Braking system for pipeline inspection vehicle - which controls vehicles speed to that of average flow velocity of fluid in pipeline

摘要

A speed control device for a pipeline inspection pig includes a braking system which imposes a continuous axial drag on a pipeline wall. A hydraulic valve of a high-pressure hydraulic fluid system is operable to vary the imposed drag between upper and lower limits in response to transducer-generated signals representing actual vehicle speed. The summation of the variable drag characteristic of the pipeline and the imposed drag remains approx. constant, and the vehicle moves at a speed equal to the average flow velocity of the fluid in the pipeline. E.g. with pigs used to detect flaws in the internal surfaces of oil or gas pipelines. The pig travels a approx. the average speed of the fluid flowing in the pipeline, showing variations only within acceptable limits without violent accelerations or deccelerations. The speed control system may be applied to a tractor vehicle or to a towed vehicle.