Dresser Universal RAI Owner's manual

The original ROOTS blower still leads the way™
Universal RAI®, URAI-DSL,
URAI-J™-DSL, URAI-G™and
Metric Series
Installation, Operation & Maintenance
Contents
Information Summary ...........................................................1
Safety Precautions................................................................3
Operating Limitations............................................................3
Installation ........................................................................ 4-6
Technical Supplement for URAI-G blowers ...........................7
Lubrication .................................................................8, 9, 17
Operation ...........................................................................10
Troubleshooting..................................................................11
Inspection & Maintenance...................................................12
Figures ......................................................................... 13-16
Tables .......................................................................... 16-17
Assembly Drawings ...................................................... 18-23
Parts List ...................................................................... 24-25
Basic Connection & Drive Shaft Information.................. 26-28
oCheck shipment for damage. If found, file claim with
carrier and notify Roots.
oUnpack shipment carefully, and check contents against
Packing List. Notify Roots if a shortage appears.
oStore in a clean, dry location until ready for installation.
Lift by methods discussed under INSTALLATION to avoid
straining or distorting the equipment. Keep covers on
all openings. Protect against weather and corrosion if
outdoor storage is necessary.
oRead OPERATING LIMITATIONS and INSTALLATION
sections in this manual and plan the complete installation.
oProvide for adequate safeguards against accidents to
persons working on or near the equipment during both
installation and operation. See SAFETY PRECAUTIONS.
oInstall all equipment correctly. Foundation design must be
adequate and piping carefully done. Use recommended
accessories for operating protection.
oMake sure both driving and driven equipment
is correctly lubricated before start-up. See
LUBRICATION.
oRead starting check points under OPERATION. Run
equipment briefly to check for installation errors and make
corrections. Follow with a trial run under normal operating
conditions.
oIn event of trouble during installation or operation, do
not attempt repairs of Roots furnished equipment. Notify
Roots, giving all nameplate information plus an outline
of operating conditions and a description of the trouble.
Unauthorized attempts at equipment repair may void
Roots warranty.
oUnits out of warranty may be repaired or adjusted by
the owner. Good inspection and maintenance practices
should reduce the need for repairs.
NOTE: Information in this manual is correct as of the date
of publication. Roots reserves the right to make design or
material changes without notice, and without obligation to
make similar changes on equipment of prior manufacture.
For your nearest Roots Office, dial our Customer Service Hot
Line toll free; 1 877 363 ROOT(S) (7668) or direct 832-590-
2600.
Do These Things To Get The Most From Your ROOTS™blower
ISRB-2002 rev. 0710

UNIVERSAL RAI®, URAI-DSL, URAI-G and Metric Series | 3
Safety Precautions
It is important that all personnel observe safety precautions to
minimize the chances of injury. Among many considerations,
the following should be particularly noted:
• Blowercasingandassociatedpipingoraccessories
may become hot enough to cause major skin burns on
contact.
• Internalandexternalrotatingpartsoftheblowerand
driving equipment can produce serious physical injuries.
Do not reach into any opening in the blower while it is
operating, or while subject to accidental starting. Protect
externalmovingpartswithadequateguards.
• Disconnectpowerbeforedoinganywork,andavoid
bypassing or rendering inoperative any safety or protec-
tive devices.
• Ifblowerisoperatedwithpipingdisconnected,placea
strong coarse screen over the inlet and avoid standing in
the discharge air stream. CAUTION: Never cover the
blower inlet with your hand or other part of body.
• Stayclearoftheblastfrompressurereliefvalvesandthe
suction area of vacuum relief valves.
• Usepropercareandgoodproceduresinhandling,lifting,
installing, operating and maintaining the equipment.
• Casingpressuremustnotexceed25PSI(1725mbar)
gauge. Do not pressurize vented cavities from an
externalsource,norrestricttheventswithoutfirst
consulting Roots.
• Donotuseairblowersonexplosiveorhazardousgases.
• Otherpotentialhazardstosafetymayalsobeassociated
with operation of this equipment. All personnel working
in or passing through the area should be trained to
exerciseadequategeneralsafetyprecautions.
Operating Limitations
A ROOTS™blowerorexhaustermustbeoperatedwithin
certain approved limiting conditions to enable continued
satisfactory performance. Warranty is contingent on such
operation.
Maximumlimitsforpressure,temperatureandspeedare
specified in TABLE 1 for various models & sizes of blowers &
exhausters.Theselimitsapplytoallunitsofnormalconstruc-
tion, when operated under standard atmospheric conditions.
Be sure to arrange connections or taps for instruments,
thermometers and pressure or vacuum gauges at or near
the inlet and discharge connections of the unit. These, along
with a tachometer, will enable periodic checks of operating
conditions.
PRESSURE – The pressure rise, between inlet and dis-
charge,mustnotexceedthefigurelistedforthespecificunit
frame size concerned. Also, in any system where the unit inlet
isatapositivepressureaboveatmosphereamaximumcase
ratingof25PSIgauge(1725mbar)shouldnotbeexceeded
withoutfirstconsultingRoots.Nevershouldthemaximum
allowabledifferentialpressurebeexceeded.
On vacuum service, with the discharge to atmospheric
pressure, the inlet suction or vacuum must not be greater
than values listed for the specific frame size.
TEMPERATURE–Blower&exhausterframesizesareap-
proved only for installations where the following temperature
limitations can be maintained in service:
• Measuredtemperaturerisemustnotexceedlisted
values when the inlet is at ambient temperature. Ambient
is considered as the general temperature of the space
around the unit. This is not outdoor temperature unless
the unit is installed outdoors.
• Ifinlettemperatureishigherthanambient,thelisted
allowable temperature rise values must be reduced by
2/3 of the difference between the actual measured inlet
temperature and the ambient temperature.
• Theaverageoftheinletanddischargetemperaturemust
notexceed250°F.(121°C).
• Theambienttemperatureofthespacetheblower/motor
isinstalledinshouldnotbehigherthan120°F(48.8°C).
SPEED–Theseblowers&exhaustersmaybeoperated
atspeedsuptothemaximumlistedforthevariousframe
sizes. They may be direct coupled to suitable constant speed
drivers if pressure/temperature conditions are also within
limits.Atlowspeeds,excessivetemperaturerisemaybea
limiting factor.
Special Note:Thelistedmaximumallowabletemperature
riseforanyparticularblower&exhaustermayoccurwell
beforeitsmaximumpressureorvacuumratingisreached.
This may occur at high altitude, low vacuum or at very low
speed. The units’ operating limit is always determined by the
maximumratingreachedfirst.Itcanbeanyoneofthethree:
Pressure, Temperature or Speed.

4 |Dresser Roots
Installation
ROOTSblowers&exhaustersaretreatedafterfactory
assembly to protect against normal atmospheric corrosion.
Themaximumperiodofinternalprotectionisconsideredtobe
one year under average conditions, if shipping plugs & seals
are not removed. Protection against chemical or salt water
atmosphere is not provided. Avoid opening the unit until ready
to start installation, as corrosion protection will be quickly lost
due to evaporation.
Ifthereistobeanextendedperiodbetweeninstallation
and start up, the following steps should be taken to ensure
corrosion protection.
o Coatinternalsofcylinder,gearboxanddriveendbearing
reservoirwithNox-RustVCI-10orequivalent.Repeatonce
ayearorasconditionsmayrequire.Nox-RustVCI-10
is petroleum soluble and does not have to be removed
before lubricating. It may be obtained from Daubert
Chemical Co., 2000 Spring Rd., Oak Brook, Ill. 60521.
o Paintshaftextension,inletanddischargeflanges,and
allotherexposedsurfaceswithNox-RustX-110or
equivalent.
oSeal inlet, discharge, and vent openings. It is not recom-
mended that the unit be set in place, piped to the system,
andallowedtoremainidleforextendedperiods.Ifanypart
isleftopentotheatmosphere,theNox-RustVCI-10vapor
will escape and lose its effectiveness.
o Protectunitsfromexcessivevibrationduringstorage.
oRotate shaft three or four revolutions every two weeks.
oPrior to start up, remove flange covers on both inlet and
discharge and inspect internals to insure absence of rust.
Check all internal clearances. Also, at this time, remove
gearboxanddriveendbearingcoverandinspectgear
teeth and bearings for rust.
Because of the completely enclosed unit design, location
of the installation is generally not a critical matter. A clean,
dry and protected indoor location is preferred. However,
an outdoor location will normally give satisfactory service.
Important requirements are that the correct grade of lubricating
oilbeprovidedforexpectedoperatingtemperatures,andthat
the unit be located so that routine checking and servicing can
be performed conveniently. Proper care in locating driver and
accessory equipment must also be considered.
Supervision of the installation by a ROOTS Service Engineer is
notusuallyrequiredfortheseunits.Workmenwithexperience
in installing light to medium weight machinery should be able to
produce satisfactory results. Handling of the equipment needs
to be accomplished with care, and in compliance with safe
practices. Unit mounting must be solid, without strain or twist,
and air piping must be clean, accurately aligned and properly
connected.
Bare-shaft Units: Two methods are used to handle a unit
without base. One is to use lifting lugs bolted into the top of
the unit headplates. Test them first for tightness and fractures
by tapping with a hammer. In lifting, keep the direction of cable
pull on these bolts as nearly vertical as possible. If lifting
lugs are not available, lifting slings may be passed under the
cylinder adjacent to the headplates. Either method prevents
strainontheextendeddriveshaft.
Packaged Units: When the unit is furnished mounted on a
baseplate, with or without a driver, use of lifting slings passing
under the base flanges is required. Arrange these slings so that
no strains are placed on the unit casing or mounting feet, or
on any mounted accessory equipment. DO NOT use the lifting
lugs in the top of the unit headplates.
Before starting the installation, remove plugs, covers or seals
from unit inlet and discharge connections and inspect the
interior completely for foreign material. If cleaning is required,
finish by washing the cylinder, headplates and impeller
thoroughly with an appropriate solvent. Turn the drive shaft by
hand to make sure that the impellers turn freely at all points.
Anti-rust compound on the connection flanges and drive shaft
extensionmayalsoberemovedatthistimewiththesame
solvent. Cover the flanges until ready to connect piping.
Mounting
Care will pay dividends when arranging the unit mounting. This
is especially true when the unit is a “bare-shaft” unit furnished
without a baseplate. The convenient procedure may be to
mount such a unit directly on a floor or small concrete pad, but
this generally produces the least satisfactory results. It definitely
causes the most problems in leveling and alignment and
may result in a “Soft Foot” condition. Correct soft foot before
operation to avoid unnecessary loading on the casing and
bearings. Direct use of building structural framing members is
not recommended.
For blowers without a base, it is recommended that a well
anchored and carefully leveled steel or cast iron mounting
plate be provided. The plate should be at least 1 inch (25 mm)
thick, with its top surface machined flat, and large enough to
provide leveling areas at one side and one end after the unit is
mounted. It should have properly sized studs or tapped holes
located to match the unit foot drilling. Proper use of a high
quality machinist’s level is necessary for adequate installation.
With the mounting plate in place and leveled, set the unit
on it without bolting and check for rocking. If it is not solid,
determine the total thickness of shims required under one
foot to stop rocking. Place half of this under each of the
diagonally-opposite short feet, and tighten the mounting studs
or screws. Rotate the drive shaft to make sure the impellers
turn freely. If the unit is to be direct coupled to a driving motor,
consider the height of the motor shaft and the necessity for
it to be aligned very accurately with the unit shaft. Best unit
arrangement is directly bolted to the mounting plate while the
driver is on shims of at least 1/8 inch (3mm) thickness. This
allows adjustment of motor position in final shaft alignment by
varying the shim thickness.
Aligning
When unit and driver are factory mounted on a common
baseplate, the assembly will have been properly aligned and is
to be treated as a unit for leveling purposes. Satisfactory instal-
lation can be obtained by setting the baseplate on a concrete

UNIVERSAL RAI®, URAI-DSL, URAI-G and Metric Series | 5
slab that is rigid and free of vibration, and leveling the top of
the base carefully in two directions so that it is free of twist. The
slab must be provided with suitable anchor bolts. The use of
grouting under and partly inside the leveled and shimmed base
is recommended.
It is possible for a base-mounted assembly to become twisted
during shipment, thus disturbing the original alignment. For this
reason, make the following checks after the base has been
leveled and bolted down. Disconnect the drive and rotate the
unit shaft by hand. It should turn freely at all points. Loosen the
unit foot hold-down screws and determine whether all feet are
evenly in contact with the base. If not, insert shims as required
and again check for free impeller rotation. Finally, if unit is direct
coupled to the driver, check shaft and coupling alignment
carefully and make any necessary corrections.
In planning the installation, and before setting the unit, consider
how piping arrangements are dictated by the unit design and
assembly. Drive shaft rotation must be established accordingly
and is indicated by an arrow near the shaft.
Typical arrangement on vertical units has the drive shaft at the
top with counterclockwise rotation and discharge to the left.
Horizontal units are typically arranged with the drive shaft at
the left with counterclockwise rotation and discharge down.
See Figure 4 for other various unit arrangements and possible
conversions.
When a unit is DIRECT COUPLED to its driver, the driver
RPMmustbeselectedorgovernedsoasnottoexceed
themaximumspeedratingoftheunit.RefertoTable1for
allowable speeds of various unit sizes.
Aflexibletypecouplingshouldalwaysbeusedtoconnectthe
driver and unit shafts.
When direct coupling a motor or engine to a blower you must
insure there is sufficient gap between the coupling halves and
the element to prevent thrust loading the blower bearings.
When a motor, engine or blower is operated the shafts may
expandaxially.Ifthecouplingisinstalledinsuchamanner
thatthereisnotenoughroomforexpansiontheblowershaft
can be forced back into the blower and cause the impeller
to contact the gear end headplate resulting in damage to the
blower. The two shafts must be in as near perfect alignment
in all directions as possible, and the gap must be established
withthemotorarmatureonitselectricalcenterifend-playex-
ists.Couplingmanufacturer’srecommendationsformaximum
misalignment, although acceptable for the coupling, are
normallytoolargetoachievesmoothoperationandmaximum
life of the blower.
The following requirements of a good installation are recom-
mended. When selecting a coupling to be fitted to the blower
shaft ROOTS recommends a taper lock style coupling to
insure proper contact with the blower shaft. If the coupling
must have a straight bore the coupling halves must be fitted
to the two shafts with a line to line thru .001” interference
fit. Coupling halves must be warmed up per coupling
manufacturer’srecommendations.Maximumdeviationinoffset
alignmentoftheshaftsshouldnotexceed.005”(.13mm)total
indicatorreading,takenonthetwocouplinghubs.Maximum
deviation from parallel of the inside coupling faces should not
exceed.001"(.03mm)whencheckedatsixpointsaroundthe
coupling.
WhenaunitisBELTDRIVEN,theproperselectionofsheave
diameters will result in the required unit speed. When selecting
a sheave to be fitted to the blower shaft ROOTS recommends
a taper lock style sheave to insure proper contact with the
blowershaft.Thisflexibilitycanleadtooperatingtemperature
problems caused by unit speed being too low. Make sure
the drive speed selected is within the allowable range for the
specific unit size, as specified under Table 1.
BeltdrivearrangementsusuallyemploytwoormoreV-belts
running in grooved sheaves. Installation of the driver is less
critical than for direct coupling, but its shaft must be level and
parallel with the unit shaft. The driver should be mounted
on the inlet side of a vertical unit (horizontal piping) and
on the side nearest to the shaft on a horizontal unit.
SEE PAGE 6 - Acceptable Blower Drive Arrangement
Options. The driver must also be mounted on an adjustable
basetopermitinstalling,adjustingandremovingtheV-belts.
To position the driver correctly, both sheaves need to be
mounted on their shafts and the nominal shaft center distance
known for the belt lengths to be used.
CAUTION: Drive couplings and sheaves (pulleys) should have
an interference fit to the shaft of the blower (set screw types
of attachment generally do not provide reliable service.) It is
recommended that the drive coupling or sheave used have a
taper lock style bushing which is properly sized to provide the
correct interference fit required. Drive couplings, that require
heating to fit on the blower shaft, should be installed per
coupling manufacturer recommendations. A drive coupling or
sheave should not be forced on to the shaft of the blower as
this could affect internal clearances resulting in damage to the
blower.
Engine drive applications often require special con-
sideration to drive coupling selection to avoid harmful
torsional vibrations. These vibrations may lead to blower
damage if not dampened adequately. It is often neces-
sary to install a fly-wheel and/or a torsionally soft elastic
element coupling based on the engine manufacturer
recommendations.
The driver sheave should also be mounted as close to its
bearing as possible, and again should fit the shaft correctly.
Position the driver on its adjustable base so that 2/3 of the total
movement is available in the direction away from the unit, and
mount the assembly so that the face of the sheave is accu-
rately in line with the unit sheave. This position minimizes belt
wear, and allows sufficient adjustment for both installing and
tightening the belts. After belts are installed, adjust their tension
in accordance with the manufacturer’s instructions. However,
only enough tension should be applied to prevent slippage
whentheunitisoperatingunderload.Excessivetighteningcan
lead to early bearing concerns or shaft breakage.
Before operating the drive under power to check initial belt
tension, first remove covers from the unit connections. Make
sure the interior is still clean, then rotate the shaft by hand.

Motor On Inlet Side of Blower (Top Shaft)
Motor On Inlet Side of Blower (Bottom Shaft)
Motor On Discharge Side of Blower (Top Shaft)
Motor On Discharge Side of Blower (Bottom Shaft)
INLET
DISCHARGE
Top Shaft
INLET
DISCHARGE
Bottom Shaft
Motor On Drive Shaft
Side of Blower
INLET
DISCHARGE
Driven Shaft
Drive Shaft
INLET
DISCHARGE
Top Shaft
INLET
DISCHARGE
Bottom Shaft
Motor On Driven Shaft
Side of Blower
INLET
DISCHARGE
Drive Shaft Driven Shaft
6 |Dresser Roots
Place a coarse screen over the inlet connection to prevent
anything being drawn into the unit while it is operating, and
avoid standing in line with the discharge opening. Put oil in the
sumps per instructions under LUBRICATION.
Piping
Before connecting piping, remove any remaining anti-rust
compound from unit connections. Clean pipe should be no
smaller than unit connections. In addition, make sure it is free
of scale, cuttings, weld beads, or foreign material of any kind.
To further guard against damage to the unit, especially when
an inlet filter is not used, install a substantial screen of 16 mesh
backed with hardware cloth at or near the inlet connections.
Make provisions to clean this screen of collected debris after a
few hours of operation. It should be removed when its useful-
ness has ended, as the wire will eventually deteriorate and
small pieces going into the unit may cause serious damage.
Pipe flanges or male threads must meet the unit connections
accurately and squarely. DO NOT attempt to correct misalign-
ment by springing or cramping the pipe. In most cases this will
distort the unit casing and cause impeller rubbing. In severe
cases it can prevent operation or result in a broken drive shaft.
For similar reasons, piping should be supported near the unit
toeliminatedeadweightstrains.Also,ifpipeexpansionis
likelytooccurfromtemperaturechange,installationofflexible
connectorsorexpansionjointsisadvisable.
Figure 3 represents an installation with all accessory items that
might be required under various operating conditions. Inlet
piping should be completely free of valves or other restrictions.
When a shut-off valve can not be avoided, make sure a full
size vacuum relief is installed nearest the unit inlet. This will
protect against unit overload caused by accidental closing of
the shut-off valve.
Need for an inlet silencer will depend on unit speed and
pressure, as well as sound-level requirements in the general
surroundings. An inlet filter is recommended, especially in
dusty or sandy locations. A discharge silencer is also normally
suggested, even though WHISPAIR™units operate at generally
lower noise levels than conventional rotary blowers. Specific
recommendations on silencing can be obtained from your local
ROOTS distributor.
Discharge piping requires a pressure relief valve, and should
include a manual unloading valve to permit starting the unit
under no-load conditions. Reliable pressure/vacuum gauges
and good thermometers at both inlet and discharge are
recommended to allow making the important checks on unit
operating conditions. The back-pressure regulator shown in
Figure 3 is useful mainly when volume demands vary while the
unit operates at constant output. If demand is constant, but
somewhatlowerthantheunitoutput,excessmaybeblownoff
through the manual unloading valve.
In multiple unit installations where two or more units operate
with a common header, use of check valves is mandatory.
These should be of a direct acting or free swinging type, with
one valve located in each line between the unit and header.
Properly installed, they will protect against damage from
reverse rotation caused by air and material back-flow through
an idle unit.
After piping is completed, and before applying power, rotate
the drive shaft by hand again. If it does not move with uniform
freedom,lookforunevenmounting,pipingstrain,excessive
belt tension or coupling misalignment.
DO NOT operate the unit at this time unless it has been
lubricated per instructions.
Acceptable Blower Drive Arrangement Options
Acceptable Unacceptable

UNIVERSAL RAI®, URAI-DSL, URAI-G and Metric Series | 7
Technical Supplement for URAI-G™
Gas Blowers
Technical Supplement for 32, 33, 36, 42, 45, 47, 53, 56,
59, 65, 68, 615 Universal RAI-GAS blowers
Precaution: URAI-GAS blowers: Care must be used when
opening the head plate seal vent chamber plugs (43) as some
gas will escape–if it is a pressure system, or the atmospheric
air will leak into the blower if the system is under vacuum.
There is a possibility of some gas leakage through the
mechanical seals. This leakage on the gear end will escape
throughthegearboxvent,andonthedriveend,through
the grease release fittings. If the gas leakage is undesirable,
each seal chamber must be purged with an inert gas through
one purge gas hole (43) per seal. There are two plugged
purge gas holes (1/8 NPT) provided per seal. The purge gas
pressure must be maintained one PSI above the discharge
gaspressure.Also,thereexistsapossibilityofgearendoiland
drive end grease leakage into the gas stream.
ROOTS Universal RAI-GAS rotary positive gas blowers are
adesignextensionofthebasicUniversalRAIblowermodel.
URAI-GAS blower uses (4) mechanical seals in place of the
standard inboard lip seals to minimize gas leakage into the
atmosphere.
These units are intended for gases which are compatible with
cast iron case material, steel shafts, 300/400 series stainless
steel and carbon seal components, viton o-rings and the oil/
grease lubricants. If there are any questions regarding applica-
tion or operation of this gas blower, please contact factory.
A simple but very effective lubrication system is employed on
the drive shaft end bearings. Hydraulic pressure relief fittings
areprovidedtoventanyexcessgrease,preventingpressure
build-up on the seals. A restriction plug and metering orifice
prevent loss of lubricant from initial surges in lubricant pressure
butpermitventingexcesslubricantundersteadilyrising
pressures.
Using a pressure gun, slowly force new lubricant into each
drive end bearing housing until traces of clean grease comes
out of the relief fitting. The use of an electric or pneumatic
grease gun could force the grease in too rapidly and thus invert
the seals and should not be used.
Gear end bearings, gears and oil seals are lubricated by the
action of the timing gears which dip into the main oil sumps
causing oil to splash directly on gears and into bearings and
seals. A drain port is provided below each bearing to prevent
anexcessiveamountofoilinthebearings.Sealslocated
inboard of the bearings in each headplate effectively retain oil
within the sumps. Any small weepage that may occur should
the seals wear passes into a cavity in each vented headplate
and is drained downward.
Proper lubrication is usually the most important single
considerationinobtainingmaximumservicelifeandsatisfac-
tory operation from the unit. Unless operating conditions are
severe, a weekly check of oil level and necessary addition of
lubricant should be sufficient.
During the first week of operation, check the oil levels in the
oil sumps about once a day, and watch for leaks. Replenish
as necessary. Thereafter, an occasional check should be
sufficient.
More frequent oil service may be necessary if the blower is
operated in a very dusty location.

8 |Dresser Roots
Lubrication
Due to sludge build-up and seal leakage problems,
Roots recommendation is DO NOT USE Mobil SHC
synthetic oils in ROOTS blowers.
Proper lubrication is usually the most important single
consideration in obtaining maximum service life and
satisfactory operation from the unit.
URAI AIR and GAS gear end bearing lubrication/oil
with splash lubrication on the gear end only (Drive end
grease lubricated).
• ThespecifiedandrecommendedoilisROOTS™
Synthetic oil of correct viscosity per Table 2, page 17.
• Tofillthegearbox,removethebreatherplug(25)and
the oil overflow plug (21) - see page 15. Fill the reservoir
up to the overflow hole. DO NOT OVERFILL. Place the
breather and the overflow plug back into their respective
holes.
• Thelubricationshouldbechangedafterinitial100hours
of operation.
• Properserviceintervalsoftheoilthereafterarebasedon
the discharge air temperature of the blower. Please refer
to the information below to “How to properly determine
the oil service intervals” shown on this page.
• Unlessoperatingconditionsarequitesevere,aweekly
check of the oil level and necessary addition of lubricant
should be sufficient. During the first week of operation,
check the oil levels in the oil sumps about once a day,
and watch for leaks. Replenish as necessary.
• Ifyouchoosetouseanotheroilotherthanthespecified
and recommended ROOTS™Synthetic, use a good
grade of industrial type non-detergent, rust inhibiting,
anti-foaming oil and of correct viscosity per Table 2,
page 17.
• RootsdoesNOTrecommendtheuseofautomotivetype
lubricants, as they are not formulated with the properties
mentioned above.
URAI-DSL blowers with splash lubrication/oil on each
end. No grease.
• ThespecifiedandrecommendedoilisROOTS™
Synthetic oil of correct viscosity per Table 2, page 17.
• Theproperoillevelshouldbehalfwayormiddleofthe
sight gauge when the blower is not operating. DO NOT
OVERFILL OIL SUMP/S as damage to the blower may
occur.
• Oillevelmayriseorfallinthegaugeduringoperationto
anextentdependingsomewhatonoiltemperatureand
blower speed.
• Theoillevelshouldnotfallbelowthemiddleofthesite
gauge when the blower is idle.
• Thelubrication/oillevelmayriseorfallinthegauge
duringoperationtoanextentdependingsomewhaton
oil temperature and blower speed.
• Thelubricationshouldbechangedafterinitial100hours
of operation.
• Properserviceintervalsoftheoilthereafterarebasedon
the discharge air temperature of the blower. Please refer
to the information below to “How to properly determine
the oil service intervals” shown on this page
• Unlessoperatingconditionsarequitesevere,aweekly
check of the oil level and necessary addition of lubricant
should be sufficient. During the first week of operation,
check the oil levels in the oil sumps about once a day,
and watch for leaks. Replenish as necessary.
• Ifyouchoosetouseanotheroilotherthanthespecified
and recommended ROOTS™Synthetic, use a good
grade of industrial type non-detergent, rust inhibiting,
anti-foaming oil and of correct viscosity per Table 2,
page 17.
• RootsdoesNOT recommend the use of automotive
type lubricants, as they are not formulated with the
properties mentioned above.
How to properly determine the oil service intervals.
Normallifeexpectancyofthespecifiedandrecommended
ROOTS™Syntheticoilisapproximately6000hourswithan
oiltemperatureof180°F(82°C)orless.Astheoiltempera-
tureincreasesbyincrementsof15°F(8°C),theoillifeis
reducedbyhalfforeach15°F(8°C)increase.Example:Oil
temperaturesof195°F(90.5°C)willproducealifeexpectancy
reduced by half or 3000 hours oil service life.
Normallifeexpectancyofpetroleumbasedoilsisabout2000
hourswithanoiltemperatureofabout180°F(82°C).Asthe
oiltemperatureincreasesbyincrementsof15°F(8°C),thelife
isreducedbyhalfforeach15°F(8°C)increase.Example:Oil
temperaturesof195°F(90.5°C)willproducelifeexpectancy
reduced by half or 1000 hours oil service life.
NOTE: To estimate oil temperature, multiply the discharge
temperatureoftheblowerby0.80.Example:ifthedischarge
airtemperatureofthebloweris200°F,itisestimatedthat
theoiltemperatureis160°F
For Units with grease lubricated drive end bearings.
URAI AIR (Non GAS) blower grease specifications.
• WhenservicingdriveendbearingsofaAIR(NonGas)
blower, use the specified and recommended Shell
Darina SD 2 NLGI #2 product code 5067628.
• Forgreaselubricateddriveendblowersseepage17,
table 4, regarding specified greasing intervals.
• Lithiumbasedgreasesarenotcompatiblewiththe
specified and recommended Shell Darina SD 2 grease
used when assembling the blower. Lithium based
grease is not approved for any ROOTS blowers.
• Table4page17hasbeenpreparedasageneral
greasing schedule guide based on average operating
conditions. More frequent intervals may be necessary

UNIVERSAL RAI®, URAI-DSL, URAI-G and Metric Series | 9
depending on the grease operating temperature and
unusual circumstances.
URAI GAS blower grease specifications.
• WhenservicingdriveendbearingsofaURAIGAS
blower, use the specified NLGI #2 premium grade
aluminumcomplex*grease,ROOTSP/NT20019001.
• Lithiumbasedgreasesarenotcompatiblewiththe
specified and recommended ROOTS Synthetic grease
used when assembling a GAS blower. Lithium based
grease is not approved for any ROOTS blowers.
• Lithiumbasedgreasesarenotcompatiblewiththe
specified and recommended ROOTS Synthetic grease
used when assembling a GAS blower. Lithium based
grease is not approved for any ROOTS blowers.
• Thelubricantsselectedmustbecompatiblewiththe
gas.
*ROOTSSyntheticOil&Greaseissuperiorinperformance
toothersyntheticlubrications.Ithashighoxidationstability,
excellentcorrosionprotection,extremelyhighfilmstrength
and low coefficient of friction.
*ROOTS™Syntheticoilissuperiorinperformancetopetroleumbasedproducts.
Ithashighoxidationstability,excellentcorrosionprotection,extremelyhighfilm
strength and low coefficient of friction. Typical oil change intervals are increased
2-3 times over petroleum based lubricants. Also, ROOTS™ Synthetic oil is 100%
compatible with petroleum based oils. Simply drain the oil in the blower and refill
the reservoirs with ROOTS™ Synthetic oil to maintain optimum performance of
your ROOTS™ blower.

10 |Dresser Roots
Operation
Before operating a blower under power for the first time,
recheck the unit and the installation thoroughly to reduce the
likelihood of avoidable troubles. Use the following procedure
check list as a guide, but consider any other special condi-
tions in the installation.
oBe certain that no bolts, tools, rags, or debris have been
left in the blower air chamber or piping.
oIf an outdoor intake without filter is used, be sure
the opening is located so it cannot pick up dirt and is pro-
tected by a strong screen or grille. Use of the temporary
protective screen as described under INSTALLATION is
strongly recommended.
oRecheck blower leveling, drive alignment and tightness of
all mounting bolts if installation is not recent. If belt drive is
used, adjust belt tension correctly.
oTurn drive shaft by hand to make sure impellers still rotate
without bumping or rubbing at any point.
oEnsure oil levels in the main oil sumps are correct.
oCheck lubrication of driver. If it is an electric motor, be
sure that power is available and that electrical overload
devices are installed and workable.
oOpen the manual unloading valve in the discharge air line.
If a valve is in the inlet piping, be sure it is open.
oBump blower a few revolutions with driver to check that
direction of rotation agrees with arrow near blower shaft,
and that both coast freely to a stop.
After the preceding points are cleared, blower is ready for trial
operation under “no-load” conditions. The following proce-
dure is suggested to cover this initial operation test period.
a. Start blower, let it accelerate to full speed, then shut off.
Listen for knocking sounds, both with power on and as
speed slows down.
b. After blower comes to a complete stop, repeat above,
but let blower run 2 or 3 minutes. Check for noises, such
as knocking sounds.
c. After blower comes to a complete stop, operate
blower for about 10 minutes unloaded. Check oil levels.
Observe cylinder and headplate surfaces for develop-
ment of hot spots such as burned paint, indicating
impeller rubs. Be aware of any noticeable increase in
vibration.
Assuming that all trials have been satisfactory, or that neces-
sary corrections have been made, the blower should now
have a final check run of at least one hour under normal oper-
ating conditions. After blower is restarted, gradually close the
discharge unloading valve to apply working pressure. At this
point it is recommended that a pressure gauge or manometer
be connected into the discharge line if not already provided,
and that thermometers be in both inlet and discharge lines.
Readings from these instruments will show whether pressure
ortemperatureratingsoftheblowerarebeingexceeded.
During the final run, check operating conditions frequently
andobservetheoillevelsatreasonableintervals.Ifexcessive
noise or local heating develops, shut down immediately and
determine the cause. If either pressure rise or temperature
riseacrosstheblowerexceedsthelimitspecifiedinthis
manual, shut down and investigate conditions in the piping
system. Refer to the TROUBLESHOOTING CHECKLIST for
suggestions on various problems that may appear.
The blower should now be ready for continuous duty
operation at full load. During the first few days make periodic
checks to determine whether all conditions remain steady, or
at least acceptable. This may be particularly important if the
blower is supplying air to a process system where conditions
can vary. At the first opportunity, stop the blower and clean
the temporary inlet protective screen. If no appreciable
amount of debris has collected, the screen may be removed.
See comments under INSTALLATION. At this same time,
verify leveling, coupling alignment or belt tension, and
mounting bolt tightness.
Shouldoperatingexperienceprovethatblowercapacityisa
littletoohighfortheactualairrequirements,asmallexcess
may be blown off continuously through the manual unloading
or vent valve. Never rely on the pressure relief valve as an
automatic vent. Such use may cause the discharge pressure
tobecomeexcessive,andcanalsoresultinunsafeoperation
of the valve itself. If blower capacity appears to be too low,
refer to the TROUBLESHOOTING CHECKLIST.
Vibration Assessment Criteria
With measurements taken at the bearing locations on the
housings, see chart below for an appropriate assessment
guide for rotary lobe blowers rigidly mounted on stiff
foundations.
In general, blower vibration levels should be monitored on a
regular basis and the vibration trend observed for progressive
or sudden change in level. If such a change occurs, the
cause should be determined through spectral analysis.
As shown on the chart below, the level of all pass vibration
will determine the need to measure discrete frequency
vibration levels and the action required.
All Pass Vibration
(in/sec)
Discrete Frequency
Vibration (in/sec) Action
0.45 or less N/R Acceptable
Greater than 0.45 but
1.0 or less
0.45 or less @ any
frequency Acceptable
Greater than 0.45 @
any frequency Investigate
Greater than 1.0 Less than 1.0 Investigate
Greater than 1.0 Investigate

UNIVERSAL RAI®, URAI-DSL, URAI-G and Metric Series | 11
Troubleshooting Checklist
Trouble Item Possible Cause Remedy
No flow 1
2
3
Speed too low
Wrong rotation
Obstruction in piping
Check by tachometer and compare with published performance.
Compare actual rotation with Figure 1, change driver if wrong.
Check piping, valves, silencer to assure open flow path.
Low capacity 4
5
6
7
Speed too low
Excessive pressure rise
Obstruction in piping
Excessive slip
See item 1, if belt drive, check for slippage and re-adjust tension.
Check inlet vacuum and discharge pressure and compare with published
performance.
See item 3.
Check inside of casing for worn or eroded surfaces causing excessive
clearances
Excessive power 8
9
10
11
Speed too high
Excessvie pressure rise
Impeller rubbing
Scale , sludge, rust or
product build up
Check speed and compare with published performance.
See item 5
Inspect outside of cylinder for high temperature areas, then check for impel-
ler contact at these points. Correct blower mounting, drive alignment.
Clean blower appropriately
Damage to bearings or gears 12
13
14
15
16
Inadequate lubrication
Excessive lubrication
Excessive pressure rise
Coupling misalignment
Excessive belt tension
Check oil sump levels in gear and drive end headplates
Check oil levels. If correct, drain and refill with clean oil of recommended grade.
See item 5.
Check carefully. Re-align if questionable.
Re-adjust for correct tension.
Vibration 17
18
19
20
21
22
23
Misalignment
Impellers rubbing
Worn bearings/gears
Unbalanced or rubbing
impeller
Driver or blower loose
Piping resonances
Scale/sludge build-ups
See item 15
See item 10
Check gear backlash and conditions of bearings and replace as indicated.
Scale or process material may build up on casing and impellers, or inside impellers.
Remove build-up to restore original clearances and impeller balance.
Tighten mounting bolts securely.
Determine whether standing wave pressure pulsations are present in the piping.
Clean out interior of impeller lobes to restore dynamic balance.
Driver stops, or will not start 24
25
26
Casing strain
Impeller stuck
Scale, sludge, rust or
prodcut build-up
Re-work piping alignment to remove excess strain
Check for excessive hot spot on headplate or cynlinder. See item 10. Look
for defective shaft bearing and/or gear teeth.
Clean blower appropiately
Excessive breather
Blow-by or excessive oil
leakage to vent area
Excessive oil leakage in
vent area
27
28
29
30
31
32
Broken seal
Defective O-ring
Defective/plugged breather
Oil level too high
Oil type or viscosity incorrect
Blower running hot
Replace seals
Replace seals and O-ring
Replace breather and monitor oil leakage
Check sump levels in gear and drive headplates
Check oil to ensure it meets recommendations. Drain then fill with clean oil
of recommended grade.
Check blower operating conditions to ensure they are within the operating
limitations defined in this manual.