InliQiratlng Burner the fuel gas Is allowed 10 es cape at high velocity into the throal of a venturi tLbe, creating a lower static pressure which draws In the air.. BURNER CONTROlLER-an
Trang 1ABSOLUTE P~ESSURE-Ihe sum of gauge pressure
plj.,js atmospheric pressure Absolute pressure can be
zero only in a perlect vacuum
ACTUAL BODY RATING-see VALVE BODY RATING
ACTWATOR-a controlled molar, relay or solenoid In
which the electric energy is converted into a rolary, lin
ear or switching action An actuator can effect a
change in the controlled variable by operating the final
control elements a number of times Valves aM damp'
ers are examples of mechanisms which can
be controlled by actuators Also see PROPOR
TIONAL, SPRING RETURN, and TWO-POSITION
ACTUATORS
AI R -the elastic, invisible mixture ofgasesthat surrounds
lr,e eanh; atmosphere Also see AMBIENT, ATOMIZ
ING COMBUSTION COMPRESSED EXCESS, IN
DUCED PREHEATED PRIMARY, SEAL,
SECONDARY, AND VENTILATION AIR
AIR-ATOMIZING OIL BURNER-see ATOMIZING OIL
BURNER
AIR CHANGE-a complete replacement of all the air in
the combusllon chamber and breaChing of a furnace or
boiler
AIRFLOW SWITCH -a conlrollerused to prove proper air
movement through a corrbustlon chamber by measur
ing wirdlox or breeching pressure or by measuring air
velocity (sail switCh) Also see LOCKOUT and RUN·
NING INTERLOCKS
AI R·FUEL RATIO - the ratio of the weight, or volume of air
to fuel measured in Ihe same unils under the same con
ditions The cptimum air-fuel ratio is the minimum ratio
that will provide complete cOlTtlusllon of the fuel with
enough excess air 10 maintain a stable flame envelope
Also see STOICHIOMETRIC AIR-FUEL RATIO
AIR HEATER-an IndirecHired venled appliance in
lended to supply heated air for space neating and other
purposes, but not Intended for permanent installation
AIR REGISTER-a burner mounting which may admit
secondary air to the corrouslion space
AIR RICH -the air-fuel ratio supplied to a furnace that pro
vide:s more air than the optimum ratio
AlA SHUTTER-an adjustable device for varying the size
of Ihe air inlet or Inlets regulating primary and/or secondary air An air shutler may be automatically or manuaUy operated
ALARM-an audible device or visible signal indicating a malfunction Of off-normal condition
ALARM CIRCUIT -an electrical circuit that includes a bell horn, or similar device to signal an unsafe condition
ALTERNATING CURRENT (ac)-a flow of eleclriclty which reaches maximum in one direction, decreases to zero, then reverses itself and reaches maximum in the opposite direction The cycle is repeated continuously
The number of such cyCles per second is the frElQJency
in hertz (HZ) The average value of voltage during any cycle is zero
AMBIENT AIR -generally speaking, the air surrounding t/1e equipment
AMBIENT TEMPERATURE-the temperature of tne air surrounding tne eqUipment
AMPUFIER-a device used to increase the magnitude at
a small input signal to proportions sufficient to perform some desirable function Also see FLAME SIGNAL AMPUFtER
AMPUFIER SATURATION-the point at whiCh an increased input signal no longer increases the amplifier output
ANGSTROM UNIT (.&.) -a unil of measurement of a wavelength of lilflt and other electromagnetic radiation, eqJalto one len-thousandth (1/10,000) at a micron ANNUNCIATOR-a device which indicates an offstandard or abnormal condition by visual and/or audible sig'lals
ANTIFLOODING DEVICE -a primary control which causes the fuel flow to be shul off LPQn a rise in fuel level or ~ receivingexC8SS fuel, and which operates before the hazardous diSCharge of fuel can occur APERTURE DISC-a thin, flat, cIrcular plate of any material with an ~nlng or hole (orifice) of predetermined diameter to restrict the area viewed through it
AOUADAG TUBE-an electron tlbe sensitive to ultraviolet radial ion, used in the C7012 Purple Peeper Ultraviolet Flame Detectors When saturated with Ultraviolet radiation this tube delivers less than' microwallto the flame $lg'lal amplifier
ARC GAP PROTECTOR-a devIce which cord.Jcls at high vollage levels 10 bypass an eleclronic network, thus protecting tne network agaj~t damage from hlgl voltage Int9lference ~ch as thai generatac:l by a sp<Irk ignilion system)
Trang 2ARMATURE-the moving eJementln an electrClllleChani
cal device, such as the movable iron core in a solenoid,
Ihe rotaling part of a generator or motor, the movable
pirt'ofa relay, or lhe spring-mounted, iron portion of a
bell or buner
ARTIFICIAL FUELS-man-made fuels, Including all
manufactured and byiJroduct fuels
ARTIST CAP - a fabricated hood, usually of sheetmelal,
placEld on tq:) of a stack to prevent downdrafts or erratic
draffs becauSe of the direcliOl'l8( wind effecls
ASH - the noncombustible mailer that remains after a fuel
is burned
ASPU?Al1NG BURNER-a burner in which the fuel in a
gasElCIU& or finely divided form is burned in suspension
the air for combustion being su~lied by bringing into
contact With the fuel, air drawn thrClUQh one or more
openings by lhe lower stalic pressure created by the
velocity of the fuel stream Also see VENTURI and
ZERO·GOVERNOR BURNER
ASPIRATOR MIXER-a gas-air ptoportioning device thaI
causes the flow 01 cOmbuslion air to induce the proper
amount of gas inlo the airstream It is used with low
pressure air and zero gas Also called a Suction Type
Mixer Also see ZERO·GOVERNOR BURNER
ATMOSPHERE-the invisible mixture 01 gasas (air) sur
rounding the earth: a unit of pressure defined 'as lhe
pressure of 760 millimelers 01 mercury at sea level and
at 0 C [32 Fl, which is equal to 14.6969 p::lUncts per
square inch (PSi), or 29.92' inchas of mercury
ATMOSPHERJC BURNER-a gas burner relying on at
mospheric pressure to bring in combustion air It si~
permits Ihe air required for combustion to enter the
CO!T1:lustion 'Chamber, or It draws air into the combus
lion chamber from the area surrounding the burner
Two methods are used 10 draw air into the combustion
space
Natural·Draft Burner the natural draft produced by
the product!> of combvstion moving L.p Ihrough
Ihe chimney, or staCK, draws air in atlhe bottom
of the burner
InliQiratlng Burner the fuel gas Is allowed 10 es
cape at high velocity into the throal of a venturi
tLbe, creating a lower static pressure which
draws In the air Also called an Injection or Ven
turi Mixing Burner
A typical atmospheriC burner draws In pari Of the c:om
bustion air by venturi action and the rast by a natural
draft
ATMOSPHERIC PRESSURE-the prBSSUre exerled on
lhe earlh's surface by the weight of lhe air and moislure
above it; a unit of pressure equal 10 about 14.7 psi (see
ATMOSPHERE) Also called ~rometfrc Pressure
ATOMJZING AIR-the air su~IiBd 10 an air·atomizing oil burll8r (usually about 10 percent) which IS used to break the oil stream into tiny droplets Ths atomizing air
is also later used 10r combustion
ATOMiZING MEDIUM-a supplementary fluid, such as
sleam or air, which assists in breaKing oil into a finely divided stale
ATOMIZING OIL BURNER-an oil burner which delivers fuel oil to the combustion ZOIl8 in the form 01 tiny dropleis It uses some form at nozzle or ori1ice to spray the oil into the combustion charrCer An atomizing oil burner is classified by the medium used to breaK up the oil into fine particles
Air-Atomizing Oil Burner compressed air Steam-Atomizing QII Burner-steam at pressuras greater Ihan 25 pounds per square inch (psig) MeC,l',anical-A\Omizinq Oil Burner no mBdium; the oil is p mped at hig'l pressures (50 to 300 psig) through a suitabie burner nozzle orifice which breaks il into a fine mist Synonymous with fressure-Atomizina Oil Burner (Also see PRESSURE-ATOMIZJNG GUN TYPE BURNER.)
Air· and Steam-Atomizing Oil Burners can be further classified by the location at which the atomization takas place
External·Mix Oil Burner-the high velocity air or steam strikas lhe oil after it has left the nozzle Internal-Mix Oil Burner the high velocity air or steam striKes jets of incoming oil in atomizing cha/Ttler, and the oil is discharged from the nozzle in completely atomized 10rm
AUTO-shan for automatic; lhe firing rate position (on a programmer) lhat provides a period during Which lhe firing fate motor is operating frem an external Controller Also see MODULATE
AUTOMATIC-self·ragJlaling or self-acting; Capable of responding to cMain predetermined Conditions AUTOMAl1CAl1.Y IGNITED BURNER - burner In which fuel 10 the main burner is aulonalically turned on and i~iled
AUTOMATIC BURNER -a burner that stMs and stops automalically
AUTOMAl1C CONTROL-ij sy6Iem thai reacts to a change or unbalance in one of its variables by adjusting the other variables 10 restore the system to the desired balance For example, a 6y8Iem for control 01 air-fuel ratio can be set up so lhat a change in the selling of the combustion air valve results in a corresponding change
in the fueJ input
Trang 3AUTOMATIC CONTROL VALVE-an electrically oper
ated valve which combines a valve l::lc.dy and a valve ac·
tuator or motor A signal from some remote point can
.e(lergize the actuator or motor to qJen or close the
valve, or 10 proportion lhe rate of flow through the valve
Also see CONSTANT·LEVEL, FIRING RATE, MODU
LATING, MOTORIZED, and SAFETY SHUTOFF
VALVES
AUTOMATIC IGNITION-a system in which a burner is ig
nited direttly, without manual intervention, by an aulo
.matically supervised ig1ltion spark or pilot
AUTOMATIC SAFETY SHUTOFF VALVE-see SAFETY
SHUTOFF VALVE
AUTOMATIC SYSTEM-a system which regJlates itself
, and requires no manual operations: a system in which
the burner is cycled completely automatically under
control of an automatic temperature or pressure
controller
AUXIUARY POTENTIOMETER-a potentiometer
mounted in or on a modulating motor, which is used to
control an external device in response to movements of
the motor
AVAILABLE HEAT-the quantlly of heat released in a
combustion chamber that is available for useful pur
poses II is the total quantity of heat released minus
both the dry flue gas loss and the moisture loss
BAFFLE-a metal or refractory plate or wall used to de
flect the flow of gases or liquids or to minimize the ef
fects of flame, heal, or flue gases
BAG ASSEMBLY - closely related parts grouped together
in a single packaQEl, purchased as 1 unit
BALANCING RELAY -a relay with an armature pivoted
between 2 etectromagnelic coils The armature con
trols the position of the Wiper on a feEKDack potenti
ometer In the electrical circuit If the currents through
the 2 coils differ, the armature moves toward the coil
with the most current (strongest electrornagnetit
force) As the armature moves, the potentiometer wiper
changes the resistance in series with both coils unlil
the currents are equal The armature stops when the
circuit is balanced Besides the electromechanical type
just dBscribed, there is also a solid slate type which per·
forms tile same functions electronically A balancing
relay is used in a Modutrol motor to position it Also
called a "mouse trap "
BAR CHART -a representalion of the ~raling se
quence 01 a flame safeguard programming control us
ing bars shaded to show the times when various
circuits are energiZed
BAROMETER-an instrument used to measure atmospheric pressure
BAROMETRIC PRESSURE - see ATMOSPHERIC PRESSURE
BASE -the main s~rting frame or structure of an assembly, excluding the legs
BATCH TYPE FURNACE-a furnace thai Is shul down
periodically to remove lhe old charQEI and add a new charQEl; as dlsllngulshed from a ContinUJUS Furnace BELLOWS-a metallic accordian-like box which can be
compressed mechanically or with fluid pressure Oike a spring}, and which will return to its normal shape when Ihe pressure is released
BENT-TUBE BOILER-see WATER-TUBE BOiLER BlAST FURNACE GAS-a gas of low Btu content resulting from burnirg coke with a defiCiency 01 air in a blast furnace
BLEEDER-an intentional leak, usually used to rectJce pressure in an impulse line
BLEEDING-intentional leak3Qe (usually of gas) Leak· age that mi'lt't occur during shutdown In a safety shutoff valve "block-and-bleed- arrangement Gas bleeds off 10 the atmosphere through a normally qJen vent valve When the safely shutoff valve(s) is opened, the
venl or bleed valve closes and "bleecjing" slq:lS Also see DOUBLE-BLOCK-AND-BLEED
BLOCK-AND·BlEED see DOUBLE-BLOCK·ANDBLEED
BLOWER -a fan used to deliver air under pressure to the desired space Also see BURNER MOTOR
BODY RATING-see VALVE BODY RATING
BOILER -a closed vessel in which a liquid is heated or vaporized; used to s'-W1y hot waler or steam for heating, processing, or power purposes Also see CAST IRON SECTIONAL, DRYBACK, FIREBOX, FIRE-lUBE, HIGH PRESSURE, HIGH TEMPERATURE, LOW PRESSURE, PACKAGED, SCOTCH, WATER·lUB~ and WETBACK BOiLERS
BOiLER HORSEPOWER (BoHP)-the EQJivalent of the heat rElQJired to evaporate 34.5 Ib [15.648 kC] of waler per hour lrom a temperature of 212 F [100 Cl into dry,
saluraled steam al the same temperature ~i\/a'enl
to 33,472 Bluh, 9.803 kilowalls, or 40 poundS of steam per hour
BONNET -see VALVE BONNET
BOOSTER HEAlER-a heater used 10 raise the tempera· ture of oil from thai tEQJired for pumping 10 thai required for atomization
BOTTLED GAS-see UQUEFIED-PETROLEUM GAS BOURDON TIJBE-a lube thai responds 10 pressure changes The ILbe, with elliptical cross section, i6
Trang 4shaped into an arc or spiral witl"l 1 end attached to an
irdcatlng, ret01ding, Of controlling deliice A pressure
wltl"lln the tlbe makes It less elliptical and more nearly
circular, thus actuating Il"Ie attached device
BOX·HEADER BOILER-see WATER·TUBE BOILER
BRAKE-WINDING -the winding in an electric motor which
floId9 lhe armature againsl a brake SilOE! to hold the
lTDIor In Its open posllion after the mOior limit swllc;h
opens;' When both the motor winding and the brake
wtr1dir1g are energiZed I,""" streng1h o1lhe motor wjnd
Ing O\Iercomes the brake Winding
BRANDi CIRCUIT -a secondary cJn;uillaading from the
mainoil circulating Ic:q::> 10 a burner or gfOl.q:l ofbUmers
BREAKDOWN (VOLTAGE}-that volla~ et which an In
sulator or dielectric r~lures
BREECHING - a passageway to condJc\ flue gases from
tne /umace or bOiler 10 Il"Ie chimney Also caffed 1!l.Ii
~ Of vanl connector
BRIDGE CIRCUJT ~an eJectrical nalwol1c arranged so
lhat the volta~ at a given poinl in the circuit lOan be z&
roed by adjusling the electrical paramelers (resistance
inciJctance, and capacitance) in the branchas until the
currents balance
BRING·UP TlME-lhe time required to raise a cold fur·
nace and its char~ if any, to operating temperature
BRITISH THERMAL UNIT (Btu)-tl"le quantity of heat ra
q.Jir9d 10 raise the temperature of t pound of water
from' degree F
BTU (8tu)-sae BRJTISH THERMAL UNIT
BTUI-! (BrUhl-one Btu per hour; 1 million Btuh is eq.;iva
lent to 7 gallons of oil per hour, 800 pounds of steam p&r
ho.Jr, or a boiler inpul of 20 boiler horsepower (Be HPJ
BUCKET BRIGADE - a colloquial term, for the elec\(onic
setf-checking Circuitry in the flame signal amplifier of
scme flame sa1egUard controls The term refers 10 lhe
periodiC "dumping" (discharQlngj of one capacitor in
the circuil info anolher 11 this dumping steps, due to a
failure in Ihe flame delection system the control shuts
d:lwn the burnElr
BUNKER ~C~ Otl-a term for heavy oil (No.6 fuel oil)
S8IB HEAVY FUEL Oll_
BURNER-a device which introduces fuel and air into a
furnace at lhe oasireo velocities 11 'rt:x;lence, and can
centration to eslablish and mainlain proper ignition and
combustion of the fust Also see ATMOSPHERIC AT·
OMIZING OIL, AUTOMATlCALLY IGNITED AUTO·
MATIC, COMBINATION INSHOT, LONG FLAME
MAIN, MANUALLY IGNITED, MULTI PORT NOZZLE
MIXING, PARTJAL-PAEMIX, POWER, PREMIX RAW
GAS, ROTARY OIL, SEMIAUTOMATiC UPSHOT,
and WARMUP BURNERS
BURNER CONTROlLER-an aulomatlc lemperalure or pl"9SSU¥9 sensing device connected In the il'lpJl Circuit
01 a flame safeguard control 1Ilndirectly acts to tum a bUrner on or off in order to maintain pressure, air tempe,ralUTe, waler temperalure, or liq.Jid level wJlhin the desired limits
BURNER HEAD-that end of a burner beyond the nozzle
or portS
BURNER-INPUT CONTROL VALVE-see FIRING RATE VALVE
BURNER MOTOR- fhe motor which ctives the blOWer or
fan thai delivers air at proper velocity into the corrt>ustion chamber
BURNER REFRACTORY-see REFRACTORY, BURNING VELOCITY - see FLAME PROPAGATION RATE
BUSHING -a usually removable lining or sleeve of melal
or other malerial lhal isc inserted or ecrewed into an q:Jening to Ifmillts size resl81 wear or erosion, ser\fe as
a guide, or protect wires from abrasion and lX'SSib!e
shOrt circuit; an internally an:::J exlernally threaded plug fOi connecting a pipe or titling with another of different size FO(exarnpls lhepart at the C7015A Intrared(lead sulfide) Flame Detector which Includes the viewing window Of magnifying lens; it1ils over Ihe plug-in lead sulfide cell ard Is held in place by the mounting collar BUTANE: - a gaseous hydrocarbon fuel; a mixture of easily liquefiable hydrocarbon gases, principally butane Bulane is one 01 tne cCll1ll=Of'l8nts of raw natural gas and is also derived from pe:roleum refini"lQ proces.se:s BUTTERFLY DAMPER-a single blade damper, pivoted abOut ils center; Ihe blade somewhat ~esembles Ihe
opened wings of a bullerfly
BUTIERFLY VALVE-a throttling valva tor a pipe, consisting of a rotating hinged plate thaI somewhal resembles the opened wir1gS of a butterfly; ol1en used as a firint;;l rale valve lhe Honeywell V51E Bullerfly Valve
~ excellent hi~'<Olume floYl characteristics, makinQ
il useful for close mocIulation of the supply of air or fuel gases to lar~ furnaces This type of ~alve cbes not cloSEl :ightly so a separate safety shutoff valve musl be US&d wilh it for final closeoff
CAD cal-see CADMIUM SULFIDE CELL
CADMIUM SULfiDE CELL-a ph'>Io.condJclive devlea that responds 10 the visible light emilledby an oil flame
In the presence 01 ~isible lighl, the eleclrkal resistance o11ha cadmium sulfide {CdS) becomes very low and the cell conducts current The cad cell is used In flame detectors 10r Oil burner Systems
Trang 5CAGE VALVE-a single-seated valve containing a frame
or box (cage) Inside which Ihe plug slides, cpening the
ports
CALL FOR HEAT-when the controlled lemperature or
pressure drops below the cperallng set p:linl, Ihe
burner controller contacts make to iniliale burner
cperation
CALQRIE-Ihe quanllty or heat required to raise the tern
peralure o~ 1 gram of waler 1 degree C
CA~pLlNG (CANDLEUGHTING}-the deterioration or
the pilot to an unsatisfactory condition, characterized
by a lazy, yellow 1lame; usually caused by a high ambi·
ent temperature or an excessively large pilot burner
orifice
CAflACInVE LOAD-a leading load; a load that is pre
oominantly capacitive, so that the alternating current
leads the alternating voltage, I.e., the voltage doeS not
change direction until afler the corresponding current
does
CAPACITY INDEX (Cvl-the quantity or waler, in gallons
per minute at 60 F, thatllows through a given valvewilh
a pressure drop or , psi The flow or a.ny fluid through
the same valve can be calculated from the C v Also
ca.lled the Flow Coefficient
CASlNG-l) a covering of sheets of metal or other mate
rial such as a 1ire resistanl comJXlSition l::::oard l.lSed 10
enclose all or a portion or a steam generating plant;
2) an enclosure torming the outside of a.n appliance, no
parts 01 which are likely to be subjected 10 intense heat
CAST IRON SECTIONAL BOILER-a OOPer comJX)S9d or
a number of separale sections 1a.stened together, re
sulting in a large heal transfer area It can be fired by an
LPShot or :nshol gas burner, or by a pressure atomizing
oil burner Sizes range up to 4 million Btuh (about 80
CELL - a single unit that produces voltage Of currEW11 by
converting radiant energy into electrica.l energy Also
see CADMIUM SULFIDE and LEAD SULFIDE CELLS
CENTRAL FURNACE-a seI1-contained, indirect-fired
furnace designed to supply heated air through ducts to
spaces remole 1rom or adjacenllo the furnace location
CENTRAL HEATER-a stationary indirect-fired, vented
awliance in one of these classes: boilers, cenlral fur
naces, 1100r furnaces, recessed healers, and floor
mounted unit heaters connecled to a ducl system
CENTRIFUGAL ATOMIZING OIL BURNER - see
ROTARY OiL BURNER
CHARACTERIZED GUIDE-a valve guide with notches
or V's cui inlo il to determine the valve flow characteris·
tic; also known as a skirted guide
CHARGE-a load; the maximum or necessary QJNItity
thaI a conla.iner or awaratus is buill to accommodate;
e.g., fuel in a furnace In electricity, the elsclricat
energy stored in a capacilor or ba!tery or held on an insulated object
CHASSIS-a sheetmelal bOx, frame, or single plate on which the components of a device are mounted; the asserrbled frame and parts
CHATTER-see RELAY CHATTER
CHECKING RELAY-a relay iri the selt-checklng circuit or some flame safeguard controls which makes ard
breaks periodically (~Checking~ or ~peCking· action) when the flame signal is strong enough While checking, it trans1ers energy to hold in the 11ame relay It slops MChecking M
it the flame signal becomes too weak
or disappears
CHIMNEY-a brick, metal, or concrete stack enclosing 1
or more 11ues for conveying 11ue gases to !he ouIside atmosphere
CHIMNEY CONNECTOR-the pipe which connects a fuel burning appliance to the chimney; a.lso called a smoke pipe
CIRCUIT-see ELECTRICAL CIRCUIT
CIRCULATING LOO P- the main loop in which oil is circulated from the storage tanks to 1M branch circuilsand then back to the storage tanks
CLOSED CIRCUIT OIL SYSTEM-a system in which oil may be pu~ completely through the circulating loop and back into the oil storage tank
CLOSED IMPELLER-see IMPELlER
CLOSE-OFF RATING -the maximum allowable pressure drop to which a valve may be subjected while fully closed It is a function of the JXlWer available from the valve actuator for holding the valve closed, and is ll'k:iependenl of the actual valve l:xxtf raling
COCK-a manually operaled faucet or valve tor shutting oft or throttling down the~ow or a li~id or gas usua.11y
by means of a tapered plug Also see PETCOCK ard
SUPERVISORY FUEL COCK
COMBINATlON BURNER-a burner by means of which more than 1 fuel can be burned eilher separa.lety or si·
multaneously Also called a Mullifuel Burner A C1.lil!:
Fuel Burner uses , prime fuel, but can switch to a stanchy 1ue1 under peak load conditions A .Gas:Ol!
~ is capable of burning either gas or oil-some types can burn OOlh at the same time Ex~les of a Combination Burner:
Pressure-Atomizing Oil/Gas Ring BuOl9f' Horizontal Rotary Oil/Gas Ring Burner
Combination of 2 burners (under separate Sl.4l9rvision) in 1 asserrbly
COMBUSTlBLE MATERIAL-material that will iglile and bum k3 pertaining to materIals ad}acent to Of in contact with heal-prodJcing Wiances, chimney connec· tors, vent connectors, steam and hoi water pipes, m
warm air wcts, II is material made or or surfacedwilh
Trang 6wood COlTpfElSsacI paper, plant fibers, or other mate
rtalthat wlllignite and burn Such material shall be con
sidaTEld as combustible even lhough flameproofed,
fire-retardant treated, or plastered
COMBUSTION-the act or process ofbutning; the rapid
oxidation of fuel accompanied by the production at
heat, or heat and light Complete col'1'bustlon req.Jires
an adequate suppl)l of oxygen Also se& COM PI.ETE,
INCOMPLETE, and PERFECT COMBUSTION
COMBUSTION AIR-the air r&q Jired tor clJl'l'lllele and
sanSfactory combustion of the fuel; ooes nol inclUde
the air used for atomization Also called main air The
actual amounl of air supplied Is usually expressed as a
percentage of the lheoretical amount required for can
p1ete combustion
, ,
COMBUSTION AIR SWITCH-se& AIRFLOW SWITCH
COMBUSTION CHAMBER-the panion of the heating or
prcx:ess equipment where fuel is burned Also called
COMBUSTION DETECTOR-see FLAME DETECTOR
COMBUSTION PRODUCTS- mailer resulting from COITI
bUstion such as flue Qi!S8S, water,vapor, and ash; but
excluding excess air
COMBUSTION RATE-se& FIRING RATE
COMBUSTION SAFEGUARD-see FLAME SAFE
GUARD CONTROL
COMMON-a terminal, connection leadwire, circuit, or
other part of an eleClricj;l1 networ'K which is shared by
olher parts of tho networ'K On a flame safeguard co~
trol, the terminal and leadwire which are in lhe circuit
for all JXlSitions 01 the firing rate swllching circuit
COMPlETE COMBUSTION-burning with stoichiometric
P'C90rtions of air and fuel pllAi a rncderale excess of air
10 ensure Ihal all of the fuel is burned
COMPRESSED AIR-air al a pressure of 5 or more
jX)Unds per SQ,Jare inch above atmospheriC pressure
COMPRESSED-AIR-ATOMIZING OIL BURNER-see
ATOMIZING OIL BURNER
COMPRESSIBLE FLOW-flow of hiQh pressure gas or air
which undergoes a pressure drop sufficient to resull in
a siglificant reduction 01 its density
CONDENSATE-condensed water resulting from the
removal of lalent heal from steam
CONDUCTION-the transfer of heat or transmission of
electricity through a materia! (cal/eel a condUclor) by
passing II from molecule to molecule
CONDUCTIVITY CiRCUIT -a flame proving circuit which operates on an ac flame aignal and utilizes the electrical corOJction of a flame, as d1sllnculsheci fran rectlficalion Also 5ElEl CONDUCTIVITY FLAME ROD SYSTEM and FLAME CONDUCTIVITY
CONDUCTIVITY FLAME ROD SYSTEM-a flame roo deteclioo system based on the ability of the flame 10 conClucl a currant; conducts the same amount of current in eUher dlrectioo, as distinguished tram flame reeliflCatioo
CONDUIT -a tlbe or trOlJl;;flfor carrying and protecting electrical wires
CONSTANT-lEVEL VALVE-an automatic control valve for maintainIng, within a reservoir, a constant level of fuel for delivery 10 the bumer
CONSTANT PILOT-se& CONTINUOUS PILOT, CONTlNUOUS CHECK RELAY-see DYNAMIC SELF CHECK
CONTlNUOUS COMPONENT CHECK-5ElEl DYNAMIC SElF CHECK
CONTINUOUS FURNACE-a furnace ~rated on an un· intern pted cyCle, In which the charge iEi being constantly added to, moved thrOUgh, and removed from the furnaCe; as diSIlngulsheel from a Batch Type Fumace
CONTlNUOUS IGNlTlON-ignition by an energ,o source which is continuously maintaineelthroughout the time the burner is in service, whether the main burner is tiring or not
CONTINUOUS PILOT -a pilot that burns without turndown throughout the entire time the burner assem· bly is in service, whether lhe main butner is firing or not The pilot ignites fuel which may leak into the corrbus· tion chamber whan the burner is off, thus prevenling a hazarcbus cordilioo at stanup (~Gontinuous Pilol" is Underwriters laboratories Inc term for the old term
"Standing PlIot.-)
CONTROL-a device which dir&crJy operates a system to
reg.Jlate the fuel, air, waler, or electrical Eiul=Ply to the controlled equipment It may bEl automatic, semiautomalic, or manual Also see AUTOMATIC FLAME SAFEGUARD, MODULATING, NONRECYClING, ON-QFF, OPERATING, PRIMARY, PROGRAMMING RECYClING, AND SAFETY CONTROLS
CONTROL AGENT -the meellum which is manipulated
by the control syslem 10 cause a change in the controlled medium For ellample, suppose a heating coil thrClllgh which steam is flowing Is used to heat a room The rcom thermostat is placeel so that it measures temperature (conl(olleel variable) in the room air (conlrolleel medium), and operates a valve which regulates Ihe flow jmanipulateel variable} of the steam (control agent) thrOlJl;;fl the heating coil Heal from the coHls thus furnished to the room air
Trang 7CONTROL POINT -the value 0: the controlled variable
which the controller operates to maintain Also see SET
POINT
CONTROL SYSTEM-the entire system, including the
controlled system And the automatic conlrol eq.Jip
ment see CONTROLLED SYSTEM
CONTROL VALVE-see AUTOMATlC CONTROL
VALVE
CONTROL lONE- the section of a furnace In which tem
perature'is controlled by the throllling action of a single
valve Also see VALVE ZONE
CONTROLLED MEDIUM-the substance (usually aIr,
water, or steam) whose characteristics (such as lem
I perature, pressure, flaw rate, volume, level, or concen·
tration) are being controlled
CONTROLLED SPACE- the volume of the controlled me
dium For example, a room in which the air temperature
is being cootrolled
CONTROLLED SYSTEM-the system made up of all
equipment In which the controlled variable exists, but
which does not include the automatic control
eqUipment
CONTROLLED VARIABLE~thatquantity or condition of a
controlled medium which is measured and controlled
For example, temperature, pressure flow rate, vol
ume, level, or concentration
CONTROLLER-a device which senses and measures
changes in the controlled variable and indireCtly acts to
maintain the controlled variable within preset limits It
direCtly affects the operation of a flame safeguard con
trol Also S99 LIMIT; and BURNER, FIRING RATE,
MODULATING, PRESSURE, PROPORTIONING,
SAFET'(, !lind VACUUM CONTROLLERS
CONVECTION-transfer of heat by moving masses of
mailer Convection currents are set l4> in a fluid by me
chanical agitation or because of differences in elensity
al different temperatures
CRACKING-the process of breaking c:bwn hydrocar
bons by heat and pressure into simpler compounds or
elements: e.g., the breaking down of petroleum Into
gasoiine
CRITICAL PRESSURE DROP-see PRESSURE DROP
CROSS'CONNECTED-two pipes or systems of flow
connected to each other, usually to proviele an equali
zation or interplay of pressures
CROSS·DRUM BOILER-see WATER-TUBE BOILER
CRUDE OlL-unrefined oil in its natural stale as it comes
tram the ground Also called petrgleum or !<II.!Q!i
CURTAIN TYPE DAMPER-a damper composed of flex
ible material, which moves in a venical plane as it is
rolled
337
CUTOFF - immediate shutdown of a system atter loss of the main burner flame, wilh no attempt to recyCle or to relight the burner
Cv-see CAPACITY INDEX
DAMPER -a elevice for introducing a variable resistance for regulating {he volumetrIc flow of gas or air Also sea BUTTERFLY, CURTAIN, FLAP, LOUVER, andSLJDE TYPE DAMPERS: and OPPOSED and PARALLEL BLADE DAMPERS
DAMPER MOTOR-see FIRING RATE MOTOA DEAD END LJNElSYSTEM-the end of a pipe line which does not lead back 10 an oil Slorage tank, so the oil in that end of the line cannot be recirculated A system which does not contain a return line 10 an all storage lank, so the oil cannot be recirculated in a closed circuit
DEFICIENCY OF AIR -a supply of air which is inadequate lor complete combustion of a fuel (This is [he same as
an excess of fuel.) Also see FUEL RICH
DELAYED MIXING-a process in which the fuet and air leave Ihe burner nozzle unmixed and, thereafter, mix relatively slowly, largely through diffusion This results
in a long, luminous 1lame called a diffusion flame, long Ilame, luminous flame, or yellow 11ame Also see LONG FLAME BURNER
DETECTOR -a elevice that produces an electrical OOlput that Is a measure of the radiation incielent on the device Also see FLAME DETECTOR, SMOKE DETECTOR, and SENSOR
DEVIATlON-the difference between the sel point and the value of the controlled variable at any inslant DIAPHRAGM VALVE-a SOlenoid-operated gas valve in which a membrane or partilion separates lhe inlat and outlet When the solenoid is d&-energlzed, the main gas supply applies pressure to the top oflhe dlaphragn
10 help hold the valve closed When the solenoid is an· ergized, a plunger opens a bleed pon in the I~ side of Ihe valve As the gas bleeds off the I~ of lhe diaphragm, main gas pressure on lhe underside of the dia· phragm cpens the valve Honeywell V4B and V88 Diaphragm Valves are generalty used on atrra;pheric type gas burners tor srTlOClth lightoff Thej fealure variable, slow q::lefling times and fast closing 1IrTeS Also see SOLENOID
DIFFERENTlAL-the sroallesl range through which the controller variable must pass in oreler to move the final control element 'rom one 10 the other of il~ 2 possible positions, such as from ON 10 OFF
DIFFUSION FLAME BU RNER -see LONG FLAME BURNER
71·97558-1
Trang 8DIRECT CURRENT (de) -an essentially ccnstanl-value
curr&/\! lhat flows In ally one direction
DIRECT·FIRED HEATER -a heater In whie" thepnxiJclS
01 e6iTb.istlon (l'lue gases) are Inlerm1xec:l with the
medium being "eatec:l (e.g., ail1 Also see DIRECT
FIRED EXTERNAL and DIRECT-FIRED INTERNAL
HEATERS
DIRECT·~IRED EXTERNAL HEATER-any oven healing
SyStEll!" in whiCh 'he products of cootlusUon frem the
burnel'\,l!\rs discharged into the oven chamber by a cir·
culating fan or blower, and in which the bul'119r'S are in a
cOlTbJstion chamber ellectively separalec:l frem Ihe
oven chamber ll"Jere are 2 types:
1 Nonreclrculating-prodJCIS of combusllon are
''discharged into the oven cl'\arrt)er and are nat
returned to the combustion charrtler
2 ReCirculating - oven chamber atmosphere is
recirculated to the combustion chamber and Is In
conlact wit" the burner flame
DIRECT-FIRED INTERNAL HEATER-any oven healilll;l
system in which Ihe burners are within the oven cham
ber, and the products of combustion are in contact with
the oven atmosphere
DIRECT SPARK IGNIllON~use of an Ignition spal1l
generated by a high voltage transformer, 10 lir,tll lhe
main burner; aw1ies 10 burners not using a pilot,
usually small oil burners Also see PROVED SPARK
iGNITION
DISCONNECT SWITCH - see MASTER SWITCH
DISSOCIATION-the process by which a chemical com·
pound breaks c:bwn inlo sil"llJler cCllTPJl1enl.6 For ex·
al"llJle breaking up CombUSliQi"l products into
cOl'Tbustibles and oxygen, aCCot'T'flanied by an absorp
tion of heal Thi.6 ·usually occurs at high tefTC)9ralures,
and Ills one of the factors limiting the maximum tem
peralure ot a flame
DJS11UATE OIL-light fraction of oil separated frem
cru& oil by fractional distillation
DIVER11NG VALVE-a three-way valve with linlel and 2
oullels A fluid entering the Inlel por1 Is diverted to
either of the 2 outlet ports in any prq:lOrtion desirec:l by
moving Ihe valve stem A diverting valve is doLble
seeted with a aisc tor each seat, so It can generally be
used in mixing ~lications also
DOUBLE-BLOCK·AND·BLEED-a valve arrangement In
which a normally open vent valve just c:bwnstream from
an automatic safety Shutoff valve (SSOV) allows any
gas that leaks past the SSOV during shutc:bwn to es
cape to the outside atmosphere A second SSOV lust
c:bwnsUearn from the vent valve blocks any gas which
is not ventec:l When the $SOV's are open, the vent
valve is closed Also see BLEEDING
DOUBLE-SEATED VALVE-a valve with 2 seats and
discs arranged so thai in Ihe closed posilion there is
very Uttle fluid pressure forCing the stem toward the open or closed position; rEQJlres less power to operate than a single-sealed valve the same size; ofIen has a larger port area tor a given pipe size; cbes not have tir,tlt shuloff (Do not contuse lhis valve with the type 01 valve with a second seal used in a valve-closed inlerlock.)
DOWNFLOW FURNACE-a forcB(j.air, central furnace with essenlially vertical airflow, whjch discharges air at
or near lhebotlom at the furnace; es distingUished 'rom
an uptJow Furnace
DRAFT-the difference between atmospheric pressure and some lower pl9SSUre existing in the furnace or gas passages of steam generating unll; also, the movement of air Into anc:I thro~ a corrtluslion charrber, breeching, stack:, anc:I chimney Drall may be natural, resulting frem the difference in denslly of the heated air rising through the stack and the cooler displacing air Artificial drall may be prOVided by mechanical means, Drall is affected by chimney height and cross section, wind, makeup air c:penlng in the boiler room and wealher conditions (barornelfic reading) Also see FORCED, INDUCED, MECHANICAL NATURAL, and OVER-FIRE DRAFT
DRAFT LOSS-the reduction of drall intensity caused by
resistance to flow of flue gases through the boiler, breaching and chimney, plus any resistance to flow of air through the burner
DRAFT REGULATOA-a device which acts to mainlain a desired draft by automatically controlling the chimney drall in:erLSily at the desired value
DRYBACK BOILER-a Scotch, fire-tube ooiler with a ceramic baffle al the back of the furnace to direct the products of cornb Islion from the combustion chamber
to the second pass ll"Je ballle is separate from the pressure vsssel and 'IS constrUCled of heal·resistant malerial (generally refractory brick and insulation) Also see FIRE-TUBE and SCOTCH BOILERS DRY CONTACTS-contacts isolated from any source 01 power
DUAL·FUEL BURNER-a burner using 1 prime fuel, but capable of using a slancbl fuel under peak load cond!lions Changeover from one fuel 10 the other can be made aUlomatically usIng an electriC temperature controlle! or by use of a manual switch Also see COMBINATION BURNER
DUCT -a passage for air or gas flow; a protective pipe through which wires or cables are run
DUCT FURNACE-a central furnace designed lor instal· lation in a duct 01 an air dislribution system to supply warm air for healing For air circulation, II depends on a blower not furnished as part of the furnace
DYNAMIC AMPU-CHECK-HonB'jYfelitrademerk:; a feature in some Infrared flame sil;1l81 amplifiers; circuitry tests only the flame signal amplifier during burner
Trang 9operation and shuts down the burner if lhe amplifier
fails (including a flame-simulating failure)
DYNAMIC SELF CHECK- Honeywell trademark; a fea
.·ture in the rectification type llame signal amplifiers or
some flame safeguard controls: circuitry tests all elec
tronic components in the flame detection system (am
plifier and detector) 60 to 240 times a minute during
burner operatior) and shuts down the burner if the
'.detection system faits (including a flame-simulating
failure)
gramming controls which allows ignition cutoff be10re
the main fuel valve(s) opens, resulting in a periOd dur
ing which onlv the pilot is on
ELECTRICAL CIRCUIT -an electrical path between 2 or
more points; the interconnection of a number of de
vices in 1 or more closed paths to pertorm a desired
electrical or electronic tunction Also see OYNAMIC
AMPLI·CHECK and OYNAMIC SELF CHECK; and
ALARM, BRIDGE, CONDUCTIVITY, FIRING RATE
SWITCHING, FUP-FLOP, HIGH-VOLTAGE, ISO
LATED LIMITED SECONDARY, LINE-VOLTAGE,
LOW-VOLTAGE, OPEN, SHORT, SOUD STATE, and
TUNED CIRCUITS
ELECTRIC IGNITION-ignition or a pilot or main burner
bV an electric spark generated by a transformer, which
is eilher automaticallV or manuallv energized Also see
DIRECT SPARK IGNITION
ELECTRODE-;-a conductor by means of which a current
passes into or 001 of a,gas; often one terminal of a lead
Examples: ignition electrcxles, ftame rods, electron
tube elements
ELECTROMAGNETIC SPECTRUM-a chart or graph
showing the relationship between all known eleclro
magnetic waveforms classified by wavelengths
ELECTROMAGNETIC WAVE-the radiant energy pro
duced by oscillation of an electric Charge lncluc\edare
radio waves; infrared visible, and ultraviolet light
waves: and X-, gamma, and cosmic rays
ELECTRONIC-of or pertaining to devices, circuits,
or systems utilizing the motion or emission of cur
rents 01 free electrons, especiallv in vacuum,
gas, or phototubes, and special conductors or
semiconduclors
EQUAL PERCENTAGE CHARACTERISTlC-a valve
flow characteristic which causes like movements of the
valve stem at any point of the now range to change ex
Isting flow an equal percenlage regardless of the exist
ing flow quantity
EXCESS AIR-air which passes through the combLstion chamber and flues in aQjiUon to the quantity which is theoreticallv required for complete corrtlustion, to enSlJre that all of the tuel is burned
EXHAUST FAN-a fan which provides a SlJcUon to remove the air, gases, and producls of combustion from the turnace or oven In some systems, it also brings in combustion air Also called a ventilator
EXPANDING PILOT -a pilot that burns throug,out the entire lime the burner assemblV is in service whether the main burner is firing or not Up:lI'I a call for heat, !he pilol flame is automaticaliV Increased in size so as to reliably Ignite the main burner This pilot may be turned down automaticaliV at the end of the main burner 1lame-ilstablishing periOd
EX PLOSION - combustion occurring within a confined environment at such a rapid rale as to cause detona
tlon, called a Fireside Explosion Also the rupturing of a
vessel due tothebuildup otprassure of water or steam,
called a Waterside Explosion
EXPLOSIVE MIXTURE-a flammable mixture in a confined space
EXTERNAL HEATER~a heater in which the burners and combustion chamber are effectivelv separated lrom the oven chamber or the medium being heated Also see DIRECT-FIRED EXTERNAL and INDIRECTFIRED EXTERNAL HEATERS
EXTERNAL-MIX OIL BURNER-see ATOMIZING OIL BURNER
FAN -any device or machine used to set up a current of air Also see BLOWER and BURNER MOTOR; and EXHAUST, FORCED-DRAFT, and INDUCED- DRAFT FANS
FANMIX BURNER-a mechanical-oraft burner which uses the energy of high-pressure gas (10 to 50 psi) to Completely premix the air and gas Gas is permitted to escape IhrClll'j"l a row of small orifices on the ecV3 of prq:>eller-Hke blades mounted on a ffee-spinning shaft Reaction of the escaping gas rotales the blades, which are mechanically CQl4)led 10 a fan that draws in the primary air The speed of the fan varies with the gas pressure, theretJy automatically adjusting the air volume [0 maintain optimum corrt:lUstion Also see MECHANICAL-DRAFT and PRE-MIX BURNERS FAN MIXER-an air blower in which gas is ad"nitled to lhe inlet to be mixed with air
FEEDBACK POTENTIOMETER-the potentiometer In a mcdJlaling motor which forms part of a briOole circuit along with lhe controller potentiometer and balancing relaV in the molor When lhe Wiper on the controller potenllcmeler l'T'lOVeS dJe 10 a change In the controlled
Trang 10variable, the motor runs and drives the wiper on the
feecback polen(fomeler in the proper direction to
rebalance the bridge circuit When the circuit Is bal
anc9d ~ElI motor stops
FIELD WIRING-wiring thaI musl be done althe Installa·
lion site (in aetjilion to 1actory wiring) in order to com-
plete an Installation
FILTER -.a device to remove solid malerial from a fluid
~i~)d Of" gas) In~electronics, a saleclive network or
resistors Il"d.Jctors, or capacitors which otters COOl
paratively 1i1lle q::positlon 10 certain fr9QUBl1cies or (0
direct current, while blocking or anenuating other
trEQJencies
FIREBOX-see COMBUSTION CHAMBER ,
FIREBOX BOILER-a horizontal, fire-lube boiler with a
small, internal corrt>usllon chamber of cubical dasi'OJ'l
TIle short, first-pass bank of lubeS Is COr"ll"l9cted be
tween the rear of the combustioo chamber and lhe rear
of lhe OOiler The remaining banks of tubes extend the
full length of the ooiler, above the combustion chamber
and the first-pass bank The combustion chamber may
be steel, refractory or waler-cooled refractory AlSO
see FIRE·TUBE, MULTIPASS and WATER-LEG
BOILERS
FIRE POINT -the minimum temperature at which a flame
is suslained for at least 5 secondS
FIRESIDE EXPLOSION-see EXPLOSION
FIRE-ruBE BOILER-a boiler in which the prCXi.Jcls 01
combustion pass through slraighttubes surrounded by
water and steam The tubeS may run horizontally or
vertically
The HOlizonlal-Return-TuOO (HRn type has a horl·
zonlal shel: conlarning the tubes The prooucls of com
bustion pass from Ihe external combusllon chamber
underneath the bottom of the she:1 to the end of the
boller, and relurn thrOl.:gh the tubes If the prOducts 01
cQfTClustion are paSSEd Ihrough the shell more than
once, it Is called a Mullipass Boller
l1leY w1!£.Il! type has a vertical, cylindrical shell Cln"
talnlng the lubes Thfl prodJcts of combustion pass
from the irternal cO/T'tlusUon charroer below the shell,
l.p IhrOLV'i the lI.bes In a Submerged VertIcal type lhe
water level exlends h;gher than the tcp endS of the
lubes
Also sea FIREBOX, MULTIPASS, and SCOTCH
BOILERS
FIRING RATE-corrbuSlion rate; the rate e! which fuel or
an air-fuel mixture is supplied 10 a burner or furnace,
expressed in volume weight, or heat units ~1ied per
unit lime Also see HIGH FIRE, LOW FIRE and
MODULAllNG FIRE
FIRING RATE CONTROLLER-a centrallar which p;::lSi
lions lhe firIng rate motor 10 automalically regUlate the
burner firing rate al a predetermined air-fuel ralio in accordance with load demand, II ma'1 p;::lSllion the air and fuel SUWI;8S for low fire or for high fire, or it may be a proportioning (mooulaling)lype which grao."al'lY varies the eir and tuel supplied wlchln limits to meet (he lOad
demand, Also see FIRING RATE MOTOR
FIRING RATE MOTOR-a modulating or a two-posilion (q::.en·closed) malar WhiCh p:::lSitions the tiring rale valve anOior Ihe damper in response to the firing rale controller,
FIRING RATE SWITCHING CIRCUIT -a circUit In a programmin\jl conlrol which switches external devices at predetermined limes 10 conlrol the firing rale 01 lhe bJrner
FIRING RATE VALVE-an automaUc control valve for reg.rlating the input of fuel to a burner in response 10 load demand Also called a Burner-Input Control yalve, Combustion Control Valve, Meterino Valve or Jh!Ql
\Iino Valve Also see BUTTERFLY, MODULATING, and MOTORIZEO VALVES
FIRST-OUT INDICATION-a device (usually a lamp) for each bur'ler in a mulliburner system The device Indi
cates the first burner having flame failure
FIRST·STAGE OIL VALVE-in oil burners wiln more lhar1
1 firing rate level (stage), the automatic safely shutoff valve which opens firslto admit the 1uel required for the lowest rale of corrtJostion In direct spark ignition sys'tams, the first stage may take the place of a gas pilot FLAME-the visible or other physical evidence of Ihe cnemical procsss 01' rapidly convening fuel end air into products 01 combustion
FLAME BlOW-OFF-the phenomenon which occurs when a llame moves awa:f from a burner, often result· ing in the flame being exlinguiStlEla A flame blows off when lhe air-fuel mix:ure leaveslhe burner af a velOCity greater than Ihe velocity wilh which the flame front pro
\jIress8S lhrough the mixture
FLAME CONDUCTIVITY -the abilit'1 01 the ionized gases
of a flame 10 conduct an electriC current
FlAME CURRENT -sea FLAME SIGNAL FLAME DETECTION SYSTEM-Ihe flame detector, flame signal ampliflS", and flame relay (In a flame safeQJard control) which logether delermine whether a sut
ficientflame is present 10 continue Ihe q::.erallon Of a burner
FlAME DETECTOR-the components of a fla:ne detection system which delect the presence or absence 01 a fJame Also see DETECTOR and FLAME ROO; and INFRARED OPTICAL, RECTIFICATION TYPE RECTlFYING PHOTOCELL and ULTRAViOLET FLAME DETECTORS
FLAME DETECTOR RELAY-a control consisting of a flame detection electronic network and a switching relay which pulls in when flame is detected This control
Trang 11is nor a primary control because it does not sequence
burner operation nor provide a safe start Check or
safety shuloown Do not confuse it with FLAME
RELAY
FLAME ENVELOPE-lhe confines (not necessarily
visible) of lhe comboslion process {Converting fuel and
air into products at combustion)
FLAME FAILURE ~ESPONSE TIME-the time interval
between the loss of name and the dr<:q:ling aut of Ihe
tJame relay in a flame safeguard control whlch then de
energizeS '{he automatic fuel valve(sj
FLAME FRONT-the plane along which combustion
starts or the base of the flame
FLAME PROPAGATION RATE-the rate at which a flame
- fronltravels through a corrbustible mixture or fuel and
air It is a function of air-fuel ratio mixture temperature,
and Ihe ambient pressure Also called burning velocity,
flame SPeed and flame velocity
FLAME RECTIFICATION-the phenomenon which
causes a name to conduct more currenl in one direc
tion than in Ihe other It,:s due to the ionizalio:'1 of air in
and around the flame and to the difference in area of
the electrodes in the flame enveiope (The ground ar9a
is at least 4 times the area at the flame rod.)
FLAME RECTIFIER PILOT-see PILOT BURNER
ASSEMBLY_
FLAME RELAY-the relay in a flame safeguard control
which pulls in when a flame or a condition simulalinga
flame, is detected It drops out on loss ot flame signal
causing Ihe flame safeguard control to shut down the
burner Do not confuse it with FLAME DETECTOR
RELAY
FLAME-RET~NTION NOZ+LE-a burner nozzle sur
rounded wilh small pOrts which act as pilots to relight
the main burner name il it blows off The velOCity
through the small ports is Jess, so the flame almost
never blows off at then'! Also called a stick-tight nozzle
FLAME ROD-a melal or ceramic rod projected into the
flame envelope to function as an electrode in a flame
detection circuil Also see CONDUCTIVITY FLAME
ROD SYSTEM and RECTIPfING FLAME ROD
FLAME SAFEGUARD CONTROL-a safely control which
provideS a means for starting the burner in the proper
sequence proving that lhe pilot or burner flame is
established, and supervising the flame during burner
operation safety snuldown occutS if Ihe pilot or burner
flame is not established or ilthe flame goes oul Also
see CUTOFF, IGNITION RETURN, and MODULAT·
ING ON-OFF, PRIMARY PROGRAMMING, RE·
CYCLING, and NONRECYCLING CONTROLS
FLAME SAFEGUARD SYSTEM-the set of equlpmenl
used to provide safe control of ourner operation This
usually includes the name safeguard control, the Ilame
- - - - I
I.><~:::::::::~:-· : GIOS¥~Y i?:,:·: ",o-,};}
detection system all controllers, all limits and intetlocks, all fuel valves, the ignition system, the firing rate conlrol system, and any other auxiliary aquipment FLAME SENSING ELEMENT - see FLAME DETECTOR and SENSOR
FLAME SIGNAL - the current measured al lhe meIer jack
of a flame signal amplifier in a name safeguard control The currenl is produced by the flame detector when II senses a flame
FlAME SlGNALAMPLIFIER~thepart of the flame delection system 'l'¥hich increases the lIame signal 10 a magnitLJje SUfficient to pull in the flame reray In the flame saleguard control TIle amplifier may be a permanent part at the flame safeguard contrOl, or It may be a replaceable, plug-in unit
FLAME SIMULATOR -a device used 10 substitute tot the presence 01 flame in a flame detection circuit II is used during trOUbleshooting, to check the performance of the flame delection system Flame simulators are avail· able for use wilh rectification or ultraviolet amplifiers In infrared systems, the flame Signal can be simulaled wllh a 'l'¥ire
FLAME SPEED-see FLAME PROPAGATION RATE FLAME VELOCiTY -see FLAME PROPAGATION RATE FLAMMABLE LIMITS-the maximum and minimum percentages of fuel in an air-fuel mixture that 'l'¥iU burn FLAP TYPE DAMPER-a damper consisting of 7 or more blades, each pivoled about 1 ec:li;;;le, and all linked together for simullaneous operation Also see OPPOSED and PARALLEL BLADE DAMPERS FLASHBACK-the phenomenon which occurs when a flame front moves back through a ourner nozzle (and lXlSSibly back to the air-fuel mixing painl) FlastOa.ck occurs because the flame pr~gation rate exceeds Ihe veloCity with which the air·fuel mixlure flows through the ourner nozzle
FLASH POINT -Ihe flash p:::tinl of a liquid is an in::lication
of the maximum temperature at 'l'¥hich it can be stored and handled 'l'¥ithout serious fire hazard
FLIP-FLOP CiRCUIT -a circuU which provides automatic aitemation between 2 possible circuit paths
FLOW CHARACTERISTICS - see VALVE FLOW CHARACTERISTIC
FLOW COEFFICIENT-see CAPACITY iNDEX
FLOW RATE-the amount at flUid passing a given paint per Uf1i! lime Also the luei input to a OUrner measured
in suitable unils; e.g.• cubic centimeters per minute, gallons per hOur, poundS per hour; referred to as the firing rate
FLUE-a duct or passageway for conveying the products
or combustion (flue gases) to the outer air
Trang 12FLUE COLlAR-the portion of an awliance desl\}"leCl10r
attachmenl of the chimney to the 1lue pipe Also see
FLUE PIPE
FLUE GAS-gaseous products of combustion in the flue
10 the stack
FLUE GAS LOSS-the sensible heat carried away by the
dry flue ~, and lhe .~nslble and latent heat carried
away by'the water vapor in the11ue gas Also referred 10
as stack loss·
FLUE PIP'e:-lhe duct connecting an appllance with the
vertical flue or a chimney; also called breaching or ~
cQlJneclor (A flue collar is the part 01 the awliance 10r
attaching the flue pipe.)
FlUID-'f3l"ly Slbstance that can flow: I.e., move and
char'lQe shape without separating when uroer pres
sure; 1iQ.lld or gas
FLUID POWER - Honeywell trademarl< tor the actuators
used wllh V5055 InckJstrial Gas Valves to provide a
1amlly 01 aulomatic safery shuloff valves; driven by a
1luid (usually oil) PJmpec:I by an electtlc motor
FORCED·AIR FURNACE-a central furnace equipped
with a 'Ian or blower to provide the primary means for
circulation 01 air
FORCED DRAFT -mechanically-produCed airflow into
and through the combustion chamt:er, blown in by a
fan or blower locatoo at the inlet air passage to the
furnace This air movement minimizes problems resull
ing from insufficient stack wind weather, and other
conditions
FORCED·DRAFT BURNER -a gas burner in which com·
bustion air is blown in by a molar driven Ian Commonly
called a Power Burner Examples are Aspirating Gun
Type, Mect)anical·Premix, and Zero-Governor
Burners Also see MECHANICAL·DRAFT BURNER
FORCED·DRAFT FAN-a 1an or blower that sUI=PlieS air
under pressure to the fuel burning equipment
FORCED VENTILATION - mechanically prodJcad air·
flow throug, a room or M area
FREQUENCY - the number of recurrences of a periodic
phenomenon in a unit of lime, usuallv expressed In
hertz (Hz)
FUEL-any material which is burned 10 SUl=Ply heat or
power
FUEL-AIR RATIO-see AIR-FUEL RATIO
FUEL OIL-any hydrocarbon oil as defined by Commer
cial Standard CS12 or ASTM 0396-1969
FUEL RICH-the ratio of air to fuel SUl=Plied to a furnace
which prOVides more tuel than the optimum air·1uel
ratio
FUll LOAD-the greatest load a piece of equipment is
designed to carry under specified conditions
FURNACE -an enClosed chant:ler or structure, including
a burner end cOlTtlustion chamber, which Is provided tor the colTt:lustlon 01 fuel The heat prodJced Is used tor healing a building or for processing materials Also see BATCH TYPE, CENTRAL CONTINUOUS, DOWN FLOW, DUCT, FORCED-AIR, HORIZONTAL INDUSTRIAL and UPFLOW FURNACES
FURNACE PRESSURE-the gauge pressure in a furnace combustion chamber The furnace pressure is said to t:e ~tt greater than atmospheric pressure, [l~: J jyj, tf less than atmospheric pressure, and ~ i1 ElQJ81 to atmospheric pressure
GAS-the fluid form of a SlhSlance In which It cen expand indefinitely a~ COrTPle1ely fill Its container; 10rm that is neither liquid nor solid; a vaj.X)l"; any mixture 01 inflammable gases used for lighting or heating Also see BLAST FURNACE, FLUE, UOUEFIED-PETROLEUM, MANUFACTURED, MIXED, NATURAL, and ZERO
GAS
GAS BURNER-a burner 10r use with gaseous fuel Also see ATMOSPHERIC, MECHANICAL-DRAFT, RAW GAS, PARTIAL-PREMIX, PREMIX INSHOT, and UPSHOT BURNERS
GAS MIXER -a device 10r mixil"l;;l gas and air such as a 1an, aspirator, or inspirator In an injection type burner,
it is the combination 01 mixer head, mixer throat, and mixer tube
GAS-OIL BURNER-a burner capable of burning either
gas or oil-some types can burn both simultaneously Also see COMBINATION BURNER
GAS-PRESSURE REGULATOR-a device for controlling and maintaining a uniform gas pressure
GAS VENT -the piping end Mings used to convey flue
gases to the outside atmosphere
GAUGE PRESSURE-the difference between atmospheric pressure and [he absolute pressure t:einlOl measured; abbreviated: psig
GLOBAR-a conductive ceramic 1rom which high tem· perature flame rods are made It has a maximum tem· perature rating of 2600 F [1425 Cl
GRACE PERIOD-the lime required to build up an explOsive charge in a burner; the maXimum lime the unigniled cOn"Oustible reactants can salely be pul into aOO retained in a combLstion chamber
GRADES OF FUEL OIL-voluntary commercial standards recommended by the U.S Bureau of Standards for dlnerenl classi1icalion of fuel oils, based on characteristics such as speCifiC graviry and viscosity GRAVITY FEED-sul=P1ying oil to a burner from a graVity tank using the force of graviry
Trang 13GROUND-a metallic connection with the earth 10 estab
lish 't!round potential
G!.Jlp!;.-see VALVE GUIDE
GUN TYPE BURNER-a power burner in w!""lch a fan, or
blower, blows air al high velocity past lurtlulators The
gas, at regulaled pressure, is released into the turbu
lent airstream -typically Irom a ring at Ihe mouth of the
purMer (in which case it is also called a Ring Burner)
The 'tJ3S es~s through orific85 around the periphery
at,lhe ring Gas 03:nd air are adjusted simultanElOllSly to
maintain Ihe proper air-fuel ratio as the firing rate
changes In Hiah-Pressure Gun Burners, the gas is
ejected al pressures l4) to 15 psi from spuds located in
the center of Ihe turbulent airstream instead of at the
putside Also see FORCED-DRAFT ancI RAW GAS
BURNERS
HEAD-see BURNER HEAD
HEADER - a manifold or supply pipe to which a nurrber of
branch pipes are connecled
HEAT BLOCK-insulation material installed between Ihe
cell mount of an infrared flame deteclor and the sight·
in't! pipe to reduce heat conduction to the cell
HEATER-an apparalus for giving heal or warmth; a fur·
nace, oven, stove, radialor, or similar device Also see
AIR, BOOSTER, CENTRAL DIRECT·FIRED, EXTER·
NAL, INDIRECT-FIRED, INTERNAL, MAKEUP AlR
RADIANT·TUBE TYPE SPACE, ancI UNIT HEATERS
HEAT EXCHANGER-any device tor trans1erring heat
trom ono rn9dium to another A direct heat exchanger
is a self-contained device which transfers heat gener
ated in the combustion charmer directly Ihrough lhe
walls of Ihe heat exchanger to lhe heatin;t medium An
Indirect heat exchanger contains a heatin't! medium
and Iransfers heat 10 anolher mediurn separately con
rained in close cbntacf with or directed through the heat
exchanger
HEATING MEDiUM-air, sleam waler, or ~heal transfer
f,uids - used 10 trans1er heat
HEATING SURFACES-all surfaces which Iransmit heat
direCtly from the flame or flue gases to lhe medium ba
ing heated
HEATING VALUE- the heat released by the combustiOl'l
01 a unit quantify of a fuel, measured in calories or Btu
HEAVY FUEL OIL-gradeS 5 and 6, used in commercial
and industrial burners; generally rsquire preheating
Heating values range trom 146,600 {o 155.900 Blu per
HIGH-PRESSURE GUN BURNER-see GUN TYPE BURNER
HIGH PRESSURE SWITCH -see PRESSURE SWITCH HIGH TEMPERATURE BOILER (hoI waler)-a boiler furnishinQ hot water at temperatures exceeding 250 F
1121 C] or at pressures exCeeding 160 pounds per square inch (psig
HIGH-VOLTAGE CiRCUIT -a circuit inVOlving a polantial
of more than 600 volts: not defined by Underwrilers Laboratories Inc
HORIZONTAL BOILER-see WATER-TUBE BOILER HORIZONTAL FURNACE-a forced-air, central furnace desi~ with essentially norizontal airflow
HORIZONTAL·RETUAN·TUBE (HRT) BOILER-see FIRE-TUBE BOILER
HORIZONTAL ROTARY OIL BURNER-see ROTARY OIL BURNER
HORSEPOWER (hpj-a unit of power eqJalto 550 bJt pounds per secord, 33,000 foot jXlUnds pel miAJte, Ot'
HOT REFRACTORY SATURA110N TEST -a test, tor a nama safeguard control using an infrared flame deleclOt', to make cenain that radiation trOll hal refractory ooes nol mask Ine fliCkering radlalion c1lhe nama itself Also called HOT REFRACTORY OVERRIDE TEST
71-97558-1
Trang 14IGNITER-any electrical or macranical device and re
Imed equipmanl used 10 I~n\te a fuel-aIr midure Also,
a burner (like a pilot) USing gas or 01110 ignite very large
gas, Oil, or pulverized coal burners In very large waler'
tlbe boilers [normally field-erected)
IGNmON lhe acl of starting c(J('l'i)usllon Also see
AUTOMATIC, CONTINUOUS, DIRECT SPARK,
ElECTRIC, INHERENT, INTERMITTENT, INTER
RUPTED, MANUAL PROVED, PROVED SPARK,
TO~€?H, and UNPROVED IGNITION
IGNmON'ELECTRODE-a metal conciJctor USOO [ogan
erale a spark across a narrow gap to grl:JJnd in order to
IlJl1ite a fuel·air m'lxlu'8
IGNlT10N INTERFERENCE- electrital noise, caused by
ignition currant feeding Ihroug, the flame 10 the llama
rod, which is superirrposed on the f1ame si~1 ~Iame
rod detectors only) lhe interference may be ad:::lilive or
subtractive (II may increase or decrease the flame Sig
nal.) S!.btractive interference may cause the flame (e
lay to drop out; severe addilive interference may
damage Ihe flame relay unless an arc gap protector is
In lhe circuij
IGNFTlON1NTEAFERENCE TEST-a test to make
certain lhal ilJl1ition current is not interfering with the
prcper q::.eralion of a flame rod See IGNITION
INTERFERENCE
IGNITION RETURN-immediate restoralion of ignilion
without pr",ignilion purging or interlock checks, af1er
loss of the rn.a,in'burnef flame.,lf Ihe main burner flame
is not re-established, safety shutdown occurs Also
called~
lGNmON SPARK RESPONSE TEST -a lest for a flame'
seleQ.Jard conlrol using an ultraviolet flame detector, to
make,certaln lhat the ignition spark Is not actuating the
trame relay
IGNmON TEMPERATURE-lhe minimum lemperature
al which combuStion becomes self-sustaining
IGNITION TIMING -a period of lima during which ig"liliOn
flleans are on This provideS a means or eslablishing
a"'ld stabililing Ihe flame to ensure prq::.er burning of
lhe fuel when the main burner is firing
IGNmON TRANSFOAMER-a deviCe which prOVides a
hig,-voflage spark which will cause Ignition
IGNmON TRIALS -a period of lime wring which the pilot
and main tlJrner musl be Igliled (main bUrner only If
t.sIng direct spark Igr'lmon) Also see PILOT FLAME
ESTABUSHING PERIOD and MAIN BURNER
of the blower rousing The walls lend to channel the air
so that most of il fiows out through the lips of the blades, bul some aIr stips out slOOways from be/ween
the bladeS end short-circuits baCk 10 the impeller inlet
A closed lf1l)eller has tover plate discs allachsd /0 lhe sides of the blades, and thus short·circuiting is minimized
INCANDESCENCE-the state of a malerial with SUCh a hiOh t~ra/(J(e tnat it gives off fight
INCH OF MERCURY -a ,il of p-essure aqual 10 the
pressure exened by a column of mercury' InCh high at
568 level and at a t~rature of 0 C132 FJ,
INCH OF WATER-a unit of pressure equal to the pressUfeexerted by a column ot liquldwaler 1 inch high at sea level anc:l at a t9l"fl)8rature of4 C (3S.2 F] INCOMPLETE COMBUSllON-cort'tlustion in which the fuel is only partially t:lJfnecl and is capable of being
bUrned further under P'~ cordilions It results from
an inadequate amount of air for the c,.Jantity of fuel provided II cen also occur, even in excess air conditions, if mixing is poor andlor the flame is chilled below Ihe ignilion tef1l)erature before lhe full combustion reaction can take place An example Is lhe burning of carbon, prodJcing carbon monoxioo (CO); with mora air, carbon dioxide (CO.) WOUld result
INDEPENDENT UGHTOFF-separate ignition of each burner in a multlburner syslem Each burner can be
started up or shut down by itself
INDIRECT·FiRED HEATER-a heater in which the products of combuStion (flue gases) are not lTlixed with the medium being healed AlSO see INDIRECT-FIRED EXTERNAL, INDIRECT-FIRED INTERNAL lind
R;z.,::llAN'T- TUBE TYPE HEATEAS
INDIRECT-FIRED EXTERNAL HEATER -any oven heal
ing system in which the oven all1lOSpl18re is kept separate from the combustion gases, and in which the
burners and cornbus!ion chamber are outside at the oven chamber There are 3 types;
1 Recirculaling-oven atmosphere is returned to
INDIRECT-FIRED INTERNAL HEATER any oven healIng system in which the oven allT'QSphare is kepl separale from the combustion gases, anc:l in which the burn&rs are conlainea In gas-ti~t radiators within the oven chamber Thera are 2 ~;
Trang 151 Explosion resisting-constructed to withstand
explosion pressure from ignition 01 a gas'air mix
ture in the radiators
2 Nonexploslon resisting-with gas·tighl radialors
which are not designed to withstand an internal
explosion
INDUCED AIR-air which flows inlO a furnace because
the furnace pres:;ure is less than atmospheric pres
Sure This includes air brought inlo (I furnace by
emr(l.inmenl' in' a high velocity stream
INDlk::ED DRAFT -air movemenl into and through the
combustlon chamber (l.nd breaChing, procluced by (I
pa;ni(l.1 vacuum within the cot1"tluslion chamber crealed
t/IJ a fan althe outlet of the chamber
INDUCED-DRAFT BURNER-a gas burner which uses
an induced dr(l.ft to bring in combustion air Also see
INDUCED DRAFT and MECHANICAL·DRAFT
BURNER
INDUCED-DRAFT FAN -a fan or blower that proc:k rces a
nega.tive pressure In the combuslion chamber, causing
(I suction which draws in air
INDUCTIVE LOAD-a lagging load: (I 103d'that is pre
dominantly inductive, so that the alternating current
lags behind the allerrlating vollage, i.e., the current
does not change direction until after the vOltage does
An example is an ignition transformer
INDUCnVE PICKUP-the generation of a voltage in one
conductor t/IJ induction- from another nearby
conductor
INDUSTRIAL FURNACE-a process type heater which
changes the charaC1erlslics of the material being proc
essed II Is usually C1J6rated at temperatures above
1200 F
INDUSTRIAL OVEN-a process type healer normally
used for drying It is generally operated at terf1)Elra
tures from 400 F to 800 F
INERnNG-introclucing an Inen medium inlo a furnace,
pulverizer, or other enclosure to reduce the ~
content of the resuJllng mixture below the limits 01
nammabilily
INERTS-noncombustible substances in a fuel
INFRARED FLAME DETECTOR-a detector lhat re
sponds to Ihe infrared radiation (wavelength between
0.75 and 1000 microns) emitted by a flame Also see
LEAD SULFIDE CELL
INFRARED (IR) RADIAnON-invisible, electromagnetic
waves ot tow frequency (long wavelength between 0.75
and 1000 microns) They are generated by thermal al;li·
tation and radiated t/IJ everything with a terTf.lElralure
above absolute zero [minus 273 C); the holler the c:tr
ject, the greater Ine Infrared radiation Infrared radia
tion corrprises about 90 percent of the light spectrum,
ranging from the low end up to Ihe while visible light
range Also see HOT REFRACTORY HOLD-IN TEST and HOT REFRACTORY SATURATION TEST INHERENT IGNITION-feed)ack of pan of the heat generated by the flame 10 1't1"lte more of the combustible mixture; il must !<eep lhe fire going after l't1"ition Is terminated
INJECTION BURNER-see INS PIRATING BURNER INPUT COMBUSTION CONTROL-see FIRtNG RATE CONTROLLER
INRUSH-in a solenoid or coil, the steadV-state current drawn from the line when the armature is In its maximum cpen position Allowable Inrush can be up to 10 times the pilOI ci.Jly rating (running currenl)
INSHOT BURNER-a gas burner In which the gas is delivered from lhe side(s) of the cot1"tluslion chamber, resulting in a horizontal flame
INSPIRAnNG BURNER-a gas burner which uses venturi action to bring in combustion air Also called an Injection Burner or Venturi Mixina Burner Also see ATMOSPHERIC BURNER and VENTURI
INSPIRATOR MIXER-a mixing device in which a jel 01 gas is used to entrain primary air at a rate proportional
to the gas flow rate Also see INSPIRATING BURNER INTEGRAL TANK-any fuel tank furnished by the manufacturer as a comfX)OEl(ll part oflhe complete assembly; eilher allached [0 the awliance, cr intended for separate mounting adjacent to the awliance
INTERLOCK-an automatic conlroUer or switch whiCh monitors the physical state of a rElQJired condition and furnishes proof to the tlame safeguard control fhalthe condition is proper for burner operation to start or to continue Also see HIGH FIRE, LOCKOUT, LOW FIRE, PREIGNlnON, RECYCLE, RUNNING, START, and VALVE-CLOSED INTERLOCKS
[NTERMITIENT IGNITION-ignilion t/IJ an ener~ source Which is automallcally energized each time there is a call for heat, and which Is maintained ciJring the entire run periocl This ensures that a means of igniting the Incoming fuel will always be present
INTERMITIENT PILOT -a pilot automatically ignited each lime there is a call for heat and maintained CiJrlng the entire run periocl It is shut off with the main burner
at the end Of heat demand
INTERNAL HEATER-a heater in which Ihe burner(s) and combustion cl"\arl1)er are within the oven charrber and
in contact with the medium being heated Also see 01· RECT-FIRED INTERNAL and INDIRECT-FIRED INTERNAL HEATERS
INTERNAL-MIX OIL BURNER -see ATOMIZING OIL BURNER
INTERRUPTED IGNmON-iglilion t/IJ an energy source Which is automatically energized each lime there i5 a
Trang 16eel! for heat, and cut off automalically after ftame Is
proved or at the end of a predelermlned lime
INTERRUPTED PILOT - a pilei automalleally Ignited
Mcn lime there Is a call for heal end cul off automati
cally at lhEl end of the maIn burner ftame-establishlng
period
IONIZATION - a proc~ by which electrons are detached
frO'lTl atoms or molecules, tnus originating ions and free
elEiclrons Thi~ is achieved by collisions or by high
Eine~~ radiation
IRIS SUDE-a thin plate with a small aperturEi Example:
the Yti13A Stack Smoke Deleclor provides a selection
of iris slides wilh dltl"rent sized apertures to permit
1i~1 source-to-sansor distances of 1-1{210 10 feet
,',
ISOLA-lED UMllED SECONDARY CIRCUIT-a circulI of
limited energy derived from an i$Olaled secondary
winding of a transformer having a maximum capacity Of
100 voll-arrperes 011<:) and an open circull secondary
\IOrtagE! raUng not exceecMg 1000 Volts
JEWF All.OY "K~ - a chromium-aluminum aUoy iron
wire which is resislanlto OXidation up to 2200 F [1200
CJ; used for flame (<Xis in flame detectors
JUMPER-8 short length of wire used to complete a cir_
cuit temporarily or 10 bypaSS par! of a circuil Also, the
aclion of using a jumper
KANTHAL A-l-a staInless Sleel alloy used in the manu
facture of flame rOds II has a mal(imum continuous
cperating temperature raling of 2462 F [1350 C]
KNOCKOUT - a removab'le portion in the side of a bol( or
cabinet During Installation, it can be readily taken out
with a hammer, screwdriver, or pliers so wires, cables,
or fillings can be allached
LA-RGE PORT BURNER-see SPREADER BURNER
LEAD SULFIDE CEll.-an infrared sensor using lead sui·
fide (PbS) as the sensing matarlal The resistance of
lead sulfide decreases when exposed 10 infrared radia
tion, resulting in Increased current now
lEAKAGE PATH-a palh, norma:ly 01 high resistanCe,
through whict] an undesirable slray current (leakage
current) flowS to ground; caused by buildup of moisture, 5001, or accumUlated dirt
LEAN MIXTURE-an air-fuel mixlure In which an el(cess
of air Is SLflPlied in pr~rtlon 10 the amounl 01 fuel Also see AIR RICH
UFT -valve slam travel
UFTING FLAMES - flames which lift from or blow off llle pilot or main burner ports Caused by an overrating of lhe burner, too hard a primary air adjustmenl, or bolh UGHT FUEL OIL - grades 1 and 2 which are distiHate fuel oils used predominantly in etmeslic heating equipment Heating values range from 132,900 to 141,800 Btu per gauon
UGHTOFF- the proceciJre of igniting a burner or sysfem
of burners Also see INDEPENDENT, SEQUENTIAL, and UNISON UGHTOFF
UMlT -a control/er which continuously monitors a condition (such as temperature, pressure, or liquid levet) in a conlrolled medium arv::l rBSjX)rw:iS Immediately to shut
down the system ~ a dangerous, predelermined condi· tion occurs II is normally set beyOnd the operatinQ rang& of the coni rolled equipmenl
LIMIT ACTION-the contacls of a limit controller ~ to shut down a burner (ard in some instances make an alarm circuit) because of an abnormal or unsafe condition
UNE-acolloquial-lerm for poW91 line; the cQr'ductors carrying powEir from llle generating equipment LINEAR CHARACTERISTIC-a valve flow Characteristic, apprQl(imaling a sltaigtlf line relationsh~, which raSllUS In equal volume Changes for equal movements of
the valve stem, regardless of the perCentage or valve cpening
LINER-see RADIATION SHIELD
llNE- VOLTAGE CiRCUIT-a circuit involving a potential of more than 30 valls and tess than 600 volts (generally 120 or 240 volts ac) Underwriters la!:oratorias Inc a/so catls thiS· at1igh-vouage circuit
LINING -Ihose interior surfaces of a cotT1l:lJslion chamber which are exposed 10 combustion during use of the device
LINKAGE-a mechanical arrangement for lrans1errirQ rootion in a desired manner, conSisting of SOlid pieces with movable joints The connections Ihrough which ij"I actuator opens closes, or positions a valve or damper: usually consists of a push roo, 2 crank arms, and 2 ball pints
LJQUEFiED-PETRQlEUM (LP) GAS -fuel gases inch.ning commercial propane /predominantly propane or propylene) or commercial bulane (predominantly bJlane, isobulane, ar4Ior butylene), which ar<a sold in metal bollies under pressure as a liquid and called bOttled cas These gases are higher hydrocarbon gases