scholarly journals Gauging the Force Effects of Valve Stem Packing on Valve Stem Actuation

2017 ◽  
Author(s):  
James Drago ◽  
Wayne Evans
Keyword(s):  
Axial Load ◽  
Compressive Load ◽  
Dynamic Interaction ◽  
Packing Material ◽  
Temperature Cycling ◽  
Actuation Force ◽  
Frictional Properties ◽  
Balanced Approach ◽  
Valve Stem ◽  
Packing Rings

Stem friction in an operating valve is a function of the dynamic interaction of a number of variables — packing material of construction, number of packing rings, compressive load, lubrication, stem surface finish, temperature, cycling, etc. Forces due to friction can be reduced by modifying these factors. Attaining low actuation force and good sealing requires a balanced approach. Packing manufacturers have their own procedures for determining the frictional properties of different packing materials. This paper will show one such procedure and how varying materials and packing set configurations affect actuation force. The focus will be on linear reciprocating valve stems. The equation F = π × d × H × GS × μ × Y can be used to calculate the force of the packing on the valve stem: Where F - Force needed to overcome packing friction; d - Stem diameter; H - Packing set height; GS - Compressive stress on the packing; μ - Packing coefficient of friction; Y - Ratio of radial to axial load transference, commonly equal to 0.50. Knowing the force, F, by test allows the calculation of the packing set’s frictional characteristics. . This knowledge can guide valve designers and builders to properly size actuating units for consistent and reliable valve performance. Paper published with permission.

Photoelastic Analysis on Different Retention Methods of Implant-Supported Prosthesis

2015 ◽  
Vol 41 (3) ◽  
pp. 258-263 ◽  
Author(s):  
Angélica Castro Pimentel ◽  
Marcello Roberto Manzi ◽  
Cristiane Ibanhês Polo ◽  
Claudio Luiz Sendyk ◽  
Maria da Graça Naclério-Homem ◽  
...  
Keyword(s):  
Stress Distribution ◽  
Axial Load ◽  
Testing Machine ◽  
Compressive Load ◽  
Lower Intensity ◽  
Photoelasticity Method ◽  
Universal Testing ◽  
Isochromatic Fringes ◽  
Photoelastic Analysis ◽  
Compressive Axial Load

The aim of this study was to evaluate the stress distribution of different retention systems (screwed, cemented, and mixed) in 5-unit implant-supported fixed partial dentures through the photoelasticity method. Twenty standardized titanium suprastructures were manufactured, of which 5 were screw retained, 5 were cement retained, and 10 were mixed (with an alternating sequence of abutments), each supported by 5 external hexagon (4.0 mm × 11.5 mm) implants. A circular polariscope was used, and an axial compressive load of 100 N was applied on a universal testing machine. The results were photographed and qualitatively analyzed. We observed the formation of isochromatic fringes as a result of the stresses generated around the implant after installation of the different suprastructures and after the application of a compressive axial load of 100 N. We conclude that a lack of passive adaptation was observed in all suprastructures with the formation of low-magnitude stress in some implants. When cemented and mixed suprastructures were subjected to a compressive load, they displayed lower levels of stress distribution and lower intensity fringes compared to the screwed prosthesis.

Analysis of Stresses and Strains in Packed Stuffing-Boxes

2014 ◽  
Author(s):  
Mehdi Kazeminia ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Design Procedure ◽  
Standard Test ◽  
Packing Material ◽  
Test Procedures ◽  
Analytical Methodology ◽  
Packing Materials ◽  
Standard Design ◽  
Packing Rings ◽  
Leak Tightness ◽  
Side Walls

Packed stuffing-boxes are mechanical sealing systems that are extensively used in pressurized valves and pumps. Yet there is no standard design procedure that could be used to verify their mechanical integrity and leak tightness. It is only recently that standard test procedures to qualify the packing material have been suggested for adoption in both North America and Europe. While the packing contact stress with the side walls is predictable using existing models there is no analytical methodology to verify the stresses and strains in the stuffing-box housing. This paper presents an analytical model that analyzes the stresses and strains of all the stuffing box components including the packing rings. The developed model will be validated both numerically using FEM and experimentally on an instrumented packed stuffing box rig that is specially designed to test the mechanical and leakage performance of different packing materials.

scholarly journals Experimental Behavior of Existing RC Columns Strengthened with HPFRC Jacket under Concentric and Eccentric Compressive Load

Buildings ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 521
Author(s):  
Paolino Cassese ◽  
Costantino Menna ◽  
Antonio Occhiuzzi ◽  
Domenico Asprone
Keyword(s):  
Reinforced Concrete ◽  
Axial Load ◽  
High Performance ◽  
Compressive Load ◽  
Bending Moment ◽  
Critical Issue ◽  
Fiber Reinforced Concrete ◽  
Rc Columns ◽  
Rc Structures ◽  
Rc Building

Reinforced concrete (RC) structures built before the 1970 represent a large portion of the existing European buildings stock. Their obsolescence in terms of design criteria, materials, and functionality is becoming a critical issue for guaranteeing adequate compliance with current structural codes. Recently, a new jacketing system based on the use of high-performance fiber-reinforced concrete (HPFRC) has been introduced for strengthening existing RC building members. Despite the promising aspects of the HPFRC jacketing technique, currently, a comprehensive and systematic technical framework for its implementation is still missing. In this paper, the experimental performance of RC columns strengthened with the HPFRC jacket subjected to pure axial load and combined axial load-bending moment uncoupled from shear is investigated. The test outcomes confirmed a significant improvement of the structural performance for the strengthened columns, especially for higher values of eccentricity. Finally, a standard-based practice-oriented analytical tool for designing retrofit interventions using the HPFRC jacket is proposed. The comparison between the calculated and experimental results revealed a satisfactory prediction capability.

Numerical analysis of axial load effects on RC bridge columns under blast loading

2020 ◽  
pp. 136943322097944
Author(s):  
Sujing Yuan ◽  
Hong Hao ◽  
Zhouhong Zong ◽  
Jun Li
Keyword(s):  
Axial Load ◽  
Near Field ◽  
Dynamic Performance ◽  
Compressive Load ◽  
Axial Loading ◽  
Blast Loading ◽  
Bridge Columns ◽  
Load Effect ◽  
Contact Explosion ◽  
Rc Bridge Columns

Blast load and its effects on transportation infrastructure especially bridge structures have received considerable attention in recent years. The RC bridge columns are considered as the most critical structural members because their failure leads to collapse of the bridge. Although RC bridge columns are typical axial load-carrying components, the studies on blast-resistant capacity of RC bridge columns usually neglect the axial load effect since it is commonly assumed that neglecting the axial load leads to conservative predictions of column responses. This assumption is true when column failure is governed by flexural response since axial compressive load generates a prestress in column which compensates concrete tensile stress induced by bending response. When subjected to blast loads, column response however could be governed by shear response. In this case neglecting axial loading effect does not necessarily lead to conservative predictions of column responses. In this study, high-fidelity finite element (FE) models for both non-contact explosion and contact explosion were developed in LS-DYNA. The FE models were validated with field blast test data. Subsequently, intensive simulations of the RC bridge columns with and without axial load subjected to a wider range of blast loading scenarios, including far-field, near-field and contact explosion were conducted. The influence of axial load on the dynamic performance of RC bridge columns corresponding to different blast loading scenarios was discussed.

Experimental Investigation of Interfacial and Permeation Leak Rates in Sheet Gaskets and Valve Stem Packing

2018 ◽  
Author(s):  
Ali Salah Omar Aweimer ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Gas Flow ◽  
Experimental Testing ◽  
High Stress ◽  
Design Criterion ◽  
Leak Rate ◽  
Environment And Health ◽  
Valve Stem ◽  
Packing Rings ◽  
Order Of Magnitude ◽  
Hazardous Pollutants

The quantities of leak rate through sealing systems are being regulated because of the global concern on the hazardous pollutants being released into the atmosphere and their consequences on the environment and health. The maximum tolerated leak is becoming a design criterion, and the leak rate for an application under specific conditions is required to be estimated with reasonable accuracy. In this respect, experimental and theoretical studies are being conducted to characterize the gas flow through gaskets and packing rings. The amount of the total leak that is present in a gasketed joint or a valve stem packing is the sum of the permeation leak through the sealing material and the interfacial leak at the mating surfaces between the sealing element and mechanical clamp assembly. The existing models used to predict leakage do not separate these two types of leaks. This paper deals with a study based on experimental testing that quantifies the amount of these two types of leaks in bolted gasketed joints and packed stuffing boxes. It shows the contribution of interfacial leak for low and high contact surface stresses and the influence of the surface finish as a result of a 32 and 250 micro-inch RAAH phonographic finish in the case of a bolted flange joint. The results indicate that most of the leak is interfacial reaching 99% at the low stress while the interfacial leak is in the same order of magnitude of the permeation leak at high stress reaching 10−6 and 10−8 mg/s in both packing and gaskets, respectively.

Dynamic interaction factor considering axial load

2007 ◽  
Vol 25 (4) ◽  
pp. 423-429 ◽  
Author(s):  
Jiang Jianguo ◽  
Zhou Xuhong ◽  
Zhang Jiasheng
Keyword(s):  
Axial Load ◽  
Dynamic Interaction ◽  
Interaction Factor

Factors Affecting Steam Generator Tube Bow

2013 ◽  
Author(s):  
Moli Cao ◽  
Jennifer Nelson ◽  
Hasan Charkas ◽  
Timothy Wiger
Keyword(s):  
Steam Generator ◽  
Axial Load ◽  
Compressive Load ◽  
Factors Affecting ◽  
Shell And Tube ◽  
Excessive Load ◽  
Generator Design ◽  
Design Analyses ◽  
Associated Design ◽  
Steam Generator Tubes

One of the challenges in straight shell-and-tube Steam Generator design is to avoid the tube to tube wear that can arise during operation due to higher than anticipated compressive tube loads and the resulting tube bow that can occur. Tube bow becomes significant when the compressive load in the tube exceeds its critical buckling capacity. This excessive load does not lead to unstable collapse of the tube as the axial load in the tube is displacement controlled. However, it does lead to significant lateral deformation for a very small increase in axial load/displacement. In this paper, several factors are investigated to determine their influence on the onset of tube bowing. Based on the studies performed in this paper there are factors that play a significant role in the behavior of steam generator tubes that have not typically been addressed in associated design analyses. Failure to address these factors can lead to unexpected behavior, premature degradation of steam generator performance, and possibly pressure boundary failure. A thorough understanding of these factors is necessary to ensure that a given design will perform as expected.

Elastoplastic Analysis of a Cantilever Beam Under Combined Compressive and Bending Load

2013 ◽  
Author(s):  
Julio A. Boix Salazar ◽  
Dirk F. de Lange ◽  
Alberto Torres Cruz ◽  
Hugo I. Medellín Castillo ◽  
Gilberto Mejía Rodríguez
Keyword(s):  
Axial Load ◽  
Compressive Load ◽  
Plastic Behavior ◽  
Cantilever Beams ◽  
Axial Loads ◽  
Elastoplastic Behavior ◽  
Bending Force ◽  
Wide Range ◽  
Bending Load ◽  
Compressive Axial Load

In this study the elastoplastic behavior of cantilever beams under a combined compressive axial load and an imposed lateral bending deflection are analyzed. Eventhough the particular condition of elastoplastic buckling has been studied before, the developed theories are limited to the prediction of the initial failure of the beam. In the current study the elastoplastic behavior of cantilever beams under compressive load at levels below the critical buckling load are studied in order to determine the remaining load bearing capacity of the beam under combined bending and axial loads, including the behavior at progressive levels of plastic deformation. The elastoplastic bending process is analyzed using the finite element method. In particular, the analysis is focused on the evaluation of the limiting bending force necessary to increase or reduce the curvature of the beam in the plastic zone. The bending force depends on the compressive axial load, the geometrical dimensions of the beam, material coefficients, such as Young’s modulus and yield stress, and the hardening model. The large number of variables involved, is reduced by introducing two dimensionless load parameters. The results of the analysis are presented and discussed for a wide range of dimensionless loads. Also the influence of work hardening on the obtained bending force is analyzed, comparing between an ideal plastic behavior and a bilinear plasticity model with a linear hardening behavior.

Influence of Load Conditions on Mechanical Behaviors of Steel Tubular Columns Filled with Steel-Reinforced Concrete Subjected to Axial Load

2014 ◽  
Vol 638-640 ◽  
pp. 132-135
Author(s):  
Ping Guan ◽  
Lan Xiang Chen
Keyword(s):  
Reinforced Concrete ◽  
Axial Compression ◽  
Axial Load ◽  
Compressive Load ◽  
Load Condition ◽  
Steel Tube ◽  
Compression Performance ◽  
Steel Reinforced Concrete ◽  
Tubular Columns ◽  
Load Conditions

By using the finite element software ADINA, the focus of the paper is about the influence of load conditions on the axial compression performance of steel tubular columns filled with steel-reinforced concrete (STSRC) with the base that the calculated results are confirmed by the experimental data. Three types of loading conditions are these that: 1. Steel pipe, steel placed in the steel tube and concrete bear the compressive load; 2. Compressive load acts on the steel and concrete and there is a good bonding between the steel and concrete; 3.The steel and concrete bear the axial load, but the bond-slip between the steel tube and concrete are considered. The results show that the calculated results based on ADINA and the experimental ones are in agreement well, the bearing capacity and the ductility of the short composite columns are not almost influenced by the load condition-one and load condition-two, while the load condition-three has a influence on the axial compression performance of STSRC.

scholarly journals Seismic behavior and retrofit of pre-1970's as-built exterior beam-column joints reinforced by plain round bars

2001 ◽  
Vol 34 (1) ◽  
pp. 68-81 ◽  
Author(s):  
A. Liu ◽  
R. Park
Keyword(s):  
Axial Load ◽  
Seismic Behavior ◽  
Compressive Load ◽  
Seismic Loading ◽  
Transverse Reinforcement ◽  
Fibre Glass ◽  
Full Size ◽  
Final Failure ◽  
Bar Buckling ◽  
Shear Distortion

Four exterior beam-column joints reinforced by plain round bars designed according to pre-1970's codes were subjected to simulated seismic loading. Each of the test units was full size in scale. The main test variables were the manner in which the longitudinal beam bars were hooked in the joint core and the level of the axial load applied to the columns. The amount of transverse reinforcement in the beams, columns and joint cores was very small, as was typical of the pre-1970's. The tests on the units demonstrated that the available stiffness and strength was low when the axial load was zero. The final failure occurred due to opening of the beam bar hooks in tension and column bar buckling, irrespective of the hook details of the beam bars. The presence of axial compressive load of 0.25fc'Ag on the columns delayed the failure initiated by the beam bar hooks, leading to much improved stiffness and strength of the units. In one unit with beam bar hooks bent away from the joint core, the column regions adjacent to the joint core were jacketed with fibre-glass and the unit when tested showed much improved stiffness and strength. When compared with the results of similar units reinforced by deformed bars, the units reinforced by plain round bars showed less joint shear distortion but more opening of beam bar hooks in tension and column bar buckling. As a result, premature concrete tension cracking failure along the outer layer of column bars adjacent to the beam bar hooks was enhanced, and the attained stiffness and the force strength were significantly lower, especially the stiffness.

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