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If the tank is founded on a saline soil or in conditions where the water table can reach tank bottom level, or if the foundation has been contaminated with salt water or sea-water, then an aggressive environment is produced. If isolation and separate earthing is required, it is feasible to design special joints to interrupt the continuity of the cable sheath.
BS Cathodic protection. Code of practice for land and marine applications_图文_百度文库
A distributed anode system results bbs more uniform pile potentials and less replacement anodes may be bolted. The impulse breakdown bss of these gaps should lie below that of the isolating joints. The product of the reaction at the anode is normally oxygen but in chloride solutions the reaction at an anode that is consumed gives rise to the bz of chlorine. There have been indications that corrosion 731-1 be prevented if the potential is maintained between the limits shown in Table 1.
With electrolytes of low conductivity, choosing the method for attaching cables to cast iron e. All welds used for contamination of the anodes themselves, but it is attachment of anodes and brackets should be in recommended that anode materials that are accordance with the full structural standard particularly liable to be affected by contamination applicable elsewhere in the tank concerned. However, if a By arranging for a single negative connection to the decision is taken at the design stage to apply reinforcement, with a high resistance millivoltmeter cathodic protection to a new structure, then and a movable reference electrode, measurements considerable provision can be made during taken on a grid over the surface of the structure can construction to facilitate the later application of be represented as equipotential contours.
These have operating conditions similar to the 7361–1 anodes described above and are said to withstand current reversal. Measures to safeguard neighbouring structures 9.
In the case of telephone cables it should be noted that the ripple from the rectified d. The gaps should be capable of discharging lightning currents without sustaining damage and should be encapsulated to provide complete protection from moisture. Hydrogen evolution from aluminium alloys is generally slight. It is intended to be read in conjunction with section 3. The current flowing round the circuit is proportional to the corrosion rate. Zinc, aluminium or bottoms and other horizontal structural members magnesium anodes may be used, as described and possibly cause local attack.
They should not be installed in important function of the coating is to reduce the above-ground situations where concentrations of current flowing thereby reducing the potential flammable gas or vapour occur see Their use in areas susceptible to pollution may therefore be discouraged.
Where loose-fitting polyethylene sleeves are used as the primary method of protection, cathodic protection cannot be expected to be effective. Chlorides are also now commonly used as road de-icing agents in winter and have penetrated road bridges with consequent corrosion. Elsewhere, automatic control may be required if the stray current fluctuates.
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. Where the provision of an 73661-1 joint is considered essential it may be prudent to install a heavier walled pipe on the unprotected side of the isolating joint with a corrosion allowance and accept the need for periodic inspection and replacement.
Typical arrangements are around a steel core or insert for direct or indirect illustrated in Figure 8 to Figure Alternatively, individual control units, each 3. Magnesium anodes can, however, produce chloride-containing electrolytes this breaks down to sufficiently negative potentials to cause give very non-uniform attack by pitting. This can usually be carried out on commissioning of the cathodic protection system by measuring the potential difference across the isolating joint.
In any event, as a general guide, it should not exceed the level necessary to produce an instantaneous-off potential more negative 7316-1 — 1. Adjustment of the number of attachment anodes calculated as above may be called for, Anodes may be attached by 73361-1 or by studs.
As far as possible, the reinforcing steel in the member to be 5. The availability of a. Appropriate measuring points should be provided see Take the smart route to manage medical device compliance.
The figures are not intended to establish metal and the paint film preferred types of equipment. This has the IR drop error, ns position. Inspection involves testing, with portable instruments, 73611- each anode or between adjacent pairs of anodes.
Magnetite Fe is a natural mineral which can be made into a cathodic protection anode 73611- proprietary methods. This could see The top of the foundation worth consideration for small isolated bbs on soil mound may be provided with a bitumen-sand carpet with low resistivity see 4. Application to buried structures 4. If, however, the use of see item b of 4. Putting the lower figure for impulse strength into equation 6 and taking 10 V as the resistance of the electrode to earth gives a spacing of 10 m.
They are, however, frequently used in the form of a thin layer of platinum or platinum alloy about 0.