Abstract: The invention relates to a process and a device for measuring the gelling of paraffin petroleum products, in particular, crude oil. The process involves: measuring, with respect to the temperature and over a given thickness, the propagation velocity and the amplitude of an ultrasonic wave in the crude oil being analysed; then determining the transition temperature T.sub.t, at which a sudden change in the thermal variation in the inverse of the propagation velocity is observed; determining the ratio of the slopes for the propagation velocity inverse obtained between the linear parts of the thermal variation of said propagation velocity, around said brake point corresponding to T.sub.t, above and below, respectively, the determined temperature T.sub.t ; determining the ultrasonic signal amplitude difference .DELTA.A between the temperature T.sub.t and a given lower reference temperature, for example T.sub.t -5.degree. C.

Abstract: A process and apparatus for manufacturing polyolefin fibers from a composition of the said polyolefins dissolved in a diluent, by subjecting the composition to flow at a velocity above a critical value in a tube or bundle of tubes, the temperature of the composition being within the range of critical temperatures of the said composition over at least a portion of the length of the tube or bundle of tubes and separating the fibers from the liquid diluent. The critical temperature range is below the temperature of solution of the polyolefin in the molten state in a diluent and is more specifically the range of temperatures in which the polyolefin remains in dissolved condition when the solution mixture is maintained at rest but precipitates when the mixture is subjected to certain disturbances such as, for instance, shearing. This typically is between 70.degree. and 130.degree. C.