The V-String zinc reference electrode has a rugged conductor with a strong overbraid of polyester fibers.
The Polatrak V-String electrode is a low-cost zinc reference electrode designed for offshore platform and pipeline monitoring. The ultra-rugged construction and ease of installation make this a viable general-purpose cathodic-protection monitoring retrofit system, or as a supplement to other Polatrak monitoring instruments such as the DR-2 dual reference cell, or the MA-1 monitored sacrificial anode. The V-String's accuracy is +/- 0.02 V, which is perfectly acceptable for a general-performance monitor.
The electrode wire consists of a galvanized-steel aircraft cord with a PVC jacket and a polyester-fiber overbraid. This combination makes the electrode almost indestructible. V-Strings have been installed on dozens of types of structures, from platforms and offshore pipelines to shallow-water wind farms.
Interrogating the electrode can be done in several ways. If installed on a traditional structure, the conductor can be wired to the surface and connected to a monitoring panel. In some instances, the panel can also be wired to a satellite transmitter. For subsea assets and offshore pipelines, the V-String can be interrogated by ROV using the SunStation subsea readout.
Offshore platform jackets and drill rigs
The V-String can be easily retrofitted to any structure with subsea tubular members. By attaching the electrode to a RetroClamp, it can be quickly installed by diver or ROV and routed to the surface.
The V-String can be easily attached to a subsea pipeline with a RetroClamp. Using a SunStation subsea readout, the readings can be taken by ROV during routine maintenance (see SmartClamp system).
Seawater ballast tanks on SPAR, TLP & FSU / FPSO structures
Ballast tanks provide a unique monitoring application for the V-String, which can be permanently installed to monitor interior cathodic protection levels.
Risers can be treated in the same way as tubular members since the RetroClamp system does no damage to the member, riser, or pipeline it is installed upon.
Inshore structures, piers, jetties, wharves
When retrofitting a cathodic-protection system on an inshore dock or harbor structure, zinc reference electrodes should always be installed to monitor the system’s performance.
Inside J-tubes and other tight spaces
V-String fits nicely into small, cramped spaces where cathodic protection has to be monitored.
The lack of copper in the conductor cable allows the electrode element to polarize any pinhole or small defects in the conductor, keeping the electrode serviceable for a long period of time (25 years).
The polyester rope that covers the conductor is designed to withstand immense amounts of friction, protecting the conductor in situations where, for example, the V-String is rubbed against a structure by moving currents.
The V-String is low-profile enough to be fitted to a RetroClamp system, which can be installed by diver or ROV on any tubular member or flange.