wherein the travel times of a pulse emitted by said probe's ultrasonic transducer module and a first echo impulse resulting from said pulse entering an adjacent wall are determined by said ultrasonic transducer module and from the time difference between said pulse emission and the return of the first echo impulse, the adjacent wall distance is determined;

and from the travel time difference between arrival of the first echo impulse, and the back wall echo, the remaining wall thickness is determined;

and wherein from particular measurement transducer data values of said probe which are within and outside of a predetermined tolerance band the data values are formed into the same data format

wherein said data values are subjected to a decompressible compression to form datasets;

wherein the data values from the ultrasound travel time measurements for the adjacent wall distance and for the wall thickness are recorded in a data format;

wherein the data format contains a prefix bit, which is not activated when said measurement value is outside the tolerance band, and a data word assigned to the measurement value is recorded

wherein, when at least two subsequent measurement values are within the tolerance band, said data word is set to be interpreted as a multiplier count for said data values in place of consecutive value recording, said method comprising the steps of:

when a change of wall thickness is recognized, narrowing the tolerance band for a short period to avoid a reduction of resolution of the measurements in an area of possible corrosion,

representing a longer series of failure of said transducer by a multiplier and placing the prefix bit ahead of the value to which said measurement value is assigned,

further compressing in a second stage of the compression, two or more subsequently compressed equal data sets by a characterizing word and a multiplier value,

taking a measurement value skip of said transducer of a wall distance signal in connection with the measurements, as a failure to measure the wall thickness and indicating the wall thickness value to be within the tolerance range and consequently, compressible,

providing for said transducer module a particular wall distance reference value which, during said probe travel, is constantly updated by continuous averaging of a predetermined number of wall distance values and which is several times redundantly stored,

maintaining for the wall thickness measurements for said transducers module of said probe only one reference value, a wall thickness value, which during said probe travel is continuously updated by arithmetic averaging of a predetermined number of consecutive data sets so as to be adjusted smoothly to changing wall thicknesses and storing several times redundantly and including all values of a data set disposed outside the tolerance band in the averaging procedure when more values are outside the tolerance band than within, and

disregarding said echo skips where the measurement values are equal to 0, in the averaging procedure for the reference values.

Abstract: In a method of compressing data obtained from ultrasonic propagation-time measurements made at a given pulse-repetition rate over a broad surface by an inspection probe which slides through the pipe in order to detect corrosion and other abnormalities in the pipe, the particular physical characteristics of the pipe are taken into consideration whereby a high data-compression factor and, for the subsequent analysis, reliable reproduction of the actual conditions in the pipe are achieved.

U.S. Class: (73/623) (364/571.04) (73/602)

IPC: (G01N 29/10)

US Patents Cited: 4909091 4953405

Priority: (DEX 19911213 41 41 123.4)