Flush mounted probe assembly

A corrosion ratemeter probe assembly especially adapted for introduction into high pressure gas pipelines. The probe assembly features positive positioning relative to the pipeline and an integral seal for leakproof installation. The probe assembly carries a probe removably mounted within an internally shouldered nipple welded to the pipeline by "hot tapping" techniques. The probe has a cylindrical body with an annular seal adjacent to a sensing head which carries a plurality of flat surfaced metal electrodes. An adjustment nut threadedly mounts on a reduced diameter rear portion of the body and engages positively the shoulder on the nipple to position precisely the electrodes adjacent the inner wall surface of the pipeline. The nut is adjusted and locked into place after measurements of the relative longitudinal dimensions from the shoulder to the interior wall surface of the pipeline.