Pressure testing of pipelines has been around in some form or another since the 1950s1–14. In its earliest form, operators used inert gases such as Nitrogen or even air to test for pipeline integrity. However, with the significant increases in pipeline pressures and inherent safety issues with a pressurized gas, the switch to using water happened in the late 1960’s15–17. Hydrostatic tests (referred to as hydrotests) have been used since then to set and reset the Maximum Allowable Operating Pressure (MAOP) for pipelines but as other technologies develop and gain acceptance will hydrotesting still play a key role in pipeline integrity in the years ahead?
Currently, hydrotesting is a topic for the impending US Pipeline and Hazardous Materials Safety Administration’s (PHMSA) Proposed New Rule Making (PNRM)18. Under the NPRM, hydrotesting is required to verify MAOP on pre-1970s US “grandfathered” pipelines, as well as on pipelines of any age with incomplete or missing testing record and include a high level test with a “spike” in pressure. But hydrotesting may not be the only method. Alternative methods and new technologies — used alone or used in combination with hydrotesting — may help provide a more comprehensive way for operators to identify and address potential problems before they become a significant threat. This paper explores both sides of the argument.
Before In-Line Inspection (ILI) technology was even available, hydrotesting was the absolute means of the proof of integrity. However, hydrotesting is under scrutiny for many reasons that this paper explores. ILI was introduced in the 1960’s with the first commercially available Magnetic Flux Leakage (MFL) tools that presented the industry with an alternative. Currently there are a huge array of available technologies on an ILI tool and so is the role of the hydrotest over? The paper looks at the benefits of the hydrotest and these are presented and balanced against available ILI technology.
Furthermore, as pipelines are being developed in even more harsh environments such as deepwater developments, the actual logistics of performing a hydrotest become more challenging. The paper will also look at both applications onshore and offshore where regulators have accepted waivers to a hydrotest using alternative methods of proving integrity.
The paper concludes with the current use and needs for hydrotesting, the regulatory viewpoint, the alternatives and also what the future developments need to focus on and how technology may be improved to provide at least a supplement if not a replacement to this means of integrity assurance.