This Part of this European Standard applies to all shell boilers as defined in EN 12953-1 which are heated by combustion of one or more fuels or by hot gases for the generation of steam and/or hot water. This Part of this European Standard applies to those components between the feedwater inlet and the steam outlet of the steam generator. The quality of the steam produced is outside the scope of this standard. This Part of this European Standard aims to ensure that the boiler is able to be operated to minimize risk to personnel, the boiler and associated plant components located near it. NOTE 1 This part of this European Standard does not aim to achieve optimum economic operation. For certain purposes, it will be more appropriate to optimize the chemical characteristics in order to: - increase the thermal efficiency; - increase the availability and reliability of the plant; - increase the steam purity; - reduce the maintenance costs - repair, chemical cleaning, etc. This Part of this European Standard sets out minimum requirements for the specific types of water to reduce the risk of corrosion, sludge precipitation or formation of deposits which may lead to any damage or other operating problems. NOTE 2 This Part of this European Standard has been prepared on the assumption that the user of this European Standard possesses a sufficient knowledge of the construction and operation of the boiler as well as an adequate appreciation of water and steam chemistry.