Shunt method to deal with the lower cathodic protective potential at single side of pipeline

Lack of cathodic protection in the inlet side of the station and overhigh cathodic protective potential in the outlet side of the station in Daxing Pump Station in Qinhuangdao-Beijing Oil Pipeline were found. Field investigation and analysis were made. It is found that the non-uniform distributed cathodic protection current caused by both the resistance difference of the connection cable at the outlet side of the station and coating differences were the major reasons for the presented problem.Experimental research on 3 solutions was launched.Results showed that changing the circuit resistance could lead to the proper distribution of the CP potential, and thus provided an effective protection for both the outlet and inlet sides of the station.Based on the computational results, reducing the resistance of inlet cable would increase the inlet current in the original conditions, increasing the resistance of inlet cable would increase the inlet current in the original current conditions.This method could enhance the cathodic protective potential temporarily.However it increased the output current of the cathodic protection.Therefore, it can really not deal with the problem, and the out-of-service maintenance shall be arranged.