Guidelines When Conducting Hydrostatic Pressure Tests and Management of Extended Dwell Times Through Dry/Wet Lay-Ups

The integrity of new pipelines is most typically demonstrated by pressure tests.  For virtually all tests, the pipeline is filled, using a convenient, local supply of water, held at a certain test pressure for a set period of time, after which the test water is removed, and the pipeline is prepared for duty in transporting liquid or gaseous products.  The test water is typically filtered, but no chemicals are added, i.e., no oxygen scavengers, biocides, nor any corrosion inhibitors.  That makes it possible to return the test water to the original source, such as the river, lake, or ocean.  It also minimizes the possible consequences from a potential leak at one of the new girth welds along the pipeline.  Crude oil and natural gas producers typically have guidelines regarding the total length of time untreated hydrostatic test water can be left within a pipeline before being removed.  These guidelines are designed to minimize the consequences of potential corrosion, including microbiologically influenced corrosion (MIC).  However, sometimes there are circumstances beyond the control of the personnel conducting the pressure tests, which allows the test waters to remain within the pipeline for an extended period of time.  This paper will discuss test guidelines and potential consequences of an extended residency, such as the internal corrosion which was observed when seawater remained within one pipeline for several months beyond the original test period.