METHOD OF HYDRAULIC RE-TESTING OF OPERATING PROCESS PIPELINES Russian patent published in 2015 - IPC G01M3/04 

FIELD: oil and gas industry.

SUBSTANCE: under method of hydraulic re-testing of the operated process pipelines the pressure pipelines are periodically loaded by increased water pressure, and absence of leaks and /or metal breaks, pressure drop below specified limits is observed. At that time interval of re-tests of the pipeline section for the given test pressure is determined. Actual data of pressure change at the studied pipeline section during year are obtained, and maximum internal pressure is determined as per actual data of pressure change. Equivalent stress of zero-to-compression stress cycle and number of cycles per year of loading by the equivalent stress of zero-to-compression stress cycle are determined. Initial size of pipeline defects is determined. Then final size of design defects is determined as critical size of defects during operation. Cyclic fatigue life is determined as number of cycles of equivalent loading during which the defect grows during cyclic zero-to-compression equivalent loading from initial depth to final depth. Interval of re-tests of the pipeline section for the given test pressure is determined at minimum cyclic fatigue life from set of values for all design defects.

EFFECT: increased reliability of tested pipeline section.