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Boiler glossary S |
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| SAFETY VALVE -- A spring loaded valve that automatically opens when
pressure attains the valve setting. Used to prevent excessive pressure from
building up in a boiler. SAFETY VALVE BLOWDOWN -- The difference between the pressure at which a safety valve opens and at which it closes. SATURATED STEAM -- Steam at the same temperature as the water from which it was formed. SATURATED TEMPERATURE -- The temperature at which evaporation occurs at a particular pressure. SATURATED WATER -- Water at its boiling point. SCALE -- Incrustation, a hard coating of deposits precipitated from solution at the boiler tube surface. SCOTCH MARINE BOILER -- Fire-tube boiler equipped with an internal furnace, fire chamber and return tubes completely surrounded by water. The design originated from the Scottish Clyde Shipyard. SCREW PROPELLER -- A boss, carrying 2, 3, 4 or more blades of helical form, that produces the thrust to drive a ship by giving momentum to the column of water which it displaces in an astern direction. SENSIBLE HEAT -- That heat which effects a change in a body that is detectable by the senses; i.e. it causes the temperature of the body to change. Measured by the product of the specific heat capacity, the mass of the body and the change of temperature. SIGHT GLASS -- The gauge glass and its fittings for attachment. SILICA -- Except in a few sections, this impurity in the boiler water is not troublesome. SKIMMING -- Procedure for cleaning the surface of the water in a boiler. This procedure should be done on all new boiler installations, and when there is a foaming condition. SL -- Steam Launch. SLIDE-VALVE -- A steam engine inlet and exhaust valve shaped like a rectangular lid. It is reciprocated inside the steam chest, over a face in which steam ports are cut, so as alternatively to admit steam to cylinder and connect the ports to exhaust through the valve cavity. SLUDGE -- A soft, water-formed sedimentary deposit that can usually be removed by bottom blowdown. Also a common name for waste-oil. SODIUM SALTS -- In some water supplies, particularly near the sea, sodium chloride occurs in large quantities. The chief difficulties caused by the sodium salts are priming and foaming, due to their concentration in the boiler, the remedy for which is more frequent blowing down. SOFT WATER -- Water which contains little or no calcium or magnesium salts. SOFTENING -- The act of reducing calcium and magnesium impurities from water. SOOTBLOWER -- A device to clean heat absorbing surfaces. SPECIFIC LATENT HEAT -- The heat which is required to change the state of a substance from solid to liquid, or from liquid to gas, without change of temperature. The numerical value of the specific latent heat is the amount of heat required to change the state of unit mass. Most substances have a latent heat of fusion (melting) and a latent heat of evaporation. In thermodynamics, heat supplied at constant pressure is called enthalpy, and thus specific latent heat of evaporation is called enthalpy of evaporation. SPRAY NOZZLE -- A nozzle from which a liquid fuel is discharged in the form of a spray. SS -- Steamship. STAYBOLT -- Bolt used in boilers to reinforce flat surfaces subjected to boiler pressure. STEAM ATOMIZING OIL BURNER -- A burner for firing oil that is atomized by steam. It may be of the internal or external mixing type. STEAM CHEST -- The chamber in which the slide-valve of a steam engine works, and to which the steam pipe is connected. STEAM DRUM -- The upper drum of a water tube boiler where the separation of water and steam occurs. The steam outlet line normally takes off from this drum. STEAM JACKET -- A jacket formed round a steam-engine cylinder; supplied with live steam to prevent excessive condensation of the working steam in the cylinder. STEAM LAP -- The amount by which the slide-valve of a reciprocating steam-engine overlaps the edge of the steam ports when in mid-position. Also called Outside lap. STEAM POP SAFETY VALVE -- A spring loaded valve that automatically opens when pressure attains the valve setting. Used to prevent excessive pressure from building up in a boiler. STEAM PORTS -- Passages leading from the valve face of the cylinder of a reciprocating steam engine; through them the steam is supplied and exhausted. STEAM SEPARATOR -- A device inside the steam drum that is used to prevent water from passing over with the steam. STEAM TRAP -- A device into which condensed steam from steam pipes, etc., is allowed to drain, and which automatically ejects without permitting the ejection of steam. STOICHIOMETRIC COMBUSTION -- Perfect combustion. The complete oxidation of all the combustible constituents of a fuel, utilizing all the oxygen supplied. STOKEHOLD -- Compartment in which steamer's fires are tended. STOKEHOLE -- Space for stokers in front of furnace. STOKER -- A mechanical device that feeds coal to a furnace, or a man who feeds and tends the furnaces of a steamer. STOP VALVE -- Valve that is used to isolate a boiler from the other parts. SUPERHEATED STEAM -- Steam heated at constant pressure out of contact with the water from which it was formed, i.e., at a higher temperature than that of saturation. SUPERHEATER -- A bank of tubes, in the exhaust gas duct after the boiler, used to heat the steam above the saturation temperature. SURFACE BLOW VALVE -- A valve with pipe connections to the interior of the boiler and overboard, used for the purpose of blowing off the scum and grease that collect on the surface of the water. |
© 2007 Lars Josefsson Boilers