Stainless Steel Flange Research Articles

Total pressure measurement down to 10−12 Pa without electron stimulated desorption ion errors

In order to measure a total pressure as low as 10−12 Pa, the avoidance of electron stimulated desorption (ESD) ion errors is more important than the x-ray limit, because even if we can contrive to reduce ESD ions in a gauge, we do not know what fraction the ESD ion error makes in the measured pressure value. This is the largest defect in the reliability of the measurements. Therefore, the development of the ion spectroscopy gauge which avoids ESD ion errors, was recalled with a historical review of the limiting processes in a hot-cathode gauge. The most advanced ion spectroscopy gauge was constructed with a fine platinum alloy spherical grid ion source, immersed in a copper block with stainless steel flanges. Gas phase ions were effectively separated from ESD ions by the actions of electron space charge in the grid and a hemispherical 180° ion energy analyzer. The x-ray limit of the advanced gauge was approximately 2.5×10−13 Pa, and the outgassing rate of 2×10−9 Pa ℓ/s (about 1/100 that of an ordinary nude Bayard–Alpert gauge) was achieved.

Stainless steel flanges from India and Taiwan February 1993

Stainless steel flanges from India and Taiwan February 1993

Simple aluminum gasket for use with both stainless steel and aluminum flanges

A technique has been developed for making aluminum wire seal gaskets of various sizes and shapes for use with both stainless steel and aluminum alloy flanges. The gasket material used is 0.9999 pure aluminum, drawn to a diameter of 3 mm. This material can be easily welded and formed into various shapes. A single gasket has been successfully used up to five times without baking. The largest gasket tested to date is 3.5 m long and was used in the shape of a parallelogram. Previous use of aluminum wire gaskets, including results for bakeout at temperatures from 20 to 550 °C, is reviewed. A search of the literature indicates that this is the first reported use of aluminum wire gaskets for aluminum alloy flanges. The technique is described in detail, and the results are summarized.

Sealing performance of gaskets and flanges against superfluid helium

A series of tests has been carried out on the sealing characteristics of different combinations of commercially available gaskets and flanges against superfluid helium. The aluminium Helicoflex gasket with a stainless steel or aluminium alloy flange was effective against leakage of normal liquid helium but exhibited leakage with superfluid helium. However, copper-, silver-, nickel- and indium-coated aluminium Helicoflex gaskets with a stainless steel or aluminium alloy flange were found to prevent leakage of superfluid helium.

Cryogenic material properties of stainless steel tube-to-flange welds

The mechanical properties of stainless steel tube-to-flange welds for a cryogenic piping application were measured. A planar specimen was developed to duplicate the constraint, loading and heat-sink properties of the circular joint, while reducing preparation time and cost. Specimens were evaluated containing welds between the tube material (21 Cr-6Ni-9Mn) and the three stainless steels being considered for the flange materials: type 304L, type 316L and 21 Cr-6Ni-9Mn. The mechanical property tests consisted of three phases: simple tensile testing to failure, tensile testing of notched specimens (where the notch simulated fabrication flaws) and fatigue testing of notched specimens for the 4 × 10 4 cycle design life of the structure. The type 316L stainless steel flange produced welds with the best combination of strength and ductility at 295 and 4 K in all three phases of testing.

Identifying type 304 stainless steel flange defects using scanning Auger microscopy (SAM)

AbstractAn unusual number of large stringer defects were found in cross‐forged type 304 austenitic stainless steel ultrahigh vacuum (UHV) flanges. These defects are cosmetically displeasing, they can affect the material's machinability and they can also affect the vacuum integrity of a UHV system. In this study, scanning Auger microscopy was used to identify accurately the defects as ferritic inclusions. This information was used to justify a change in forging and heat‐treating procedures, resulting in the reduction of large ferrite segregants and creating a more homogeneous microstructure. Subsequently, the rejection rate was reduced more than 50‐fold.

Diamondlike carbon high-temperature diffusion barrier for copper-gasketed stainless-steel flanges

Diamondlike carbon films of 5−15 nm were deposited on copper gaskets which were sealed in 304−stainless steel flanges. The carbon films acted as a diffusion barrier during high temperature bakeout (550 °C at 1 x 10−5 Torr for up to 200 hours) which prevented carbon diffusion into the copper. (AIP)

TiN high temperature diffusion barrier for copper‐gasketed stainless‐steel flanges

Klystrons manufactured at the Stanford Linear Accelerator Center are typically baked at temperatures of 550 °C for times as long as 200 h. During these long bakeouts the copper‐gasketed type 304 stainless steel flange joints (seven in all) diffusion bond so intimately that the flanges can be separated only with a jacking fixture, and copper is left on the sealing surfaces. Removal of this copper necessitates the use of abrasive materials, which can result in contamination of the klystron body and compromise its reuse. We report on the use of 50 and 150 Å TiN thin films as a diffusion barrier between the Cu gasket and the stainless‐steel flange.

A large aluminum alloy molecular beam epitaxy chamber with an ultimate pressure of 7.5×10−12 Torr

An ultimate pressure of 7.5×10−12 Torr was reached in a large molecular beam epitaxy (MBE) chamber made of aluminum alloy A1050, after baking and after liquid nitrogen was introduced. Most of the components were made of aluminum alloys, except a gauge and the Ti-sublimation pump. For the seals between aluminum and stainless steel flanges, aluminum gaskets or helicoflexes were used and no problems resulted. It was also found that the Ti-sublimation pump was effective in the 10−10 Torr range but not in the lower 10−11 Torr range. The pressure limits of the turbomolecular pump used in the system was 6×10−11 Torr. Pumping speeds of the ion pump and the shroud cooled with liquid nitrogen were about 60 and 250 l/s, respectively. The outgassing rate of the chamber was estimated to be 1×10−13 Torr ⋅ l/s cm2. After a situation in which the ion pump was turned off at room temperature and in a second case in which the liquid nitrogen supply was stopped, surface conditions of the system were studied.

The edge-loaded metal flange seal—its characteristics and applications

An edge-loaded metal ring flange seal has been developed for ultrahigh bakeable vacuum operation that requires closing forces comparable to elastomeric seal systems. Sealing is accomplished using a deformable rectangular cross-sectioned copper ring confined between stainless steel flanges in a manner that produces high radial compressive forces upon alternate edges of the ring section during flange closure. Conformation to the geometry and macrostructure of the confining elements of the flanges produces a leak-tight seal capable of ultrahigh vacuum operation with 400 °C bakeout. The seal ring deformation has been analyzed and the seal configuration has been tested for reliability and loading characteristics and found to require axial forces as low as 45 pounds per circumferential inch of seal for the system. A simplified analysis has been developed to predict loading characteristics and has been compared to loading studies made during the development of the seal system. Tests in ambient and elevated temperature environments show the seal to be as reliable as existing ultrahigh vacuum seal systems while requiring as little as 1/40 the bolt forces and 1/10 the time to accomplish closure. The flange seal has utility in radiation induced environments where human exposure time may be severely restricted, or where remote handling techniques for flange assembly and disassembly may be required.

Effect of channel restrictions on the axial heat transport in subcooled superfluid helium

The present study investigates the influence of partial restrictions on the axial heat transport and critical heat flux limits in subcooled superfluid helium (helium II) channels. Different size orifices are used to simulate partial plugging of superconducting magnets cooling channels by frozen oxygen, nitrogen, hydrogen, neon or moisture during the cool down process. Thin stainless steel sharp edged orifices of sizes 0.5, 1, 2 and 5 mm id are mounted between stainless steel flanges attached to 9 mm diameter (helium II) channel. The helium II channel is heated at one end with a copper block heater while the other end heat sinks to an atmospheric superfluid helium heat exchange. Temperature drop across the restriction is measured by two calibrated carbon resistors. Measurements are carried out at both temperatures ranging from 1.8 to 2.2 K. As the orifice/channel area ratio decreases, data show a considerable decrease in the axial heat transported by internal convection process resulting in lower critical heat flux at the phase transition from helium II to helium I by the destruction of superfluidity and inititation of boiling. A linear correlation between critical channel heat flux and orificeI channel area ratio gives a good fit to the experimental data. For heat fluxes higher than the critical heat flux, transient temperature measurements for a step heat input are correlated with the time required to reach the phase transition.

超流動ヘリウムＩＩでの気密シール

A series of of tests on the sealing characteristics of a number of gaskets and flanges against the superfluid helium below 2.17°K has been made. Commercially available aluminum Helicoflex with stainless steel and aluminum alloy flanges is tight to the normal liquid helium but leaks at the superfluid temperatures. However copper, silver and indium coated aluminum Helicoflex and Sureket (a gasket made of stainless steel tubing with silver coating) with stainless steel and aluminum alloy flanges are found to be tight to the superfluid helium.

Inexpensive modification of a Polytron for rapid mincing of pancreases for islet isolation

Attaching an inexpensive stainless-steel flange to a Polytron generator and operating the Polytron at a reduced speed prevent recycling of pancreas pieces through the generator and complete homogenization of the tissue. Using the modified Polytron significantly shortens the time required for mincing a large number of pancreases prior to the collagenase digestion step used in preparing isolated pancreatic islets.

Improved vacuum seals for magnesium fluoride windows

Improvements and extensions have been made to the techniques of sealing oriented magnesium fluoride crystals to metals, with a suitable glass solder. The technique for sealing a 38 mm diameter window in a 90 mm diameter stainless steel flange, 12 mm thick is described. The sealing of windows to all-glass devices is relatively simple using standard graded seals to soda glass and then with the solder glass to the window. The method of cleaning the mounted windows is also described.

Large diameter cryogenic seals

Cryogenic vacuum seals are discussed with emphasis on large diameter reusable connections. Both theoretical considerations and experimental results are presented. The main subject is large diameter cryogenic vacuum seals in a horizontal vessel, where thermal distortions are encountered in particular during the cool down stage. We show a large diameter stainless steel flange design that can take large repeatable thermal shocks and maintain a good vacuum seal at liquid helium temperatures.

Thermal desorption of gases from aluminum alloy Al 6061, their rates and activation energies

The use of Al in the construction of the vacuum chamber of intersecting proton storage rings has several advantages over the use of stainless steel. We have, therefore, undertaken UHV studies on long pipes made of Al alloy 6061 to see whether this material could be used in the proposed proton intersecting storage accelerator facility ISABELLE at Brookhaven. The outgassing rates, measured by two different methods, are compared for several surface treatments and three bakeout temperatures. The lowest outgassing rate of less than 1×10−14 Torr l s−1cm−2 was obtained with Ar and O2 discharge cleaning. The residual gas in the pipe contained more than 99% H2 with traces of CO and CO2. By observing the temperature dependence of the desorption of these gases, we have measured the heat of diffusion of H2 (EH2=10.5±1.0 kcal/mole) and the thermal activation energies of CO (ECO=29±2 kcal/mole) and CO2 (ECO2=25±2 kcal/mole). Ar, with a peak desorption at 280°–300 °C, also appears to be embedded in the metal. Since all commercially available UHV equipment uses stainless steel flanges, we have investigated the behavior of the stainless steel to Al transitions up to 350°C.

Sigma phase in 321 stainless steel

AbstractThe failure of a 321 stainless steel flange due to the presence of sigma phase was used to check etching procedures for sigma phase in 321 SS as well as to establish the time‐temperature diagram for sigma phase in this material.

Quadrupole mass spectrometers. (USSR): A F Kazmin and A E Rafalson, Encykoped Izmereniy Kontrlya Avtomatiz, Energiya 1970, 17–18 (in Russian)

The Taiwan Photon Source (TPS) uses high-heat-load (HHL) absorbers to protect downstream ultrahigh-vacuum chambers from overheating. In this work, we propose to use the CuCrZr alloy (ASTM C18150) for the HHL absorber body and the ConFlat® flanges. We use the throughput method to measure the thermal outgassing rate and a helium leak detector to verify the vacuum seal between the CuCrZr alloy and stainless-steel flanges. The measured outgassing rate of the CuCrZr alloy was 5.8×10−10 Pa m/s after 72 h of pumping and decreased to 2.0×10−10 Pa m/s after 100 h of pumping. The leak rate through the vacuum seal between a CuCrZr flange and a stainless-steel flange was less than 1×10−10 Pa m3/s even after mounting and unmounting the flanges ten times and baking them at 250 °C. These results indicate that CuCrZr alloy is suitable for integrating HHL components with ConFlat® CuCrZr flanges for the absorption of the synchrotron radiation generated by the TPS.

Probability method of pressure estimation. (USSR): L N Kosmarskiy et al, Elektrofizichesk Apparatura Elektrich Izolatsya, Moscow, Energiya, 1970, 195–199 (in Russian)

The Taiwan Photon Source (TPS) uses high-heat-load (HHL) absorbers to protect downstream ultrahigh-vacuum chambers from overheating. In this work, we propose to use the CuCrZr alloy (ASTM C18150) for the HHL absorber body and the ConFlat® flanges. We use the throughput method to measure the thermal outgassing rate and a helium leak detector to verify the vacuum seal between the CuCrZr alloy and stainless-steel flanges. The measured outgassing rate of the CuCrZr alloy was 5.8×10−10 Pa m/s after 72 h of pumping and decreased to 2.0×10−10 Pa m/s after 100 h of pumping. The leak rate through the vacuum seal between a CuCrZr flange and a stainless-steel flange was less than 1×10−10 Pa m3/s even after mounting and unmounting the flanges ten times and baking them at 250 °C. These results indicate that CuCrZr alloy is suitable for integrating HHL components with ConFlat® CuCrZr flanges for the absorption of the synchrotron radiation generated by the TPS.

Arrangement for slow mass scanning in a mass spectrometer type KM—1. (USSR): G I Slobodenyuk and V F Fedotov, Prib Tekh Eksper, No 3, May/June 1970, 271 (in Russian)

The Taiwan Photon Source (TPS) uses high-heat-load (HHL) absorbers to protect downstream ultrahigh-vacuum chambers from overheating. In this work, we propose to use the CuCrZr alloy (ASTM C18150) for the HHL absorber body and the ConFlat® flanges. We use the throughput method to measure the thermal outgassing rate and a helium leak detector to verify the vacuum seal between the CuCrZr alloy and stainless-steel flanges. The measured outgassing rate of the CuCrZr alloy was 5.8×10−10 Pa m/s after 72 h of pumping and decreased to 2.0×10−10 Pa m/s after 100 h of pumping. The leak rate through the vacuum seal between a CuCrZr flange and a stainless-steel flange was less than 1×10−10 Pa m3/s even after mounting and unmounting the flanges ten times and baking them at 250 °C. These results indicate that CuCrZr alloy is suitable for integrating HHL components with ConFlat® CuCrZr flanges for the absorption of the synchrotron radiation generated by the TPS.