Protection systems applications

Nuclear safety of reactors of the damaged NSs is ensured through the application of emgineering and organizational measmes excluding extraction from (displacement in) the core of control rods and shim rods (no way for power supply to actuating mechanisms of the control and protection system, application of mechanical stops, impossibility of using hand drives). 

Johnson WE. Cathodic Protection System Application and Maintenance Guide. EPRI Report 1011905. Palo Alto, Calif. Electric Power Research Institute, 2005. Broomfield JP. Corrosion of Steel in Concrete. London, U.K. E FN Spon, 1997. Roberge PR. Handbook of Corrosion Engineering. New York, N.Y. McGraw-Hill, 2000. 

The preparation of this third edition after about 10 years since publication of the second edition of this handbook has required a complete revision of the major part of the book. The reason is not only new developments in technology and application, but also the identification of vital factors in the protection system. Developments in standards and regulations also had to be taken into account. 

The processes of cathodic protection can be scientifically explained far more concisely than many other protective systems. Corrosion of metals in aqueous solutions or in the soil is principally an electrolytic process controlled by an electric tension, i.e., the potential of a metal in an electrolytic solution. According to the laws of electrochemistry, the reaction tendency and the rate of reaction will decrease with reducing potential. Although these relationships have been known for more than a century and although cathodic protection has been practiced in isolated cases for a long time, it required an extended period for its technical application on a wider scale. This may have been because cathodic protection used to appear curious and strange, and the electrical engineering requirements hindered its practical application. The practice of cathodic protection is indeed more complex than its theoretical base. 

Wave propagation in an inhomogeneous anisotropic material such as a fiber-reinforced composite material is a very complex subject. However, its study is motivated by many important applications such as the use of fiber-reinforced composites in reentry vehicle nosetips, heatshields, and other protective systems. Chou [6-56] gives an introduction to analysis of wave propagation in composite materials. Others have applied wave propagation theory to shell stress problems. 

The spray is based upon either a natural plate-like material, such as vermiculite bound together with cement, or mineral fibers. Application is fast but not precise or clean, and is generally only suitable for areas where the steel will be hidden (by a false ceiling, for example). Sprays for external applications are available. However, the steel must first be provided with a compatible corrosion protection system. 

The analysis and understanding of the operation of protection systems and the application of protective devices to power systems is wide ranging and complex. This section considers only the objectives of protection systems, discrimination and its importance to protection, and describes the most common types of relay used in industrial power systems. Many publications covering the subject of protection systems are available (e.g. Power System Protection, edited by the Electricity Council). 

Where appropriate, designs should facilitate the application of adequate corrosion-protection systems that can be readily maintained. This can be achieved by attention to the geometry of the initial and any retrofitted design and methods of construction, and by making provision for good inspectability and accessibility. 

Numerous materials fall into the category of electronic conductors and hence may be utilised as impressed-current anode material. That only a small number of these materials have a practical application is a function of their cost per unit of energy emitted and their electrochemical inertness and mechanical durability. These major factors are interrelated and —as with any held of practical engineering—the choice of a particular material can only be related to total cost. Within this cost must be considered the initial cost of the cathodic protection system and maintenance, operation and refurbishment costs during the required life of both the structure to be protected and the cathodic protection system. 

The anode may be installed in conventional groundbeds or be laid in close proximity to the cathode, e.g. parallel to a pipeline route. The anode may be buried either directly in soil or in carbonaceous backfill. The major applications for this material are tank protection, internal protection, mitigation of poor current distribution and hot spot protection, i.e. to supplement conventional cathodic protection systems and provide increased levels of cathodic protection in areas that exhibit low levels of protection. 

The following structures are those which in given circumstances can benefit from the application of a cathodic-protection system ... 

Estimate of current required The surface area of the structure is calculated and the current density required for the particular environment is selected (Table 10.26). In the case of an existing structure the condition of the coating may be unknown and the application of a temporary cathodic-protection system may be necessary to determine the amount of current required for protection, as established by the potential. Such a test to determine the... 

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. 

Although the principles of cathodic protection are essentially simple and were in fact first outlined by Sir Humphry Davy in 1824, the application of the method to practical problems remains more of an art than a science. A properly designed cathodic protection system will be both economical and effective. On the other hand an incorrectly designed scheme will be inefficient, uneconomical and under certain circumstances may accelerate corrosion instead of controlling it. 

Although the first industrial application of anodic protection was as recent as 1954, it is now widely used, particularly in the USA and USSR. This has been made possible by the recent development of equipment capable of the control of precise potentials at high current outputs. It has been applied to protect mild-steel vessels containing sulphuric acid as large as 49 m in diameter and 15 m high, and commercial equipment is available for use with tanks of capacities from 38 000 to 7 600000 litre . A properly designed anodic-protection system has been shown to be both effective and economically viable, but care must be taken to avoid power failure or the formation of local active-passive cells which lead to the breakdown of passivity and intense corrosion. 

Personal protection Systems to ensure provision of Overalls special requirements (flame retardant, antistatic), frequency of laundering Protective clothing suits, spats, armlets, helmets, gloves for specific applications, footwear (industrial and/or antistatic) Hearing protectors Eye protection specific provision for various duties Respirators specific types for different applications... 

If the deviation is applicable, determine possible causes and note any protective systems. 

Accumulation The rise of pressure above the MAWP of the protected system, usually expressed as a percentage of the gauge MAWP. Maximum allowable accumulations are established by applicable codes for emergency operating and fire contingencies. 

In 1993, the Center for Chemical Process Safety (CCPS) published Guidelines for Safe Automation of Chemical Processes (referred to henceforth as Safe Automation). Safe Automation provides guidelines for the application of automation systems used to control and shut down chemical and petrochemical processes. The popularity of one of the hazard and risk analysis methods presented in Safe Automation led to the publication of the 2001 Concept Series book from CCPS, Layer of Protection Analysis A Simplified Risk Assessment Approach. This method builds upon traditional process hazards analysis techniques. It uses a semiquantitative approach to define the required performance for each identified protective system. 

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