7
G5-991-400B
G/H-25 Installation
Minimizing Acceleration Head and Frictional Losses
To.minimize.the.acceleration.head.and.frictional.losses:
•.. Keep.inlet.lines.less.than.3.ft.(1.m).long
•.. Use.at.least.1-1/.in..(38.mm).I.D..inlet.hose
•.. Use.soft.hose.(low-pressure.hose,.non.collapsing).for.the.
inlet.lines
•.. Minimize.fittings.(elbows,.valves,.tees,.etc.)
•.
Use a suction stabilizer on the inlet.
Net Positive Suction Head
NPSHa. must. be. equal. to. or. greater. than. NPSHr.. If. not,. the.
pressure.in.the.pump.inlet.will.be.lower.than.the.vapor.pressure.
of.the.fluid.—.and.cavitation.will.occur.
Calculating the NPSHa
Use.the.following.formula.to.calculate.the.NPSHa:
NPSHa.=.Pt.+.Hz.-.Hf.-.Ha.-.Pvp
where:
Pt.=.Atmospheric.pressure
Hz.=.Vertical.distance.from.surface.liquid.to.pump.centerline.(if.
liquid.is.below.pump.centerline,.the.Hz.is.negative)
Hf.=.Friction.losses.in.suction.piping.
Ha.=.Acceleration.head.at.pump.suction
Pvp. =. Absolute. vapor. pressure. of. liquid. at. pumping.
temperature
NOTES:
•. In. good. practice,. NPSHa. should. be. . ft. greater. than.
NPSHr
•. All.values.must.be.expressed.in.feet.of.liquid
Atmospheric Pressure at Various Altitudes
Altitude
Pressure
Altitude
Pressure
(ft)
(ft of H
2
O)
(ft)
(ft of H
2
O)
.
0.
33.9.
1500.
3.1.
.
500.
33.3.
000.
31.5.
.
1000.
3.8.
5000.
8.
Discharge Piping
NOTE: Consult the Factory before manifolding two or more
pumps together.
Hose and Routing
Use.the.shortest,.most-direct.route.for.the.discharge.line.
Select.pipe.or.hose.with.a.
working pressure
rating.of.at.least.
1.5.times.the.maximum.system.pressure..EXAMPLE:..Select.a.
1500-psi.W.P.-rated.hose.for.systems.to.be.operated.at.1000-
psi-gauge.pressure.
Use.about.6.ft.(1.8.m).of.flexible.hose.between.the.pump.and.
rigid.piping.to.absorb.vibration,.expansion.or.contraction.
Support.the.pump.and.piping.independently..Size.the.discharge.
line.so.that.the.velocity.of.the.fluid.will.not.exceed.7-10.ft/sec.
(-3.m/sec):.
For.pipe.in.inches:..Velocity.(ft/sec)..=..0.408.x.GPM/Pipe.ID
.
.
For.pipe.in.mm:..Velocity.(m/sec)..=..1..x.LPM/Pipe.ID
.
.
Pressure Regulation
Install a pressure regulator or unloader in the discharge
line.
.Bypass.pressure.must.not.exceed.the.pressure.limit.of.
the.pump.
Size.the.regulator.so.that,.when.fully.open,.it.will.be.large.enough.
to.relieve.the.full.capacity.of.the.pump.without.overpressurizing.
the.system.
Locate.the.valve.as.close.to.the.pump.as.possible.and.ahead.
of.any.other.valves.
Adjust.the.pressure.regulating.valve.to.no.more.than.10%.over.
the.maximum.working.pressure.of.the.system..Do.not.exceed.
the.manufacturer’s.pressure.rating.for.the.pump.or.regulator.
Route.the.bypass.line.to.the.supply.tank,.or.to.the.suction.line.
as. far. as. possible. from. the. pump. (to. reduce. the. chance. of.
turbulence.and.cavitation).
If.the.pump.may.be.run.for.a.long.time.with.the.discharge.closed.
and.fluid.bypassing,.install.a.thermal.protector.in.the.bypass.line.
(to.prevent.severe.temperature.buildup.in.the.bypassed.fluid).
CAUTION: Never install shutoff valves in the bypass line or
between the pump and pressure regulator or relief valve.
Provide.for.permanent.or.temporary.installation.of.a.pressure.
gauge.to.monitor.the.discharge.pressure.at.the.pump...
For.additional.system.protection,.install.a.safety.relief.valve.in.
the.discharge.line,.downstream.from.the.pressure.regulator.