MR210 Metering Pump Tech

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Metering Pump Technology

Bulletin 210The Metering Pump . . . . . . . . . . . . . . . . . . . . . . . .1

Metering Pump Basic Components . . . . . . . . . . . . .1

Metering Pump Characteristics . . . . . . . . . . . . . . . .2

Capacity and Pressure Capabilities Chart . . . . . . . .3

Liquid End Designs . . . . . . . . . . . . . . . . . . . . . . . . .4

Packed Plunger . . . . . . . . . . . . . . . . . . . . . . . . .4

Dics Diaphragm . . . . . . . . . . . . . . . . . . . . . . . . .5

Mechanically Actuated Diaphragm . . . . . . . . . . .6

Metallic Diaphragm and Critical Service Head . . .7

High Performance Diaphragm -Advanced Liquid End Design . . . . . . . . . . . . . . . . . .8

Metering Pump Drive Mechanisms . . . . . . . . . . . .10

Hydraulic Bypass . . . . . . . . . . . . . . . . . . . . . . .10

Polar Crank . . . . . . . . . . . . . . . . . . . . . . . . . . .11

CENTRAC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Capacity Adjustment . . . . . . . . . . . . . . . . . . . . . . .14

Modifications . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Metering Pump System Components . . . . . . . . . .16

Other Milton Roy Products . . . . . . . . . . . . . . . . .18



The metering pump is a positive displacement chemical dosing device with the ability to vary capacity manually orautomatically as process conditions require. It features a high level of repetitive accuracy and is capable of pump-ing a wide range of chemicals including acids, bases, corrosives or viscous liquids and slurries.

The pumping action is developed by a reciprocating piston which is either in direct contact with the processfluid, or is shielded from the fluid between the piston and the diaphragm.Metering pumps are generally used in applications where one or more of the following conditions exist.

Low flow rates in ml/hr or GPHare required

• High system pressure exists

• High accuracy feed rate isdemanded

• Dosing is controlled by computer,microprocessor, DCS, PLC, orflow proportioning

• Corrosive, hazardous, or hightemperature fluids are handled

• Viscous fluids or slurries need tobe pumped

DriverThe pump is usually driven by an

AC constant speed motor. Variablespeed, pneumatic,and hydraulic driversare also utilized.

Liquid End The liquid end design and materi-

als of construction are determinedby the service conditions, and the

nature of the

fluid beinghandled.Temperature,flow rate, fluidviscosity, corro-siveness and

other factors are considered.

Drive MechanismThe drive mechanism translates

the rotary motion of the driver intoreciprocatingmovement.Industrial dutypumps willsubmerge thisportion of thepump in an oil bath to assure relia-bility during continuous operation.

Flow AdjustmentPump flow rate is adjustable by

varying stroke length, effectivestroke length, or stroking speed.Most meteringpumps aresupplied witha micrometerscrew adjustmentsimilar to theone shown here.The micrometercan be also be replaced by an elec-tronic or pneumatic actuator to

adjust pump flow rate in responseto process signal.

Liquid End

Driver

Drive Mechanism

Flow Adjustment

Metering Pump Basic Components

The Metering Pump



The pump action is developedby a reciprocating piston.Thisreciprocating motion develops

a flow sine wave.Actual flow rate isdetermined by the following formula:

Flow rate = Displacement xCycles per unit of time.

Unlike centrifugal pumps, flowrate is not greatly affected bychanges in discharge pressure.

The metering pump flow vs. stroke character-istic curve is linear. It is not, however, necessarilyproportional in that 50% stroke setting is notequal 50% flow.This is due to the fact that thecalibration line may not pass through 0 on bothaxes simultaneously. By measuring flow at 2stroke settings, plotting both points and drawinga straight line through them, other flow rates vs.stroke can be accurately predicted.

The steady rate accuracy of a correctlyinstalled industrial grade metering pump isgenerally + 1.0% or better.

Although a metering pump can generally be

adjusted to pump at any flow rate between 0and its maximum capacity, its accuracy is meas-ured over a range determined by the pump'sturndown ratio. Most metering pumps have aturndown ratio of 10:1, which simply means thatthe pump is within its accuracy rating anywherebetween 10% and 100% of capacity. Centrac is anew generation of metering pump that featureshigher accuracy, and a greater turndown ratio of 100:1.Therefore, this design will accurately doseanywhere between 1% and 100% of capacity.

Metering Pump Characteristics

Average Flow

Suction

Time

Peak Flow- π

x Average Flow

One Complete Cycle

Discharge

Metering Pump

Centrifugal Pump

Flow Q

Pressure P

Flow

RateQ

0 50 100

Point 2Q2. S2

Point 1Q1. S1

% Setting “S” Stroke Length Driver Speed



The maximum capacity of eachpump is determined by gear ratio,

piston diameter, and motor RPM.Maximum pressure rating applies

to smaller piston diameters in eachmodel.As the piston diameter andstroking speed increase, pressurecapacity decreases. See specificproduct data sheet for actual pres-sure rating at desired flow rate.

Capacities shown are for simplexpumps. For those pumps that canbe supplied with more than onehead, multiply the capacity by thenumber of heads to determinetotal capacity.

Capacity and Pressure CapabilitiesCapacity Per Head–GPH

0 5 1 0 2 0 3 0 4 0 5 0 7 5 1 0 0 1 5 0

2 0 0 3 5 0

5 0 0 7 5 0

1 0 0 0

1 5 0 0

2 0 0 0

3 0 0 0

24”

mRoy XT & XWMaximum Pressure

1800-3000 psi

Maximum No. Heads2

23”

mRoy XTMaximum–

1.6 GPH (6 LH)

Minimum– 0.4 GPH (1.5 LH)

mRoy A & BMaximum Pressure

350-1500 psiMaximum No. Heads

2

mRoy AMaximum–

30 GPH (114 LH)Minimum–

0.065 GPH (.246 LH)

8”

13”-24”

maxRoy BMaximum Pressure

150 psiMaximum No. Heads

1

maxRoy BMaximum–


13.5 GPH (51.1 LH )

Milroyal BMaximum Pressure


8

Milroyal BMaximum–


0.11 GPH (42 LH)

Centrac BMaximum Pressure


2

Centrac BMaximum–


0.45 GPH (100:1 Turndown)

121/4”-271/2”

Centrac SMaximum Pressure


2

Centrac SMaximum–

39.7 GPH (150 LH)Minimum–

4.0 GPH (15 LH)

11”

18”

Milroyal CMaximum Pressure


5

Milroyal CMaximum–


0.43 GPH (1.628 LH)

PrimeRoyalMaximum Pressure

30,000 psiMaximum No.Heads

3

PrimeRoyalMaximum–


0.43 GPH (1.628 LH)

72”

mRoy BMaximum–


0.475 GPH (1.79 LH)

mRoy XWMaximum–

6.7 GPH (25 LH)

Minimum– 2.8 GPH (9.8 LH)

27”

MacRoyMaximum Pressure


1

MacRoyMaximum–


0.018 GPH (0.068 LH)

m R

o y X T

m R

o y X W

Milroyal DMaximum Pressure


6

Milroyal DMaximum–


0.0081 GPH (0.0307 LH)

25”



The liquid end, which is thewetted part of the pump, isselected to meet the specif-

ic service conditions of the applica-tion. Required flow and pressureratings are considered, as well asthe physical and chemical proper-ties of the liquid.The liquid end'sability to protect the environmentis also a major considerationwhen dealing with toxic or haz-ardous materials.

All liquid ends have several fea-tures in common. First, the liquidis drawn into the wetted end bythe rearward motion of a piston,and expelled by the forwardmotion.To achieve this, the meter-ing pump is supplied with check valves at the suction and dischargeconnection points.

During the suction portion of thestroke, the motion of the piston liftsthe suction ball check from its seat

allowing liquid into the pump.At thesame time, the piston's motion andsystem back pressure holds theupper check valve (discharge) closed.This is then reversed during the dis-charge stroke.

Check valves are available in sever-al different designs and configura-tions.The choice of ball or poppetstyle is determined by Milton Roy'sEngineering department based oncapacity of the specific pump.

Most pumps feature either single or double ball configuration as standard. Theuser can also select single or double ball when the application is better served by

one or the other. For example, slurries or liquids with large fibers or particles can cause a single ball to leak if particles are trapped between the ball and seat.Therefore, a double ball check offers more stability and accuracy. On the other

hand, since each check valve causes some resistance in the flow path even when open, viscous fluids are better handled with a single ball suction check valve.

Single Ball CheckValve

Double Ball CheckValve

Poppet StyleCheckValve

Packed PlungerThe packed plunger style liquid end is the onlyliquid end in which the piston is in direct contactwith the process fluid.This direct contact offersa number of advantages, including: high suctionand discharge pressure capabilities; high temper-ature resistance, and lowest NPSH requirements.

The reciprocating piston requires packing toseal the wetted parts from the atmosphere.Thissimple design is effective, but places limitationson the use of packed plunge pumps in certainapplications.

Because a small amount of controlled leakagepast the packing must be expected, this styleliquid end should not be used with hazardous ortoxic chemicals.Additionally, the friction betweenthe piston and the packing results in wear thatincreases leakage. Periodic packing adjustment isnecessary to maintain volumetric efficiency.Toavoid problems associated with leakage, considera diaphragm style liquid end.

The packed plunger can handle pressures upto 15,000 psi, and temperatures to 600oF (withspecial modifications).

Available on: Milroyal B, Milroyal C, Milroyal D, Centrac, and Maxroyal Standard Materials of Construction: 316 SS, Alloy 20,Cast Steel (larger models)

Liquid End Designs

Discharge

Suction

Piston

Discharge Ball Check Valve

Process Fluid

Process Fluid

Ball Check

Seat

Suction Ball Check Valve


Grease Fitting

Packing Lantern Ring


Piston



Available on: mRoy A, mRoy B, Milroyal B, Milroyal C Standard Materials of Construction: 316 SS, Alloy 20, Plastic

Process Fluid

Hydraulic Fluid

Reservoir Hydraulic

Fluid


Relief Valve

Piston

Automatic Air-Bleed Valve

Teflon Diaphragm


Contour Plates

The disc diaphragm liquid endhas a teflon diaphragm which actsas a barrier between the pistonand the process fluid.The piston's

pumping motion is applied tohydraulic fluid which causes thediaphragm to flex back and forthas the piston reciprocates.

The hydraulically actuateddiaphragm operates with equalpressure between the hydraulic andprocess fluids.This eliminatesdiaphragm stress, since the pressureis essentially equal on both sides atall times.Two contour plates encase

the diaphragm to contain its travel.The hydraulic and process fluidspass through carefully engineeredholes in the contoured plates in

order to come into contact withthe diaphragm. Relief and refillvalves control the volume of hydraulic fluid.An automatic airbleed valve continuously purges airfrom the hydraulic fluid.

The diaphragm style pump is leak-proof. It therefore is an excellentchoice for hazardous, toxic, or cor-rosive chemicals. For extra protec-tion, double diaphragm and leak

detection modifications are avail-able, although they are consideredredundant since this design isextremely durable.

Because the process fluid mustpass through relatively small holesin the contour plate, the discdiaphragm liquid end is not the bestchoice slurries.With the exceptionof the mRoy P design, discdiaphragms are usually not the bestchoice when pumping viscous fluids.

The disc diaphragm is capable of handling pressures up to 3500psi,and temperatures to 250oF.

Disc Diaphragm





The Milton Roy Series of Metallic Diaphragms are unparalleled for use in critical, high pressure appli-cations such as oil and gas platforms and specialty industrial applications.They are especially usefulwhere temperatures and pressures of both the environment and the process chemical can be vari-

able or otherwise difficult.The Metallic diaphragm lines are preferred for their longevity and durability in

many difficult applications.

Metallic Diaphragm Liquid End and Critical Service Head

Available on: Milroyal C and PrimeRoyal: 316 SS, Alloy 20, Plastic

Metallic diaphragm meteringpumps are hydraulically-actuated inthe same manner and style as a stan-dard hydraulically-actuated drive liq-uid end. However, the teflon orother usual diaphragm material isreplaced with a special metal alloyparticular to the application to

produce higher pressures than moretraditional materials.The metaldesign of the diaphragm also man-ages difficult chemicals such asabrasives, slurries and other specialrequirements compounds easierand more efficiently than its morestandard version.

Many oil and gas offshore drillingplatforms require metallicdiaphragms because of their highreliability and longevity. In any appli-cation where critical service isrequired, the Milton Roy MetallicDiaphragm is the product of choicefor these chemical dosing situations.

Diaphragm Head


Diaphragm Head Bolts /Nuts

DisplacementChamber

Set Screws

Plunger Adapter Nut

Plunger Sleeve

Plunger

Detail B

Diaphragm

O-Ring

O-Ring

O-Ring BackupO-Ring

BackupO-Ring

Screws

Hydraulic Fluid

Process Fluid



The High Performance Diaphragm liquid end, HPD, combines all of the best characteristics of traditionalliquid ends into one technologically advance design. It’s operating characteristics and simplicity of opera-tion make the best pump to consider first for most metering pump applications.

HPD operations is similar to the disc diaphragm in that it is hydraulically actuated and utilizes the sameshape and diaphragm. It is similar to a tubular diaphragm in the respect that the process fluid has a “straightthrough” path through the liquid end. It is low NPSH requirements requirements are similar to that of apacked plunger liquid end. But the primary advantages of the HPD are the unique design features that sepa-rate it from traditional designs.

The MARS AdvantageA hydraulically actuated diaphragm

liquid end design requires a refill sys-tem to compensate for hydraulic fluidthat bleeds past the piston or throughan air bleed valve during normal oper-ation.Hydraulic fluid is also expelledfrom the chamber through the inter-nal relief valve when the system expe-

riences excess pressure, and there-fore must also be replenished.

The HPD features a MechanicallyActuated Refill System (MARS) thatoffers a number of advantages overtraditional refill systems.To under-stand the advantages of MARS,tradi-tional refill systems must first beexplored.

Traditional DesignsTraditional designs use a system thatrefills the chamber when a vacuum is

created by the inability of thediaphragm to move beyond thehydraulic contour plate. It also refillswhen the suction is momentarily orpermanently starved by accidentalvalve closure, insufficient NPSH,orother similar occurrences.When thishappens, the hydraulic fluid chamberis overfilled because a vacuum hasbeen created even though thediaphragm has not been able to travelrearward.To avoid diaphragm rupturedue to overfilled hydraulic oil, aprocess side contour plate stops thediaphragm's forward travel, and forcesthe hydraulic relief valve to open,thusexpelling the excess fluid.

The contour plate is a concave(actually, concave-convex) disc thatsupports the diaphragm and limits itstravel.The plate has a series of holesbored through it to permit the fluid

to come into contact with thediaphragm.The pattern and size of these holes requires careful engineer-ing to maintain the contour platestrength required to withstand theforce of the diaphragm experience atthe operating pressure.

The hydraulic contour plate doesnot cause any problems in pumpoperation since the hydraulic fluidpasses easily through the contourplate holes.However, a process con-

tour plate, required by traditional discdiaphragm liquid ends, places limita-tions on the types of process fluidsthe pump can handle (such as slur-ries) since the process fluid must alsopass through contour plate holes.Theprocess contour plate also creates apressure loss which raises the NPSHrequirement of the liquid end.

The MARS SystemThe MARS System eliminates the

need for a process contour plate byassuring that the hydraulic fluid canonly be refilled when the diaphragmhas traveled all the way back to thecontour plate.The diaphragm pressesagainst the MARS valve,which onlythen permits a poppet valve to openfrom the vacuum created by insuffi-

cient hydraulic fluid. (See the illustra-tion lower right)Hydraulic overfill is therefore

impossible.With the process contourplate gone, the straight through pathof the process liquid makes the HPDa perfect choice for slurries and vis-cous materials. It also lowers theNPSH requirements of the pump,since pressure loss through a processcontour plate is eliminated.

The MARS system also simplifiesHPD start-up. Unlike otherhydraulic liquid ends, the refill valvedoes not need adjustment.Additionally, since the HPDhydraulic fluid cannot be overfilled,there is no need to perform deli-cate procedures to synchronizehydraulic fluid balances (a difficulttask required for tubular and otherdouble diaphragm liquid ends).WithHPD, you just fill the reservoirs, andturn it on.

Traditional Liquid End with Process and Hydraulic contour Plates (refill system not shown)

Typical Contour Plate(Section cutaway)

High Performance Diaphragm...

Discharge

Suction

Process Contour Plate

Process Fluid

Hydraulic SideContour Plate

Hydraulic Fluid

Piston

Diaphragm



The HPD features a pre-shaped PTFE/elastomercomposite disc diaphragm.

On the process side, the chemicalresistance of PTFE is utilized. Onthe hydraulic side, the elastomerimparts favorable elastic andmechanical factors.

The composite diaphragm elimi-nates the inherent problems of pure PTFE diaphragms. PTFE tendsto cold flow when compressedbetween two metal parts (such asthose required to seal thehydraulic side from the process

side).The HPD compositediaphragm features an integral "O"ring seal around the perimeter of the diaphragm, which provides abetter seal between hydraulic andprocess fluids than conventionaldiaphragm materials.

The HPD is capable of handlingpressures up to 3025 psi and tem-peratures up to 300oF (with spe-cial modifications).

Available on: Milroyal C., Milroyal D, Centrac and Maxroyal. Standard Materials of Construction: 316SS. Alloy 20, Plastic.

HPD Pre-shaped Composite Diaphragm

MARS System Operation

Pre-shapesComposite

Diaphragm.

Figure 1 Diaphragm (A) and piston (C) are full forward. Mars valve (B) in forward position holds poppet valve (D) closed, preventing refill line hydraulic oil from entering the chamber.

Figure 2 Diaphragm (A) and piston (C) are full rearward. Mars valve (B) is also rearward due to diaphragm position, thus freeing poppet (D) to open if required. Poppet (D) is shown closed, indication hydraulic oil refill is not required.

Figure 3 Diaphragm (A) and piston (C) are full rearward, once again forcing Mars valve(B) to its rearward position, which allows

poppet (D) to open if required. Low oil volume creates a vacuum and opens poppet, permitting hydraulic fluid to enter the chamber from the refill line.

...Advanced Liquid End Technology

Full side view of HPD Liquid End on MilRoyal Drive

Air Bleed/Relief Valve

Piston

Hydraulic Refill Line

RemovableCheck Valve

Composite Diaphragm

Mechanically Actuated Refill System (MARS)

MARS Valve Poppet

Process Fluid

Hydraulic Fluid

Reservoir Hydraulic Fluid

A

B

C

D

A C

D D

A C

PTFE Elastomer

B B

Standard Materials:316SS. Alloy 20, Plastic.

Milroyal B HPD Low Flow



All Milton Roy drive mechanisms feature gears that are submerged in an oil bath to assure long life. Capacitycan be adjusted while the pump is running or stopped, + 1.0% accuracy over a 10:1 turn-down ratio.

Hydraulic By-PassThe hydraulic by-pass mechanism features a piston with a constant stroke length that pumps hydraulic fluid,

thus transferring the pumping motion to a diaphragm.Therefore, this type of drive can only mate with a hydrauli-

cally actuated diaphragm liquid end.Capacity is varied by changing the location of a hydraulic by-pass port over the piston's path of travel. If the

port is positioned at 50% of the piston's stroke length, hydraulic fluid will be relieved through the port during thefirst half of the piston's stroke, and pumped against the diaphragm during the remaining half.This type of drive isoften called "hydraulic lost motion," because a portion of the piston's travel does not transmit pumping energywhen the capacity adjustment is less than 100%. Both the mRoy and the Maxroy are hydraulic by-pass stylepumps. Both develop reciprocating piston motion by way of a worm gear and eccentric.

maxRoy BIn the maxRoy, capacity is varied by positioning a stroke adjust sleeve over by-pass ports bored through the hol-

lowed piston.When operating at 100%, the ports are covered,which traps hydraulic fluid in the hydraulic pumpingchamber. Once trapped, the piston's pumping action forces the hydraulic fluid to flex the diagram.

A cup valve, which is attached to the diaphragm, closes all hydraulic paths to the diaphragm when it comes to thediaphragm when it has reached the full forward position.This eliminates a process contour plate, as well as excessivehydraulic pressure on the diaphragm, since any excess hydraulic fluid in the hydraulic pumping chamber cannot reach

the diaphragm, and is forced through theinternal relief valve to the fluid reservoir.

The maxRoy drive features:

• Maximum flow rates between 135 GPHand 227 GPH

• Maximum discharge pressures of 150 psi

The maxRoy is an excellent choice formid-range metering pump capacity at lowpressure. Its design is more economical thanhigh pressure pumps in the same capacityrange, without sacrificing ruggedness andaccuracy.The "straight through" process fluidpath allows maxRoy to be applied to many of the same services as the HPD liquid end.

mRoy A, mRoy BIn the mRoy, the piston pumps

hydraulic fluid, which either forces the

diaphragm to flex, or is relievedthrough the by-pass port.A controlvalve positions the port based on adesired capacity setting.

The mRoy drive with its standarddisc diaphragm liquid end features:

• Simplex or Duplex liquid ends

• Maximum capacities rangingbetween 0.43 GPH and 85 GPH(170 GPH Duplex)

• Maximum pressures up to 1800 psi

The mRoy drive withit’s standard disc

diaphragm liquid end.

Eccentric

Metering Pump Drive Mechanisms

Hydraulic Fluid


WormGear Set

Piston Hydraulic Oil in Pumping Chamber Suction

Discharge

Eccentric

Stroke Adjust Sleeve

Cup Valve

Diaphragm

Capacity Adjustment

By-Pass Ports

Worm Gear Set

Stroke Length

Suction

DischargeControl

Valve

Motor

By-Pass Control Plunger

By-Pass Port

Diaphragm

Hydraulic Fluid


Process Fluid

10



To achieve a high thrust capacityand extend component life, theMilroyal B and C polar crank drives

feature a pressurized lubrication sys-

tem.This positive oil pressure lubrica-tion ensures long bearing life and per-mits the Milroyal pump to operate at

very high suction and discharge pres-sures.As the

crossheadmoves forwardduring the dis-charge stroke,oil from thereservoir isdrawn upthrough a bailcheck into a

cavity in the crosshead. During thesuction (rearward) stroke the lubri-cant is trapped. It is then forced

through the crosshead, into thecrosshead connecting rod bearing,through the hollow connecting rod,and finally to the crank connectingrod bearing.By forcing the oil throughthis path, every moving part is lubri-cated during ever complete cycle of the pump.

To reduce the wear of moving partsand extend oil life, a magnetic strainercleans the oil before it enters thepressurized system.

The unique polar crank driveis the heart of the Milroyalseries metering pump. It is

considered the most advanced and

reliable variable stroke length driveavailable in high pressure/high flowindustrial duty metering pumps.

In the polar crank drive, a highspeed worm gear reduces the RPMsupplied by the motor, and providesthe lower RPM to a rotating crank. Aconnecting rod with spherical bear-ings on each end links the crank tothe crosshead and piston assembly.

The worm gear and crank assemblypivots in an arc about the worm shaft

center to change stroke length.Thepiston stroke length is determined bythe angle of the assembly.

For example, when the pump is atzero stroke, the worm/crank assem-bly is in a vertical position. (Figure 1)The crank then rotates in a vertical

plane and one end of the connectingrod revolves with it.The crossheadand the piston remain stationarybecause no reciprocating action isproduced.When the pump is adjust-ed full stroke (or maximum capacity),the rotating crank is moved to itsmaximum angle from the verticalaxis. (Figure 2) At the top of the rota-tion cycle the connecting rod ispushed forward,moving thecrosshead and piston to the full for-

ward position at the end of the dis-charge stroke.As the crank continuesto rotate, the angle of the crank

causes the connecting rod to pullthe crosshead and piston until itreaches the full rearward positionat which point the connecting rod

has reached the bottom of therotation cycle.

Regardless of the stroke lengthsetting, the top of the rotationcycle always forces the crossheadand the piston to the full forwardposition at the end of each dis-charge stroke.This assures com-plete scavenging of the liquid endduring each stroke cycle.

The angle of the polar crank canbe adjusted in infinite increments

between zero and maximum strokefor extremely accurate controlledvolume pump settings.

Polar Crank

Lubricating Oil Relief Valve

Lubricating Oil

High Speed Worm

Worm Gear

Connecting Rod Magnetic Strainer

Crosshead

Piston

Micrometer Stroke

Adjustment

This illustration demonstrating the polar crank at full and zero strokes

High Speed Worm

MicrometerCapacityControl

Worm Gear

Rotating Crank

Lubricating Oil

Lubricating Oil Relief Valve

Figure 1 Zero Stroke

Connecting Rod

Cross Head

High Speed Worm

WormGear Rotating

Crank

Suction

Discharge

Stroke Length

Figure 2 Full Stroke

The Milroyal polar crank drive features:

• Maximum capacity rangesbetween 0.033 GPH (125mL/hr.)and 2510 GPH depending onframe size, stroking speed, andplunger diameter

• Discharge pressures up to7500 psi

• Up to 8 pumps multiplexedand driven by one motor

• HPD, packed plunger, discdiaphragm, or tubulardiaphragm liquid ends

Pressurized Lubrication System



Centrac's impressive operatingcharacteristics are the result of aunique constant stroke length drivemechanism that depends on a spe-cial electronic variable speed drive

to vary pump flow rate.This offersa number of advantages.

Traditional designs utilize wormgear sets to convert motor rotationto reciprocating motion through aneccentric or similar mechanism.Worm gears are the best choicewhen the drive mechanism isrequired toincorpo-rate a vari-able stroke

lengthadjustment.They oper-ate well athigh rotaryspeeds,dueto an oilshield thatdevelopsbetweenthe gear surfaces.Unfortunately, theylose that shield at lower speeds,

which causes wear and raises motortorque requirements.This limitsworm gears to a 10:1 turndownratio.

Centrac, on the other hand, uti-lizes a special helical gear set. Sincethere is no need for stroke lengthadjustment, the gear set is verysimple.Also, helical gears are knownfor operating with low noise andlow friction. Combined with a basicscotch yoke mechanism to develop

reciprocating motion, this gear setruns quietly and efficiently with fewmoving parts.All moving parts aresubmerged in oil to ensure long life.

The graph below indicates the

greatest advantage of Centrac's spe-cial gear design.The flat torque curve(vs. the worm gear set) allowsCentrac to operate at or below 1%of speed without placing extrademand on the motor, thus permit-ting Centrac's 100:1 turndown ratio.

The simple drive mechanism alsoallows Centrac to beeasily duplexed withinthe same housing byadding a second pis-

ton and liquid endopposite the primaryliquid end.Centrac'scapacity can thereforebe doubled economi-cally and efficiently.

Centrac's Advanced Electronic Variable Speed Drive

Conventional AC and DC variablespeed drives are limited to turn-down ratios between 5:1 and 30:1.This is insufficient to take advantage

of the turndown capabilities of Centrac's gear design.

New technology in brushless DCmotors and controllers has createdadvanced drives capable of strongoperation at low speeds. Centrac's

variable speeddrive deliversrated torqueat less than1% (100:1turndown) of

maximumrated RPMwhile main-taining steadystate speedcontrol atbetter than +0.1%. It is theperfect matchfor Centrac'sdrive mecha-nism.

12

Centrac represents a newconcept in metering pumpdrive design. It is the first

true innovation in metering pump

drives to be introduced in decades.Centrac was developed by combin-ing the highest level of gear reductiondesign, and the latest technology inelectronic variable speed drives.The

result is a metering pump that boaststwice the accuracy over a turndownratio ten times greater than tradition-al designs.

Centrac's name clearly announcesits capabilities:CENT-100:1 turndown ratioR-Response & ReliabilityAC - + 0.5% steady state accuracy

Centrac is different from tradition-al designs in many ways.The mostsignificant way is the close relation-ship between the driver and drive

mechanism and how they enhanceoverall pump performance.Tounderstand Centrac better, thesetwo design elements and their inter-dependence need to be explored.

Advanced Drive Technology

CENTRAC – The Automatic Process

CENTRAC ScotchYoke Drive

Torque vs. Motor Speed-CENTRAC and Worm Gears

Motor Speed-RPM

200

180

160

140

120

Block transfers Rotating Eccentric Motion to Reciprocating Motion

Full Load

0 10 20 50 100 175 200

Low Speed Eccentric & Gear

Motor Drive Gear(18 to 1800 RPM)

10:1 Turndown

T y p i c a l o f W

o r m

G e a r P u m p D r i v e s

100%

1400 1500

100:1 Turndown

Operator Control Station

Centrac's Unique Gear Reduction System



Centrac's variable speed drivefeatures:

• 100:1 turndown ratio

• + 0.1% steady state speedcontrol

• smart commutation - permitsaccurate feedback signal

• no brushes (low maintenance)

• constant torque at low speeds -permits efficient driver sizing

100:1 Turndown RatioThe flexibility of a 100:1 turn-

down ratio permits Centrac to beapplied where a wide range of dosage rates are required. It alsoprovides built-in growth potential

by pumping efficiently in systemsrequiring a fraction of the pump'scapacity for the short term duringstart-up or early phases of anexpanding project. Centrac providesall this without compromising accu-racy or drive power.

ResponseCentrac responds instantly to

changes in dosage rate. Its constantstroke length does not upset bal-ance within the liquid end hydraulicsystem, that is, hydraulic fluid vol-ume remains constant.When the

hydraulic balance is disturbed, as invariable stroke length designs, thefull result of dosage changes cantake minutes or hours.

Centrac's instant response providessmoother operation in closed loop orautomated systems. It also assuresproper dosage at all time in systemsrequiring very close dosage tolerance.

AccuracyCentrac's + 0.5%

steady state accura-cy over its fullturndown ration is

a result of theconstant strokelength, and the pre-cise speed controlof Centrac's drive.This level of accura-cy provides maxi-mum chemical econ-omy while assuringstable automaticoperation and opti-mum process quality.

Centrac's features include:

• 100:1 turndown ratio

• + 0.5% steady state accuracy

• Instant response to dosagechanges

• Simple but robust design for

reliability• Precise feedback signal

• Efficient drive sizing

• Mates with advanced HPD liquidend for maximum performance

• Capacity range between 0.45GPH minimum and 1100 GPHmaximum

Metering Pump

Liquid End

Mounting Surface

Main Gear

Driver ShaftGear Assembly

Optional DuplexConfiguration

Motor Mount

Eccentric Eccentric CageCrosshead

Connection Diagram

Drive Motor

Motor Control Optional RemoteOperator Control

AC Input Power Remote Speed (Flow Rate)Control Signal

Speed (Flow Rate)Output

Signal



Metering pumps allow the user to vary capacity as the process requires.All Milton Roy metering pumpspermit adjustment whether the pump is running or not.With the exception of the Centrac (see Centrac drive), Milton Roy pumps are supplied with a manual

micrometer for performing manual capacity adjustments. Depending on the type of drive mechanism and theapplication requirements, one of several capacity adjustment options can be supplied.

Capacity Adjustment

Manual MicrometerThe manual micrometer can be

used to adjust the metering pump'scapacity anywhere between 0 and100%.While not directly propor-tional to flow, this calibrated adjust-ment can be used to accurately setpump capacity based on the pumpperformance curve within + 1.0%over the turndown ratio.

Electronic ActuatorOption Available for: mRoy A & B, MaxRoy, Milroyal B & CThe Milton Roy Electronic Actuator responds to electronic process signals or remote manual adjust-

ments. In addition, a local handwheel is provided to permit manual adjustments when unpowered.Milton Roy's electronic actuator is different from electric actuators in that it utilizes electronic

limits. It is built around stepper motor technology, which allows it to travel precisely to positionwithout overshoot or hunting.

This design also provides superior operating characteristics such as:

• 100% duty cycle• + 0.5% position accuracy or better• low maintenance

Remote control stations are available for local/remote selection and manual capacity adjustment.Specifications:

• NEMA 4 (Explosion proof available)

• 4-20 mA input signalstandard

• Direct or reverse acting

Pneumatic ActuatorsOption Available for: mRoy A & B, Milroyal B & CAutomatic systems that supply a pneumatic process signal benefit from the Milton Roypneumatic actuator.A separate air control panel is available for remote control andauto/manual switching.

Specifications:

• 3-15 or 3-27 psi pneumatic signal• Direct or reverse acting• Requires 60 psi supply air pressure

Manual Micrometer

• 1-5 VDC stroke positionoutput signal

• Single phase 50/60cycle 115 VAC

Electronic Actuator on mRoy A

Pneumatic Actuator



Milton Roy's diaphragm liquid endsare, by design, leakproof and durable.In some applications, however, addedassurance is desired to protect the

pump from hostile chemicals, or pro-tect the process from contaminationby hydraulic fluids. For these situa-tions, Milton Roy has developed ahighly reliable diaphragm rupturedetection system.

The system consists of two sepa-rate diaphragms, a hollow intermedi-ate ring, and a pressure gauge orswitch. During the normal operation,

the two diaphragms are pushed tight-ly together and are separated onlyaround their outside edge by theintermediate ring.The rupture detec-

tion system senses a pressure onlywhen a diaphragm ruptures.The sys-tem is not affected by changes inpump discharge pressures.

This system is available for metallicliquid end mRoys,maxRoys, andHPD's. A different design centeredaround sensing changes in conductiv-ity is also available for a number of liquid ends.

Modifications Double Diaphragm With Diaphragm Rupture Detection System

Milton Roy offers a wide variety of standard pumps to satisfy most applications. In addition, our ApplicationsEngineering department is capable of supplying specialty engineered products.

Application Engineering: Custom Modifications

Capabilities include:

• Special liquid end materialsincluding diaphragms, diaphragmheads, check valves, etc.

• Special piston diameters

• High temperature or pressuremodifications

• Unique multiplex arrangements• Application counseling

• Special sensors, indications, orinstrument interface

• Special drive modifications orgear ratios



Proper metering pump system operation depends upon the selection of appropriate system components.Milton Roy offers high quality accessories to suit your application requirements.

Metering Pump System Components

4.Calibration ColumnsAll Milton Roy metering pumps

are factory tested. Once installed,pump calibration should be periodi-cally determined to verify properoperation, especially after the per-formance of any maintenance.Milton Roy calibration columnsprovide an inexpensive means of assuring pumping accuracy.

5.Mixroy® MixersAccurate dosing requires proper

mixing of the solution beingpumped. Mixroy mixers are directdrive, high speed units designed formixing medium and low viscosityfluids and dispersion of light solids.

6.Tanks and Chemical Feed Systems

Milton Roy offers tanks (up to250 gallons capacity) in steel, stain-less steel, and polyethylene.Theyare also available with pumpsmounted, plumbed, and ready forinstallation.

1.Safety ValvesMost piping systems require the

use of an external safety valve to

protect the piping from over-pres-sure. Diaphragm pumps featureinternal safety valves to protect thepump, but external safety valves arestill recommended. Milton Roy man-ufactures safety valves for pressuresto 1500 psi and flow rates to 550GPH. Standard safety valves areavailable in steel, 316 SS, alloy 20,and PVC.

2.Back Pressure ValvesTo prevent unmetered liquid from

free-flowing through the pump,

metering pump systems require agreater pressure in the dischargeline than the suction or inlet line.When the process does not supplyminimum of 25 psi above the suc-tion pressure, a back pressure valveis required. Back pressure valves areavailable for flow rates to 460 GPHand pressures to 200 psi.

3.Pulsation DampenersThe metering pump's reciprocat-

ing motion provides a pulsating dis-

charge flow.Applications requiring asteady flow can eliminate over 90%of the pulsations with a pulsationdampener. Dampeners are availablefor pressures to 1000 psi. Sizing isbased on cubic inch/stroke displace-ment of the specific pump.



7 Strainers/Sludge TrapsThe metering pump's check valves

should be protected from particles anddebris by installing a strainer in thesuction line.

When pumping concentrated sulfuricacid, a sludge trap is required to trapsludge particles while providing easycleaning or flushing.

Foot valves and strainers are availablefor applications that pump fluid fromreplaceable drums. "Y" type strainerscan also be supplied for in-line protec-tion in standard systems.

Typical Installation

Pump

3 Pulsation Dampener

2 Back

PressureValve

1 SafetyValve

To Process

4CalibrationColumns

7 Strainer

6Tank

5 Mixroy®

Mixer

Ball Valve

Ball Valve

Ball Valve

Ball Valve

Tank Cover

Pipe

PlugWire Screen

Fiberglass

Balls

Wire Screen

Lower Housing

Bushing Pipe Plug



Streaming Current Detector

Milton Roy's Streaming Current Detector(SCD) is used to monitor and control

coagulants in water or wastewater treatment.The SCD is an on-line instrument, therefore

consistent effluent quality is assured.In addition to water and wastewater treat-

ment, the SCD is widely used in paper making,petroleum, food, chemical, and other indus-tries where close control of coagulant orcharge altering chemicals is beneficial.

Electronic ActuatorsA broad line of electronic actuators, similar to those used on Milton Roy pumps, is available for control valve

actuation and other applications requiring precision and dependability.These advanced electronic actuators out-perform standard electric designs by utilizing stepper motor technology.

Other Milton Roy Products

Milton Roy's electronic actuators offer the following advantages:

• 100% duty cycle

• Electronic limit switches

• Direct to position operation-nohunting or overshoot

• Rotary or linear designs• AC and DC units

• Responds to 4-30 mA, split range,digital and other process signals

• Maximum torque - 3800 in-lbs(317 ft-lbs)

• Maximum thrust - 1100 lbs

• Optional controllers and failsafe units

The Milton Roy Family of Streaming Current Detectors





Documents

MR210 Metering Pump Tech