A closed [[vessel]] in which [[water]] is converted to pressurized [[steam]].<ref>http://www.energy.ca.gov/glossary/glossary-b.html#b</ref>
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A '''boiler''' is a closed [[vessel]] in which [[water]] is converted to pressurized [[steam]].<ref>http://www.energy.ca.gov/glossary/glossary-b.html#b</ref>