Practical Evaluation of PTFE Thermal Behavior Using the Hot Blowout Thermal Cycling Test

2012 ◽  
Author(s):  
Anita R. Bausman ◽  
A. Fitzgerald (Jerry) Waterland
Keyword(s):  
Thermal Cycling ◽  
Compressive Load ◽  
Temperature Limit ◽  
Cycling Performance ◽  
Current Status ◽  
Test Results ◽  
Sealing Performance ◽  
Practical Evaluation ◽  
Bolted Flange

Differential thermal expansion between polytetrafluoroethylene (PTFE) gasket materials and metallic flange/bolt systems, combined with thermally influenced creep relaxation characteristics of all PTFEs, creates limitations in the ability of some PTFE gasket materials to provide long term, reliable sealing performance in process or thermal cycling applications. ASTM F-36 gasket recovery data is sometimes used to assess a gasket’s thermal cycling capabilities; however, it is a poor means of establishing suitability for cycling performance as it is a short duration, ambient temperature test that measures recovery, or springback, of the gasket after the compressive load has been completely released. In order to provide a direct qualification of thermal cycling performance and capabilities, the Hot Blowout Thermal Cycling (HOBTC) test was developed under the guidance of the PVRC (Pressure Vessel Research Council)Bolted Flange Connection Committee as part of the 1995 PTFE Gasket Protocol. The HOBTC test results provide a practically applicable temperature limit under which the tested material, typically a PTFE, can operate safely. In addition, test data reported graphically provide additional insight about the long term behavior of the PTFE material. This paper reviews the current status of the HOBTC test, in the process of being made into an ASTM standard, and practical application of test results to achieve reliable gasket performance.

Effects of Post-Tightening on the Residual Bolt Force and the Sealing Performance of Flanged Connections With PTFE Gaskets (Long Term Effects at Room Temperature)

2011 ◽  
Author(s):  
Taiki Hagiri ◽  
Takashi Kobayashi ◽  
Kengou Nishiura ◽  
Kazuaki Uchiyama
Keyword(s):  
Room Temperature ◽  
Test Results ◽  
Long Term Effects ◽  
Viscoelastic Characteristic ◽  
Sealing Performance ◽  
Nominal Size ◽  
Gasket Material

It is known that bolt forces reduce significantly after tightening bolted flanged connections in which expanded PTFE gaskets are used. Bolts are often post-tightened in practice after a while to compensate for the reduction of bolt forces. The viscoelastic characteristic of expanded PTFE gaskets is the main cause for the phenomenon. However, the long term effects of the post-tightening on the residual bolt forces and the sealing performance of flanged connections have not been clarified yet. In this study, two sets of flanged connections (2 inch in nominal size), in which PTFE gaskets were used, were prepared and tightened. One of the flanges was post-tightened after a designated time. The reduction of bolt forces and the change in the sealing performance were measured for about two months. The results were compared with those of flanges without post-tightening. Based on the test results, the effectiveness of post-tightening was discussed from the viewpoint of the residual bolt force and the sealing performance. It has been clarified that the effectiveness of post-tightening depends on gasket material and that post-tightening is effective for expanded PTFE gaskets.

Visco-Elastic FEM Stress Analysis of Bolted Flange Connections With PTFE-Blended Gaskets Under Elevated Temperature

2012 ◽  
Author(s):  
Koji Sato ◽  
Shinya Kurokawa ◽  
Toshiyuki Sawa
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Fluid Temperature ◽  
Long Term Conditions ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Strain Relationship ◽  
Bolted Flange ◽  
Relationship Of

Bolted flange connections with gaskets have been used under high temperature and long-term conditions. Sometimes leakage accidents occur from the gasket interfaces due to the creep and relaxation phenomena. In the present paper, the changes of the gasket stress in bolted flange connections under high temperature conditions for a long-term are analyzed using FEM calculations taking into account the gasket temperature dependency. The gaskets used are PTFE-blended (V#GF300). It’s shown that the effect of the temperature on the stress-strain relationship of the gasket is substantial. The changes in the gasket stress of the connections for 12 months are analyzed using the FEM. The effects of nominal diameter of flanges, retightening and the fluid temperature (20 to 300 °C) on the change of gasket stress in the connections under elevated temperature are examined using the FEM calculations. It is found that the reduction in the gasket stress is over 40%. In addition, experiments to measure the axial bolt force were carried out. The calculated results are in a fairly good agreement with the experimental results. The results reveal that the long-term behavior of the bolted flange connections can be estimated in our study. Discussion is made on the effects of the bolt preload and retightening on the reduction of the gasket stress and the sealing performance.

Improvement of Flange Tightening Method for Small Bore Low Rating Bolted Flanges

2010 ◽  
Author(s):  
Masako Mori ◽  
Akira Nebu ◽  
Takashi Kanno
Keyword(s):  
Axial Force ◽  
The Other ◽  
Test Results ◽  
Other Hand ◽  
Sealing Performance ◽  
Bolted Flange ◽  
Seating Surface ◽  
Spiral Wound

An appropriate flange tightening methods for small bore and low rating piping flange joints are clarified to improve the sealing performance of the bolted flange joints and the workability of flange tightening work. It is said that lubricant on the screw of the bolts and the nut-seating surface can minimize the variability of axial force acting on flange bolts, while this process might make it harder to tight the bolts uniformly especially for small bore low rating flanges. So, in this paper the appropriate condition to apply lubricant is clarified by a series of bolt tightening tests and sealing tests results. On the other hand, for the bolted flanges applying spiral wound gaskets, measuring the gasket compress dimensions help us to prevent uneven tightening balance and to perform the appropriate tightening work. Appropriate gasket compress dimensions are also clarified to ensure the sealing performance for the flanges based on the sealing tests results. Based on these test results, recommended flange-tightening methods have been summarized as an instruction and tightening work procedure to improve the sealing performance of the bolted flanges and the workability of flange tightening work.

A Determination Method of Bolt Preload for Bolted Pipe Flange Connections With Metal Gaskets Under Internal Pressure

2015 ◽  
Author(s):  
Koji Kondo ◽  
Toshiyuki Sawa
Keyword(s):  
Internal Pressure ◽  
Room Temperature ◽  
Bolted Joints ◽  
Test Results ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Bolted Flange ◽  
The Given ◽  
Outside Diameter ◽  
Better Than

FEM calculations and leakage experiments are carried out for bolted flanged connections with metal flat gaskets. It is found that the sealing performance of bolted flanged connections with raised face metal gaskets under internal pressure is improved significantly when the contact gasket stress reaches the gasket yield stress. In our FEM calculations it is demonstrated that the contact gasket stress at the outside diameter is bigger than that at the inside diameter due to the flange rotation. It is also found from the leakage test results and the FEM calculations that the sealing performance of the bolted flange connections with metal flat gasket is better than that of the metal gasket in platen device tests,. In addition, the contact stress in the joints with RTJ (ring type joint) gasket is examined and 4 stress peaks on the oval type and 8 peaks on the octagonal type are found. From the obtained results, a method for determining the bolt preloads in the bolted joints using flat metal gaskets and RTJ gaskets under internal pressure is proposed taking account the given allowable leak rate. Finally, the leak rates for bolted flanged connections tightened under internal pressure are compared with the experimental results. The new method can be proposed for determining the bolt preload for bolted flange connections with metal gaskets under internal pressure at room temperature.

Flange Tightening Evaluation Method for Flat Face Flange With Full Face Gasket

2013 ◽  
Author(s):  
Masako Mori ◽  
Akira Nebu ◽  
Takashi Kanno
Keyword(s):  
Evaluation Method ◽  
Large Diameter ◽  
Test Results ◽  
Axial Loads ◽  
Tightening Torque ◽  
Japanese Industrial Standard ◽  
Sealing Performance ◽  
Pressure Tests ◽  
Full Face ◽  
Bolted Flange

Appropriate flange tightening methods for flat face flanges with full face gaskets are discussed to improve the sealing performance of the bolted flange joints and the workability of flange tightening work. In general, relatively larger tightening torque is required for a flat face flange with a full face gasket compared to the flange with a ring gasket when we calculate the required tightening torque based on the latest Non-mandatory Japanese Industrial Standard (JIS) evaluation method, “JIS B 2205-1991, Basis for calculation of pipe flanges”[1]. Especially, for the flat face flanges with large diameter and with fewer tightening bolts, this tendency becomes stronger. This problem sometimes causes a conflict when the flange torque calculation of the minimum required torque value to resist hydrostatic end force at the maximum design pressure of the flange is larger than the maximum allowable torque derived from flange or bolt strength. So, in this paper, surface stress of several diameter flange faces were measured to clarify whether or not the required stress is applied on the surface of the flat face flanges with full face gaskets. In addition, pressure tests were carried out to clarify the sealing performance under the condition of circumferentially non-uniform tightening load in each diameter flat face flange with full face gasket. Based on these test results, minimum flange-tightening bolt axial loads have been summarized to ensure the sealing performance of the flat face bolted flanges with full face gaskets.

Optimization of Valves Packings Through Characterization and Calculation

2019 ◽  
Author(s):  
Hubert Lejeune ◽  
Frédéric Joulain
Keyword(s):  
Emissions Reduction ◽  
Test Results ◽  
Fugitive Emissions ◽  
Low Friction ◽  
Friction Forces ◽  
Full Characterization ◽  
Energy Efficiency Improvement ◽  
Sealing Performance ◽  
Low Load ◽  
Bolted Flange

Abstract In the valve industry, there is combined demand from the end-users for fugitive emissions reduction and energy efficiency improvement through the reduction of stem/packing friction forces. These two different goals will involve opposite trends on the load to be applied on the packing i.e. high load for good tightness and low load for low friction. Thus, the ability to define optimal ranges of packing tightening is important. Nevertheless, no standardized method for packing calculation nor packing full characterization (mechanical, friction, sealing performance vs. packing load,..) exists in Europe, as for bolted flange joints and associated gasket with EN1591-1 [1] and EN13555 [2]. In collaboration with ESA (European Sealing Association, www.europeansealing.com) and FSA (Fluid Sealing Association, www.fluidsealing.com), the Fluid Equipment Committee of CETIM has developed a tool for the optimization of packing. A set of tests enables to get the packing characteristics needed for the calculation. These tests can also be used for the comparison of packing materials and/or installation procedures performances in defined test conditions. This paper details the proposed calculation method and describes the associated test rigs and procedures. First test results and a calculation example are also given to show how the method works.

Improvement of Flange Tightening Method for Small Bore Low Rating Bolted Flanges

2010 ◽  
Author(s):  
Masako Mori ◽  
Akira Nebu ◽  
Takashi Kanno
Keyword(s):  
Axial Force ◽  
The Other ◽  
Test Results ◽  
Other Hand ◽  
Sealing Performance ◽  
Bolted Flange ◽  
Seating Surface ◽  
Spiral Wound

An appropriate flange tightening methods for small bore and low rating piping flange joints are discussed to improve the sealing performance of the bolted flange joints and the workability of flange tightening work. The lubricant on the thread of the bolts and the nut-seating surface can minimize the variability of axial force acting on flange bolts, however this process might make it harder to tight the bolts uniformly especially for small bore low rating flanges. In this paper the appropriate condition to apply lubricant is clarified by a series of bolt tightening tests and sealing tests results. On the other hand, for the bolted flanges using spiral wound gaskets, measuring the gasket compressed dimensions help us to prevent uneven tightening balance and to perform the appropriate tightening work. Appropriate gasket compressed dimensions are also clarified to ensure the sealing performance for the flanges based on the sealing tests results. Based on these test results, recommended flange-tightening methods have been summarized as an instruction in tightening work procedure to improve the sealing performance of the bolted flanges and the workability of flange tightening work.

Fatigue Testing of Copper Nanoparticle Based Joints and Bonds

2021 ◽  
Author(s):  
Rajesh Sivasubramony ◽  
Maan Z. Kokash ◽  
Sanoop Thekkut ◽  
Ninand Shahane ◽  
Patrick Thompson ◽  
...  
Keyword(s):  
Thermal Cycling ◽  
Flip Chip ◽  
Fatigue Testing ◽  
Maximum Temperature ◽  
Nano Particle ◽  
Test Results ◽  
Fine Pitch ◽  
Effects Of Aging ◽  
Sintered Ag

Abstract Fused or sintered Cu nanoparticle structures are potential alternatives to solder for ultra-fine pitch flip chip assembly and to sintered Ag for heat sink attach in high temperature microelectronics. Meaningful testing and interpretation of test results in terms of what to expect under realistic use conditions do, however, require a mechanistic picture of degradation and damage mechanisms. As far as fatigue goes, such a picture is starting to emerge. The porosity of sintered nano-particle structures significantly affects their behavior in cycling. The very different sensitivities to parameters, compared to solder, means new protocols will be required for the assessment of reliability. The present study focused on fatigue in both isothermal and thermal cycling. During the latter, all damage occurs at the low temperature extreme, so life is particularly sensitive to the minimum temperature and any dwell there. Variations in the maximum temperature up to 125 °C did not affect, but a maximum temperature of 200 °C led to much faster damage. Depending on particle size and sintering conditions deformation and damage properties may also degrade rapidly over time. Our picture allows for recommendations as to more relevant test protocols for vibration, thermal cycling, and combinations of these, including effects of aging, as well as for generalization of test results and comparisons in terms of anticipated behavior under realistic long-term use conditions. Also, the fatigue life seems to vary with the ultimate strength, meaning that simple strength testing becomes a convenient reference in materials and process optimization.

The Residual Bolt Force and the Sealing Performance of Flanged Connections With Expanded PTFE Gaskets (Based on Test Results for One Year)

2012 ◽  
Author(s):  
Takashi Kobayashi ◽  
Taiki Hagiri ◽  
Kengou Nishiura ◽  
Masaaki Hiratsuka ◽  
Katsutoyo Itoi
Keyword(s):  
Thermal Expansion ◽  
Room Temperature ◽  
Early Stage ◽  
Thermal Characteristic ◽  
Temperature Dependency ◽  
Test Results ◽  
Viscoelastic Characteristic ◽  
Sealing Performance ◽  
One Year

It is known that bolt forces reduce significantly after tightening bolted flanged connections in which expanded PTFE gaskets are used. Bolts are often post-tightened in practice after initial tightening to compensate for the reduction of bolt forces. The viscoelastic characteristic of expanded PTFE gaskets is thought to be the main cause for the phenomenon. Some gasket users are not confident whether the bolt forces remain above a minimum required gasket load until next maintenance. However, the long term characteristics of the residual bolt forces and the sealing performance of flanged connections have not been clarified yet. In this study, using flanged connections with expanded PTFE gaskets, the reduction of bolt forces and the change in the sealing performance were measured at room temperature for one year. Based on the test results, the residual bolt force and the sealing performance were studied. It was clarified that bolt forces converges to a certain level at early stage within almost 1000 hours. After that, the bolt forces were significantly affected by the ambient temperature change. This is because the thermal expansion of PTFE material is high and also the thermal characteristic of PTFE material has a temperature dependency. It was confirmed that although the bolt force reduced significantly at early stage, it is maintained in long-term. The sealing performance was improved due to the increased compression of gasket.

Parents' long-term adjustment to the genetic test results of minors at risk for Long QT Syndrome

2004 ◽  
Author(s):  
K. S. W. H. Hendriks ◽  
F. J. M. Grosfeld ◽  
A. A. M. Wilde ◽  
J. van den Bout ◽  
I. M. van Langen ◽  
...  
Keyword(s):  
At Risk ◽  
Long Qt Syndrome ◽  
Genetic Test ◽  
Test Results ◽  
Long Qt ◽  
Genetic Test Results ◽  
Qt Syndrome
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