Combined Effect Of Pressure Research Articles

Stress Studies on Piping Expansion Bellows

Abstract As a result of numerous and costly failures of the stainless-steel bellows used to take up thermal expansion in the piping of petroleum and chemical processing equipment, a basis has been developed for designing these bellows to operate within reasonable stresses. A formula has been derived to show the total stress induced in the material as a result of the combined effects of pressure and movement. The validity of the approximations used in this formula has been verified by laboratory strain-gage measurements on an experimental bellows. A relationship between several variables in the design of the disks has also been determined and serves as a basis for dimensioning them to achieve the most economical proportions. When this relationship is satisfied, the maximum permissible movement per disk can be obtained. This is shown graphically. Several supplementary formulas are given for determining bellows characteristics which may affect the design of adjacent piping. The problem of designing an expansion joint for high-pressure service is discussed briefly, and some preliminary laboratory data are presented on a commercial joint of this type.

Effects of Pressure and Temperature on Condensation of Distillate from Natural Gas

Deep drilling has led to the development of numerous pools which yieldproducts consisting predominantly of natural gas accompanied by high-gravitywater-white or slightly straw-colored liquid. Yields of this"condensate" or "distillate," as it is commonly called, vary fromtraces to over a hundred barrels per million cubic feet of gas. The fact thatthis liquid exists in the reservoir as an integral part of the gas phase and isformed by condensation attending simultaneous reduction of pressure andtemperature after its entry into the well was apparently first recognized about1932.1 The nature of the physical phenomena involved in this condensation wasclarified for the petroleum industry in 1933 by a report by Sage, Schaafsma, and Lacey of the results of an experimental investigation of the behavior ofmixtures of methane and propane. Search of the literature has revealed that the condensation of liquid fromgaseous mixtures by isothermal pressure reduction is not a new discovery.Kuenen was led by theoretical considerations to expect such a phenomenon, andin 1892 reported the results of experimental verification of his deductions.This was followed by a considerable amount of work on the phase relations ofmixtures by Kuenen and by others, mostly in European universities. Since 1930investigators in this country have reported experimental data on the properties and behavior of a number of hydrocarbon systems. It is now generally known that in the presence of natural gas the solubility inthe gas phase of the heavier and normally liquid hydrocarbons increasesrapidly with increasing pressure above 500 to 1000 lb. per sq. in. Thus, at pressuresof 2500 lb. per sq. in. or higher a gas may contain appreciable quantities ofhydrocarbons with normal boiling points as high as 600?F., which in turn may becondensed from the gas phase by the reduction of their solubility thereinattending pressure reduction. The combined effects of pressure and temperatureon condensation and vaporization of mixtures are most readily visualized by thestudy of phase diagrams. Since the construction, application, andinterpretation of such diagrams have been described fully in readily availableliterature, this paper will not review the theoretical aspects of thissubject. While the behavior of gas-distillate systems is now clearly understood, atleast in a qualitative way, most of the published work deals with the resultsof laboratory studies of binary systems or of synthetic mixtures ofhydrocarbons, and although several systematic investigations of the effects ofseparator pressure and temperature on the yields of liquid product fromgas-distillate wells have been made it appears that in all cases thelimitations have precluded the construction of even approximately completephase diagrams for naturally occurring systems. T.P. 1269

The Effect of Pressure on the Rigidity of Rocks. I

A dynamical method has been adapted to the measurement of the velocity of torsional waves in cylinders of rock exposed to pressures as high as $$4,000 kg/cm^{2}, at 30^{\circ} C$$. and at 100° C. From these results the rigidities of the rocks under these conditions are derived, as well as approximate values for the pressure and temperature coefficients of velocity and rigidity. Very large changes of rigidity are observed in many cases upon the application of the first few hundred atmospheres; at high pressure the change of rigidity with pressure becomes nearly linear and small. The following questions are discussed: stress conditions in aggregates of crystals, the effect of anisotropy upon velocity, the calculation of other elastic parameters from rigidity and compressibility, damping and dispersion in rocks, the effect of combined pressure and temperature on velocity in the earth's crust, and the identification of materials in the crust by comparison with seismological data.