Metal Gaskets Research Articles

On the Characteristics of Bolted Joints with Gaskets : stress analysis of full face metallic flat gaskets interposed between pipe flanges

This paper deals with a contact stress distribution in bolted joints when a full face metallic flat gasket is interposed between two pipe flanges. Replacing a gasket and pipe flanges by finite hollow cylinders the contact stress distribution is analyzed using three-dimensional theory of elasticity. By numerical computations, effects of the thickness and the stiffness of gaskets on the contact stress distribution are shown. Next, the force ratio of bolted joints with gaskets, which is the ratio of an increment of bolt axial force to an internal pressure and the sealing performance are analyzed. With an application of the internal pressure, a bending moment is produced in bolts. The maximum stress produced in bolts taking this bending moment into consideration is also analyzed. For verification, experiments are performed. Analytical results are in a fairly good agreement with experimental one.

On the Characteristics of Bolted Joints with Gaskets : Stress Analysis of Full-Face Metallic Gaskets Compressed by a Cover of Pressure Vessel

This paper deals with a contact stress distribution in bolted joints when a full-face metallic gasket is used between a cover and a base of pressure vessel. Replacing the cover, the gasket and the base with a finite cylinder and two finite follow cylinders respectively, the contact stress distribution is analyzed using three-dimensional theory of elasticity. Effects of the thickness and the stiffness of gaskets on the contact stress distribution are shown by numerical computations. Next, the force ratio of bolted joints with gaskets, which is a ration of an increment of bolt axial force to an inner pressure, and the sealing performance are analyzed. A bending moment is produced in bolts by the inner pressure. The maximum stress produced in bolts is also analyzed taking the bending moment into consideration. For verification of the analytical method, experiments are performed. Analytical results are in a fairly good agreement with experimental ones.

On the Characteristics of Bolted Joints with Gaskets : Stress analysis of rectangular metallic flat gaskets interposed between two T-flanges

In this paper, discussion is made on a contact stress distribution of bolted joints in the case where a rectangular metallic flat gasket is interposed between two T-flanges. Replacing gasket and T-flanges by finite strips, the contact stress distribution is analyzed using two-dimensional theory of elasticity. By numerical computations, effects of the thickness and the stiffness of gaskets on the contact stress distribution are shown. Next, the force ratio of bolted joints with gaskets, which is the ratio of an increment of bolt axial force to a load, is analyzed. With an application of the load the bending moment is produced in bolts. By taking this bending moment into consideration, the maximum stress produced in the bolts is also analyzed. Experiments are performed to verify these analyses. Numerical results are in a fairly good agreement with experimental ones.

On the Characteristics of Bolted Joints with Gaskets : Stress Analysis of Full Face Metallic Flat Gaskets Compressed by Pipe Flanges

On the Characteristics of Bolted Joints with Gaskets : Stress Analysis of Full Face Metallic Flat Gaskets Compressed by Pipe Flanges

Seals for large ports on the Tokamak Fusion Test Reactor

The Tokamak Fusion Test Reactor (TFTR) is a large fusion device being constructed at the Plasma Physics Laboratory of Princeton University. This unit is designed for bakeout at 250 °C, and for a base pressure of 10−8 Torr. The machine has a total of 57 large ports that are removable and are sealed with ‘‘Helicoflex’’ metallic gaskets. There are two seals on each port, a primary and a secondary, with flange bolts between seals. This arrangement balances the load on either side of the bolts, eliminating flange roll that could result from the high sealing forces. The dual seal arrangement also aids in leak detection and permits recovery from a failed primary seal by pumping between seals. All of the large ports have been leak-checked with a helium mass spectrometer leak detector, and all primary seals have been found to be leak tight.

Thermal cycling and torque analysis of an ultrahigh vacuum flange

A major design objective of a vacuum assembly in a specialized ultrahigh vacuum exhaust/leak detection processing system was to incorporate replaceable vacuum sealing flange ports. The vacuum processing operation with which the system was to be used required that these ports be capable of repeatable thermal cycling, from ambient to 525±25 °C and be torqued between the range of 17 to 50 ft lb prior to each thermal cycle while guaranteeing a leak-free seal to less than 1×10−12 std cm3/s. This design concept was proven to be feasible through computer analysis and documented experiments. One of the major breakthroughs was the employment of nickel metal gaskets for sealing as opposed to OFHC copper (standard high vacuum gasket material). This nickel gasket was proven to be vastly superior to copper in its sealing reliability with respect to thermal cycling at elevated temperatures. Torque analysis results have shown that these ports could be torqued to as high as 50 ft lb, both at ambient and elevated temperatures, and still be leak free.

On Characteristics of Bolted Joints with Gaskets : Stress Analysis of Flat Metal Gaskets between Two Hollow Cylinders

On Characteristics of Bolted Joints with Gaskets : Stress Analysis of Flat Metal Gaskets between Two Hollow Cylinders

A viscosity gauge for pressure measurement in the range 10 −6 to 10 −4 torr

A pressure gauge based upon the pressure dependence of molecular damping forces on a vane swinging with a pendulum-like motion in a vacuum system is described. This instrument has a useful operating range from 10 −4 to below 10 −6 torr. The control and monitoring of the vane oscillation is entirely electronic allowing operation as either a decrement or as a direct reading gauge. In the latter case a driving force is applied to the vane so as just to balance the gas damping, thus maintaining a constant amplitude of swing. The level of the driving force is taken as a measure of the pressure. The demountable gauge head has metal gaskets making it bakeable to over 300°C and therefore suitable for incorporation in an ultrahigh-vacuum system. The main advantage of this gauge is its freedom from thermal gradients and ionization phenomena therefore making it completely inert with respect to the gases and vapours in the vacuum system.

High-Vacuum Dual-Motion Feedthrough

This paper describes several versions of a single, simple device to provide rotary and linear motion within a vacuum chamber without causing even a temporary rise in pressure. Through the use of metal gaskets, bellows, seals, and magnetic couplings, many difficulties arising from the transmission of rotary and linear motion through vacuum-chamber walls are overcome. In the device described, freedom of rotation is unlimited in either direction, but linear movement is limited to 2 in. Actually, stroke limits are determined by choice of bellows and space considerations. The device makes use of magnetic coupling for the rotary component, and a bellows-sealed, lead-screw mechanism controls linear movement.

Symposium on Some Aspects of Vacuum Science and Technology, London, January 1962

Design problems in cryogenic pumping with liquid gases of space simulators and high speed, low pressure aerodynamic test chambers were outlined. Details were presented of experiments on the use of molecular sieve sorption to provide the fore-pressure requirements of Penning and hot-cathode ion pumps. Ultra-high vacuum systems constructed primarily of stainless steel were described and comparisons made between the various approaches to design. Bakeable metal gaskets for ultra-high vacuum systems received much attention and discussion as also did Viton A as a sealing material. Details of a new, all-metal, bakeable, ultra-high vacuum valve which, in its largest size, has an open conductance of 400 1. sec-1 aroused much interest. Types of mass spectrometer suitable for residual gas analysis in the total pressure range below 10-4 μtorr were surveyed and compared and, together with some design details, experimental results were given by different speakers on, first, a magnetic deflection type and, second, a cycloidal pattern. A short account was read of a simple probe gas-leak detection method making use of the sensitivity of the current through a Penning getter-ion pump to different gases. A four-electrode, hotcathode ionization gauge was described of conventional design except that the x-ray current could be separated from the pressure-dependent current by chopping the latter.

Spectroscopy in Liquid-Rare-Gas Solvents. Infrared Spectra of CH4 in Argon and of HCl in Xenon

A low-temperature cell employing barium fluoride windows and indium metal gaskets has been built and is being used for the study of rotational, vibrational, and electronic motions of molecules in liquid rare gases. The ν3 fundamental of CH4 in liquid argon shows a single, relatively sharp Q branch. The P and R branches are probably present but apparently are lost in the wings of the Q branch. The infrared spectrum near 3.5 μ of HCl in liquid xenon shows well-resolved P, Q, and R branches, but the individual rotational lines are not resolved. The O branch is not resolved from the tail of the P branch, but there is some indication of the S branch on the high-frequency side of the spectrum. The Q branch is shifted 36 cm—1 to the low-frequency side of its gas-phase position. The appearance of O, Q, and S branches is expected because of the presence of an induced dipole moment through the polarizability of the solvent. The agreement between the observed spectrum and that anticipated on the basis of nearly free rotation gives good evidence for the existence of quantized rotational motions of HCl in liquid xenon.

Seals and gaskets for ultra high vacuum systems

There has been increasing interest in demountable metal seals and gaskets for use on “clean” vacuum systems or on equipment in which very low pressures have to be achieved. Of particular interest in the latter case are seals which remain vacuum tight while being baked at high temperature to promote rapid degassing. Demountable joints have been made employing thin wires, solid rings of various shapes, and metal foil gaskets. The design of suitable flanges, shaped projections, and any associated springs are considered. Data are given of experimental results achieved with various seals covering a range of materials and dimensions. A general requirement is that seals should stand up to temperature cycling to both high and very low temperatures and the behaviour is reported of the different designs when subjected to these conditions. A further requirement is that seals should be readily broken and remade after carrying out changes to the equipment and observations are given on experiences gained with some types of seals in this respect.

Metal gaskets for the Berkeley 88-inch cyclotron

The Berkeley 88-inch cyclotron uses metal gaskets in a number of places where rubber would normally be used, because rubber probably would fail due to radiation damage. There are several large openings sealed with metal gaskets. Steel serrations biting into copper make the seal between the magnet pole and the main vacuum tank. One of these seals has failed. Tin-plated iron wire is used extensively as the gasket material. By sanding with 120-grit paper, a suitable surface finish for sealing is provided. Metal gaskets work best when used between very rigid components. Care must be taken to place and hold the wire in the desired place while making a seal.

The gas sorption characteristics of Penning pumps and titanium films

The gas sorption characteristics of evaporated Ti-films about 100 Å thick and of a Penning pump with titanium electrodes have been studied and compared. The Penning pump also served as an ion-source with the Ti-films. The sorption apparatus consisted of a bakable stainless steel getter chamber of 1400 cm 2 area and a Penning pump of 75 mm diameter. The vacuum seals were made with metal gaskets and the pressure measured with a hot filament ion-gauge. The gas to be sorbed was admitted to the getter chamber from a reservoir via a calibrated leak. Sorption rates were measured in the pressure interval 0.001-1 μ Hg. The pumping speed of an evaporated Ti-film alone was neglible (<0.1 l.sec), but greatly enhanced when the Penning ion-source was in operation as previously found by Gale. Inert gases were only sorbed by the Penning pump. Instantaneous speeds measured at 10 -6 Torr for fresh Ti-films with the ion-source in operation were, in l./sec., as follows: Air, 56; N 2, 56; O 2, 56; H 2, 234. When the sorption rates of either the Penning pump alone or the Penning pump with a Ti-film were plotted in terms of mass sorption rates (litre microns/sec) as a function of pressure it was found that the resultant curves were parallel to the ionization current/pressure curve of the Penning discharge, i.e. the mass sorption rate at a given pressure was directly proportional to the discharge current at that pressure. The sorption characteristics of mixed gases were studied to find the effect of one molecular type on the clean up of another. It is shown that the sorption rate of hydrogen is reduced by the presence of organic vapours, e.g. methane. Sorption rates were also measured for gas mixtures of argon/hydrogen, and nitrogen/“Calor” gas (butane). Measurements were rendered difficult when using hydrocarbon/gas mixtures due to the uncertainty in determining the sensitivity factor to be used with the ion-gauge. The role of ionization in enhancing the gas sorption rate is discussed by Holland in an appendix. The increase in the rate of clean up by titanium was not due to ions flowing to the film because the getter chamber was at a positive potential. The high sorption rate of H 2, O 2, and N 2 when ionized was attributed to their atomization in the Penning discharge. Thin films of titanium are composed of densely packed grains and the enhanced rate of clean up is attributed to the atomic gas being able to penetrate the interstices between the grains and reaction products on the porous film.

Static Testing High-Pressure Piping Components

A method for testing high-pressure piping systems for service in the 20,000 to 40,000-psi range is described. Tubing systems were pressure tested and their behavior followed by means of resistance-wire strain gages mounted on the exterior surface. A method is described for graphically determining the pressure at which a tube wall becomes fully plastic. The allowable working pressure of a tube is determined by applying a safety factor to this pressure. Tubing bends and fittings, including metal gaskets, flanges, and tees, are evaluated by comparing their behavior under pressure with that of the tube with which they are to be used.

Metal gaskets for demountable vacuum systems

Metal gaskets for demountable vacuum systems