Fixed monitoring reduces an operator's dependence on costly, often inaccurate subsea-corrosion surveys.
Deepwater manufactures a range of instruments and readouts designed to allow an operator to monitor all aspects of corrosion control on any type of offshore asset. A permanent monitoring system provides a constant, reliable stream of information about an asset's cathodic protection system. A traditional corrosion survey carried out correctly, while effective, is costly and time-consuming to organize, especially when problems occur outside of the normal inspection schedule. Polatrak monitoring systems allow asset integrity managers to feel confident about the cathodic protection systems they have in place. By providing them with ample warning before an anode system is ready to be replaced, fixed monitoring can also allow operators to budget and plan an anode retrofit before the situation becomes critical.
A typical monitoring system is comprised of two main components: fixed subsea instruments for generating cathodic protection data, and readouts for interrogating the instruments to collect data. Any combination of instruments and readouts is possible, depending on the asset in question and the particular interests of the asset manager. Systems can be installed on new structures quite easily, and retrofitting a system to an existing structure requires only minor modifications. New technologies are constantly becoming available for communicating data via satellite and other wireless mechanisms, and Deepwater has several test units in place to explore the viability of these technologies. Once we have proven their durability, they will be incorporated into the range of “readout” mechanisms offered for collecting CP data. This is a field of cathodic protection science very much still in flux, and Deepwater is proud to be at the forefront.
Fixed instruments - The DR-2 and DR-3 (dual reference electrodes) are our standard electrodes for collecting cathodic-protection potentials. Both utilize silver-chloride and zinc reference electrode elements. The MA-1 (monitored anode) provides data specifically about anode current output and consumption. For a more comprehensive portrait of the CP system, the DR-2 CD provides both potential readings and current density data, which allows the operator to monitor polarization.
Readouts - Monitoring instruments are usually hardwired to the surface, where any number of different monitoring panels or data recorders can interpret the data provided. Data brought topside has also been successfully transmitted through existing SCADA systems. In addition, Deepwater has developed a subsea readout call the SunStation, which requires no outside power source or interface with the surface. This new technology has allowed fixed-monitoring to go into deep-water fields and other previously inaccessible areas. The SunStation is powered by the lights of a diver or ROV and can provide readings for multiple instruments. It must be interrogated locally, which can be done during any routine subsea maintenance.
Pipelines and structures located offshore of Alaska face unique challenges to monitoring cathodic protection. Advances in cathodic- protection monitoring technology are discussed.
Offshore production facilities and pipelines are being installed in new, more hostile environments. Advances in cathodic protection monitoring have become more attractive to operators as the risks associated with a corrosion failure increase.
In many markets, the measurement of cathodic-protection potentials on offshore structures is a regulated activity required by local governing bodies. It makes sense to get as much benefit from a survey as possible.
In many cases it is not the actual water depth but rather the nature of the production hardware that determines optimum maintenance and inspection strategies of CP systems.
The introduction of subsea pipelines in the Arctic Ocean has provided an opportunity to collect accurate steady state polarization data in this environment.
For CP potentials, the DR-2 has dual-reference electrodes (Zn and Ag/AgCl) housed in a single instrument. It can be welded, bolted, or retrofitted to a tubular member or pipeline with two RetroClamps.
For CP potentials, the DR-3 is a general-purpose zinc and silver chloride reference electrode, which can be retrofitted to a subsea tubular or pipeline with a variety of clamps (including RetroClamp).
For polarization data, For polarization data, the DR-2 CD has a current-density monitor atop a normal DR-2 unit. This combination allows the operator to calculate polarization on the monitored structure.
For anode consumption, the MA-1 acts like a fuel gauge for a CP system. It is a standard platform anode or pipeline bracelet, fitted with a special monitor that can also be applied to other anode shapes.
For topside interrogation, instruments can be hardwired to topside monitoring panels, customized for any method of interrogation, from a simple voltmeter stab point to a fully integrated SCADA interface.
For subsea interrogation, the SunStation readout is activated by the light of an ROV or diver. Rated for up to 3,000-meter depths, it eliminates the need for surface access and allows monitoring almost anywhere.
"Smart" pipeline test station - Deepwater’s standard RetroClamp fitted with a V-String zinc reference electrode and a SunStation monitor creates a stand-alone subsea pipeline cathodic-protection test station.