VALIDATION OF RISK INDICATORS IN ASSESSING THE SAFETY OF ELECTRICAL EQUIPMENT BOILER HOUSE IN THUNDERSTORM

Introduction. Today requires the introduction and arrangement of modern enterprises automation of the technological process using various electronic and electrical equipment. The breakdown of one sensor leads to a stoppage of the technical process and thousands of losses. This equipment is sensitive to impulse overvoltages that occur for various reasons, as well as when hit by lightning. There is a misconception that the danger of lightning arises only when struck directly, forgetting about the socalled secondary phenomena, namely electromagnetic and electrostatic pulses. Pulse overvoltage is a short-term increase in voltage above the allowable value. Lightning protection systems are designed and designed to protect objects from dangerous lightning.Purpose. Given the automation of the process and the saturation of boilers with electronic and electrical equipment, there is a high risk of lightning and high potentials, which can lead to large-scale accidents. The purpose of this article is to validate the risk indicators for the boiler environment that occur during a thunderstorm.Methods. The use of various methods of calculation, assessment and ordering of risks during the design and layout of the system allows to implementation system lightning protection of buildings, equipment and people. General principles of risk assessment for the boiler environment must take into account: risk and determine the need for protection; the contribution of various risk components to the overall risk; the effect of various protection measures to reduce risk; selection of protection measures taking into account their economic efficiency.Results. Neglecting the high risk of a dangerous event leads to excessive damage and m irreparable losses, with which a person or community will not be able to achieve sustainable development. Therefore, it is a comprehensive, systematic approach to achieving safety, starting from the assessment stage, should take into account both the characteristics of the hazard, including a fire in the relevant facilities, and personal, the individual risk of death or injury. Lightning is an unpredictable natural event, no one in the world fully understands the mechanism of lightning and it is impossible to provide 100% protection under any circumstances under any standardization. For this purpose, the following calculations are given: loss of human life, including injuries; loss of the ability to provide public services; losses of cultural heritage and economic value of the building (structure) and economic losses required for the installation and operation of the system. Based on the obtained data, it is seen how the reduction of each risk is achieved depending on the proposed solution and the economic effect in general.Conclusion. Statistics on deaths and injuries from lightning hazards, losses from damage to property, buildings and struc-tures confirm that in risk assessment, which is standardized in DSTU EN 62305-2, it is necessary to introduce a methodology that would meet the conditions of Ukraine. The arrangement of the lightning protection system depends on the risk assessment, the reaction of the owner, the influence of control bodies. Therefore, it is important to decide on fire protection measures in lightning risk assessment procedures, but it can also be taken regardless of the results of the risk assessment where there is a desire to avoid unacceptable risk. Equipment that is often associated with two different services, e.g. power lines and data lines suffer a lot of surge damage. This case is not covered by the RX risk component. However, appropriate protection measures can be selected and established (see IEC 62305-4).

Improving the hot corrosion resistance of boiler tube steels by detonation gun sprayed coatings in actual boiler of thermal power plant

Purpose This paper aims to investigate the hot corrosion behavior of Ni-Cr and Cr3C2-NiCr coatings, deposited on T11, P91 boiler steels by detonation gun spray coating (D-Gun) process to enhance high temperature corrosion resistance. Design/methodology/approach Hot corrosion studies were conducted in secondary super heater zone of boiler at 900 °C for 10 cycles on bare and D-Gun coated steel specimens. The microhardness and porosity values of as-sprayed coatings were measured before exposing the specimens in the boiler environment. Each cycle consisted 100 h of heating in the boiler environment followed by 20 min of cooling in air. The weight change measurements were performed after each cycle to establish the kinetics of corrosion using thermogravimetric technique. X-ray diffraction, SEM techniques were used to analyze the corroded specimens. Findings Uncoated boiler steel experienced higher weight loss. The Cr3C2-NiCr coating was found to be more protective than Ni-Cr coating. The phases revealed the formation of oxide scale on coated specimens, mainly consist of nickel and chromium, which are reported to be protective against the hot corrosion. Originality/value There is very limited reported literature on hot corrosion behavior of Ni-Cr and Cr3C2-NiCr coatings deposited on the T11 and P91 substrates by detonation gun (D-gun) spray technique. T11 and P91 alloy steels have been chosen for this study because these two alloys are used to manufacture boiler tubes used in Indian thermal power plants.