Cathodic Protection Monitoring
V-String™ zinc reference electrode

The V-String zinc reference electrode has a rugged conductor with a strong over-braid 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 tool general purpose cathodic protection monitoring retrofit systems, or to supplement 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 adequate for a general performance monitor.

The electrode wire consists of a galvanized steel aircraft cord with a PVC jacket and an over braid of polyester fibers. This combination makes the electrode virtually indestructible. V-Strings have been installed on dozens of different types of structures, from platforms and offshore pipelines to shallow water wind farms.

Interrogating the electrode can be done in several different 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.

Applications

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 installed by diver or ROV quickly, and then routed to the surface.

Offshore pipelines

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

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 the cathodic protection system on an inshore dock or harbor structure, zinc reference electrodes should always be installed to monitor systems performance.

Inside J-tubes and other tight spaces

V-String fits nicely into small, cramped spaces where cathodic protection has to be monitored.

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Key design points

Reliable cathodic protection measurement

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).

Protective polyester over-braid

The polyester rope that covers the conductor is designed to withstand immense amounts of friction, protection the conductor in situations where the V-String is rubbed against a structure by moving currents etc.

Monitoring system retrofits

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.