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The cathodic The current capacity of the system in ampere years protection system should have sufficient capacity to will then be determined by the life required from the take account of the deterioration of the protective anodes, which should be related to the usual periods coating during the docking cycle.
Immersed structures excluding off-shore applications 7. The fact that the current is spread more uniformly may reduce the number of points at which cathodic protection need be applied see also 3. The current bd required can be determined by means of a drainage test carried out after isolating the pipeline as far as possible from other structures in contact with the soil.
BS Cathodic protection. Code of practice for land and marine applications_图文_百度文库
More specific information on pipe coatings and their application, handling coated pipe, coating of welded joints etc. This method is referred to as necessary for the precise arrangements for the unidirectional electric drainage. If the Figure 7 b. The mechanical strength of the bond should be adequate to withstand the effects of backfilling etc. The fact that the current is spread more uniformly may reduce the number of points at which cathodic protection need be applied see also 3.
Additional anodes will replacement of anodes. Samples of finely ground concrete obtained from the structure either by drilling or by slicing removed cores may be analysed for chloride and cement content.
Their low density and high driving potential make them particularly useful as suspended anodes and for temporary protection where the number of anodes should be limited for example, for ships that are laid up or being fitted out. A stable oxide film is being electropositive, the current density required may be established on the surface of the metal to be protected by making increased.
In some cases anodic protection is used see 8. The applied current remains protected include fittings, such as bearing plates, interrupted and the off potential measurement is services, drains or road signs, care must be taken to repeated.
The method of attachment to the pipeline will vary according to circumstances, but whatever method is selected, care should be taken to ensure that a sound electrical connection is made.
Any metal across each joint, taking care that all intermediate exposed to the electrolyte soil or water will be parts are connected. Alternatively, individual control units, each with a suitably positioned sensing electrode, can be connected in each anode circuit.
Unless positive action is taken to establish a low resistance electrical contact between the propeller shaft and the hull see 6. A rectifier or other unidirectional device is therefore usually provided for this purpose as illustrated in Figure 14 a and Figure 14 b. The major axis of the ellipse, Lo, is given by the The radius in m of a shield for a disc-shaped equation: For this reason the inclusion of isolating joints in, for example, pipelines containing sea-water or strong brine is inadvisable see also 9.
This standard has been updated see copyright date and may have had amendments incorporated. Operators should therefore bear in mind the possible significance of a. This is because the pH at the constituents of hydrated cement may react with the cathode will be increased. The performance, and hence the suitability of a particular alloy for a specific application, will depend on the composition of both the alloy and electrolyte, temperature of operation and anode current density.
Special insulating gaskets are needed for ring type joints. Any measurement taken with the stressed high tensile steel. Hydrogen evolution from aluminium alloys is generally slight.
Care should be taken in joint. BS Code Steel Constru The potential difference is also dependent on the types of chemical bx occuring at the bbs surface. Ripple frequencies less than Hz distribution of protective current. If cathodic cathodic protection will significantly reduce the protection is to be applied, for example, because of incidence and severity gs this form of corrosion.
Significant current leakage does not normally occur with systems employing an insulated fourth rail as a return conductor. Cathodic protection equipment may give rise to certain hazards, particularly in areas where there are flammable liquids or gases. This is principally due to increased turbulence near the propeller 73361-1 and the formation of a cell between a bronze propeller and the steel hull.
The life of anode systems in general appears to be Soldering, welding and brazing of reinforcing bars governed not by the primary anode material itself, involving high heat input is to be avoided but pin but by the efficiency with which it can preserve the brazing or thermit welding could be considered.
BS – Cathodic protection. Code of practice for land and marine applications
In the case of open-topped tanks, aggressive coolants, a moderate increase of anodes of silicon iron or platinized titanium, or lead thickness will generally ensure a reasonable life. This effect is known as cathodic polarization. The carrier pipe should be supported by non-metallic spacers which should be designed to prevent coating damage during installation. 77361-1
With electrolytes of low conductivity, e. Formation of gaseous cathodic products which are unable to diffuse away from the interface, could lead to disruption of this interfacial adhesion. For ground conditions where the soil is unsuitable as backfill, consideration should be given to the importation of selected fill, such as clean sand, or to some form of mechanical protection which has a minimal shielding effect on the cathodic protection e.
In any event, as a 7361- guide, it should not exceed the level necessary to produce an instantaneous-off potential more negative than — 1. The inserts may project outside the body of the anode to provide means for attaching the anodes to the structure by welding or bolting see Figure 10 and Figure It is unlikely to be possible to demonstrate satisfactorily that this is, or is not, so throughout.
Permits anodes to be more compact owing to the use of suitable materials; thus drag is negligible. Cathodic protection has been applied to a large NOTE 2 The potential difference between the metal and its variety of structures, including pipelines, storage environment is liable to be less at a coating defect.
Anodes cast from high purity zinc, grade Zn 1of BSbut selected to contain less than 0. It is possible in both these cases to protect, without using excessively negative potentials, lengths up to about 2 km from the point of application.