Maintenance and overhaul of the potentiostat
A cathodic protection constant potentiometer was working properly in an area. One day, the output of the constant potentiometer suddenly became unstable. Finally, the constant potentiometer automatically alarmed and changed to constant current output. After the constant potentiostat was restarted, the output of the constant potentiostat still fluctuated greatly and finally changed to constant current output automatically.
After technical analysis, the constant potentiometer can output, indicating that there is no problem with the cathodic protection circuit; the constant potentiometer can not work in the constant potentiometer state, indicating that the reference electrode feedback pipeline protection potential is unstable, affecting the output, so it is judged that the stray current interference is serious.
Therefore, we use a long-term anti-interference reference electrode to eliminate the interference of the stable point data feedback to the constant potentiometer. The constant potentiometer can work normally. During the operation of long-distance oil and gas pipelines, corrosion usually comes from both internal and external environments, and internal corrosion is mainly formed by the joint action of the transport medium, fluid accumulation, fouling and internal stress in the pipeline. External corrosion is usually caused by coating damage and failure.
For internal corrosion, it is usually dealt with by methods such as pipe cleaning and adding corrosion inhibitors. In recent years, with the strengthening of pipeline operation and management by pipeline owners and the strict requirements of the transport medium, the internal corrosion of pipelines has been controlled to a large extent. At present, the main development direction of corrosion control of oil and gas pipelines at home and abroad is the external corrosion protection, so pipeline testing is also mainly for coating defects and defects caused by external corrosion of the pipeline. Pipeline corrosion detection is divided into two branches: internal detection technology and external detection technology. Usually, the broken and failed coating under the pipeline is also corroded. The purpose of external detection technology is to detect defects such as internal and external corrosion, local inspection and weld cracks of the coating on the basis of the effectiveness of the coating and cathodic protection, and to judge the integrity of the coating.
External corrosion control of buried pipelines is usually the result of the combined action of a protection system consisting of a coating and electrical protection. The two methods play complementary roles:The coating is cathodically protected, which is both economical and effective, and the cathodic protection also controls pinholes or damage to the coating. This method is now recognized as the best protection method and has been widely used to control corrosion in buried pipelines.
