| LABOUR -- A vessel is said to labour when she rolls or
pitches heavily.
LABYRINTH PACKING -- A type of gland, with radial or axial
clearance, used e.g., in steam engines and turbines.
LAGGING -- A light gauge steel covering used over a boiler,
usually combined with insulation, to provide a low temperature outer
surface.
LAMINAR FLOW -- Very smooth flow in which all the molecules
are traveling in generally the same direction. For internal flows, it occurs at
Reynolds numbers less than 2000.
LAMONT BOILER -- A once-through or semi-flash boiler
in which the feed is supplied to the upper ends of a long closely spaced tubes
of mall diameter, from which the water and the steam pass to a separating
drum.
The boiler is named after the engineer Navy Lieutenant Commander Walter Douglas
Lamont.
LANCASHIRE BOILER -- A cylindrical steam boiler having two
longitudinal furnace tubes containing internal grates at the front. After
leaving the tubes the gases pass to the front along a bottom flue, and return
to the chimney along side or wing flues.
Sir William Fairbairn developed the Lancashire boiler in 1844
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.
LIFT-OFF -- This condition occurs when the fuel or fuel/air
mixture velocity is too high, thus allowing the fuel to exit the stabilizing
zone before it has achieved its ignition temperature.
LINING -- The material used on the side of a furnace wall. It
is usually of high grade refractory tile or brick or plastic refractory
material.
LINK-MOTION -- A valve gear, invented by
Stephenson, for reversing and controlling the cut-off of a steam-engine. It
consists of a pair of eccentrics, set for ahead and reverse rotation, connected
to the ends of a slotted link carrying a block attached to the valve rod.
Variation of the link position makes either eccentric effective, and also
varies the cut-off.
LIVE STEAM -- Steam available directly from a boiler under
full pressure.
LOW DRAFT SWITCH -- A control to prevent the burner operation
if the draft is too low. Used primarily with mechanical draft.
LOW FIRE START -- The firing of a burner with controls in a
low-fire position to provide safe operating condition during light off.
LOW LOW WATER LEVEL TRIP -- A device that shuts down
the fuel supply when the water level in the boiler drops below its operating
level. This prevents burning out of tubes, boiler damage or possible boiler
explosion.
LOW Nox BURNER -- A burner designed to reduce Nitrogen oxides
emissions.
LOW PRESSURE AIR ATOMIZER -- The fuel is forced to
rotate in a fixed cup by means of a forcefully rotating primary airflow.
LOWER HEATING VALUE -- LHV, The theoretical heat the
combustion process can release if the fuel and oxidant are converted to 100%
efficiency to CO2 and H2O vapor.
LUG -- Any projection, like an ear, used for supporting or
grasping.
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