Impressed current cathodic protection systems are a technique for controlling the corrosion of a metal surface by making that surface the cathode of an electrochemical cell. Impressed current cathodic protection systems are in widespread use at thousands of oil and gas surface production facilities, and serve to prevent failure of piping and other facilities which may lead to uncontrolled release of products, resulting in safety hazards to workers and the public, and environmental contamination.
Cathodic protection rectifiers are used to convert AC current to DC current in order to supply impressed DC current to the protected facilities. The interiors of these rectifiers contain numerous energized electrical components; and for a cathodic protection worker, the interiors of these rectifiers pose the highest risk of electric shock hazard in the cathodic protection system. Tragically, a cathodic protection worker was electrocuted in 2004 as a result of accidentally contacting energized components inside of a cathodic protection rectifier. It is the intent of the joint industry committee which has compiled this guideline that the designs of these cathodic protection rectifiers be made as safe as practical, and that new rectifiers available on the market incorporate these safety features as much as possible for the benefit of the protection of the personnel who must operate and maintain this equipment.
Over the last several decades there have been numerous manufacturers supplying the market, models, and variations in the design of these rectifiers; and many of these units are still in service in the oil and gas industry. It is not the intent of this guideline to address these existing installations; however, cathodic protection system owners and operators are advised that these existing installations may need to be periodically reviewed for safety risks, and modifications and/or replacement may be necessary in some cases. If replacement is desirable, then this guideline will be useful in helping to specify a replacement rectifier.
This guideline contains the following information:
A glossary of cathodic protection terms;
Codes and standards related to cathodic protection rectifiers;
Equipment certification requirements;
Worker qualifications for cathodic protection system operation and maintenance and their bearing on cathodic protection rectifier designs;
A basic description of how cathodic protection systems work and the main components of cathodic protection rectifiers (some essential information to help the user interpret and apply the recommendations found in this guideline);
A gap analysis identifying safety risks and potential mitigation approaches;
A description of the recommended safety features and example rectifier designs incorporating those features;
A template purchasing specification to be used for specifying cathodic protection rectifiers with increased safety; features