pressure equalizer design features in the radial direction [13].*

#### **Figure 2.**

*B type swaging circle; radial swaging designs with pressure against axial tension and pressure booster [13].*

#### **Figure 3.**

*Swaging type C; radial swaging by tightly compressing the pressure booster (wedge) fitting to the swaging circle fitting by axial pressure force [13].*

and mathematically solved using the finite element method. Due to the nature of the numerical method, swaged circle pipe parts and pipes that are connected to each other and may be in different materials are subject to elastic–plastic (bi-linear material definition) deformations. For this reason, the numerical solution could only be realized with a non-linear method [14–16]. In addition, since the material is exposed to plastic pressure and there is friction between the elements, the solution with the non-linear method becomes inevitable again [14, 16]. The nonlinear solution of the mathematical numerical model was carried out using the finite element method (FEM) with the help of a commercial program on the computer. Different swaging circle fitting designs were analyzed and compared, and the connection has been improved by optimizing with swaging circle fitting design changes.

The numerical method proposed in this study are useful for the practicing engineers in the rational design of pipe connections in detail designing and structural analysis.
