Integrated Impressed Current Cathodic Protection for Wet Crude Handling Vessels

Abstract

A cathodic protection system includes a vessel for containing a fluid or a mixture of fluids, a plurality of anodes positioned inside the vessel, an encapsulant encapsulating the plurality of anodes, the encapsulant being a wax repellant material that is sufficiently porous to allow ions to pass therethrough, and an impressed current source electrically connected to each of the anodes and the vessel. The impressed current source produces a continuous high current output, and the vessel acts as a cathode when current is applied from the impressed current source. The anodes are monitored and controlled from outside of the vessel using one or more adjustable resistors, which are installed in a junction box located either inside or outside the vessel. The resistors are configured to adjust the individual anode current output based upon a predetermined cathodic protection criteria.

Description

BACKGROUND OF THE INVENTIONField of the Invention[0001]Embodiments relate in general to cathodic protection and specifically to internal cathodic protection of a fluid-containing vessel.Description of the Related Art[0002]Corrosion protection is required for steel structures that are exposed to corrosive fluids. The steel structures can be any structure exposed to corrosive fluids including, for example, a vessel that contains or is exposed to water or corrosive fluids. A protective coating on the steel or cathodic protection can be used to protect steel from corroding.[0003]Cathodic protection for vessels is typically done with galvanic anodes in a technique known as galvanic anode corrosion protection (“GACP”). There are three types of galvanic anodes that are typically used for corrosion protection, namely, magnesium, aluminum and zinc anodes. The magnesium anodes often demonstrate high potential and, thus, corrode in less than one year in vessel protection. The aluminum anodes a...

AI Technical Summary

Benefits of technology

This patent is about using a special type of anode (a dimensionally stable impressed current anode) to prevent the formation of paraffin wax layers on the surfaces of precious metals like MMO, PtNb, or PtTi, which can prevent further corrosion. The anode is encapsulated in a wax-repellent layer to prevent cement layers from cracking as the anode corrodes away. The technical effect is a more durable and effective anode that can prevent corrosion and maintain their size during use.

Problems solved by technology

Precious anodes such as MMO, PtNb, or PtTi have been tested in real conditions but failed when a layer of paraffin wax developed on their surfaces, which prevented them from further corrosion.

When cement was used around conventional anodes (galvanic or impressed current), the cement layer tends to crack as the anode corrodes away.

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