Electricity protective means

Electric Drainage means of electric protection of an underground system against the corrosive action of stray currents arising from a d.c. electric traction system employing one or more connections (drainage bonds) made between the system to be protected and the return circuit of the traction system (rail, return current feeder, negative busbar of the sub-stations). 

During electrical protective equipment safety talks, you may want to review the electrical hazards most commonly found at your jobsite(s) and present examples of the types of electrical protective equipment you require at your company. Inform trainees where to find the equipment class and type markings and what they mean. Instruct trainees never to use defective or damaged electrical protective equipment, and show them photos of damage or defects, so employees know what to look out for. 

As a vessel is loaded, it moves downward because of deflection of the load cells and support stmcture. Pipes rigidly attached to a vessel restrict its free movement and assume some portion of the load that cannot be measured by the load cells. This is very detrimental to scale accuracy. Deflection of the load cell is unavoidable deflection of the vessel support stmcture should be minimized. Anything which increases vessel deflection, eg, mbber pads used for shock protection, must be avoided. The total number of pipes should be minimized and be of the smallest diameter, thinnest wall possible. Pipe mns to weigh vessels must be horizontal and the first pipe support should be as far as possible from the vessel. Alternatively, a section of mbber hose or flexible bellows should be used to make the final connection to the vessel. The scale should be caUbrated using weights, not by means of an electrical simulation method, which cannot account for the effects of the piping or test the correct functioning of the scale. 

Electrochemical corrosion is understood to include all corrosion processes that can be influenced electrically. This is the case for all the types of corrosion described in this handbook and means that data on corrosion velocities (e.g., removal rate, penetration rate in pitting corrosion, or rate of pit formation, time to failure of stressed specimens in stress corrosion) are dependent on the potential U [5]. Potential can be altered by chemical action (influence of a redox system) or by electrical factors (electric currents), thereby reducing or enhancing the corrosion. Thus exact knowledge of the dependence of corrosion on potential is the basic hypothesis for the concept of electrochemical corrosion protection processes. 

CoiTosion prevention is achieved by correct choice of material of construction, by physical means (e.g. paints or metallic, porcelain, plastic or enamel linings or coatings) or by chemical means (e.g. alloying or coating). Some metals, e.g. aluminium, are rendered passive by the formation of an inert protective film. Alternatively a metal to be protected may be linked electrically to a more easily corroded metal, e.g. magnesium, to serve as a sacrificial anode. 

In the UK the most common method of reducing interaction is to connect the protected and unprotected structures together by means of metallic bonds. This method is more successful if care has been taken to ensure that the unprotected structure is electrically continuous. If possible, bonds should be connected to points on the unprotected structure where maximum positive changes in potential are observed, but it may be more practicable to install a shorter bond between points where access can conveniently be obtained for periodic inspection and tests. 

A type of assembly calculated to favour maximum galvanic action was developed by the Bell Telephone Laboratories and is illustrated in Fig. 19.32. Here, the less noble metal is in the form of a wire wound in the grooves of a threaded specimen of the metal believed to be more noble. Good electrical contact is achieved by means of set screws covered with a protective coating. This assembly favours accumulation of corrosive liquids around the wire in the thread grooves. Corrosive damage is also favoured by the high ratio of surface to mass in the wire specimens. 

The worst hazard scenarios (excessive temperature and pressure rise accompanied by emission of toxic substances) must be worked out based upon calorimetric measurements (e.g. means to reduce hazards by using the inherent safety concept or Differential Scanning Calorimetry, DSC) and protection measures must be considered. If handling hazardous materials is considered too risky, procedures for generation of the hazardous reactants in situ in the reactor might be developed. Micro-reactor technology could also be an option. Completeness of the data on flammability, explosivity, (auto)ignition, static electricity, safe levels of exposure, environmental protection, transportation, etc. must be checked. Incompatibility of materials to be treated in a plant must be determined. 

The main devices used for mosquito protection in households have been mosquito coils, electric mosquito mats, and liquid vaporizers, all of them methods that vaporize insecticides into the air using heating by means of fire or electricity to control the insects. In recent years, new anti-mosquito products have been commercialized such as fan vaporizers, paper strip type emanators, and resin net type emanators which vaporize insecticides without heating. In all of these products pyrethroid insecticides are used as active ingredients because they are superior in what is called knockdown effect, where noxious insects are rapidly paralyzed and cannot bite, and have a high level of safety for humans. 

G5. Gohlich, H., Investigations to improve precipitation of plant protectives by means of electrical charges, Forsch. Gebiete Ingenieurw., VDl-Forschungsh. 467 (1958). 

Galvanize. To protect an easily oxidizable metal (such as iron) with a less oxidizable metal (such as tin or zinc) by electric means Ref Hackh s Diet (1944), 366-R... 

Cathodic protection is an electrical means of eliminating corrosion in pipelines, where corrosion occurs, and corroding current... 

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