Abstract

Abstract: Mathematical models may be used for design or evaluation of cathodic protection (CP) systems. This chapter provides a historical perspective and a mathematical framework for the development of such models. The mathematical description accounts for calculation of both on- and off-potentials at arbitrarily located surfaces, thus making this approach attractive for simulation of external corrosion direct assessment (ECDA) methods. The approach also allows simulation of independent CP systems. Application of the model is presented for three cases: (a) enhancing interpretation of ECDA results in terms of the condition of the buried pipe; (b) simulating the detrimental influences of competing rectifier settings for crossing pipes protected by independent CP systems (e.g., rectifier wars); and (c) simulating the influence of coatings and coating holidays on the CP of above-ground tank bottoms. Document type: Part of book or chapter of book

Abstract

The S-Farm overground transfer (OGT) line will bypass the existing line(s), between valve pits 241-S-B and 241-S-D that no longer meet system requirements. The new OGT line will provide a waste transfer pipeline between these valve pits in support of saltwell pumping activities. The length of the OGT line is approximately 180 ft from pit to pit. The primary pipe is nominal 1-in. diameter stainless steel (SST) braided Ethylene-propylene Diene Monomer (EPDM) hose. The encasement pipe is a nominal 3-in., flanged, SST pipe made up of several different length pipe spool pieces (drawing H-2-829564, sh. 1 and sh. 2). The OGT line slopes from valve pit 241-S-B toward valve pit 241-S-D. At each end, the primary and encasement pipe connect to a pit entry spool piece. The pit entry spool pieces are constructed of prefabricated SST materials. These spool pieces allow for the separation of the primary and encasement pipelines after the pipes have entered the valve pits (drawing H-2-818280, sh. 2). The pit entry spool pieces also allow for leak detection of the encasement pipe at each end (drawing H-2-829564, sh. 2). The OGT encasement pipeline is supported above ground by adjustable height unistrut brackets and precast concrete bases (drawing H-2-829654, sh. 1). The pipeline is heat-traced and insulated. The heat tracing and insulation supply and retain latent heat that prevents waste solidification during transfers and provides freeze protection. The total length of the pipeline is above ground, thereby negating the need for cathodic corrosion protection. This Construction Integrity Assessment Report (CIAR) is prepared by Fluor Daniel Northwest for Numatec Hanford Corporation/Lockheed Martin Hanford Corporation, the operations contractor, and the U. S. Department of Energy, the system owner. The CIAR is intended to verify that construction was performed in accordance with the provisions of Washington Administrative Code, WAC-173-303-640 (3) (c), (e), (f) and (h). Document type: Report

Abstract

Third-party contact with pipelines (typically caused by contact with a digging or drilling device) can result in mechanical damage to the pipe, in addition to coating damage that can initiate corrosion. Because this type of damage often goes unreported and can lead to eventual catastrophic failure of the pipe, a reliable, cost-effective method is needed for monitoring and reporting third-party contact events. The impressed alternating cycle current (IACC) pipeline monitoring method consists of impressing electrical signals on the pipe by generating a time-varying voltage between the pipe and the soil at periodic locations where pipeline access is available. The signal voltage between the pipe and ground is monitored continuously at receiving stations located some distance away. Third-party contact to the pipe that breaks through the coating changes the signal received at the receiving stations. In this project, the IACC monitoring method is being developed, tested, and demonstrated. Work performed to date includes (1) a technology assessment, (2) development of an IACC model to predict performance and assist with selection of signal operating parameters, (3) investigation of potential interactions with cathodic protection systems, and (4) experimental measurements on operating pipelines. Based on information recently found in published studies, it is believed that the operation of IACC on a pipeline will cause no interference with CP systems. Initial results on operating pipelines showed that IACC signals could be successfully propagated over a distance of 3.5 miles, and that simulated contact can be detected up to a distance of 1.4 miles, depending on the pipeline and soil conditions. Document type: Report

Abstract

The development of two external waste tank and pipeline leak detection systems based on the electrical potential fields is reviewed. The Boeing system measured the distortion of an imposed ac potential field. The Battelle--Northwest system measured the change in the magnitude of the existing dc potential field generated by the cathodic protection system and the local electrochemical potential near the electrodes in the sediment. It was found that in a dry area the systems can detect as low as 200 liters of leakage. The engineering assistance to the tank farm management in assessing the suspected leakers is also presented. Document type: Report