A boiler, which includes drums, tubes, flues, ducts, auxiliary equipment, and their associated supports, is subject to continual stressresulting from expansion and contraction and from elevated temperatures when it is in service. Boilers must be made adequately strongand with suitable materials to withstand these forces and temperatures. Boiler design requires a detailed study of the forces that areexerted on the various parts and of the temperatures to which theywill be exposed. In addition, because of the corrosive properties ofsubstances contained in fossil fuels and in water, attention must begiven to the selection of the proper materials to ensure a high availability of the boiler system.Pressure-vessel construction codes adopted by federal, state, andlocal jurisdictional authorities play an important part in determiningsafety requirements and thus the construction features of pressurevessels. The most widely used of these is the ASME Boiler andPressure Vessel Code, published by the American Society ofMechanical Engineers. This code gives excellent guidance and basicrequirements to the boiler designer.This code sets rules of safety for the design, fabrication, and inspection of boilers, pressure vessels, and nuclear power plant components.The purpose of these rules is to assure that life, equipment, and property are safely protected during normal and abnormal service conditions.This requires a margin for safety for these service conditions, as well asthe expected deterioration over the life of the plant.
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