Cathodic protection pipeline

Turbo-alternators These find an application in pipeline cathodic protection systems, particularly where the liquid or gaseous product in the pipeline can be used as a fuel. The turbo-alternator is usually supplied as part of a complete and fully assembled package incorporating fuel pressure controls, filters, a.c./d.c. conversion and d.c. output controls. System capacity would typically fall within the range 200-3(XX)W. 

Sydberger,T., Evaluation of Inspection Methods for Offshore Pipeline Cathodic Protection Systems , Materials Performance, 22 No. 5, 56 (1983)... 

Remote Potentials in dealing with a pipeline cathodic-protection system, it is often advantageous to refer all measurements to a half-cell located at a distance from the pipe. Such measurements are referred to as remote potentials. 

Pipeline Cathodic Protection—Part 2 Cathodic Protection of Offshore Pipelines, ISO/TC 67/SC2 NP 14489, International Standards Organization, May 1, 1999. 

The problem of corrosion of steel in concrete was first ascribed to stray current flows from trams and DC railway systems Hime, 1994). Once chloride, in the form of deicing salt, was identified as the major culprit (when trams disappeared but corrosion increased), an enterprising engineer in the California Department of Transportation (Caltrans) took a standard pipeline cathodic protection design and flattened it out on a bridge deck. 

The system was straightforward. One of the popular impressed current pipeline cathodic protection anodes of that time was made of a corrosion resistant silicon iron, surrounded by a carbon cokebreeze backfill. A well was dug near the pipeline, the anode put in surrounded by the backfill and the system connected to a DC power supply, with the negative terminal connected to the pipeline to make a cathodic protection system. Richard Stratfull look pancake silicon iron anodes, fixed them on a bridge deck and applied a carbon cokebreeze asphalt overlay (Stratfull, 1974). The systems installed in 1973 and 1974 were reviewed in 1989 and were still working (Broomfield and Tinnea, 1992),... 

Figure 8.16 shows an equivalent electrical circuit that simulates the pipeline cathodic protection depicted in Figure 8.9. Both pipeline and sacrificial anode (galvanic anode or inert anode) are buried in the soil of uniform resistivity. The pipehne is connected to the negative terminal and the anode to the positive terminal of an external power source (battery). The arrows in Figure 8.16 indicates the direction of the ciurent flow from the anode to the pipehne. The electron flow is also toward the pipehne to support local cathodic reactions and the protechve current (Ip) flows from the pipehne to the power supply. The soil becomes the electrolyte for complehng the protective electrochemical system or cathodic protechon circmt [24].

Figure 12.12 Detailed code for the basic events leading to a natural gas pipeline cathodic protection deficiency.

A Russian ammonia pipeline of nearly 2400 km extends from Togliatti on the Volga River to the Port of Odessa on the Black Sea, and a 2200-km, 250-mm dia branch line extends from Godovka in the Ukraine to Panioutino. The pipeline is constmcted of electric-resistance welded steel pipe with 7.9-mm thick walls but uses seamless pipe with 12.7-mm thick walls for river crossings. The pipeline is primed and taped with two layers of polyethylene tape and suppHed with a cathodic protection system for the entire pipeline. Mainline operating pressure is 8.15 MPa (1182 psi) and branch-line operating pressure is 9.7 MPa (1406 psi) (11). 

Corrosion. Anticorrosion measures have become standard ia pipeline desiga, coastmctioa, and maintenance ia the oil and gas iadustries the principal measures are appHcation of corrosion-preventive coatings and cathodic protection for exterior protection and chemical additives for iaterior protectioa. Pipe for pipelines may be bought with a variety of coatiags, such as tar, fiber glass, felt and heavy paper, epoxy, polyethylene, etc, either pre-apphed or coated and wrapped on the job with special machines as the pipe is lowered iato the treach. An electric detector is used to determine if a coatiag gap (hoHday) exists bare spots are coated before the pipe is laid (see Corrosion and corrosion control). 

The low cost, light weight, and exceUent electrical conductivity of graphite anodes have made this impressed current protection system valuable for cathodic protection of pipelines, storage vessels, process equipment, and also for weU casings both on- and offshore. 

If scratches and breaks occur in the zinc layers by accidental damage - which is certain to occur when the sheets are erected - then the zinc will cathodically protect the iron (see Fig. 24.4) in exactly the way that pipelines are protected using zinc anodes. This explains the long postponement of rusting. But the coating is only about 0.15 mm thick, so after about 30 years most of the zinc has gone, rusting suddenly becomes chronic, and the roof fails. 

Slides Covering pipelines with polymeric films cathodic protection of pipelines, ships, etc.. With zinc bracelets use of inert polymers in chemical plant galvanic corrosion in architecture (e.g. A1 window frames held with Cu bolts) weld decay. 

The first anode installation for the cathodic protection of gas pipelines in New Orleans consisted of a 5-m-long horizontal cast-iron tube. Later old tramway lines were used. Since in downtown New Orleans there was no suitable place to install impressed current anodes and to avoid detrimental effects on other pipelines, Kuhn recommended the use of deep anodes which were first installed in 1952 at a depth... 

Fig. 3-1 Computer-aided data storage system for monitoring the cathodic protection of a long-distance pipeline.

For determining the off potentials of cathodically protected pipelines, time relays are built into the cathodic protection station to intermpt the protection current synchronously with neighboring protection stations for 3 s every 30 s. The synchronous on and off switching of the protection stations is achieved with a synchronous motor activated by a cam-operated switch. The synchronization of the protection station is achieved as follows a time switch is built into the first protection station. An interruption of the protection current is detectable at the next protection station as a change in the pipe/soil potential. Since the switching time is known, the time switch of the second protection station can be activated synchronously. The switching of further protection stations can be synchronized in the same manner. 

In analyzing the results on a cathodically protected pipeline, the protection current density and coating resistances should be calculated for individual sections of the pipeline in addition to the on and off potentials, the pipe current, and the resistances at insulating points and between the casing and the pipeline. The results should be shown by potential plots to give a good summary [15] (see Fig. 3-20). 

The values calculated using Eqs. (3-36) and (3-37) are only true for welded pipelines. Extension joints, fittings, and screwed or caulked joints can raise the longitudinal resistance of a pipeline considerably and therefore must be bridged over for cathodic protection. 

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