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Plating as an aid in the brazing of stainless steel
VACUUM Classified Abstracts
I -
General
Sciencezzd
Engineering
-
Abstract No. and R.efewncea
I
Plating as an Aid in the Brazing of Stainless Steel C&ted Slaks. Plating of types 304 and 347 stainless steel with 1-2 mils Xi, aud sintering of the plate in a H furnace at 1,000’ for 30 minutes makes possible the use of simple H brazing techniques at low temperature and high dew point (25”) for obtaining vacuum-tight seals on intricate assemblies. ( Chew icnl ‘4 hst~acts) Somn~aire
: On decrit un pro&de pour It: brasage de l’acier inoxydahle Ctanche au vide.
Bursting Disc Assembly for Alternating
0
Pressure and Vacuum at Elevated Temperatures
Unilpd Kingdom. Platens in presses for the moulding of thermosetting resins must be heated, preferably by steam, to a temperature of 350°F. In the particular case referred to a closed system had been proposed which consisted of a small gas-heated flash boiler raising the steam which condensed in passages in the body of the platen, the condensate returning to the boiler by gravity. The authorities waived the usual safety requirements such as the provision of a pressure gauge, safety valve, water level indicator and low water alarm but insisted on the provision of a thermometer and bursting disc assembly, working to the following specifications : The disc should burst at 300 lb./sq. inch steam pressure, withstand 200 lb./sq. inch, withstand the vacuum created by the condensation of the steam when the system is cool, be steam and airtight under pressure and vacuum and be easily replaceable. It was decided to mount the disc in a plug screwed into the side of the platen. ;\ltogether three designs were developed. The first two showed deficiencies on test in the main due to differential expansion of the materials used and a danger of twisting during the tightening operation. The final design consisted of a plug polished at both ends, one end bears against the platen when the plug is screwed in, the other end serving as a seat for the disc. The disc of a free area of # inch. diameter was held down by a hollow cone which in turn was secured by a clamping cap. The question of a suitable material for the disc proved more difficult and has only partly been solved so far. The stress calculations were based on equations by Lake and Inglis. As the disc diameter was small, the thickness had to be small. Nickel, otherwise well suited to withstand the continuously alternating stress, had to be ruled out for this reason. Materials of lower tensile strength were required. Aluminium and copper were useless due to work hardening and silver showed intolerable creep. An 0.5% gold-platinum alloy was finally chosen and preliminary tests with discs of 0.003 inch. thickness gave bursting pressures of 225 lb. sq. inch. and 275 lb. sq. inch for t inch and ) inch diameters respectively. -4 thickness of 0.0033 inch proved to fulfill the specified requirements. The bursting of twenty discs, however, cut from two different strips, indicated that there was a difference in the bursting pressure which could not be entirely explained by variations in thickness. A closer metallurgical control of the material is therefore desirable and forms the subject of a separate investigation. Sommaive pression.
: L’installation
d’un disque dit
’ eclatant ’ est decrit, ctanche au vide ct alternativement
15 The Micro-Analysis See .4bstract No.
0
PHYSICS
-
1 grande
15 97/I
of the Inert Gases
: 111 iI 99/r
The Motion of a Gas Cloud Expanding into a Vacuum United States. The motion of interstellar clouds has been studied by considering the flow of a semi-infinite ideal gas cloud bordering on vacuum. These clouds consist almost exclusively of hydrogen and consequently the ratio of specific heats y may be taken as 5/3. but the theory developed is valid for any value of y. The effect of viscosity and heat conduction was neglected. The method of Riemann invariants and characteristic curves of the differential equations of the motion were used. These characteristic curves were then plotted to represent the flow in the case of problems previously examined by Burgers and Copson for a hydrogen cloud. Burgers’ problem involved an initial discontinuity of density at the front of a homogeneous cloud while Copson stipulated an initial region of inhomogeneity between the vacuum surface and the main homogeneous cloud without any actual discontinuity in density. Both solutions involved gas flows which are continuous. The method of characteristic curves developed showed that unless special initial conditions are satisfied by the cloud the subsequent flow cannot remain indefinitely continuous and shock waves appear within the gas. Other initial conditions were also investigated and illustrated by characteristic flow diagrams. When the speed of sound increased linearly at first a limiting case of Copson’s solution was obtained : The characteristics of one family shrank to a point on the wave front at the same instant of time. In the case of the flow remaining continuous the wave front was shown to move ultimately with a velocity of three times the speed of sound in the homogeneous cloud, whereas in the case of initial conditions leading to shock waves in the flow the wave-front attained even greater velocities. Thus the high eventual velocity of these gas clouds which was considered to be a physically unsatisfactory feature of previous solutions of the problem could not be avoided by a change in the initial inhomogeneities. Somnraire : On a fait des recherches theoriques sur le mouvement vide interstellaire.
Awl,
1953
d’un gaz d’hydrogene
Vacuum Vol. III No. 2
se rependant dans un
l??%&
Mon. Not. Roy. Am. LGc. 113, &I953
180
I -
General
Sciencezzd
Engineering
-
Abstract No. and R.efewncea
I
Plating as an Aid in the Brazing of Stainless Steel C&ted Slaks. Plating of types 304 and 347 stainless steel with 1-2 mils Xi, aud sintering of the plate in a H furnace at 1,000’ for 30 minutes makes possible the use of simple H brazing techniques at low temperature and high dew point (25”) for obtaining vacuum-tight seals on intricate assemblies. ( Chew icnl ‘4 hst~acts) Somn~aire
: On decrit un pro&de pour It: brasage de l’acier inoxydahle Ctanche au vide.
Bursting Disc Assembly for Alternating
0
Pressure and Vacuum at Elevated Temperatures
Unilpd Kingdom. Platens in presses for the moulding of thermosetting resins must be heated, preferably by steam, to a temperature of 350°F. In the particular case referred to a closed system had been proposed which consisted of a small gas-heated flash boiler raising the steam which condensed in passages in the body of the platen, the condensate returning to the boiler by gravity. The authorities waived the usual safety requirements such as the provision of a pressure gauge, safety valve, water level indicator and low water alarm but insisted on the provision of a thermometer and bursting disc assembly, working to the following specifications : The disc should burst at 300 lb./sq. inch steam pressure, withstand 200 lb./sq. inch, withstand the vacuum created by the condensation of the steam when the system is cool, be steam and airtight under pressure and vacuum and be easily replaceable. It was decided to mount the disc in a plug screwed into the side of the platen. ;\ltogether three designs were developed. The first two showed deficiencies on test in the main due to differential expansion of the materials used and a danger of twisting during the tightening operation. The final design consisted of a plug polished at both ends, one end bears against the platen when the plug is screwed in, the other end serving as a seat for the disc. The disc of a free area of # inch. diameter was held down by a hollow cone which in turn was secured by a clamping cap. The question of a suitable material for the disc proved more difficult and has only partly been solved so far. The stress calculations were based on equations by Lake and Inglis. As the disc diameter was small, the thickness had to be small. Nickel, otherwise well suited to withstand the continuously alternating stress, had to be ruled out for this reason. Materials of lower tensile strength were required. Aluminium and copper were useless due to work hardening and silver showed intolerable creep. An 0.5% gold-platinum alloy was finally chosen and preliminary tests with discs of 0.003 inch. thickness gave bursting pressures of 225 lb. sq. inch. and 275 lb. sq. inch for t inch and ) inch diameters respectively. -4 thickness of 0.0033 inch proved to fulfill the specified requirements. The bursting of twenty discs, however, cut from two different strips, indicated that there was a difference in the bursting pressure which could not be entirely explained by variations in thickness. A closer metallurgical control of the material is therefore desirable and forms the subject of a separate investigation. Sommaive pression.
: L’installation
d’un disque dit
’ eclatant ’ est decrit, ctanche au vide ct alternativement
15 The Micro-Analysis See .4bstract No.
0
PHYSICS
-
1 grande
15 97/I
of the Inert Gases
: 111 iI 99/r
The Motion of a Gas Cloud Expanding into a Vacuum United States. The motion of interstellar clouds has been studied by considering the flow of a semi-infinite ideal gas cloud bordering on vacuum. These clouds consist almost exclusively of hydrogen and consequently the ratio of specific heats y may be taken as 5/3. but the theory developed is valid for any value of y. The effect of viscosity and heat conduction was neglected. The method of Riemann invariants and characteristic curves of the differential equations of the motion were used. These characteristic curves were then plotted to represent the flow in the case of problems previously examined by Burgers and Copson for a hydrogen cloud. Burgers’ problem involved an initial discontinuity of density at the front of a homogeneous cloud while Copson stipulated an initial region of inhomogeneity between the vacuum surface and the main homogeneous cloud without any actual discontinuity in density. Both solutions involved gas flows which are continuous. The method of characteristic curves developed showed that unless special initial conditions are satisfied by the cloud the subsequent flow cannot remain indefinitely continuous and shock waves appear within the gas. Other initial conditions were also investigated and illustrated by characteristic flow diagrams. When the speed of sound increased linearly at first a limiting case of Copson’s solution was obtained : The characteristics of one family shrank to a point on the wave front at the same instant of time. In the case of the flow remaining continuous the wave front was shown to move ultimately with a velocity of three times the speed of sound in the homogeneous cloud, whereas in the case of initial conditions leading to shock waves in the flow the wave-front attained even greater velocities. Thus the high eventual velocity of these gas clouds which was considered to be a physically unsatisfactory feature of previous solutions of the problem could not be avoided by a change in the initial inhomogeneities. Somnraire : On a fait des recherches theoriques sur le mouvement vide interstellaire.
Awl,
1953
d’un gaz d’hydrogene
Vacuum Vol. III No. 2
se rependant dans un
l??%&
Mon. Not. Roy. Am. LGc. 113, &I953
180