Large standoff magnetometry (LSM), a novel screening technology, has shown strong industry relevance in several pipeline integrity investigations. LSM is used to detect changes in the magnetic field of a pipeline due to changes in the magnetic susceptibility of steel. These changes are known as inverse magnetostriction (a.k.a. the Villari effect) and occur when a ferromagnetic material (steel) is subjected to mechanical stress, such as the presence of stress on the wall of a pipeline. Geometric anomalies (ovalities, dents, wrinkles), hoop stress, ground and slope movement, bend strain, thermal expansion, cracks, and material defects are examples of potential sources of stress that LSM can detect from aboveground.
This paper summarizes the use of LSM as a complimentary tool in several pipeline integrity assessments conducted on oil and gas pipelines, in this case, to pinpoint a lost inline inspection pig and to identify dents, cracks, buckles, slope movement, casing ends, unknown valve locations and other pipeline integrity and direct assessment applications. Ongoing development programs and lessons learnt from practical, real-life projects and validations of the technology are presented to demonstrate the effectiveness of LSM for pipeline integrity investigations.
Marine environments can be very aggressive and present significant challenges in maintaining key infrastructure from the effects of corrosion. In Florida, thousands of bridges are in coastal areas and are continually, or periodically exposed to saltwater conditions. A clear majority of these bridges were constructed using steel reinforced concrete and are supported by precast pilings situated in saltwater, so for this reason, cathodic protection is a necessary strategy for controlling the effects of saltwater induced corrosion.
Toward the early 1980s, the Florida Department of Transportation (FDOT) began the evaluation of different approaches to control saltwater induced corrosion. Some of these included the use of integral pile jackets, specialty materials for concrete repairs, surface applied coatings and other innovative approaches utilizing galvanic anode technology. One such system was jointly developed with industry partners and sponsored by the Federal Highway Administration (FHWA) using integral pile jackets lined with expanded zinc mesh anodes to apply cathodic protection. This innovative approach provides for the problem of concrete repair while at the same time stopping the on-going process of corrosion both combined in one application. Both laboratory and field trials validated the benefits to this approach and confirmed that the system can mitigate corrosion and extend the useful service life of pilings by more than 20 years.
Direct current (DC) sources are a critical component of many cathodic protection (CP) systems. In order to assess the performance of these CP systems, momentary interruption of the DC current output is often utilized to help obtain true polarized potentials of protected structures1. This is achieved with a relay that is either integral to the DC current source or installed externally. Traditionally, these relays use a mechanical or mercury contactor, but solid-state relays are becoming more popular for their increased performance and reduced environmental footprint. Recent experience has indicated that interruption of current with an inductive load can damage solid state relays by momentarily exceeding their voltage rating. This has been observed by some CP technicians when they return to site to check on a previously installed interrupter, only to find it overheated and not interrupting. This study will examine the various sources of inductance in impressed current CP systems and discuss methods for mitigating the inductive effects during interruption. To demonstrate the effectiveness of these methods, an electrical circuit was created to mimic a cathodic protection circuit, and the effectiveness during interruption was measured using an oscilloscope.