Showing papers on "Pressure measurement published in 1979"

Absolute pressure measurements and analysis of diamonds subjected to maximum static pressures of 1.3–1.7 Mbar

Abstract: Force per unit area measurements made in the megabar pressure cell, independently of other pressure calibration systems, are consistent with the ruby R1 scale of Mao, Bell, Shaner, and Steinberg and its extrapolation to 1.4 Mbar. Physical analysis of diamond anvils removed after experiments to maximum pressures of 1.3-1.7 Mbar suggests that the nitrogen platelet concentration may be related to the strength of the diamonds. The pressure face of one of the diamonds from the 1.7-Mbar experiment was deformed plastically by a macroscopic amount.

Real Gas Pseudo-Time - A New Function For Pressure Buildup Analysis Of MHF Gas Wells

Abstract: A new time function has been defined which considers variations of gas and compressibility as a function of pressure, which in turn is a function of time. This function appears to be similar to the real gas pseudo-pressure, M(P) of Al-Hussainy et al., which takes into account the variations of gas viscosity and Z-factor as a function of pressure. However, this is an approximate function as opposed to M(P). This time function is referred to in this work as the real gas pseudo-time, TA(P). This function has aided in post-treatment pressure buildup analysis of fractured (including MHF) gas wells by type-curve analysis. Results of computer simulated pressure buildup analysis indicate that the use of TA(P) provides satisfactory values of computed fracture lengths in fractured gas wells. In this work, the real gas pseudo-time is described and its application is demonstrated by means of example problems. Although the discussion in this study is limited to pressure buildup analysis of vertically fractured gas wells. The utility of this function is not meant to be restricted to such wells only. 10 references.

Flow regimes in submerged gas injection

Abstract: The behavior of gas discharging into a liquid has been investigated in the labora-tory and in plant. The laboratory work has involved the injection of different gases from a submerged, horizontal tuyere into water, zinc-chloride solution, and a mercury bath. High speed cinematography and pressure measurements in the tuyere have been carried out to characterize the flow regimes. In the case of the mercury bath, a novel “half-tuyere” has been developed to permit visual observation of the gas. In this way, two regimes of flow, bubbling and steady jetting, have been delineated as a function of the modified Froude number and the ratio of gas to liquid densities. Pressure measurements at the tuyere tip have been correlated to the different stages of bubble growth in the bubbling regime, and can be used to distinguish one flow regime from the other. The measured bubble frequency and volume correspond reasonably well to predictions of a simple model of bubble growth under conditions of constant flow. The forward penetration of the jet centerline from the tuyere tip has been measured and found to depend both onN Fr′ andρg/ρl. In the industrial tests, pressure taps have been installed in the tuyeres of a nickel converter to monitor the pressure wave of the jets under normal, low pressure blowing operations. The measurements show that the converter jets operate in the bubbling mode with a bubble frequency of 10 to 12 s−1, similar to a gas jet in mercury. Tests involving higher pressure injection indicate that the steady jetting, or underexpanded, regime obtains at pressures of about 340 kPa (50 psi). Based on equivalent experiments in the laboratory, it is clear that low pressure blowing has the disadvantage of poor penetration of air into the bath so that the jets rise close to the back wall and locally accelerate refractory wear. Moreover between the formation of successive bubbles, the bath washes against the tuyere mouth and contributes to accretion formation. This necessitates periodic punching of the tuyeres which also contributes to refractory wear at the tuyere line. The use of high pressure injection to achieve steady jetting conditions, as currently practiced in the new bottom blown steelmaking processes, should be considered to solve these prob-lems, and possibly usher in a new generation of nonferrous converters.

Media compatible pressure transducer

Abstract: There is disclosed an absolute pressure transducer which is adaptable for use in various deleterious mediums. A single wafer contains a gage sensor configuration on one portion and an absolute sensor configuration on another adjacent portion. An active diaphragm area is defined for each sensor configuration by forming a depression beneath the sensor locations. A base member is bonded or secured to the wafer at the side containing the depressions. An aperture is directed through the base member to communicate with the depression associated with the gage sensor configuration and is employed as an external pressure port. The top surface of the wafer which contains the sensors is exposed to a relatively clean source of pressure to thereby enable the absolute sensor section to monitor this pressure, while the gage sensor section responds to both pressures.

Propagation velocity and reflection of pressure waves in the canine coronary artery.

Abstract: In this study the pressure wave velocity in the anterior descending branch of the left coronary artery (LADC) of the dog was measured by determining the delay time between pressure pulses along this artery. This method can only be applied if reflections of the pressure wave distal to the sites of pressure measurement are insignificant. From araldite casts of the coronary arteries the following relation between the diameter proximal to (dprox) and distal to (ddist 1, ddist 2) a bifurcation was found: dprox2.55 = ddist12.55 + ddist 22.55, indicating that reflections at a bifurcation areminimal. In dogs reflections were studied by inducing during diastole a pressure pulse in the aorta and measuring pressure and volume flow proximal to and pressure distal to a segment of the LADC at various levels of the coronary peripheral resistance. Reflection of high-frequency components (greater than 7 Hz) was found to be insignificant, allowing application of the above-mentioned method for measuring the wave-front velocity, which is insensitive to low-frequency reflection. At a pressure in the LADC of 13.3 kPa this velocity was 8.6 +/- 1.4 m.s-1 (mean +/- SD). The calculated dynamic cross-sectional stiffness (deltaP/(deltaA/A)) of the LADC was 97 +/- 11 kPa (mean +/- SE) at an arterial pressure of 13.3 kPa.

A simple technique for surface area determination

Abstract: An inexpensive apparatus for BET (Brunauer, Emmett and Teller) surface area measurement using krypton with a lower limit of 0.001 m2 has been developed. Operation is made simple by the use of an MKS Baratron pressure gauge and a constant-volume system.

Device for pressure measurement using a resistor strain gauge

Abstract: A pressure measurement device and a method for making it are disclosed. A plurality of thick-film resistors are screen-printed onto a deformable substrate, after which they are preferably fired. The resistors are then connected to circuitry for measuring changes in their respective resistances due to deformation of the substrate by an external force or pressure to be measured.

Wellbore pressure testing method and apparatus

Abstract: An apparatus for sensing the pressure of a well fluid in a subsurface wellbore in which a first, elongated tubing is adapted to extend from the surface of the earth to a subsurface location at which the pressure is to be measured, a fluid receiving chamber is disposed on the lower end of the first tubing, a second, elongated tubing, of smaller cross-section than the first, is disposed in the first tubing with its upper end at the surface of the earth and its lower end sealed within the lower end of the first tubing or the upper end of the fluid receiving chamber and is adapted to receive a pressure transmitting fluid and to be placed in fluid communication with the fluid receiving chamber and a pressure responsive closure element closes the lower end of the first tubing, the upper end of the fluid receiving chamber or the lower end of the fluid receiving chamber and is adapted to open at a pressure above the pressure of the well fluid and permit the pressure of the well fluid to be balanced against the pressure of the pressure transmitting fluid within the fluid receiving chamber. A method of sensing the fluid pressure at a subsurface location in a wellbore is also disclosed in which a pressure transmitted fluid is disposed in the second tubing, the pressure of the pressure transmitting fluid is increased to a pressure sufficient to open the closure, the pressure of the pressure transmitting fluid is balanced against the pressure of the well fluid in the fluid receiving chamber and the pressure of the pressure transmitting fluid is sensed at the surface of the earth.

Uniform stress conditions in the diamond anvil cell at 200 kilobars.

Abstract: Pressure gradients in a diamond anvil cell have been measured with a 4:1 methanol:ethanol mixture as a pressure medium up to 350 kilobars. When pressure is applied rapidly, stress gradients are shown to be negligible up to 200 kilobars and probably above. With this procedure it is possible to significantly increase the precision of pressure measurements above 100 kilobars.

Interpretation Of The Pressure Response Of The Repeat Formation Tester

Abstract: The analytical theory of the buildup pressure response associated with the pretest stage of the repeat formation tester operation is given. Both an infinite system and the case of a reservoir layer bounded above and below by impermeable barriers are considered. The spherical flow analysis method for the infinite acting case yields the equivalent spherical permeability which is influenced by formation anisotropy. For the bounded case, 2 different types of spherical buildup are shown to occur and an analysis technique for each one is presented which yields the spherical permeability and an estimate of the layer thickness. In circumstances where radial cylindrical buildup is observable, in principle, the anisotropy may also be determined. A quantitative result relating the depth of investigation of the permeability measurement to the pressure gage resolution is given. Computer simulations of composite systems involving a filtrate-invaded zone around the well and an outer oil zone have shown how these affect the shape of buildup plots. Recommendations regarding the choice of water or oil physical properties in data analysis are made.

Calibration of the Ruby-Pressure-Scale at Low Temperatures

Abstract: Development and accurate calibration of the ruby manometer [1–4] led to rapid progress in diamond anvil cell high-pressure techniques [5]. Applications of the ruby manometer at low temperatures [6], however, suffered from the fact that the pressure dependence of the ruby R1 luminescence line had been calibrated accurately only at room temperature [4], and the same physical reasons which are responsible for the temperature dependence of the R lines at normal pressure could also lead to a Variation in the pressure dependence of these lines with temperature.

Nicolas Andry Award. Increased tissue pressure and its effects on muscle oxygenation in level and elevated human limbs.

Abstract: Increased tissue pressure is an important cause of local circulatory compromise. In both rabbit and human model systems known external pressures were applied to otherwise normal limbs. Side-by-side comparison of the wick and the infusion techniques revealed that both methods of pressure measurement yielded essentially identical results when tissue pressure was elevated. Measured tissue pressure significantly exceeded the external pressure applied to the limb. Using a mass spectrometer-Teflon membrane catheter system, we monitored muscle PO2 and PCO2 at different applied pressures. Muscle PO2 decreased progressively with increasing tissue pressure but did not approach zero until tissue pressure exceeded local arterial pressure. Comparison of results with level and elevated limbs indicated that elevation of an extremity dramatically lowered its tolerance for increased tissue pressure. Although they may be clinically useful modalities, these are conditions in which compression and elevation have a significant potential for compromising local circulation.

Air/fuel ratio management system with calibration correction for manifold pressure differentials

Abstract: An air fuel ratio management system having a calibration correction for the pressure differentials between the exhaust and intake manifolds of the engine is disclosed. The differential calibration corrects the air/fuel ratio of the system for the variable internal exhaust gas recirculation occasioned by changing restrictions to flow found in the intake and exhaust manifolds. In one implementation a differential pressure sensor communicates with both the intake and exhaust manifolds to develop a differential pressure signal. The differential pressure signal is thereafter applied to a function circuit which generates a pressure correction signal. An electronic control unit receives the pressure correction signal and utilizes it to modify the air/fuel ratio calibration according to the functional conversion. In the preferred embodiment the function circuit comprises a voltage controlled linear current source. In another implementation individual pressure sensors are used for each manifold to generate signals to a difference circuit which subtracts the intake manifold absolute pressure from the exhaust manifold absolute pressure to form the differential pressure signal. In either implementation incremental or proportional modification of a variable duration fuel pulse from the electronic control unit can be obtained by the pressure correction signal.

Method of and apparatus for compensating for temperature in leak testing

Abstract: A method and apparatus for testing for leaks in a test item which has a temperature different from ambient temperature in which the test item is sealed at atmospheric pressure and the pressure of the sealed air in the test item is measured. The rate of change of the pressure of the sealing air due to the non-ambient temperature of the test item is calculated for providing a temperature correction signal proportional to the temperature of the test item and the temperature correction signal is stored. The test item is then subjected to a leak test pressure, any change in the pressure of the pressurized test item is measured and the stored correction signal is applied to the pressure measurement for determining the extent of any leak in the test item while compensating for the temperature of the test item. The temperature correction signal is obtained by differentiating the pressure measurement of the sealed test item in ambient air at ambient pressure, is stored, is integrated, and is inverted and applied to the pressure measurement obtained during the normal pressure decay test time.

Technique for remotely measuring surface pressure from a satellite using a multicolor laser ranging system

Abstract: The optical path length from a satellite to the earth's surface is strongly dependent on the atmospheric pressure along the propagation path. Surface pressure can be measured by using a multicolor laser ranging system to observe the change with wavelength in the optical path length from the satellite to a ground target. The equations which relate surface pressure to the differential path lengths are derived and the accuracy of the pressure measurement is evaluated in terms of the ranging system parameters. The results indicate that pressure accuracies of a few millibars appear feasible.

Pressure Gradient and Leading-Edge Effects on the Corner Bounday Layer

Abstract: Results are presented of velocity and pressure measurements made in the initially laminar boundary layer in a streamwise corner formed by two flat plates at 90° to each other set at various incidences. The leading edges of the plates were sharp in contrast to earlier tests with an aerofoil type leading edge. It was found impossible to obtain a steady enough flow for useful measurements to be made at zero incidence and pressure gradient, a small incidence associated with a favourable pressure gradient was necessary. This is believed to be because of the development of separation bubbles at the sharp leading edge at very small incidences due to small variations of flow direction to be expected in a wind tunnel. The profiled nose used in earlier tests afforded flow conditions much closer to the ideal theoretical model involving zero pressure gradient, but it is argued that any nose however shaped may introduce disturbances in the form of characteristic secondary flows that may well determine the downstream response of the boundary layer. In any case the corner flow is highly unstable at all but very low Reynolds numbers, and in the absence of a region of favourable pressure gradient a Reynolds number in terms of distance downstream of the leading edge greater than about 105 is unlikely to be attained in practice with the flow remaining smooth and laminar.

Manometer for infusion apparatus

Abstract: A manometer for measuring the hydrodynamic pressure of fluids parenterally administered to a patient. The manometer includes a transparent housing which has a passageway formed in the housing that accommodates continuous flow of fluid therethrough. A pressure measuring chamber is formed in the housing and one end of the pressure measuring chamber is in fluid communication with the passageway. The other end of the pressure measuring chamber communicates with an enclosed air space. The fluid flowing through the passageway enters the pressure measuring chamber and rises to a level which is dependent upon the pressure of the fluid flowing through the passageway. Markings are provided on the housing of the manometer which permit the pressure exerted on the fluid flowing through the passageway to be read directly from the level of the fluid in the pressure measuring chamber. In one embodiment of the manometer, the enclosed air space may be adjusted so that the manometer may be normalized for use at any one of several different altitudes. A valve is provided so that the enclosed air space may be vented to the ambient atmosphere when it is desired to set the pressure reading to zero. In another embodiment of the manometer, the pressure measuring chamber is provided with a progressively decreasing cross-sectional flow area from its bottom to its top so that the pressure may be read in a linear fashion.

Methods and apparatus for sensing wellhead pressure

Abstract: This invention relates to methods and apparatus for monitoring fluid pressure in a subsea petroleum installation or other similarly inaccessible system while isolating the well fluid from the production control system. In one particular form of the invention, a body of secondary fluid is pressure-responsively coupled to but isolated from the oil or other primary fluid of interest by a piston, which subjects the secondary fluid to the pressure existing on the primary fluid. In addition, a measuring device is connected to the secondary fluid to derive an electrical signal representation of the pressure on the secondary fluid as a correlative indication of the wellhead or other pressure actually sought to be measured. Further, the isolating device is constructed and arranged to effectively seal off the primary fluid from escape into the environment or into the production control apparatus and the pressure of the primary fluid is maintained in the event of damage to any portion of the chamber enclosing and holding the secondary fluid. It is a particular feature of this invention to provide at least a minimum pressure on the secondary fluid of a magnitude such as to effectively limit the further compression of the secondary fluid by the piston, when the piston is initially subjected to the primary pressure.

Effusion Studies of the Vaporization/Decomposition of Potassium Sulfate

Abstract: The vaporization of was studied by the torsion‐effusion method and by mass spectrometry in the range 1180°–1280°K, from which the total pressure, molecular weight, and composition of the effusing vapor were determined. Both the sublimation process and the decomposition process contribute to the vaporization flux, with the sublimation pressure about 63% of the total pressure in the range of our measurements. The directly measured vapor molecular weights are in good agreement with values deduced from the magnitudes of the sublimation and decomposition pressures. A small but reproducible variation of pressure with effusion orifice area was observed, equivalent to an upper bound of 0.03 to the over‐all sublimation coefficient. Second law slope heats derived from the temperature dependence of parent K+ and ions were in close agreement with each other and with the heat of decomposition calculated from established thermochemical data. Similar measurements on parent showed the temperature dependence of sublimation and decomposition pressures to be virtually identical. The heat of sublimation of at 298°K was determined as , leading to the standard heat of formation . From the slope heat and the absolute pressure, one evaluates the entropy.

Mass flow/pressure control system

Abstract: An input valve having an input that can be coupled to a source of pressurized gas is open during first portions of successive cycles and closed during the remainder. A volume V is connected between the output of the valve and a load, and gas flows through the volume V to a load during the entire cycle. Pressure in the volume V is measured at the end of the first portion of each cycle and/or at the end of each cycle, and means responsive to a pressure can be used to control the flow of gas through the input valve so as to maintain the pressure on the load at a predetermined value or the difference in the pressures can be used to maintain a constant flow to the load. An output valve can be inserted between the volume and the load and closed while pressure measurements are being made so that the pressure is constant during the measurement. In one embodiment, a reserve volume can be coupled to the output valve and a third valve can be coupled between the reserve volume and the load so as to smooth out variations in pressure on the load. In this last embodiment, the output and third valves are operated out of phase and in such manner that the input valve and output valve are closed when the measurement is taken at the end of a first portion of a cycle, and the input and third valves are shut when the pressure is being measured at the end of a cycle.

Welding gas shield control

Abstract: An inert gas is supplied in a conduit system at a pressure high enough to provide a desired shielding gas volume at each and all arc welding sites spread over a substantial work area and each welder is responsible for the performance of a lightweight, readily portable, security protected, fixed pressure output regulator of high accuracy preferably having a pressure gauge and two independent visible output flow meters and flow valves easily adjusted separately to provide proper shielding at the front and back of a weld simultaneously, but independently, under the personal control of each welder at each welding site with excellent mobility regardless of floor elevation, for an acceptable and individualized responsibility for each certified weld performed.

Studies on an experimental quartz tube hollow cathode

Abstract: An experimental study is described in which a quartz tube, hollow cathode was operated in a test fixture allowing the simultaneous measurement of internal cathode pressure, insert temperature profiles, and the emission currents from various cathode components as a function of discharge current and propellant (mercury) mass flow rate for a number of different cathode orifice diameters. Results show that the insert temperature profile is essentially independent of orifice diameter but depends strongly on internal cathode pressure and emission current. The product of internal cathode pressure and insert diameter is shown to be important in determining the emission location and the minimum keeper voltage.

Method and means for measuring flow of a two phase fluid

Abstract: A Pitot tube is provided for measuring fluid momentum in a transmission line. A signal is transmitted through the Pitot tube to the fluid, and return energy is detected to determine the gas or liquid phase of the fluid at the point of momentum measurement, thus providing a more accurate measurement of fluid flow. Two Pitot tubes may be employed to determine absolute pressure or momentum and static pressure, from which the dynamic pressure is determined. The transmitted signal may be ultrasonic, electrical, or optical.

Noninvasive measurement of ventricular pressure throughout systole

Abstract: A simple method is proposed for measuring right or left ventricular systolic pressure based on analysis of the right or left ventricular time-activity curve, obtained with a scintillation camera or cardiac probe after intravenous injection of technetium-99m albumin or red blood cells. The method is based on three principles: (1) intraventricular pressure equals force per area of the aortic opening; (2) force equals mass (of blood) times its acceleration; and (3) acceleration can be derived from the ventricular volume curve. The following differential equation was derived ( ∂ P ∂ t ) x = ϱ A 2 α 2 da dt d 2 a dt 2 where ( ∂ P ∂ t ) x is the first derivative of left ventricular pressure; ϱ is the density of blood; A is the area of the aortic opening ∗ ; α is the ratio of blood volume to radioactivity (a) measured within the ventricle, da dt is the first derivative (velocity) of the activity (a) within the ventricle and d 2 a dt 2 is the second derivative (acceleration). The integration of this equation is readily accomplished, and the integrated curve reflects the pressure changes. Absolute calibration in millimeters of mercury requires knowledge of the end-diastolic volume and the area of the aortic opening. It is assumed that the area of aortic opening is relatively constant, that blood flow is laminar and that the pressure pulse travels with the velocity of blood through the aortic opening. In validation studies in dogs, calculated and observed ventricular pressure curves were nearly identical in shape and absolute value. In patients, although an absolute pressure measurement still awaits an accurate method for calculation of left ventricular enddiastolic volume, differences in the shape and amplitude of the curves were found. The procedure can be performed easily, and the calculation can be made within minutes. With further validation, the method may provide noninvasively a pressure and volume relation that is valuable in characterizing the function of the heart as a pump, both at rest and during graded exercise.

SAW Resonator Frit-Bonded Pressure Transducer

Abstract: A useful configuration of surface acoustic wave (SAW) devices for pressure, force, or displacement application, employs two SAW devices. An absolute pressure sensor of simple design was fabricated and tested. The sensor consisted of two ST-cut quartz SAW resonator plates bonded together and vacuum sealed with a devitrifying frit ring. This device d isplayed a full scale frequency deviation o f 43 KHz (200 ppm of the 194 MHz resonator frequency) over its designed 1 atmosphere range, and the readout resolution was 0.001 ppm of the r esonator frequency. The resulting frequency versus p ressure characteristic showed aslight, parabolic deviation from a perfectly l inear relationship. The device hysteresis was very low. Quartz-frit bond strength s tudies demonstrated a strong structure capable of withstanding temperatures as low as - 196OC,

Stabilized DC amplifier

Abstract: A pressure responsive system includes a piezoresistive transducer (10) mounted in a housing (20) with the temperature of the housing and the transducer maintained by heater (22). Operating characteristics of the transducer (10) are normalized by a normalization circuit (18) that interconnects the output of the transducer to a heater control (24). The heater control (24) generates a control signal to the heater (22). A signal varying with pressure is output from the normalization circuit (18) and applied to a DC stabilized gain stage (26) that is corrected for zero signal error and produces an amplification of the transducer output for application to a function generator (12). The function generator (12) converts an absolute pressure signal from the transducer (10) into a signal varying with pressure altitude for utilization in an autopilot system.

Pressure sensing of the atmosphere by solar occultation using broadband CO2 absorption

Abstract: A technique for obtaining pressure at the tangent point in an IR solar occulation experiment is described. By measuring IR absorption in bands of atmospheric CO2 (e.g., 2.0, 2.7, or 4.3 microns), mean pressure values for each tangent point layer (vertical thickness 2 km or less) of the atmosphere can be obtained with rms errors of less than 3%. The simultaneous retrieval of pressure and gas concentration in a remote-sensing experiment will increase the accuracy of inverted gas concentrations and minimize the dependence of the experiment on pressure or mass path error resulting from use of climatological pressure data, satellite ephemeris, and instrument pointing accuracy.

A Method and Applications of a Theoretical Calculation for on-load Pressure Rises in Puffer Type Gas Circuit Breakers

Abstract: An on load pressure rise in a puffer chamber of puffer type gas circuit breakers (GCB) is higher than a no-load pressure rise. A method of calculation of the on-load pressure rise has been developed. The calculation results show good agreement with the on-load pressure rises measured with an experimental puffer type GCB.