scholarly journals Influence of Tightening Torque of Emergency Cooling Heat Exchanger Flange Studs on Strength

2020 ◽  
pp. 56-63
Author(s):  
O. Koroliov ◽  
V. Iniushev ◽  
T. Pyrohov ◽  
V. Posokh ◽  
A. Koliadiuk
Keyword(s):  
Heat Exchanger ◽  
Static Strength ◽  
Flange Joint ◽  
The Finite Element Method ◽  
Permissible Stress ◽  
Tightening Torque ◽  
Tightening Force ◽  
Flange Connection ◽  
Design Values ◽  
Reducing Stress

Previous efforts on assessing static strength of the flange joint components of the emergency cooling heat exchanger 08.8111.335 SB (ECHE) performed using the finite element method (FEM) revealed that there is an excess of permissible stress values for flange joint components of heat exchanger Dn2130 and Dn2080. These static strength calculations considered the design values for tightening of flange studs. Failure to meet the strength conditions flange joint components is due to the fact that the effect of «protrusion» under pressure of the bottom and shell attached to the flanges, as well as depending on the tightening force of the studs, the system of equilibrium applied force changes. This, in turn, leads to deformation of flange joint components. The paper presents an approach to reducing stress in flange joint components of ECHE first used at ZNPP-4. As a result of additional iterative calculations, the boundary conditions under which the strength conditions in all flange joint components of the heat exchanger are met are determined. In addition, the compliance with tightness condition for flange connections is considered. Thus, the analysis of the calculations established that when the tightening value of flange connection Dn2080 studs equal to 6800 kgf (corresponding to the torque on the key of 65 kg ∙m), the strength conditions for all groups of reduced stresses in all elements of the flange unite. In addition, at this value of stud tightening, the tightness of the flange connection Dn2080 is maintained. Analysis of similar iterative calculations of flange connection Dn2130 shows that for this flange connection it is recommended to reduce the tightening of the flange connection studs to the value of 14600 kgf, which is equal to the torque on the key of 145 kg ∙ m.

scholarly journals Analysis of the thermal stress state of the flange connections elements of the emergency cooling heat exchangers during accidents of the WWER-1000 nuclear installation

2020 ◽  
Vol 19 (4) ◽  
pp. 23-30
Author(s):  
T. V. Pyrohov ◽  
◽  
A. V. Korolev ◽  
Keyword(s):  
Thermal Stress ◽  
Heat Exchanger ◽  
Stress State ◽  
Boundary Conditions ◽  
Heat Exchangers ◽  
Static Strength ◽  
Thermal Stress State ◽  
Flange Connection ◽  
Design Values ◽  
Nuclear Installation

During the assessment of the static strength of the flange connections elements Dn2130 and Dn2080 of the emergency cooling heat exchangers 08.8111.335 SB (TOAR), it was found that there is an excess of the allowable stress values. These calculations of static strength performed using the finite element method (FEM). The analysis of the static strength of the flange joints was performed taking into account the design values of the tightening of the studs, equal to 22,527 kgf and 8,836 kgf, accordingly. At the same time, one of the main purposes of heat exchangers TOAR nuclear installation (NI) WWER-1000 is the work until accidents. The analysis of accidents of NI WWER-1000 showed that the largest values of change of parameters of environments in heat exchangers of TOAR correspond to accident “LOCA: Bilateral rupture of MCT”. Based on this, we considered the thermal stress state of heat exchangers for this accident. To determine the thermal stress state of the TOAR heat exchanger elements, during accidents of the nuclear installation, strength calculations were performed in the non-stationary formulation of the problem. One of the boundary conditions for these strength calculations is the distribution of temperatures along the thickness and length of the walls of the elements of the heat exchanger, which changes over time. Numerical thermohydraulic calculations were performed to determine these boundary conditions. In the article for the first time the results of calculations of thermal stress state of separate elements of heat exchangers TOAR, for work of heat exchangers during accidents of nuclear installation are received. It is established that the elements of the flange connection Dn2130 are one of the most critical elements of TOAR heat exchangers. To determine the thermal stress state of the heat exchanger elements, analytical thermal calculations, numerical thermohydraulic and strength calculations were performed using the FEM method. As a result of the analysis of the performed strength calculations, it was concluded that it is necessary to reduce the tightening value of the flanges of the flange connection Dn2130 to 14600 kgf.

Design and Application of the FROMO® Preload Nut

2012 ◽  
Vol 538-541 ◽  
pp. 2718-2721
Author(s):  
Ying Liu ◽  
Jian Chu Shen
Keyword(s):  
Tensile Stress ◽  
Screw Thread ◽  
Tightening Torque ◽  
Tightening Force ◽  
Large Size ◽  
Design And Application

The design of a new pre-tensional structure(FROMO® preload nut) applied in the large size of screw thread was introduced, the preload bolt is only beared with the pure tensile stress. The pre-tightening force for the preload bolt and pre-tightening torque for the jack bolts were calculated. The practice elongation value of the preload bolt was measured, and compared with its theoretical elongation value. The result shows that: the new pre-tensional structure has adequate strength, it can control the pre-tightening force accurately with manual acting spanner, it increases efficiency and ensures the safety of operating , and which has promised the good performance in the application of the projects.

Leak Behavior and Prediction of Metal Ring Joint Gaskets in Simplified Leak Test With Grooved Platen

2019 ◽  
Author(s):  
Yuya Omiya ◽  
Masahiro Fujii
Keyword(s):  
Internal Pressure ◽  
Evaluation Method ◽  
Compressive Force ◽  
Metal Ring ◽  
Leak Test ◽  
Tightening Force ◽  
Flange Connection ◽  
Sealing Performance ◽  
Sealing Mechanism ◽  
Very High

Abstract Pipe flange connection with metal gasket is used under high temperature and pressure in place required high sealing performance. It has been known that gasket compressive force, which is closely related the leakage decreases by internal pressure action. Since the pressure is very high in metal gaskets, the sealing performance evaluation in internal pressure action is important. However, there is little research that evaluates a little leakage, metal gasket is empirically used up to the present time. Therefore, evaluated sealing performance of metal gasket, it is necessary to clarify the sealing mechanism. In this study, evaluated effect that decreasing of gasket compressive force affects leakage in both octagonal type and oval type in ring joint gasket by simplified leak test using grooved platen and finite element method stress analysis, evaluation method of leakage in metal gasket is proposed. Based on this evaluation method, decision method of initial tightening force that guaranteed one amount of leakage to design internal pressure is shown in pipe flange connection with metal gasket.

FEM Stress Analysis and Sealing Performance in Bolted Flange Connections With Cover of Pressure Vessel Subjected to Internal Pressure

2003 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Rie Higuchi
Keyword(s):  
Internal Pressure ◽  
Contact Stress ◽  
Pressure Vessel ◽  
The Finite Element Method ◽  
Flange Connection ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Bolted Flange ◽  
Contact Stress Distribution ◽  
Spiral Wound

The stresses of a bolted flange connection with a cover of pressure vessel (CPV) in which a spiral wound gasket is inserted, under internal pressure are analyzed taking account a hysteresis of the gasket by using the finite element method (FEM). The leakage tests were also conducted using an actual bolted flange connection with a CPV with a spiral wound gasket. Using the contact stress distribution of the bolted flange connection with a CPV under internal pressure and the tightness parameter, the values of the new gasket constants were obtained by taking into account the changes in the contact stress. A difference in the new gasket constants between the estimated values obtained from the actual bolted flange connection with a CPV and the values obtained by the PVRC procedure was small. In addition, a method to determine the bolt preload for a given tightness parameter was demonstrated. The obtained results of the bolt preload for the bolted flange connection with a CPV were in a fairly good agreement with those obtained by the PVRC procedure under a lower pressure application. However, a difference in the bolt preload was about 7% when the internal pressure was increased.

FEM Analysis and Evaluation of the Sealing Performance in Flexible Box-Shape Flanged Bolted Joints With Gaskets Subjected to Internal Pressure: Effect of the Bolt Pitch

2007 ◽  
Author(s):  
Toshiyuki Sawa ◽  
Ryo Kurosawa ◽  
Yasuaki Tatsumi
Keyword(s):  
Internal Pressure ◽  
Fem Analysis ◽  
Bolted Joints ◽  
Stress Distributions ◽  
The Finite Element Method ◽  
Analysis And Evaluation ◽  
Flange Connection ◽  
Sealing Performance ◽  
Helium Gas ◽  
Bolted Flange

Bolted joints with gaskets such as non-circular flange connections have been widely used in mechanical structures, nuclear and chemical industry, and so on. They are usually used under internal pressure as well as other loadings such as thermal, impact loadings and so on. In designing the non-circular flange connections with gaskets, it is important to evaluate the sealing performance of the non-circular flange connections with gaskets subjected to internal pressure. An important issue is how to evaluate the sealing performance in the box-shape bolted flange connections by using the contact gasket stress distributions at the interfaces, how to reduce a number of bolt and nuts, that is, how to enlarge the bolt pitch, and how to determine the initial clamping bolt force (preload) by using the new gasket constants. In this paper, the stresses of box-shape flange connection with gaskets subjected to an internal pressure are analyzed using the finite element method (FEM), taking account a hysteresis in the stress-strain curves of the gasket. The contact gasket stress distributions when the internal pressure is applied to the connection are analyzed. The leakage tests were conducted using an actual box-shape flange connection with a gasket Using the contact gasket stress distributions at the interfaces under an internal pressure (Helium gas was used) and the amount of the leakage measured in the experiment, the sealing performances are evaluated experimentally and theoretically by changing the bolt pitch in the connections. Discussion is made on the effect of the bolt pitch on the sealing performance in the above connections.

scholarly journals Improved Analysis on the Fin Reliability of a Plate Fin Heat Exchanger for Usage in LNG Applications

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3624
Author(s):  
Mustansar Hayat Saggu ◽  
Nadeem Ahmed Sheikh ◽  
Usama Muhamad Niazi ◽  
Muhammad Irfan ◽  
Adam Glowacz ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Heat Exchanger ◽  
Temperature Gradient ◽  
Large Temperature ◽  
The Finite Element Method ◽  
Lower Face ◽  
Brazed Joints ◽  
Brazed Joint ◽  
Liquefaction Process

A plate fin heat exchanger (PFHE) is a critical part of the cryogenic industry. A plate fin heat exchanger has many applications, but it is commonly used in the liquefied natural gas (LNG) industry for the gasification/liquefaction process. During this gasification to the liquefaction process, there is a large temperature gradient. Due to this large temperature gradient, stresses are produced that directly influence the braze joint of PFHE. Significant work has been carried out on heat transfer and the flow enhancement of PFHE; however, little attention has been paid to structural stability and stresses produced in these brazed joints. Due to these stresses, leakages in PFHE are observed, mostly in braze joints. In the current study, standard fin design is analyzed. In addition, the structural stability of brazed joints under standard conditions is also tested. Two techniques are used here to analyze fins, using the finite element method (FEM), first by examining the whole fin brazed joint on the basis of experimentally calculated yield strength and second by dividing the braze seam into three sections and defining individual strength for each section of the seam to find stress magnitude on the basis of heat-affected zones. Moreover, by using two different techniques to analyze brazed joints, the stresses in the lower face of the brazed joint were increased by 13% and decreased by 18% in the upper face using different zone techniques as compared to standard full braze seam analysis. It can be concluded that different zone techniques are better in predicting stresses as compared to simple full braze seam analysis using the finite element method since stresses along the lower face are more critical.

Identification of Internal Stresses in Bolted Flanged Joints

2010 ◽  
Vol 165 ◽  
pp. 353-358 ◽  
Author(s):  
Tadeusz Smolnicki ◽  
Jacek Karliński ◽  
Damian Derlukiewicz
Keyword(s):  
Stress Fields ◽  
Internal Stresses ◽  
Local Models ◽  
Flange Joint ◽  
The Finite Element Method ◽  
Equivalent Models ◽  
Heating Surfaces ◽  
Calculation Methodology ◽  
Bending Loads ◽  
Bolted Flange

In bolted flange joints of flexible constructional elements, bolts are subjected not only to tension and torsion but also to bending loads. Identification of straining of each bolt is only possible by means of numerical methods e.g. the finite element method. In the case of large objects, the calculation problem is faithful projection of the phenomena occurring in direct zone of the contact of screw-nut pair. The application of global equivalent models of the whole joint is necessary in order to make it possible to precisely determine internal loads in individual bolts and then local models to establish stress fields necessary to assign durability. Calculation methodology based on the construction of two coherent models has been described: global - for the entire flange joint, and local - for a single bolt joint. The elaborated methodology was applied to evaluate a flange joint in a heat exchanger with rotating heating surfaces that was subject to damage. The causes of damage of the flange joint were determined.

Structural strength analysis of the bogie frame in Taipei rapid transit systems

1998 ◽  
Vol 212 (3) ◽  
pp. 253-262 ◽  
Author(s):  
C Oyan
Keyword(s):  
Fatigue Strength ◽  
Complex Geometry ◽  
Static Strength ◽  
Rolling Stock ◽  
Strength Analysis ◽  
Rapid Transit ◽  
Bogie Frame ◽  
Transit Systems ◽  
Permissible Stress ◽  
Dynamic Loadings

The importance of bogie fatigue in railway rolling stock has been recognized as a contributing factor in structural failure. A bogie frame designed for Taipei rapid transit systems is analysed in order to confirm the technical strength requirements for static and dynamic loadings. A numerical finite element analysis is utilized in view of the complex geometry, and detailed plots are also presented in this report to give a complete understanding of the behaviour of the bogie frame. The von Mises stresses are adopted as equivalent stresses in the static strength calculation while the principal stresses are adopted in fatigue strength evaluation. Material yield stress and modified Goodman diagrams showing the permissible stress ranges are used as failure criteria respectively for static and dynamic loadings. It is demonstrated that the static strength and fatigue strength of the bogie frame satisfy the strength requirements specified by Taipei rapid transit systems.

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