Data Sheet

Bulletin 71.2:627F
5
Principle Operation
The superior performance of a Type 627F regulator is
due to the amplifying effect of the pilot and the two-path
control system (Figure 2). Changes in outlet pressure
actquicklyonthemainregulatordiaphragmwhich
repositions the valve disk to provide fast response to
systemchanges.Simultaneously,thepilotamplies
system pressure changes to position the main
regulator valve disk for precise pressure control.
Inlet pressure is used for the pilot supply pressure.
Ifdownstreamowincreases,loweringtheoutlet
pressure below the regulator setpoint, pressure on the
pilot diaphragm and the lever side of the main regulator
diaphragm decreases. The pilot opens to supply the
requiredloadingpressureincrease.Theincreased
loading pressure from the pilot overcomes the main
regulator spring force, and the main regulator valve
diskmovesfartheropentosupplytherequiredow.
When downstream pressure increases due to lowered
demand, greater pressure is registered on the pilot
diaphragm and the lever side of the main regulator
diaphragm.Thepilotcloses,andtheexcessloading
pressure bleeds off to downstream, through the pilot
restriction. With the lower loading pressure, the spring
canmovethemainregulatordiskclosertotheorice.
Undernoowconditions,theexcessloadingpressure
bleeds through the pilot restriction to the downstream
system until the loading pressure and outlet pressure
equalize.Themainvalveisclosedbythespringand
the bleed stops.
Installation
The Type 627F regulators may be installed in any
position,aslongasowwillbeinthesamedirection
as that indicated by the body arrow. These regulators
should be installed so that their spring case vents are
protected from anything that might clog them.
Emerson™ provides an instruction manual with
every regulator shipped. Refer to this for complete
installation, operation, and maintenance instructions.
Included is a complete listing of individual parts and
recommended spare parts.
Overpressure Protection
Overpressurizinganyportionofaregulatororassociated
equipmentmaycausepersonalinjury,leakage,or
property damage due to bursting of pressure-containing
partsorexplosionofaccumulatedgas.
To avoid overpressure, provide appropriate pressure
relieving or pressure limiting devices to ensure that
noneofthelimitsinthespecicationssectionis
exceeded.Regulatoroperationwithinratingsdoes
notpreventthepossibilityofdamagefromexternal
sources such as debris in the pipeline. Inspect the
regulator for damage after any overpressure condition.
Refertothereliefsizingcoefcientsinthe
specicationstableandtheCapacityInformation
sectiontodeterminetherequiredexternalrelief
valve capacity.
Capacity Information
Natural gas regulating capacities at selected inlet
pressures and outlet pressure settings are given in
Tables6through8.FlowsareinSCFH(60°Fand
14.7psia)of0.6specicgravitynaturalgas.To
determinetheequivalentcapacitiesforothergases,
multiply the table capacity by the following appropriate
conversionfactor:0.775forair,0.789fornitrogen,
0.625forpropane,or0.548forbutane.Forgasesof
otherspecicgravities,multiplythegivencapacityby
0.775,anddividebythesquarerootoftheappropriate
specicgravity.
Then, if capacity is desired in normal cubic meters
per hour (Nm
3
/h)at0°Cand1.01325bar,multiply
SCFHby0.0268.
Todeterminewide-openowcapacitiesforreliefsizing
use the following formula:
where,
C
1
= C
g
/C
v
(seeSpecicationstable)
C
g
 = Gassizingcoefcient(seeSpecicationstable)
 G = Gasspecicgravity(air=1.0)
P
1
= Valve inlet pressure, psia
P = Pressure drop across valve, psi
 Q = Gasowrate,SCFH
 T = Absolutetemperatureofgasatinlet,°Rankine
To obtain the published capacities, the inlet and outlet
pipingshouldbethesameastheregulatorsize.
Q = C
g
P
1
SIN DEG
520 3417 P
GT C
1
P
1