Abstract: In a process for monitoring the tightness of pipelines, in particular sewage pipeline systems, one or several control channels or tubular openings are arranged in the wall of the pipeline in its longitudinal direction. The mutually facing ends of the pipelines are interconnected so that the mutually facing ends of the control channels or tubular openings are tightly interconnected. The interconnected control channels or tubular openings form a closed pressure chamber for the whole pipeline system. The control channels or tubular openings are filled with a test medium under static pressure, pressure measurement means are associated with the control channels or tubular openings, and a leakage in the area of a sleeve or wall of the pipeline is detected when the pressure of test medium falls between two measuring points.

Abstract: A method and apparatus is provided for monitoring a variable in a system. Actual values of the variables are sensed to produce sensed values. An initial threshold is set below an initially sensed value by a predetermined difference. Thereafter, the threshold is selectively maintained constant and adjusted to follow below the sensed values by a difference which is a function of the sensed values if the sensed values remain constant or increase, with the threshold remaining constant if the sensed values decreases. The threshold is compared with the sensed values and an indication of an unsatisfactory quality is provided if the sensed values fall below the threshold.

Abstract: A method of determining leaks and loose couplings in a pipe system which transfers liquid medium, and an apparatus for implementing that method. The pipe system includes a conduit having a beginning, an end, an inner pipe which carries the liquid medium and an outer pipe which surrounds the inner pipe. The conduit has a filler material which fills in an annular space between the inner and outer pipes. The leaks and loose couplings are detected and isolated by measuring only resistances of the filler material between the beginning of the conduit and ground yielding a first resistance value, between the end of the conduit and ground obtaining a second resistance value, and finally between the beginning of the conduit and the end of the conduit obtaining a third resistance value. The defect is then detected and located in the conduit using the first, second and third resistance values.