Zenith® Pumps H-SeriesGear Pumps

Installation,Care And Maintenance

ZenithHigh-TemperatureGear Pumps

High Volumetric EfficiencyMaximum efficiency is achieved with optimum operating clearances and assured under pressure by built-in alignment dowels.

Minimum PulsationUnique design offers virtually pulselessflow without valves or flexible elements to hinder performance.

Precision ConstructionGround and lapped components for close control of operating clearances.

Zenith® Pumps

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Thoroughly read and understand this entire manual before installation and operation of pump.

In 1926, Zenith Pumps was approached by the synthetic fiber industry to design a pump to provide a precise, pulseless,repeatable flow and assure better qualitycontrol. The options then were the same as those in the chemical process industrytoday–diaphragm, lobe, coarse gear, pis-ton, plunger and screw pumps. Each hadproblems with pulsation, flow inaccuracies,multiple seal areas and slip, which requiredconstant calibration, high maintenance andextended downtimes.

Zenith Pumps met the challenge anddesigned a rotary external gear pump ofunique precision and simplicity.

Specifications Pump Type: Rotary external spur gear, single stream.

Rotation: Refer to pump drawing.

Operating Speed: 3-180 rpm depending upon application conditions and fluid viscosity.

Temperature: To 645° F (350° C),(950° F maximum with special fasteners and seals).

Manufacturing techniques were devel-oped to hold tolerances to .00005", andan inter-nal pressure relief mechanismassured reliable precision metering. Thepump’s simple design of only three mov-ing parts–two metering gears and adrive shaft–provided long life and easy maintenance.

For years since, Engineers haverelied on Zenith to provide precision fluid handling solutions for their most difficult pumping applications. Zenithgear pumps can be found wherever precise, pulseless, repeatable meteringof fluids is required.

High AccuracyStable, repeatable flows are assuredeven under varying conditions of pressure, viscosity, and temperature.

High Temperature CapabilityOperating temperatures to 950° F (510° C).

Maximum LifeOnly three moving parts; components are through-hardened tool and die steels to 62 HRc or better. Replaceablesleeve bearings for low-cost rebuilds.

Benefits

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Operation

Design Zenith H-Series metering pumps consistof two gears rotating in mesh within aclosely fitted housing that is comprised ofthree plates. The center gear plate fitsclosely around the outside diameter of themetering gears. The front and rear platessand-wich the center plate and restrictaxial movement of the gears. Power istransmitted to the gears by the drive shaftwhich is either a through shaft, as in thepacking gland type pump, or a shaft witha tang that engages a universal seal cou-pling. The coupling is both a connectionto external power and the rotating mem-ber of a mechanical seal.

The two seal designs, mechanical face seal and packing seal, have differentoperating requirements. As mentionedabove, the mechanical face seal designconsists of a rotating universal seal cou-pling that seals against a fixed seal plate.The all-metal seal design is dependentupon sufficient inlet pressure (usually 25 -50 psi) to force the inner rotating couplingagainst the outer stationary anchor. Thisdesign is commonly used in abrasive fluidor high temperature applications.

Since the metal seal requires sufficientinlet or working pressure to be effective, apacking seal design is also available.Pumps with this type of seal can have twoto four packing rings. Common availablematerials are Grafoil and Teflon. To sealeffectively, fluid must be able to travel axially along the shaft. Weepage in these

pumps is a common occurrence andshould be expected.

H-Series pumps are precision instruments requiring skilled and careful maintenance. Constructed of high-quality tool and die steels such as AISI D2, M2, M4and CPM-M4, or other high-performancealloys, they are tempered after heat treat-ment to hardnesses ranging from HRc 58to HRc 64. Since the thermal expansionrates for all three steels are almost identicaland are otherwise entirely compatible, it ispossible to combine them so as to takeadvantage of their best qualities in themost economical way.The Type D2 toolsteel is often selected for the side andcenter plates as it offers good abrasionresistance, and it is the most economicalof the three steels we most commonlyuse. Type D2 will also provide a higherdegree of corrosion resistance than M2 or M4.

The portion of the side plate subject to the most wear is the shaft bearing hole, which has an easily replaceable,inexpensive sleeve bearing that can bemade of the extremely wear resistant Type M4 tool steel. Types M2 and CPM-M4steels are commonly used for the meteringgears, drive shaft, and universal seal coupling, due to their superior torsionalstrength and abrasion resistance for theseitems that are the most critical to propermetering performance.

All H-Series pumps are rear ported. Fluidenters the pump through a port drilled intothe rear side plate (the side opposite thedrive shaft). The fluid fills the exposed geartooth volumes and is transported aroundthe outer diameter of the gear pocket. Asthe gears mesh together, the fluid is dis-placed in a very precise amount outthrough the discharge port that is drilledalongside the inlet port in the rear plate.

Since Zenith pumps are not self-prim-ing, a flooded suction is usually the mini-mum inlet pressure required. However,when high-viscosity fluids are used, moretime is required to fill the tooth volumes.As a result, the inlet pressure must beincreased, or the gears must rotate at aslower speed to ensure complete volumefilling and to prevent cavitation.

Zenith pumps rely on the metered fluid for lubrication of internal bearingareas. The pump should never beallowed to run dry or be allowed to run

with non-lubricating fluids such as water.Because of the close clearances in thebearing areas, lack of sufficient lubricationcan cause pump seizure or some othercatastrophic failure.

Slip can occur across the faces of thegears from the high-pressure side to thelow-pressure side. The amount of slipdepends on four factors: fluid viscosity,speed, differential pressure, and pumpclearances. Under reasonably stableoperating conditions, slip is repeatableand predictable,and pump operation canbe adjusted to compensate.

The Zenith H-Series are designed for high-temperature and high-pressure operation. As such, operating tempera-tures to 950° F can be achieved. Whenoperating at temperatures above ambient,heat jackets should be used and pumpsshould be heated slowly and uniformly toavoid warpage and internal componentinterference.

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Installation Pumps should be carefully unpacked tomake sure that the shipment is complete. If any items are missing or damaged, thefreight carrier and Zenith should be notifiedimmediately.

While the pump is composed of steel, it is a precision instrument. Dropping thepump or hitting with a non-yielding materialcan cause serious damage to the compo-nents. All materials are through-hardened to maximum hardness resulting in a brittlematerial. Treat them as you would anyother precision gaging instrument.

Zenith pumps are shipped filled with arust preventative oil. Flush the oil thoroughlywith a cleaning solvent. It may be necessaryto disassemble the seal arrangement toremove all traces of the oil, but disassembleonly if necessary.

After flushing, the pump should be lubri-cated internally for start-up purposes. Poura suitable high-temperature lubricant intothe inlet port. Rotate the metering gearsuntil lubricant appears at the discharge port.

Mount the pump to a block with a flat-ness of true flat to .0001" convex and a surface finish of 4 to 8 rms to preventleakage between the pump and block.Mounting bolts should be a Grade 8 orbetter. Make sure mounting bolts are lubri-cated with a high-temperature anti-seizecompound such as DAG Dispersion #154.Bolts should be alternately torqued ineven increments up to Zenith’s recom-mended limit for the bolt size used. SeeTable 2 on page 10 for torque values.

The following is a brief “standard”installation procedure. For special applications, considerations, or simply to ask our advice, please contact ourApplications Engineering Group.

To prepare the pump for use:1) Always flush out the plumbing

system before connecting the pump.2) Filters should be installed prior to

the pump inlet that filter ideally to half thepump running clearances.

3) Turn pumps by hand before running. Pumps should turn freely.

4) Engage the outer drive shaft care-fully, making sure that it does not bottom in the slot of the coupling,* and that it isaligned within 1° angular and .005" paral-lel with the true pump drive axis.*NOTE: The coupling is the rotating mem-ber of the seal and depends on the inter-nal operating pressure of the pump toforce it forward and effect a seal againstthe carbon or metal seal plate.

5) In pumps with a through shaft andcompression packing seal, the pump-to-driver axis may shift unevenly due topump heating expansion. To remedy this,we recommend connecting the pumpdriver to the pump shaft with the appropri-ate Zenith SJM Coupling or with a doubleuniversal joint arrangement. This type ofjoint will prevent bending loads frombeing transmitted to the pump shaft whenmisaligned. This greatly reduces the pos-sibility of premature shaft failure due tofatigue. To prevent seizure, be sure toapply adequate high-temperature lubrica-tion to the universal joints.

6) Heat the pump thoroughly andevenly (including the seal arrangement). Atime-saving heating alternative would beto maintain a clean and ready-to-usepump in an oven at operating tempera-ture. This avoids thermal shock and savesvaluable heating time. Be sure to checkthe pack-ings prior to use as extendedheat soaks tend to dry out some packingmaterials.

7) Tighten the mounting bolts andcoupling housing screws to Zenith's recommended torque at that operatingtemperature.

8) Make sure fluid is in the pumpbefore starting. Be sure to apply positiveinlet pressure when metering high-viscosi-ty fluids. Pumps with universal face sealsrequire an inlet pressure of approximately25-50 psi to set the seal.

9) Start pump slowly and, if possible, run it with a lubricating fluid.

10) When satisfactory operation isachieved, the pump and system may begradually brought up to normal processspeeds and pressures.

11) If your pump has a packing seal,take up firmly and evenly on the seal gland screws to compress the packing,then back off 1/2 turn of the screws oruntil slight weepage occurs. Be sure toadjust the gland properly. Do not over-tighten. Overtightening can cause thepackings to burn.

12) Be sure to follow up closelythroughout the running-in period of thepacking until the seal is thoroughly seated.Do not completely seat the packing in one adjustment.

13) If at any time during operation thepump does not appear to be runningsmoothly, stop the pump immediately toavoid any serious internal damage.

Cleaning,Inspection and Repair

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Table 1

AISI Type Tempered at HRc

D2 950° F (510° C) 58-60M2 1,050° F (566° C) 61-64M4 1,050° F (566° C) 61-64

REMEMBER: Zenith metering pumps aremade for exacting duty. In order to devel-op the high pressure demanded, theclearance between the metering gearsand their housing must be as small aspossible, yet large enough to allow ade-quate lubrication. All parts are machined to extreme accura-cy; critical dimensions are held betweenone and two ten-thousandths of an inch(.0001"/.0002"). Because of these closerunning clearances, Zenith pumps requirecareful maintenance and handling, espe-cially of component parts. The slightestburr, nick or particle of foreign matter cancause scoring or even seizure. Zenithpumps are precision instruments; youcan't keep them too clean. Please treatthem with care, and if it’s at all possible,set aside a separate clean area for pumpmaintenance.

To clean H-Series metering pumps,place them in a suitable furnace andgradually heat in an inert atmosphere forthe initial hour to prevent flashing of thepolymer. Time at temperature will be relat-ed to the pump size and the degree ofpolymer contamination and should bedetermined by trial.NOTE: Careful control of the furnacetemperature and atmosphere is critical.Should the temperature exceed the origi-nal tempering temperature, the steel hardness will draw back and thedimensional stability of the pump may be upset. Consult Table 1 for proper tem-pering temperature.

Another acceptable cleaning methodis to immerse the pump in a fluidized bedcleaning bath. The bath should be heatedto a temperature that is sufficient to car-burize the polymer. The carburizationprocess usually takes between 3 to 12hours, depending on the polymer type,temperature, pump size, and furnace load.

CAUTION: Avoid exposing the pump tothermal shock when using this method ofcleaning.

After gradually cooling to room tem-perature, the pump should be thoroughlyflushed in a clean solvent. It may be necessary to disassemble the sealarrangement to remove polymer ash.

Always replace the carbon seal plate(if equipped) and fasteners after pumpburnout. If the pump was performing satisfactorily when removed from serviceand still turns freely after burnout, pres-sure test it and add a high-temperaturelubricant to prepare it for return to service.To store for future use, simply add a rustpreventative oil.

It is recommended that pump users institute a program of dimensionalinspection of critical parts in order to keepmaintenance and operating costs at aminimum. By noting the performance of apump immediately before removing it fromservice and correlating the performanceto measured component wear, the usercan establish the maximum wear limits forthe pump’s critical components. Further,he can predict the service life of thepump, and schedule his down-timeaccordingly.

As with any other Zenith pump, H-Series pumps may be returned to Zenithfor complete rehabilitation as necessary.This procedure may be desirable if only afew pumps are involved. If a large numberof pumps are to be maintained at theuser’s plant, it may be worthwhile to havekey personnel attend a maintenance seminar at the Zenith factory to view themanufacturing, gaging, and assemblytechniques involved in producing the H-Series pump. In addition, Zenith alsooffers a contract service program. Pleasecontact Zenith for further information onthese items.

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28 Screw, Packing

12 Packing Gland

14 Spacer Ring

15 Spacer Ring

13 Packing Housing

48 Binder Screw

49 Sleeve Bearing

1 Front Plate

5 Arbor2 Center Plate

10 Dowel

7 Driven Gear

4 Drive Shaft

3Rear Plate

50Sleeve Bearing

29Retaining Ring

8Key

6Driving Gear

27Screw, Packing Housing

17Seal Packings

2.50''

3.81''

X

Zenith SingleStream PumpType HMB-5740

HMB Series

Diagram 2

Zenith SingleStream PumpType HPB-4647-1.168

27 Coupling Housing Screw (4)

12 Seal Plate

17 Carbon Seal Plate

13 Coupling Housing

14 Universal Seal Coupling

48 Long Binder Screw (4)

47 Short Binder Screw (2)

1 Front Side Plate Assembly

5 Arbor (press fit in front side plate)

7 Driven Metering Gear

6 Driving Metering Gear

10 Hollow Dowel (press fit in front side plate)

3Rear Side Plate Assembly

2Center Plate

8Round Key (Square End)

4Drive Shaft

49Sleeve Bearing(press fit)

49Sleeve Bearing (press fit)

HPB Series

Diagram 1

7

4.00''

6.06''

X

13 Packing Housing

12 Packing Gland

27 Screw, Seal Packing

1 Front Plate

5 Arbor

7 Driven Gear

2 Center Plate

10 Hollow Dowel

4 Drive Shaft

22Sleeve Bearing

30Outer Key

8Round Key

6Driving Gear

3Rear Plate

48Binder Screw

11Seal Plate

28Nut

14Seal Packings

50Spacer Ring

Zenith SingleStream PumpType HLB-5592

HLB Series

Diagram 3

6.00''

8.00''

X

27 Screw, Packing Housing

12 Packing Gland

58 Screw, Packing

1 Front Plate

7 Driven Gear

2 Center Plate

50 Sleeve Bearing

5 Arbor49Shoulder Bearing

30Outer Key

8Round Key

6Driving Gear

3Rear Plate

21Binder Screw

43Seal Packings

59Dowel

Zenith SingleStream PumpType HXB-4980

4 Drive Shaft

HXB Series

Diagram 4

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H-Series Disassembly

If pumps are to be disassembled on aregular basis, we recommend that youestablish a pump room with all the neces-sary tools and equipment for disassemblyand cleaning with a separate “clean” areafor assembly, testing and storing of rebuiltpumps.

If maintenance is required due to lowdelivery or seizure, the following proce-dure is recommended for disassembly.NOTE: Be sure to note the location andorientation of all parts to ensure reassembly.

Refer to diagrams on pages 6 and 7for your correct pump type.NOTE: Discard all fasteners, packings orcarbon seal plates after burn-out.

1) Remove the seal arrangement .2) Remove all binder screws.3) Remove dowels (10) and arbor (5)

with an arbor press in the direction whichdisengages the press fit in the shortestdistance.NOTE: Dowels and arbors for the HPB,HLB and HXB are press fit in the frontside plate (1) and slip fit in the center (2)and rear side plates (3). In the HMB, theyare press fit in the rear side plate. For theHPB, HLB and HXB, press these parts outfrom the front (drive) side and for theHMB, from the rear (port) side.

4) Separate the plates by lightly tap-ping them with a soft head hammer. If pryslots are available in the pump, you mayuse them instead of, or in conjunctionwith, the above method. In either case,great care should be taken not to scratchor damage the internal pump surfacewhen prying the plates apart.

5) After disassembly, clean all com-ponents in a glass bead blast cabinet toremove any debris remaining after heatcleaning. Alternative, non-destructivecleaning methods such as water jet or solvents are also acceptable.

6) Wash components in an ultrasoniccleaning tank and air dry. Be careful notto bang parts together.

7) Inspect all parts for nicks, burrs, scoremarks and other signs of wear. The plates and faces of the gears may behand blocked on 400/600 grit paper andany nicks, burrs or sharp edges can belightly removed with an Arkansas stone.Be careful not to round off the edges ofthe gear teeth while lapping.CAUTION: Since the thickness relation-ship between the metering gears andcenter plate is critical to metering per-formance, and the center plate is non-wearing on its sides, lapping these com-ponents is not necessary and should notbe done under any circumstances.

Place a layer of 400 Grit Emery Clothon a lapping block or plate–a granite flatis suitable. Apply light pressure to thecomponent and turn it in a figure 8 fash-ion (as shown in Figure 1 on page 9)approximately 10 times until a smooth fin-ish appears. Turning in a circular fashion,or other non-uniform motion, may causethe ground holes to lose their perpendicu-larity to the faces.

Always use clean, lint-free rags andcompressed air to clean components.Paper towels are not acceptable; theymay leave small pieces of paper and duston the components. Use chemical brush-es to clean between gear teeth, bores,and reliefs.

8) Replace sleeve bearings as nec-essary and hone in the plate to the origi-nal new part specifications.

9) After each resurfacing, carefullygauge the area between the inlet and dis-charge ports at the mesh of the gears.This area, commonly referred to as the“throat,” is the most critical part of theplate. Scoring or wear marks here willallow increased slip from the high-pres-sure discharge port section across thethroat to the lower inlet port reducing effi-ciency. Therefore, carefully gauge thisarea for flatness after each resurfacing.

10) After all components are “hospitalclean,” the pump is ready for assembly.

* *

* *

* *

H-SeriesReassembly

Figure 1

NOTE: During and between eachreassembly step, manually turn the meter-ing gears to ensure that they are free turn-ing. If binding occurs at any time, deter-mine the cause and correct it immediately.A tiny nick, burr, or foreign particle canextensively damage a valuable pumpcomponent. Never use force in reassem-bling or turning a Zenith pump. If properlyaligned, the pieces will fit easily intoplace, and the pump will turn freely.

The HMB has a press fit arbor in therear plate. As such, some of these instruc-tions may need reversal of the front andrear plates.NOTE: Replace all fasteners, packings orseal plates with new parts prior to assembly.

Reassemble the pump as follows:1) After all worn parts have been

refinished or replaced, all parts should bethoroughly cleaned in a solvent and dried.

2) Using the driven gear (7) as anup-righting fixture, carefully locate thearbor (5) over its press fit hole in eitherthe front or rear plate. Smoothly drive thearbor into its hole with the help of anappropriate arbor press.

3) Place the front side plate (1) withthe arbor in position in a soft-jaw vise orholding fixture.

4) Slip together the driving meteringgear (6), drive shaft (4) and key (8). Positionin the front of the side plate by installing thedrive shaft through the bearing (49).

5) Place the driven metering gear onits arbor and carefully mesh with the drivingmetering gear.

6) Carefully lower the center plate (2) over the gears.

7) Position the rear side plate (3).8) Rotate the gears to ensure free

rotation.9) Press the dowels (10) into place

moving in the direction of the shortestpress distance. (Usually from the rear sideof the pump.)

10) Lubricate the binder screws (47,48) with DAG dispersion #154 or a similarheat re-sistant lubricant and install. Torquethe screws in even increments, using acrossing pattern, to the manufacturer’s

recommended limit. It is especially impor-tant to rotate the gears frequently duringthis operation. See Table 2 on page 10 forscrew torque specifications.

11) Reassemble the seal arrange-ment, making sure the sealing surfacesare perfectly clean and free of scratches,nicks,or burrs. When a carbon seal plateis used, always use a new carbon sealthat has been lightly polished on 400/600grit paper. When using a carbon seal, thecoupling housing screws (27) should betorqued to the manufacturer’s recom-mended limit. For pumps with a compres-sion packing seal, be sure all old packingis removed from the packing housing.

12) Inspect the drive shaft at the sealarea making sure that it is not scored,shouldered or worn. Worn shafts will resultin premature seal leakage and should bereplaced.

13) Dip the packing rings into high-temperature oil and graphite. This aids inassembly and running-in of the packing.

14) Place the first packing over theshaft and force it firmly and evenly to thebottom of the packing housing. Tap it firmlyinto place.

15) Rotate the drive shaft by handafter each ring is installed to aid in seat-ing the packing. Continue to install therings in this manner until the proper num-ber of rings have been installed.

16) Firmly compress the packing byalternating and evenly tightening up thegland screws, then back off 1/2 turn. Besure to adjust the gland evenly. The pumpshould not turn now.

17) In pumps with a universal sealcoupling, the seal area should be lubricat-ed with a high- temperature lubricant priorto installation.

18) Make sure that the rotating seal coupling is positioned with the shallow slottowards the internal pump shaft. Scoring onthe seal faces is detrimental to pump per-formance. Lapping should only be done onthe seal plate and not on the rotating cou-pling. Lapping the rotating coupling willincrease the end play of the seal resulting inpossible leakage and/or shaft misalignment.

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10

Screw Torque

Screw Torque Values* (Standard Alloy Steel)

Screw Size &Thread Torque (Lubricated Threads)(UNC Alloy Steel) lbs.-in. lbs.-ft.

#10-24 (w/ Carbon Seal Gasket) 50#10-24 (w/o Carbon Seal Gasket) 64#12-24 120 101/4-20 150 12.55/16-18 305 253/8-16 545 451/2-13 1,300 110

* In critical applications where control of bolt preload is important, the torque-tensionrelation should be determined by experimenting on the actual parts involved (includingthread lubricants). At elevated temperatures, it is often desirable to reduce screw stressbecause of deformation (creep) under sustained loading. Screws constructed of type H-11 high-temperature alloy steel provide extremely high creep resistance.

Table 2

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Troubleshooting

Trouble Probable Cause Remedy

Pump will not turn 1) Low pump temperature Check thermocouple and control loop for proper setting/operation. Allow sufficient heat-up time.

2) Drive malfunction Verify drive is powered.Check to assure all alarm circuits are clear.Check drive motor currentand speed settings.Check all drive couplings.

3) Process conditions Check process conditionschanged for proper melt tempera-

ture, pressures, viscosi-ties and materials.

4) Entrained particle Disassemble and clean pump; replace any damaged parts.

5) Possible internal damages Disassemble and clean pump; replace damaged parts. Consult factory.

Excessive seal 1) Worn seal plate Replace seal plate and assembly leakage coupling if necessary.

2) Drive shaft bottoming Readjust drive shaft.in coupling slot

3) Insufficient inlet pressure Increase inlet pressure.

4) Worn packings* Replace packings.

Reduced pump efficiency 1) Worn gear(s) Replace worn gear(s).

2) Worn bearings Replace worn bearings.

3) Process conditions Consult factory for changed clearance recommenda-

tions on new process conditions.

* A minor seal leak or weep is not abnormal and may be desirable for lubricating the seal surfaces.

FAILURE, IMPROPER SELECTION OR IMPROPER USE OF THE PRODUCTS AND/OR SYSTEMS DESCRIBED

HEREIN OR RELATED ITEMS CAN CAUSE DEATH, PERSONAL INJURY AND PROPERTY DAMAGE.

This document and other information from Zenith Pumps, itssubsidiaries and authorized distributors provide product and/orsystem options for further investigation by users having technicalexpertise. It is important that you analyze all aspects of your application and review the information concerningthe product or system in the current product catalog. Due to thevariety of operating conditions and applications for these productsor systems, the user, through its own analysis and testing, is solelyresponsible for making the �nal selection of the products and systems and assuring that all performance, safety and warningrequirements of the application are met.

The products described herein, including without limitation, product features, speci�cations, designs, availability and pricing, are subject to change by Zenith Pumps and its subsidiaries at any time without notice.

WARNING

© Copyright 1992 Zenith Pumps H C&M 10/04

Zenith® Pumps1710 Airport Road

Monroe, NC 28110Phone: 704-289-6511 • Fax: 704-289-9273

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