Gasket Seals Research Articles

Overview of recent ITER TBM Port Plug R&D activities

The objective of ITER project is the demonstration of the scientific and technological feasibility of fusion energy. Tritium fuel is required for the fusion reaction in DEMOnstration reactors and future commercial reactors but it is not available in nature because of its instability. To investigate tritium breeding self-sufficiency, two equatorial ports in ITER are dedicated to operating test blanket modules (TBMs) using the TBM Port Plug (TBM-PP). The TBM-PP design should be investigated with the physical mock-ups to validate the leak tightness in the primary vacuum boundary and to ensure TBM replacement and refurbishment compatible with Remote Handling (RH) operations in the ITER Hot Cell Facility during the ITER lifetime. This paper summarizes the achievements on the two most relevant R&D topics as described herewith. Several TBM-PP components (i.e., back parts of the TBM-Frame, the Dummy-TBMs, the TBM-Shields, and the TBM feeding pipes) are part of the vacuum boundary implying that these components are Vacuum Quality Classification (VQC) 1A. To test and develop high vacuum sealing for the TBM-Frame flange and the TBM-Set or Dummy-TBM flange, the ITER Large Seal Test Rig (LSTR), and metallic gasket seals for the TBM application have been manufactured and installed in the ITER site. The helium leak tests were performed at different operating temperatures to investigate the vacuum performance of metallic gasket seals with VQC 1A. The TBM-PP design shall guarantee the feasibility of a rapid replacement and refurbishment compatible with ITER Remote Handling (RH) operations by using RH tools in the Hot Cell Facility during the ITER's lifetime. Therefore, an experimental program has been performed to demonstrate the feasibility of the critical RH refurbishment tasks including the insertion and removal of TBM-Set/Dummy-TBM and the RH bolting.

Cinema as Prosthesis: Errol Morris’s Use of the Interrotron in <em>Mr. Death: The Rise and Fall of Fred A. Leuchter, Jr.</em>

Cinema as Prosthesis: Errol Morris’s Use of the Interrotron in <em>Mr. Death: The Rise and Fall of Fred A. Leuchter, Jr.</em>

Mechanical degradation of proton exchange membrane along the MEA frame in proton exchange membrane fuel cells

Mechanical degradation, caused by local stress concentration and variation, significantly affects the lifetime of proton exchange membrane fuel cells. This study constitutes the first numerical investigation of stress evolution in the membrane between the frame of the membrane exchange assembly (MEA) and gas diffusion layer (GDL) throughout the processes of assembly, operation and gas filling in fuel cells. A finite element model is outlined to determine mechanical deformation of the membrane by exerting assembly displacement, hygrothermal conditions and gas pressure in turn. It is observed that severe stress concentration and bending deformations occur in the joint-area membrane. The results show that a plastic deformation occurs after the temperature and water content are increased, and would be substantially enhanced by the gas pressure difference between the anode and cathode. The in-plane stress may throw some light on the rapid degradation of the membrane between the frame and GDL. The gas pressure difference, which exceeds 10 kPa, leads to a rapid increase in the in-plane stress and plastic deformation. Decreasing the joint width may not be a good approach for reducing the stress/strain concentration. It is suggested that additional gasket seals or adhesive protection layers are helpful in joining frame and GDL.

Short Stack Kit for the Open Flange™ Set-up Using Soft Mica Seals

Fiaxell has been active since 2008 in the Solid Oxide Fuel Cells (SOFC) industry and has been developing components and products for SOFC research. Fiaxell is the inventor of the “2R-Cell”, an anode supported cell able to withstand full re-oxidation and thermal cycles. The 2R-Cell is robust and has demonstrated high fuel utilization (85-90%) and electrical efficiency up to 50% with pure hydrogen on button cells. Fiaxell has developed the Open Flange™ Set-Up in order to test SOFC and SOEC cells. The Set-Up allows researchers to do various experiments, such as current-voltage characteristics, polarization, impedance spectroscopy measurements, electrolysis, co-electrolysis and in situgas processing (POX, SR) thanks to its integrated steam generator. Fiaxell is now offering a complete short stack kit that can be directly mounted onto the Open Flange™ Set-Up platform. This kit allows researchers to perform a range of experiments and to study stack parameters such as flow distribution, electrical contact resistance, and to investigate protective coatings to avoid chromium evaporation, in situfuel processing and sealing gas tightness. Each parameter can be independently characterized and optimized by combining ideal and real stack conditions on both sides of the cell, for instance Crofer steel on the anode and gold mesh on the cathode. Fiaxell is proposing Crofer 22H interconnects with different flow pattern designs for 50 X 50 mm and 80 X 60 mm cells. Alternatively, customers can propose their own customized design which can then be chemically grooved and laser cut by Fiaxell. The short stack kit comes with soft mica sealing but can also be made gas tight with any glass paste or other sealants. The soft mica seals have been designs to be easily removed and replaced, contrary to the use of glass based sealants that require mechanical grinding to remove. Mechanical simulations and calculations have been made to ensure that the design of the end Flange™ is adequate to compress the entire stack without any distortion or stress concentration points, especially on the interconnect plates. In order to see the gas distribution in the interconnect pattern, Fiaxell has developed an alternative, and complementary method to simulation, which consists of direct visualization and image analysis of the real flow motion. Screen captures will be included and discussed. In this paper, we present the experimental results of the short stack tests using two different interconnect patterns and also discuss the effectiveness of the soft mica gasket seals. Image caption: Exploded view of two cells short stack showing the three bipolar plates (interconnect) and soft mica gaskets (in beige). The short stack has been designed as a kit to be integrated directly on the Open Flange™ Set-Up platform. Figure 1

Gamma Ray Measurements at OMEGA with the Newest Gas Cherenkov Detector “GCD-3”

Initial results from the newest Gas Cherenkov Detector (GCD-3) are reported demonstrating improved performance over previous GCD iterations. Increased shielding and lengthening of the Cherenkov photon optical path have resulted in a diminished precursor signal with increased temporal separation between the precursor and the primary DT Cherenkov signal. Design changes resulted in a measured GCD-3 sensitivity comparable to GCD-1 at identical 100 psia CO2 operation. All metal gasket seals and pressure vessel certification to 400 psia operation allow for a GCD-3 lower Cherenkov threshold of 1.8 MeV using the fluorinated gas C2F6 as compared to the 6.3 MeV lower limit of GCD-1 and GCD-2. Calibration data will be used to benchmark GEANT4 and ACCEPT detector models. The GCD-3 acts as a prototype for the Super GCD being fielded at the National Ignition Facility (NIF) as part of the National Diagnostics Plan and will be installed at NIF in early 2016.

Literature Research in Relevant Fields to Understand Pressure Relief Valve Leak Tightness in a Static Closed State

Currently, no review of literature exists which attempts to understand the leakage phenomenon of metal-to-metal seal contact Pressure Relief Valves (PRV) for static closed positions as they reach the set pressure point. This paper attempts to do just that by drawing on inspiration from other research areas such as: metal-to-metal contact and gasket seals. The key topics of interest surrounding the leakage of fluid through a gap are: fluid flow assumptions; surface characteristics and its deformation; and experimental techniques used to quantify leakage. The fluid flow assumptions relating to the gap height such as transmissivity and diffusivity are found to be directly linked to the surface roughness and the surfaces deformations. Traditionally the summing method has been used to represent two rough surfaces at a micro scale from which the Tsukizoe and Hisakado theory has been applied for deformation of the micro contact in a plastic manner. The path the fluid also takes through the gap is investigated with recent work using computational methods to determine that path. Current experimental leakage quantification techniques are also discussed. Finally, the future development of PRV static leakage is examined.

Polycarbosilazane passivation on graphite foil used as gasket seal

Gasket seals are often used in industry and laboratories where a leak-proof installation is needed in order to avoid loss of products or dangerous materials. Many of products transported inside tubes are at relatively high temperatures excluding polymeric gaskets. In the same line, many of transported materials contain solvents which can attack polymer sealings, therefore limiting their use. An alternative is to use graphite joints as sealings. These joints are a sandwich of graphite foil and stainless steel mesh as forming core. The problem that raises using graphite in contact with steel is that at temperatures of about 500 °C an interdiffusion of carbon on the steel structure occurs which produces adhesion of the graphite gasket on the metallic flange. Therefore this adhesion increases the time to change each gasket, since rests of previously adhered graphite has to be removed from the flange. In order to avoid the adhesion of the graphite on the flange, polycarbosilazane precursor was used as protective finishing on the graphite foil surface. After thermal transformation of the polymer into the corresponding PDC finishing, it acts in two manners: It avoids the direct contact between the carbon and the steel and it allows the sealing of liquids and gases. Adhesion tests were done and showed that the foils passivated with PDCs did not adhere to the steel flange. Moreover, the production methods and products are compatible to industrial environment and processes. The results found here show that the time to change the gasket in industry can be clearly reduced by using the PDC finishing on graphite gasket.

Effect of different curing systems on cell structure, mechanical properties and aging resistance of nitrile butadiene rubber foam coating with liquid compounds

Gaskets made of acrylonitrile butadiene rubber (NBR) coating and metal plate were one of the classified seals used in automotive engine. In the present study, NBR foam–metal composite gaskets were prepared by liquid NBR overlain metal plate. The foam coating was thinner and more uniform compared with solid rubber forms usually used. Two different curing systems of dicumyl peroxide (DCP) system and a combined system of sulphur with DCP (S/DCP system) were investigated for curing NBR foam coating. The effects of curing system and agent content on cell structure, mechanical properties and resistance to fluid and heat of NBR foam, and the interfacial adhesion between NBR foam coating and metal plate, were examined. It was found that the S/DCP system gave NBR foam coating with bigger cell size, higher porosity and cross-link density compared with the DCP system. Furthermore, the S/DCP system had better tensile property and played a better role in the protection of the gasket seals against fuel B and hot air.

Effect of reducing impurity concentration of microcrystalline silicon thin films for solar cells using radio frequency hollow electrode enhanced glow plasma

Microcrystalline silicon (μc-Si) thin films with low impurity (oxygen) concentrations were prepared by radio frequency hollow electrode enhanced glow plasma (RF-HEEPT). By using metal gasket seals with the RF-HEEPT system, the oxygen concentration in the thin films was reduced to 3.0 × 1017 cm−3, which is approximately two orders of magnitude less than that of films fabricated in a system using rubber gasket seals. Under the reduced oxygen conditions, we were able to deposit μc-Si thin films at a maximum deposition rate of 10.0 nm/s. We also investigated the spectral response of μc-Si thin-film solar cells. The spectral response of the solar cells fabricated with a low oxygen concentration was improved, especially in the near-infrared region. However, with increasing deposition rate of the thin films, the peaks of the spectral response shifted toward shorter wavelengths and the magnitudes decreased, especially in the near-infrared region, indicating that grain boundaries or defects in the thin films increased at higher deposition rate.

Performance of individual cells in polymer electrolyte membrane fuel cell stack under-load cycling conditions

The performance of a ten-cell 50 cm2 100 W polymer electrolyte membrane fuel cell (PEMFC) stack was evaluated under dynamic load cycling conditions utilizing the 2005 United States Department of Energy durability test protocol for PEFCs. An enhancement of performance was observed during the first 240 h, while an irreversible degradation of stack performance was observed after 480 h (∼4700 cycles). In particular, the stack voltage at 100 mA cm−2was decreased by 2.8% after 480 h and individual cell voltage was decreased up to 8%. An analysis of cell overpotentials for activation, Ohmic, and mass transport losses revealed that the predominant source of performance degradation was due to kinetic losses. The loss of catalyst utilization was estimated to be 39% based on the electrochemically active surface area (ECSA) measurements. Electron microscopic images of some of the cells showed growth in cathode Pt particle size from 5.3 to 6.2 nm. However, these microscopic images did not show any membrane damage or electrode thinning. Severe degradation of both the anode and cathode silicone gasket seals was observed during the durability test.

Thermo-mechanical induced deformation simulation studies for metal gaskets for UHV application

In vacuum technology, metal gasket seals are extensively employed to achieve a UHV with reduced contamination considering the pressure and temperature variations as it performs a static seal between two stationary members of a mechanical assembly. The optimum sealing is attained over the balancing of the forces effective, which are function of temperature, governs the surface deformation for the metal gasket seal follows into degradation in the leak tightness at elevated temperatures. The prime component exerting the most deformation force over metal gasket seals, gasket seating force is a constant value generated by the bolting of the stationary members of a mechanical assembly. The paper address to metal gasket seals, copper and aluminum, behavior under thermo-mechanical load is analyzed (simulation), with ANSYS platform, workbench. The major concern is to investigate the typical deformation behavior as a function of thermal variation, baking/ cooling. For copper and Aluminum gasket seals, 16mm to 250mm internal diameter, exposed to pre-established gasket seating force under wide temperatures range. The deformation, average and the deformation range, observed to move in a very specific manner and runs to a wide range for a given material and size. The data reported here deserves to be substantial enough to establish the prediction of thermal behavior of metal gasket seals for standardization.

Contact Model of Sealing Surfaces for Flange and Metallic Gasket Based on Fractal Theory

Metallic gasket seals are widely used in pressure vessels and piping. The failure of sealing systems is mostly caused not by the strength of flanges or bolts but by the leakage of the connections. The contact area of sealing surface has a major influence on the leakage of the bolted flange connections. The contact model of sealing surfaces of the flange and the metallic gasket was established on the basis of the modified M-B model, and the relationship between the contact area and the compressive stress is obtained. It’s found that the bigger the compressive stress, the bigger the contact area. When the compressive stresses are identical, the bigger fractal dimension and the less scale coefficient, the bigger the contact area. These can be used in the evaluation of sealing behavior of metallic gaskets.

Development of anaerobic gasket seals for the automotive industry

The influence of components on the properties of anaerobic gasket seals is studied using the mathematical design of experiment. The efficiency of anaerobic gasket seals is determined. The equipment for applying gasket seals during in-line assembly is developed.

Experimental Study of the Performance of Static Seals Based on Measurements of Real Contact Area Using Thin Polycarbonate Films

To clarify the sealing characteristics of metal gasket seals, leakage rates of gas and the real contact area of the seal surfaces were measured under several closing loads. The static seal consisted of a ring-shaped copper gasket and the two steel flanges that held the gasket in place. Gasket widths in the radial direction were 2 mm, 3 mm, and 5 mm. The contact surfaces of the flanges were finished by lathe turning. To determine the leakage flow paths between the gasket and the flanges, the real contact situation between them was observed using a thin polymer film 1 μm in thickness. The results indicated the leakage flow paths on the gasket surface were the radial direction perpendicular to the lathe-turned groove and the circumferential direction along the groove. As the closing loads increased, the leakage flow in the radial direction ceased and only that in the circumferential direction remained. Therefore, the cross-section of the aperture for the leakage flow in the circumferential direction was evaluated from the measured real contact area, and the leakage rates were estimated by assumption of laminar flow. The results agreed well with the measured leakage rates.

Effect of inorganic additives on some properties of NBR vulcanizates

PurposeThe purpose of this paper is to study the effect of incorporating some inorganic fillers, namely aluminium oxide and aluminium hydroxide on the rheological, mechanical and thermal behaviour of acrylonitrile‐butadiene rubber (NBR) vulcanizates.Design/methodology/approachFor improving physico‐mechanical properties of NBR vulcanizates, various compositions were made by incorporating different concentrations of employed fillers with NBR. These properties included the torque, cure time, tensile strength, elongation at break, swelling, diffusivity, as well as thermal behaviour of the loaded and unloaded NBR with fillers were characterised.FindingsThe incorporation of the two investigated fillers improves the thermal behaviour of the vulcanizates, especially aluminium hydroxide. All samples showed more or less a first order decomposition kinetics, for which the activation energy ranged from 177 to 187 kg/mol.Research limitations/implicationsNBR is extensively used industrially for its single, most important property, which is an exceptional resistance to attack by oils and solvents. However, incorporation of fillers in (NBR) leads to the development of improved, competitive properties of the vulcanizate. A further study must be carried out on the flame retarding effect of the fillers, beside the effect of surface treatment of the fillers on the dispersibility and physico‐mechanical properties of the vulcanizates.Practical implicationsThe use of two investigated fillers provided a simple and practical solution to improving the resistance to swelling in motor and break oil as well as the thermal behaviour of the NBR.Originality/valueThe use of these fillers was novel and could be used in many rubber industries especially in gasket and oil seals.

2112 広視野レーザ顕微鏡を用いた金属平形ガスケット密封面の接触観察(表面・接触,一般講演)

To clarify the sealing characteristics of metal gasket seals, the observation of the real contact area on seal surfaces is very important. In a previous work, to determine the leakage flow paths between the gasket and the flanges, the real contact situation between them was observed using a thin polymer film 1 μm in thickness. In this research, we use a laser microscope with wide field of view recently developed in our laboratory. The static seal consisted of a ring-shaped copper gasket and the two steel flanges that held the gasket in place. Gasket width was 5 mm in the radial direction. The gasket surfaces were finished by polishing with emery paper. The contact surfaces of the flanges were finished by lath turning. After unloading, the whole seal surface of the copper gasket indented by the ridges of the flange was directly observed with the laser microscope. The observation indicated that the leakage flow paths on the gasket surface were the radial direction perpendicular to the lathe-turned groove and the circumferential direction along the groove.

S1104-1-2 広視野レーザ顕微鏡を用いた金属ガスケット表面の接触観察(トライボロジーの基礎と応用1)

To clarify the sealing characteristics of metal gasket seals, the relationship between leakage rates of gas and the real contact area of the seal surfaces is very important. In a previous work, to determine the leakage flow paths between the gasket and the flanges, the real contact situation between them was observed using a thin polymer film 1μm in thickness. In this research, we use a laser microscope with wide field of view recently developed in our laboratory. The static seal consisted of a ring-shaped copper gasket and the two steel flanges that held the gasket in place. Gasket width was 5 mm in the radial direction. The contact surfaces of the flanges were finished by lathe turning. After unloading, the whole seal surface of the copper gasket indented by the ridges of the flange was directly observed with the laser microscope. These observations indicated that the leakage flow paths on the gasket surface were the radial direction perpendicular to the lathe-turned groove and the circumferential direction along the groove. As the closing loads increased, the leakage flow in the radial direction ceased and only that in the circumferential direction remained.

Analytical screening of polyadipates and other plasticisers in poly(vinyl chloride) gasket seals and in fatty food by gas chromatography–mass spectrometry

Fourteen poly(vinyl chloride) (PVC) gasket seals and 15 samples of pesto, tomatoes sauces, olive oil and olives in oil were analysed for the additives and plasticisers. The systematic screening of the representative samples revealed that epoxidised soybean oil (ESBO) was the principal plasticiser in eight gaskets and the concentrations of the substance ranged from 15% to 42%. Diisodecyl phthalate (DIDP) as main plasticiser was revealed in three samples and the amount ranged from 37 to 41%. Polyadipate was added in four samples at 16-46%. The concentration of ESBO exceeded 60 mg kg(-1) in three food samples with extreme at 281.9 mg kg(-1) and average 61.3 mg kg(-1). Di-(2-ethylhexyl) phthalate (DEHP) was detected in six food samples and it ranged from 2.5 to 8.7 mg kg(-1). The concentration of DEHP exceeded SML (3 mg kg(-1)) in five cases. The concentration of total polyadipate (PA) was 16.3 mg kg(-1) in average. All eight positive food samples for total PA showed the concentrations below SML (30 mg kg(-1)), which are specified for the fraction of polyadipates lower than 1000 Da. The migration rate of polyadipate in the food ranged from 1 to 7%. At such low transfer rate the polyadipates could be promising plasticisers for PVC gasket seals used in food industry.

A simple continuous-flow cryostat for optical microscopy in the range 10-350K

A simple continuous-flow cryostat suitable for use with optical microscopes is described. Its working range is from 10K to 350K with stability +or-0.1K. The specimen is mounted within an exchange-gas filled cell to ensure thermal equilibrium. Access to the specimen is via small easily demountable vacuum-tight low-temperature windows made using PTFE gasket seals.

Superleaktight wire solder gasket seals for use at low temperature

Superleaktight wire solder gasket seals for use at low temperature