PTFE Seals Research Articles

Wear of Seal Materials in Magnetorheological Fluid: Effect of Seal Material Selection

This paper is focused on magnetorheological (MR) dampers and their critical parts in terms of damper`s durability, which seems to be a piston-rod seal. An option to reduce the wear is to choose the proper material for that purpose. The wear measurements were conducted in an accelerated and simplified mode in a modified pin-on-flat (cylinder-on-flat) configuration, which was supposed to be more suitable for laboratory testing than original configurations. Suitable commercial materials for seals, like PTFE, NBR, SBR and polyurethanes, were tested and compared in commercial MR fluid MRF-132DG by LORD Corporation. It turned out that material H-PU95FDA had had the biggest wear resistance from all tested materials and therefore it was the most suitable material for durable seals, while PTFE seals are expected to be suitable in non-durable applications with low frictional forces.

Simulation and experimentation study on the performance of metal hydride storage vessels

This paper details the process of designing, analysing, manufacturing, and testing an integrated solid-state hydrogen storage system. Analysis is performed to optimise flow distribution and pressure drop through the channels, and experimental investigations compare the effects of profile shape on the overall power output from the fuel cell. The storing of hydrogen is given much attention in the selection of a storage medium, and the effect of a cooling system to reduce the recharging time of the hydrogen storage vessel. The PTFE seal performed excellently, holding pressure over 60 bar, despite requiring changing each time the cell is opened. The assembly of the vessel was simple and straightforward, and there was no indication of pressure damage owing to the FEA analysis that was performed. The cooling chamber, although producing minor leaks due to design oversight, increased performance dramatically, showing a reduction in internal powder temperature from 130°C, down to 25°C during the absorption process, as well as reducing the absorption time down from 30 minutes to just over 5 minutes. The novel idea of implanting a sheathed thermocouple into the centre of the hydride powder proved to be highly valuable asset and provided important information, especially during desorption where the outside container could be heating up, while the inner powder is still cooling down, data that have not been seen before.

Piston Rod Coating Material Study of Reciprocating Sealing Experiment Based on Sterling Seal

Sterling seal is a commonly used reciprocating seal, in which the PTFE ring of the seal and the surface material of the piston rod play an important role in the reciprocating sealing process. In this paper, a reciprocating sealing test bench was built, four sets of carbon fiber PTFE sealing rings were used to perform reciprocating sealing bench experiments with Cr-coated piston rods and DLC-coated piston rods. After the experiment, the used four sets of seals were taken as experimental samples, and a new, unused carbon fiber PTFE seal was taken as a reference sample. The surface topography, surface wear, and wear surface elements of the test specimens were measured by three-dimensional white light interference surface topography instrument, field emission environment scanning electron microscope, and field emission scanning electron microscope. Through experimental determination, it is found that the coating material is detached to form abrasive grains, which causes the surface of the sealing ring to wear. This paper also proposes optimization suggestions for the processing method of the sealing ring and the selection of the material of the piston rod coating.

Sliding wear performance of metallic laser coatings against composite PTFE seals

Sliding wear performance of metallic laser coatings against composite PTFE seals

Direct Ethanol Fuel Cell for Portable Power

Introduction Portable Non-Destructive Inspection (NDI) equipment, such as Eddy Current (EC) and Ultrasonic Testing (UT), provide important tools for the Air Force to characterize flaws, cracks, and/or defects in aircraft, thus monitoring potential safety issues. Most NDI equipment is powered by a battery (alkaline, NiCad, NiMH, or Li-ion) that typically comprises a large percentage of the size and weight of the equipment. The Air Force is interested in finding alternative forms of energy for NDI equipment, due to issues with existing battery technologies that include logistical challenges, battery reliability/degradation, limited portability, and safety. Direct Ethanol Fuel Cell (DEFC) systems could potentially provide a significant advantage over conventional battery technologies, including nearly instantaneous recharging, lighter weight, longer operational times, higher power, and improved cycle life. Further, the 25-Watt power requirements of the NDI equipment are similar to a number of other portable electronics that could benefit from the technology. Materials and Methods Single cell direct ethanol fuel cells were prepared using both commercially available anion exchange membranes and experimental reduced crossover membranes. The cell anode was prepared by depositing a hydrothermally synthesized Pd-based catalyst onto a conductive carbon backing. The cell cathode consisted of pH Matter’s non-metal based oxygen reduction reaction catalyst (COR). The COR catalyst was treated with a PTFE additive to reduce ethanol crossover. The catalyst was deposited onto a commercial carbon paper (Toray) and annealed in air. Testing was completed in a nickel metal set-up with PTFE seals and consisted of mechanical compression of each component to form the cell assembly. The anode was supplied with a fuel composition consisting of 5M KOH and 5M ethanol in distilled water. Air was supplied to the cathode at approximately 25 sccm/cm2 and at ambient pressure. Cell temperature was controlled between ambient and 60°C as to prevent degradation of the cell membrane. Cyclic voltammetry curves were obtained using a PAR Versastat 3 potentiostat between OCV and 100 mV. Simulated load testing was carried out by operating the cell at a steady state current of 65 mA/cm2. Significance Fuel cells provide electricity through an efficient, pollution free, and quiet electrochemical process. However, the adoption of commercial fuel cell systems has been hampered by the logistics of providing a reliable, high purity, and low cost hydrogen [1]. Some fuel cell systems, such as SOFC and Direct Methanol, offer an opportunity to use more readily available fuels, such as liquid methanol or methane. However, these systems have been unable to achieve wide-scale commercialization due to technological challenges, such as stability and lifecycle performance.[2-3] Furthermore, methanol is considered toxic and poses environmental disposal challenges [4]. In contrast, ethanol is readily available in most markets, is liquid at room temperature, has very low toxicity, and can be readily disposed upon dilution with water. Furthermore, logistics of alcohol transport are minimal, a critical requirement for adoption in the Air Force application. In this effort, direct ethanol fuel cells were demonstrated to achieve transient power densities of 80 mW/cm2 at an operational temperature of 60°C and steady state power in excess of 20 mW/cm2, the target power required for use in NDI equipment, for greater than 20 hours. Furthermore, the replacement of fuel allowed for performance recovery of the fuel cell and continued operation in excess of 100 hours. Finally, the cells were incorporated into a full-scale stack and demonstrated under NDI operating conditions. In future work, the stack will be demonstrated with a 25-Watt prototype power system. References C. Huang, et al, Journal of Power Sources 303 (2016) 267-277T. Skalar, et al, Journal of Thermal Analysis and Calorimetry (2017) 127:265–271C. Xu, et al, Journal of Power Sources 168 (2007) 143–153Y.S. Li, et al, Journal of Power Sources 187 (2009) 387–392 Figure 1

The Role of Gas Diffusion Layer in Cationic Contamination and Mitigation in Polymer Electrolyte Fuel Cells

Cationic impurities may get introduced into Polymer Electrolyte Fuel Cells (PEFC) from the ambient air (e.g. roadside contaminants) and from the corrosion of stack and balance of plant components. Recovery from cationic impurities is investigated by simulating the cationic contamination with equilibrium uptake of the membrane electrode assembly (MEA) in a salt solution. The cation uptake into the ionomer was performed by soaking the MEA in 0.9 mM CaSO4 and 29.1 mM H2SO4 solution following Kienitz’s procedure (1). Three different methods were used to soak the MEA into the solution to understand the role of the gas diffusion layers (GDL) (as shown in Figure 1): (A) entire CCM is exposed (50 cm2), (B) portion of the CCM is covered with GDL and the remainder is exposed, and (C) portion of the CCM is covered with GDL and the remainder is covered with PTFE seals used in cell assembly. Prior to soaking, all MEAs were tested to obtain baseline performance. In the first two methods (A and B), significant performance drop were observed due to Ca2+ presence inside the CCM (shown in Figure 2). In case of the third method (C), there were no significant performance changes. Even when the soaking time was increased to more than 4 times in method C compared to method A, cell performance did not change significantly. It is clear that GDL acts as a barrier to the transport of Ca2+ to the CCM. When surfactant was added to the cationic solution to increase the wettability of the GDL, a drop in the performance was observed.To recover the cell performance, we re-protonated the CCMs in an acidic solution similar to Qi et al. (2). They re-protonated CCMs contaminated at different levels of Al3+ (similar to method A in Figure 1) with ex-situ soak in the acid solution (1 M H2SO4) and recovered the full performance decay. We also recovered the performance back near to the baseline when only the CCM is soaked (method A), but for the other two methods, the cell performance is partially recovered. We also performed in-situ injection of 1-10 mM H2SO4, and the cells were seemingly not affected by the in-situ injection of the acid solution. We conclude that the GDL is hindering the transport of Ca2+ in and as well as out of the MEA. Thus, recovery appears to be possible but additional factors need to be identified that hinder this process. Acknowledgements The authors are grateful for the financial support of the Department of Energy (DOE)-EERE, DE-EE00000467 (University of Hawaii, prime contractor, Jean St-Pierre, PI). References B. Kienitz, B. Pivovar, T. Zawodzinski and F. H. Garzon, J. Electrochem. Soc., 158, 9 (2011).J. Qi, X. Wang, U. Pasaogullari, L. Bonville and T. Molter, J. Electrochem. Soc., 160, 9 (2013).

시일과 스틸면 사이에 구형 입자가 있는 미끄럼 접촉 해석

In this paper, a three elastic body sliding contact problem is modeled to investigate more precise wear mechanisms related with the sealing surface. A 3-D finite element contact model, a small spherical elastic particle, PTFE seal and steel surface, is solved using a nonlinear finite element code MARC. The deformed seal and steel surface shapes, von-Mises and principal stress distributions are obtained for different seal sliding distances. The entrapped small particle within PTFE seal results in very high stresses on the steel surface which exceeded its yield strength and produce plastic deformation such as groove and torus. The sealing surface could also be worn down by sub-surface fatigue due to intervening small particles together with the well-known abrasive wear. Therefore the proposed contact model adopted in this paper can be applied in design of various sealing systems, and further studies are required.

Analysis on the mechanical characteristics of PTFE oil seal for the rear part in the automotive engine

This study analyzed the mechanical characteristics and evaluated their subsequent performance for two types of seals which reinforce characteristics with lower friction and anti-wear functions among the foremost important features in the automotive engine seals; one with the addition of glass fiber to PTFE; the other with the addition of self-lubricant molybdenum in addition to the glass fiber. Based on the configuration design of seal installed to the rear part in the automotive engine, this study carried out interpretations on the stress and reaction for those two types of oil seals to compare the maximum stress and contact load generated from the seal steel, rubber and PTFE lip. This study also verified the stress concentration and anti-wear performance through the coefficient of friction, torque and durability test by producing two types of PTFE seals actually.

Sealing system for a rotary expander

A sealing system for a rotary expander is described. In this machine, the work chamber is bound by four identical rotors and two side plates. The rotors turn at the same speed and in the same direction. Each rotor requires two apex seals and two side seals. Configurations for the apex and side seals were arrived at on the basis of the particular requirements of the engine, not encountered in other types of rotary engines. The apex seals come in contact with one another at certain points and a smooth passage past each other is required. The side seals run along the edge of the rotors rather than some distance in. Apex and side seals of novel design were built and subjected to preliminary testing in the engine operating with compressed air. No significant problems were encountered. The performance of the sealing system appears to be satisfactory in the case of seals made out of lead bronze. Carbon filled PTFE seals are to be tested in the next phase of the development program.

Implementation and Effect of Stabilized Lithium Metal Powder on Mesocarbon Negative Electrodes

Techniques for implementing stabilized lithium metal powder (Lectro® Max Powder 150, SLMPTM) as a surface application onto mesocarbon cathodes have been studied. These techniques included dip coating, draw-down coating and spray coating already prepared electrodes in a dry room environment. This testing resulted in electrodes that demonstrated a reduced apparent loss, which has the potential to improve the overall capacity of commercial cells. Of these three techniques, spray coating was determined to be the most applicable method of depositing the SLMPTM onto the coating with appropriate precision. More specifically, a low volume, low pressure off-the-shelf sprayer with a standard modification to replace the PTFE seals with polyethylene seals could be used to spray the coating to the proper loading. With proper mixing techniques, large numbers of electrodes could be sprayed with one batch of SLMPTM slurry, allowing eventually for larger prismatic lithium ion cells to be developed.

Fenner acquires PTFE seal manufacturer

Fenner Plc has announced the acquisition of substantially all of the operating assets and liabilities of EGC, a Houston-based manufacturer of fluoroplastic seals and other related fluoroplastic precision components.

A Desorption Electrospray Ionization Mass Spectrometry Study of Aging Products of Diphenylamine Stabilizer in Double‐Base Propellants

AbstractDouble‐base propellants consisting of nitrocellulose, nitroglycerin and stabilizer undergo chemical and physical changes upon aging, leading to changes in ballistic power and presenting explosive hazards. During aging, PTFE seals of the glass ampoules used in the aging studies undergo a yellow discoloration. This report studies the discoloration of the liners using desorption electrospray ionization (DESI), a gentle surface analysis technique based on electrospray ionization. The color bodies in the PTFE liners were identified by DESI together with tandem mass spectrometry to be the nitrated derivatives of the diphenylamine stabilizer: dinitro‐, trinitro‐, and tetranitrodiphenylamine. While increased nitration decreases vapor pressure of the DPA species, an increase in solubility in the PTFE liners occurs. This may account for these species not previously being observed during early aging studies as they are preferentially absorbed into the liners, which were not extracted prior to high performance liquid‐ chromatography analysis.

Composite seal material to compete with PTFE

The X-Slide range of polyurethane composite seals is designed to take over from PTFE seals, according to the materials development scientists at Economos. The performance of these new materials is said to be superior to the PTFE grades that have traditionally been used for composite seals. The X-Slide range is the latest to be developed by the company in the Ecopur material range. The new materials have been specially developed for use in the manufacture of composite type seals that operate at temperatures up to 100°C. The company considers that tests and extensive field trials show the new material family to provide a number of benefits.

Investment sealing

Pioneer Weston seals has recently invested more than $250,000 in new production machinery, testing equipment and factory modifications. The improvements have allowed the custom design, manufacture and testing of rotary PTFE seals. Further, the Mechanical Seals Division’s has extended its capacity to manufacture and renovate mechanical seals up to 1m in diameter on a quick response basis to service the repair market. This is only a short news story. Visit www.worldpumps.com for the latest pump industry news.

GlaxoSmithKline find the right seal to heal production problem

Seal failures on a centrifugal dosing pump at GlaxoSmithKline’s (GSK) plant in County Durham, Northeast England, were causing downtime and wasting valuable product. The duty, metering GSK’s anti-viral cream Zovirax, was proving to be too difficult for the existing PTFE seal and a replacement was needed quickly if the pump was to perform to the best of its capability.

Freudenberg-NOK expands PTFE seal product range by acquiring High Quality Plastics

Freudenberg-NOK expands PTFE seal product range by acquiring High Quality Plastics

Optimising durability of PTFE seals — mix and geometry — a good match

The use of PTFE and PTFE compounds as materials for seals provides additional security in terms of durability, friction, robustness and product design. Success is achieved by optimally matching the sealing material with the counter-rotational surface.

Force Analysis for a Ball-Seating Valve with PTFE Seal

Force Analysis for a Ball-Seating Valve with PTFE Seal

Wear and friction of PTFE seals

Radial lip seals made from PTFE-compounds are used more and more frequently for the sealing of crank shafts in the automotive industry. Due to wear the seal loses material and finally fails. State-of-the-art is the experimental determination of the tribological behaviour on a test rig with pin-on-disc apparatus with the help of which the wear behaviour of sealing systems, especially of PTFE seals, can be predicted. Because of the non-linear elasto-viscoplastic material properties of the sealing material the history-dependent seal mounting process has to be followed in the finite element analysis (FEA). A new FEA procedure is presented which can meet these demands. It is based on a modified iterative `rezoning' procedure. Under the assumption that the lip wears out according to the magnitude of the contact stress (maximum wear at maximum contact stress) the node coordinates of the seal contact surface are modified according to the node contact forces. Comparisons between numerical simulations and long-term service seals are made. The experiments also indicate under which radial load the seal can withstand insufficient lubrication which occurs in practical use without much wear.

Energised PTFE seals spring into action

Energised PTFE seals spring into action