Boiler glossary

Boiler glossary N


NAPHTA -- An oil distillate. Naphta is an intermediate product between gasoline and kerosene. It is known as a light product because of the low molecular weight of the hydrocarbons making it up.
NAPHTHA -- A generic term applied to a petroleum fraction with an approximate boiling range between 50°C and 205°C.
NATURAL CIRCULATION -- The circulation of water in a boiler caused by differences in density.
NATURAL DRAUGHT -- The draught or airflow through a furnace induced by a funnel and dependent on the height and the temperature difference between the ascending gases and the atmosphere.
NAVY SHIPS PROPULSION -- Navy ships was originally propelled in the same way as the merchant marine steamships, but son the navy steamships become provided with water tube boilers with higher steam-pressure. The navy's of many countries still use steam-engines to propel their ships. Marine nuclear boilers are used in large navy ships and icebreakers serving in Arctic waters.BR> Nuclear boilers have been used, without commercial success, in a few merchant ships, e.g. the US-built NS Savannah, the German-built NS Otto Hahn and the Russian-built NS Sevmorput. Nuclear ships are steamships although there steam generators are heated by means of nuclear reactors.
NITROGEN DIOXIDE -- NO2 This compound of nitrogen and oxygen is formed by the oxidation of nitric oxide (NO) that is produced by the combustion of solid fuels. Below 17°C the formula is N2O4 and the molecule is colorless. Decomposed by water, forming a mixture of nitric and nitrous acids.
NORMAL CUBIC METER -- Nm³ The quantity of a gas in one m³ at the thermodynamic conditions of one atm and 0ºC. There are 22.41 Nm³ in one kmol of an ideal gas.
NORMALIZING -- A heat treatment applied to steel. Involves heating above the critical range, followed by cooling in air. Is performed to refine the crystal structure and eliminate internal stress.
NORMALLY CLOSED CONTROL VALVE -- A control valve that closes when the diaphragm pressure is reduced to atmospheric.
NORMALLY OPEN CONTROL VALVE -- A control valve that opens when the diaphragm pressure is reduced to atmospheric.
NORMAND BOILER -- A water tube boiler.
NOx -- Abbreviation for all of the family of oxides of nitrogen.
NOZZLE -- A short flanged or welded neck connection on a drum or shell for the outlet or inlet of fluids; also an orifice for spraying a liquid like fuel oil.
NPSH -- Net Positive Suction Head is the liquid pressure that exists at the suction end of a pump. If the NPSH is insufficient, the pump can cavitate.
NUCLEAR BOILER -- A high pressure water tube boiler heated by means of an nuclear reactor.