savings as long as considerableattention is given on selecting the bestavailable sealing device technology.The high flush water flow rates actuallymask any inadequacies in amechanical seal or mechanicalpacking being used. The designcriterion of a mechanical seal ormechanical packing becomes muchmore critical when flush flow rates arereduced or eliminated. Plants todaycontinue to use what is referred to asflush in/flush out through a seal ormechanical packing. This practice isconsidered a huge waste of flushwater, seeing as the water is piped tothe floor or the nearest drain where iteventually ends up going to the

wastewater facility. A controlledamount going directly to the seal ormechanical packing is the best way toreduce overall flush waterconsumption.

New braided packing fibers andconstruction allow for reduced waterconsumption. Use of a SpiralTrac™centrifugal device as an ancillarydevice will reduce water usage evenfurther.

New single mechanical sealstechnology has been developed to runflush-free in stock service up to 4%.The use of single or split mechanicalseals with a SpiralTrac™ offersreduced or zero water consumption ina variety of mill applications. New

Water use and its reductionhas become a major focalpoint for pulp and paper

mills around the world. The adoption ofenvironmental laws such asEnvironmental Protection Agency’s(EPA’s) Cluster Rules in the UnitedStates and the European mills needingto comply with Integrated PollutionPrevention and Control Directive (IPPC-Directive) has driven many pulp andpaper mills around the world to reduceplant water usage and effluent streams.

Water use on rotating equipment isoften high and with today's advancedsealing systems can be dramaticallyreduced. By reducing water usage andleakage from rotating equipment, millscan realise significant reductions in theamount of effluent treatment.

Along with environmental concerns,various economic concerns with waterare also driving water conservation inthe pulp and paper industry. The costof water ranges widely depending onaccess, region and accountingpractices. Biological effluent treatment,advanced effluent treatment, limitedwater supply or municipal water useresults in charges range from as low as€0.02/m3 to €1.05/m3. In pulp millsusing black liquor as fuel, 1 l/min ofwater dilution can cost over €965 peryear to evaporate. An area oftenneglected is the reheating cost incurredwhen diluting an elevated temperatureprocess such as stock. Flush waterreheating costs can easily reach over€75 to €220 per year for each liter perminute of flush water injected into anelevated temperature processes.

Reducing flush water use on rotatingequipment can result in significant

technology dual mechanical seals withproper environmental controls offerwater conservation in more severeservices. Table 1 references achievableflush water reductions with today’sadvanced sealing systems: the use ofnew technologies within the frame of acost reduction programme cancontribute to mill wide savings well inexcess of €100,000 annually. Table 2is a typical example of a Make UpLiquor Pumps reheat savings at a mill.

WATER AND ENERGY SAVINGS ANDTHEIR FINANCIAL PERSPECTIVE

Today’s pulp and paper industry isfacing challenging times due to theworld financial crisis. Major pulp andpaper corporations are making painfuldecisions such as reducing productionoutput and head count across all theirmills just to remain competitive in themarket so they can deliver a profit totheir shareholders. If we want to take alook at the financial perspective on thesaving potentials, let’s have a look atthe simple Economic Value Added(EVA) calculation scheme including theexplanations (see Fig. 1, above)

To read this EVA scheme isrelatively simple. The first line is amathematical formula and if we wantto make the number on the right hand

side higher, we should decrease thenegative elements on the left handside. The problem is that we could notjust simply decrease them.

Cost of raw materials:The saving potential is relatively limitedas the raw material prices are drivenby the world market prices.Taxes:In some countries the localgovernment is supporting thosecompanies who are paying highattention to environmentally safe andpollution reduction programmes withdocumented results, but this is basedon the local governments and theirown rules.Conversion costs:The conversion costs are the onlyplace for significant saving potential formills to reduce their total operatingcost reduction goals. The conversioncost element has different factors as itis shown in the EVA figure. Let’sinvestigate the water related costfactors from the water saving point ofview:Safety and environmental:The water in the pulp and paperprocess is present everywhere. Waterleakage that is collected to the drainchannel has a potential risk for safety,

WORLD PULP&PAPER 37

FLUSH WATER REDUCTION

By Bob Martin and Zoltan Homoky, A.W. Chesterton International

WORLD PULP&PAPER 36

Reduce flush water usage and increase plantprofitability

Some pulpand papermills havethe opinion

that thewater is freefor them, for

example,“We are

taking thewater from

undergroundquells, which

is free…”

Sealing Device

MechanicalSealsMechanicalSealsMechanicalPackingMechanicalPackingMechanicalPacking

Equipment

Pumps

Agitators

Pumps

Agitators

Refiners

Previous(gal/min)

1-4

5-10

2-8

5-10

15-18

Reduced(gal/min)

0.0-0.2

0.5-1

0.25-0.50

0-1

2.5-5

Reduction

92%-100%

90%

88%-94%

90%-100%

72%-80%

Current -Recommended- Savings -

CurrentlyPacked

RecommendedSuperSet

Savings

EquipmentName

Packed MakeUp Liquor

Pumps inDigester Area.

Total

30.33

2.00

19.25

Dilution

28.83

2.00

26.83

To Drain

1.50

0

1.50

Evaporation

NA

NA

NA

WaterTreatment

NA

NA

NA

Reheat

€156,072

€10,827

€145,245

Totals

€156,072

€10,827

€145,245

Water Usage (Gallons per minute) Annual Water Costs €

Table 1: Achievable flush water reductions

Table 2: Make Up Liquor Pumps reheat savings

Figure 1 Economic Value Added calculation schemeBob Martin,global businessdevelopmentmanager

Zoltan Homoky,Key AccountManager, Pulp& Paper

eg. slippery surfaces. The environ-mental perspective is the less watergoing to the drain, less water having tobe cleaned and filtered which meansautomatic water and cost savings.Operations, maintenance, utilities,electricity and water:Being able to reduce flush water andservice water to rotating equipment canresult in significant freshwater andeffluent treatment cost savings. So thefinancial perspective is that if we areable to pump less water for rotatingequipment, the result is less electricityand energy output. The free water subject:Some pulp and paper mills have theopinion that the water is free for them,for example, “We are taking the waterfrom underground quells, which isfree…” or “We have the river next tothe mill and we are just taking thewater out from the river…”

Even this looks simple and easy, butis not 100% true, so let’s look at thewater related cost and the water loop(Fig. 2).There are always fresh watercosts like pumping the water from theoriginal source, filtration to make waterquality available for the process. Thereare always treatment costs like wastewater treatment, treatment and coolingof recycled water.

There are sometimes heat lossesespecially at pulp production. Thereare sometimes evaporation losses atthe evaporators in chemical pulp lines.

PULP AND PAPER’S OPERATING COSTSAND ENVIRONMENTAL CHALLENGESOperating costs and environmentalpressures are making an impact on theway we approach sealing pumps and

PAP2p36-44Chesterton* 8/3/10 1:45 pm Page 36

savings as long as considerableattention is given on selecting the bestavailable sealing device technology.The high flush water flow rates actuallymask any inadequacies in amechanical seal or mechanicalpacking being used. The designcriterion of a mechanical seal ormechanical packing becomes muchmore critical when flush flow rates arereduced or eliminated. Plants todaycontinue to use what is referred to asflush in/flush out through a seal ormechanical packing. This practice isconsidered a huge waste of flushwater, seeing as the water is piped tothe floor or the nearest drain where iteventually ends up going to the

wastewater facility. A controlledamount going directly to the seal ormechanical packing is the best way toreduce overall flush waterconsumption.

New braided packing fibers andconstruction allow for reduced waterconsumption. Use of a SpiralTrac™centrifugal device as an ancillarydevice will reduce water usage evenfurther.

New single mechanical sealstechnology has been developed to runflush-free in stock service up to 4%.The use of single or split mechanicalseals with a SpiralTrac™ offersreduced or zero water consumption ina variety of mill applications. New

Water use and its reductionhas become a major focalpoint for pulp and paper

mills around the world. The adoption ofenvironmental laws such asEnvironmental Protection Agency’s(EPA’s) Cluster Rules in the UnitedStates and the European mills needingto comply with Integrated PollutionPrevention and Control Directive (IPPC-Directive) has driven many pulp andpaper mills around the world to reduceplant water usage and effluent streams.

Water use on rotating equipment isoften high and with today's advancedsealing systems can be dramaticallyreduced. By reducing water usage andleakage from rotating equipment, millscan realise significant reductions in theamount of effluent treatment.

Along with environmental concerns,various economic concerns with waterare also driving water conservation inthe pulp and paper industry. The costof water ranges widely depending onaccess, region and accountingpractices. Biological effluent treatment,advanced effluent treatment, limitedwater supply or municipal water useresults in charges range from as low as€0.02/m3 to €1.05/m3. In pulp millsusing black liquor as fuel, 1 l/min ofwater dilution can cost over €965 peryear to evaporate. An area oftenneglected is the reheating cost incurredwhen diluting an elevated temperatureprocess such as stock. Flush waterreheating costs can easily reach over€75 to €220 per year for each liter perminute of flush water injected into anelevated temperature processes.

Reducing flush water use on rotatingequipment can result in significant

technology dual mechanical seals withproper environmental controls offerwater conservation in more severeservices. Table 1 references achievableflush water reductions with today’sadvanced sealing systems: the use ofnew technologies within the frame of acost reduction programme cancontribute to mill wide savings well inexcess of €100,000 annually. Table 2is a typical example of a Make UpLiquor Pumps reheat savings at a mill.

WATER AND ENERGY SAVINGS ANDTHEIR FINANCIAL PERSPECTIVE

Today’s pulp and paper industry isfacing challenging times due to theworld financial crisis. Major pulp andpaper corporations are making painfuldecisions such as reducing productionoutput and head count across all theirmills just to remain competitive in themarket so they can deliver a profit totheir shareholders. If we want to take alook at the financial perspective on thesaving potentials, let’s have a look atthe simple Economic Value Added(EVA) calculation scheme including theexplanations (see Fig. 1, above)

To read this EVA scheme isrelatively simple. The first line is amathematical formula and if we wantto make the number on the right hand

side higher, we should decrease thenegative elements on the left handside. The problem is that we could notjust simply decrease them.

Cost of raw materials:The saving potential is relatively limitedas the raw material prices are drivenby the world market prices.Taxes:In some countries the localgovernment is supporting thosecompanies who are paying highattention to environmentally safe andpollution reduction programmes withdocumented results, but this is basedon the local governments and theirown rules.Conversion costs:The conversion costs are the onlyplace for significant saving potential formills to reduce their total operatingcost reduction goals. The conversioncost element has different factors as itis shown in the EVA figure. Let’sinvestigate the water related costfactors from the water saving point ofview:Safety and environmental:The water in the pulp and paperprocess is present everywhere. Waterleakage that is collected to the drainchannel has a potential risk for safety,

WORLD PULP&PAPER 37

FLUSH WATER REDUCTION

By Bob Martin and Zoltan Homoky, A.W. Chesterton International

WORLD PULP&PAPER 36

Reduce flush water usage and increase plantprofitability

Some pulpand papermills havethe opinion

that thewater is freefor them, for

example,“We are

taking thewater from

undergroundquells, which

is free…”

Sealing Device

MechanicalSealsMechanicalSealsMechanicalPackingMechanicalPackingMechanicalPacking

Equipment

Pumps

Agitators

Pumps

Agitators

Refiners

Previous(gal/min)

1-4

5-10

2-8

5-10

15-18

Reduced(gal/min)

0.0-0.2

0.5-1

0.25-0.50

0-1

2.5-5

Reduction

92%-100%

90%

88%-94%

90%-100%

72%-80%

Current -Recommended- Savings -

CurrentlyPacked

RecommendedSuperSet

Savings

EquipmentName

Packed MakeUp Liquor

Pumps inDigester Area.

Total

30.33

2.00

19.25

Dilution

28.83

2.00

26.83

To Drain

1.50

0

1.50

Evaporation

NA

NA

NA

WaterTreatment

NA

NA

NA

Reheat

€156,072

€10,827

€145,245

Totals

€156,072

€10,827

€145,245

Water Usage (Gallons per minute) Annual Water Costs €

Table 1: Achievable flush water reductions

Table 2: Make Up Liquor Pumps reheat savings

Figure 1 Economic Value Added calculation schemeBob Martin,global businessdevelopmentmanager

Zoltan Homoky,Key AccountManager, Pulp& Paper

eg. slippery surfaces. The environ-mental perspective is the less watergoing to the drain, less water having tobe cleaned and filtered which meansautomatic water and cost savings.Operations, maintenance, utilities,electricity and water:Being able to reduce flush water andservice water to rotating equipment canresult in significant freshwater andeffluent treatment cost savings. So thefinancial perspective is that if we areable to pump less water for rotatingequipment, the result is less electricityand energy output. The free water subject:Some pulp and paper mills have theopinion that the water is free for them,for example, “We are taking the waterfrom underground quells, which isfree…” or “We have the river next tothe mill and we are just taking thewater out from the river…”

Even this looks simple and easy, butis not 100% true, so let’s look at thewater related cost and the water loop(Fig. 2).There are always fresh watercosts like pumping the water from theoriginal source, filtration to make waterquality available for the process. Thereare always treatment costs like wastewater treatment, treatment and coolingof recycled water.

There are sometimes heat lossesespecially at pulp production. Thereare sometimes evaporation losses atthe evaporators in chemical pulp lines.

PULP AND PAPER’S OPERATING COSTSAND ENVIRONMENTAL CHALLENGESOperating costs and environmentalpressures are making an impact on theway we approach sealing pumps and

PAP2p36-44Chesterton* 8/3/10 1:45 pm Page 36

FLUSH WATER REDUCTION

WORLD PULP&PAPER 38

rotating equipment today. This meanssealing methods are required to lowercosts and comply with local regulatorsby addressing the following costconcerns (fig. 3):

Whether the equipment is sealedwith packing or mechanical seals, thepercentages vary but maintenancecost and sealing water cost are the twoprimary cost drivers.

To improve on this and to help youto drastically lower the operationalcosts for sealing your rotatingequipment, Chesterton has developedthe Mill Wide Sealing Program. Thisprogram focuses on reducing the twoprimary cost drivers, maintenance costand sealing water costs, with

standardised system solutions thatimprove reliability while reducing oreliminating the need for externalsealing water.

Before we look at the systemsolutions, let’s first look at what are thesealing issues for mechanical seals inmills and look at ways to resolve these.

Let’s take a standard open stuffingbox, equipped with a common singlemechanical seal. What happens in thisstuffing box when the pump is started?First of all, because of the centrifugalforce generated by the rotation of theshaft, the stock in the stuffing box isthrown against the bore and collectsright there. Because of the rotatingaction of the impeller, an additional

The facts are that the two largestcontributors to the operational costs forsealing pumps and rotating equipmentin mills today are maintenance costsand sealing water costs (both beingcontrollable).

Effluent treatmentDilutionReheatDisposal

WaterConsumption Evaporation EnergyPollution

Figure 2 The water loop

Figure 3 Cost concerns

axial flow is introduced into the stuffingbox that drives the paper stock alongthe bore towards the end of thestuffing box.

The net axial flow is towards the endof the stuffing box and as a result thepapers stock collects at the seal faces.The heat generation of the faces andthe presence of air in the paper stockwill dry out the stock and the endresult is excessive heat generationcausing the seal to leak. This leakagewill get progressively worse and lead toseal failure as shown below in fig. 4(the seal and pump manufactures haverealised this and have provided youwith fixes to address this).

The most common fix to makemechanical seals work in paper stockapplications is by using a flush. Theexternal flush fluid is injected throughthe seal at higher pressure then theprocess and keeps the paper stockaway from the faces.

Flushing takes away the source ofthe problem and is therefore veryeffective. Yet, it is only as reliable asthe external supply system for flushwater. In many mills, the flush watersupply system is used for a variety ofservices including equipment hosedowns. This can easily lead to pressure

Figure 4: Flow patterns in enhanced open bore seal chamberPaper stock dries-out due to heat generation of facesDried-out paper stock causes excessive heat generationcausing seal failure

To helpdrasticallylower the

operationalcosts forsealingrotating

equipment,Chesterton

hasdeveloped

the Mill WideSealing

Program ad

PAP2p36-44Chesterton* 8/3/10 1:45 pm Page 38

liquor solids from the seal faces. For agitators, the key issue is

difficulty and cost of installation. Someof this equipment, such as fan pumpsare critical to the operation of thepaper machine and cannot be takenout of service. In those cases, packingis often used as repacking can bedone without equipment disassembly.

The split seal technology overcomesthis problem and allows easyinstallation of mechanical seals withoutequipment disassembly. Together witha split version of the SpiralTrac™ thisgives a fully split and reliable sealingsystem for larger pieces of equipmentsuch as fan pumps and chestsagitators as well as some of the largerstock pumps.The split sealing systemis a low flush solution and typicallygives 90% reduction in flush waterusage. It’s recommended to use a self-cleaning flow meter to control theselow flush rates.

ENVIRONMENTAL CONTROL SYSTEMSIn addition to the seals, we offer all

the needed environmental controlsystems to support the mechanicalseals. These environmental control

systems are designed for use in mills,taking into consideration the typicaloperating conditions and maintenancepractices that exist in mills. From self-cleaning flow meters that won’t clog todual seal support tanks thatautomatically maintain fluid level andrequire no regulator checks.

The SpiralTrac™ EnvironmentalController is a bushing that is fixed atthe bottom of the seal chamber thatfeatures a spiral groove on its insidediameter. This groove collects abrasiveparticles and expels them from thestuffing box.

The result is a clean seal cavity, freefrom abrasive which prolongs the lifeof the mechanical seal. There’s noneed to flush or the flush can bereduced by 90% compared to aconventional sealed seal chamber, theSpiralTrac™ works purely on therotation of the shaft and activelyremoves abrasives every time thepump is started.

In addition, the SpiralTrac™ ventsthe seal chamber to remove anytrapped air in the stuffing box thatcould cause drying-out or dry-running.It also improves circulation inside the

FLUSH WATER REDUCTION

drops in other areas of the supplysystem and can cause the flush waterto backflow, causing clogging. Inaddition, the clean external waterneeds to be supplied, heated andeventually evaporated out and treatedwhich all adds operational costs.

When we review the way a stockpump operates and with the fixes theindustry has been using commonly(fig. 5), we believe that flushing andquenching is not a very reliable andcost effective way of operating yourpumps:● The reliability of the system isdetermined only by the reliability of itsexternal support system: the flushwater supply.● The water required for flushing andquenching seals is expensive,especially if treatment and re-heatingcosts are taken into account.● Lastly, flushing or quenching iscertainly not in line with the principlesof ISO-14000 that suggests the 4-Rprinciple of Reduce, Re-use, Recoverand Recycle.

Let’s look at a different way tooperate your stock pumps that is costeffective and does give you extendedreliability. First of all, let’s start by usingthe right seal designs:

As the two primary reasons of failureare drying-out and abrasive wear, we

need to use seal designs that are ableto survive in the actual conditionsfound in mills.

Drying-out can be avoided by usinglow-heat generation seal designs suchas balanced seals with monolithic sealfaces. At the same time we need tomake sure that heat is dissipatedeffectively by using the rightenvironmental control such as theSpiralTrac™ device.

Abrasive wear can be drasticallyreduced by using hard, monolithicfaces that remain flat and parallel inservice and do not deflect or distort asis common with shrink-fitted sealfaces. Furthermore, abrasives shouldbe removed from the stuffing box byusing a low controlled flush or aSpiralTrac™ device that eliminatesexternal flushing completely.

Balanced seals that featuremonolithic seal face designs and havesprings outside the fluid are commonlyknow as third generation seals. Thirdgeneration seals offer the latest inadvanced seal technology and the bestguarantee for extended reliability.

This brings us to the best practicefor fibreline pumps. Best practice is toimprove shaft slenderness ratio toreduce any vibrations andmisalignment that affects the seal dueto off-curve operation, start-stop

WORLD PULP&PAPER 40 WORLD PULP&PAPER 41

The splitsealing

system is alow flush

solution andtypically

gives 90%reduction inflush waterusage. We

recommendusing a self-cleaning flow

meter tocontrol these

low flushrates

Figure 5: MostCommon FixFlush● Keeps paperstock away fromthe seal faces Disadvantages● System is onlyas reliable as theflush line● Water supply,reheating andtreatment cost

operation and system upsets such asplugs in the piping. Many pumps usedtoday have relatively slender shafts thatoffer no contribution to extended sealand bearing life. Replacing a sleevedshaft by a solid shaft already gives abig improvement and greatly helps tomake seals and bearings run morereliable for extended periods of time.

Note: Some pump companies offerpaper stock pumps that do have strongshaft designs so this first step may notbe necessary.

The second step is to utilise thirdgeneration seals that allow lowest heatgeneration and lowest susceptibility toabrasives.

The final element that completes theenhanced sealing system is theSpiralTrac™ bushing that activelyremoves the abrasives from the stuffingbox and provides additional cooling tothe seal. The SpiralTrac™ requires noflush to function unless the consistencyis over 3%. At these higherconsistencies, the entrained air in theprocess becomes more problematicand a small flush is best used to keepthe air out of the stuffing box. TheSpiralTrac™ however only requires verysmall amounts of flush to do so andsaves 70%-90% on water in mostapplications.

The best practice for liquor pumps isfollowing the same concept.

First, improve the shaft slendernessration to handle cavitations that may bepresent in some of the liquor pumps,such as in the evaporation area.

Then use third generation dual sealson most services, except for weakspent liquor applications. On the weakliquor applications, single seals maybe used.

Lastly, install the SpiralTrac™bushing to remove solids and preventcrystallisation. As the SpiralTrac™promotes circulation in the stuffing box,it is also very effective in preventingcrystallisation and removing black

Figure 6: Bestpractice forfiberline pumps● Improve shaftSlenderness ratio● Utilise thirdgenerationcartridge seals ● InstallSpiralTrac™: - No flushrequired - Use limitedflush over 3% orwhen there areother sources ofair entrainment

442 Split Seal

Split SpiralTracTM

Replacing asleeved shaft

by a solidshaft alreadygives a big

improvementand greatly

helps tomake seals

and bearingsrun more

reliable forextendedperiods of

time Figure 7: Best Practice For Liquor Pumps● Improve shaft slenderness ratio to handle commoncavitations in evaporation. ● Utilise third generation cartridge seals. - Weak liquors may use single seals. ● Install SpiralTrac™ to prevent crystallisation and removeblack liquor solids. ● With the use of closed loop water systems, water can beeliminated to the drain

PAP2p36-44Chesterton* 8/3/10 1:45 pm Page 40

liquor solids from the seal faces. For agitators, the key issue is

difficulty and cost of installation. Someof this equipment, such as fan pumpsare critical to the operation of thepaper machine and cannot be takenout of service. In those cases, packingis often used as repacking can bedone without equipment disassembly.

The split seal technology overcomesthis problem and allows easyinstallation of mechanical seals withoutequipment disassembly. Together witha split version of the SpiralTrac™ thisgives a fully split and reliable sealingsystem for larger pieces of equipmentsuch as fan pumps and chestsagitators as well as some of the largerstock pumps.The split sealing systemis a low flush solution and typicallygives 90% reduction in flush waterusage. It’s recommended to use a self-cleaning flow meter to control theselow flush rates.

ENVIRONMENTAL CONTROL SYSTEMSIn addition to the seals, we offer all

the needed environmental controlsystems to support the mechanicalseals. These environmental control

systems are designed for use in mills,taking into consideration the typicaloperating conditions and maintenancepractices that exist in mills. From self-cleaning flow meters that won’t clog todual seal support tanks thatautomatically maintain fluid level andrequire no regulator checks.

The SpiralTrac™ EnvironmentalController is a bushing that is fixed atthe bottom of the seal chamber thatfeatures a spiral groove on its insidediameter. This groove collects abrasiveparticles and expels them from thestuffing box.

The result is a clean seal cavity, freefrom abrasive which prolongs the lifeof the mechanical seal. There’s noneed to flush or the flush can bereduced by 90% compared to aconventional sealed seal chamber, theSpiralTrac™ works purely on therotation of the shaft and activelyremoves abrasives every time thepump is started.

In addition, the SpiralTrac™ ventsthe seal chamber to remove anytrapped air in the stuffing box thatcould cause drying-out or dry-running.It also improves circulation inside the

FLUSH WATER REDUCTION

drops in other areas of the supplysystem and can cause the flush waterto backflow, causing clogging. Inaddition, the clean external waterneeds to be supplied, heated andeventually evaporated out and treatedwhich all adds operational costs.

When we review the way a stockpump operates and with the fixes theindustry has been using commonly(fig. 5), we believe that flushing andquenching is not a very reliable andcost effective way of operating yourpumps:● The reliability of the system isdetermined only by the reliability of itsexternal support system: the flushwater supply.● The water required for flushing andquenching seals is expensive,especially if treatment and re-heatingcosts are taken into account.● Lastly, flushing or quenching iscertainly not in line with the principlesof ISO-14000 that suggests the 4-Rprinciple of Reduce, Re-use, Recoverand Recycle.

Let’s look at a different way tooperate your stock pumps that is costeffective and does give you extendedreliability. First of all, let’s start by usingthe right seal designs:

As the two primary reasons of failureare drying-out and abrasive wear, we

need to use seal designs that are ableto survive in the actual conditionsfound in mills.

Drying-out can be avoided by usinglow-heat generation seal designs suchas balanced seals with monolithic sealfaces. At the same time we need tomake sure that heat is dissipatedeffectively by using the rightenvironmental control such as theSpiralTrac™ device.

Abrasive wear can be drasticallyreduced by using hard, monolithicfaces that remain flat and parallel inservice and do not deflect or distort asis common with shrink-fitted sealfaces. Furthermore, abrasives shouldbe removed from the stuffing box byusing a low controlled flush or aSpiralTrac™ device that eliminatesexternal flushing completely.

Balanced seals that featuremonolithic seal face designs and havesprings outside the fluid are commonlyknow as third generation seals. Thirdgeneration seals offer the latest inadvanced seal technology and the bestguarantee for extended reliability.

This brings us to the best practicefor fibreline pumps. Best practice is toimprove shaft slenderness ratio toreduce any vibrations andmisalignment that affects the seal dueto off-curve operation, start-stop

WORLD PULP&PAPER 40 WORLD PULP&PAPER 41

The splitsealing

system is alow flush

solution andtypically

gives 90%reduction inflush waterusage. We

recommendusing a self-cleaning flow

meter tocontrol these

low flushrates

Figure 5: MostCommon FixFlush● Keeps paperstock away fromthe seal faces Disadvantages● System is onlyas reliable as theflush line● Water supply,reheating andtreatment cost

operation and system upsets such asplugs in the piping. Many pumps usedtoday have relatively slender shafts thatoffer no contribution to extended sealand bearing life. Replacing a sleevedshaft by a solid shaft already gives abig improvement and greatly helps tomake seals and bearings run morereliable for extended periods of time.

Note: Some pump companies offerpaper stock pumps that do have strongshaft designs so this first step may notbe necessary.

The second step is to utilise thirdgeneration seals that allow lowest heatgeneration and lowest susceptibility toabrasives.

The final element that completes theenhanced sealing system is theSpiralTrac™ bushing that activelyremoves the abrasives from the stuffingbox and provides additional cooling tothe seal. The SpiralTrac™ requires noflush to function unless the consistencyis over 3%. At these higherconsistencies, the entrained air in theprocess becomes more problematicand a small flush is best used to keepthe air out of the stuffing box. TheSpiralTrac™ however only requires verysmall amounts of flush to do so andsaves 70%-90% on water in mostapplications.

The best practice for liquor pumps isfollowing the same concept.

First, improve the shaft slendernessration to handle cavitations that may bepresent in some of the liquor pumps,such as in the evaporation area.

Then use third generation dual sealson most services, except for weakspent liquor applications. On the weakliquor applications, single seals maybe used.

Lastly, install the SpiralTrac™bushing to remove solids and preventcrystallisation. As the SpiralTrac™promotes circulation in the stuffing box,it is also very effective in preventingcrystallisation and removing black

Figure 6: Bestpractice forfiberline pumps● Improve shaftSlenderness ratio● Utilise thirdgenerationcartridge seals ● InstallSpiralTrac™: - No flushrequired - Use limitedflush over 3% orwhen there areother sources ofair entrainment

442 Split Seal

Split SpiralTracTM

Replacing asleeved shaft

by a solidshaft alreadygives a big

improvementand greatly

helps tomake seals

and bearingsrun more

reliable forextendedperiods of

time Figure 7: Best Practice For Liquor Pumps● Improve shaft slenderness ratio to handle commoncavitations in evaporation. ● Utilise third generation cartridge seals. - Weak liquors may use single seals. ● Install SpiralTrac™ to prevent crystallisation and removeblack liquor solids. ● With the use of closed loop water systems, water can beeliminated to the drain

PAP2p36-44Chesterton* 8/3/10 1:45 pm Page 40

FLUSH WATER REDUCTION

WORLD PULP&PAPER 42

adstuffing box allowing more efficientcooling and prevents crystallisationwith liquor pumps.

Now that we have looked at bestpractices for mechanical seals, let’slook at what can be improved onregular packed stuffing boxes.

Mechanical packing has traditionallybeen the common method of sealingrotating equipment. Many mills haveadopted mechanical seals to somedegree, some more then others. Stilltoday, many mills use packing forsome applications where a mechanicalseal does not work or where costs arejust too high.

FACTORS INFLUENCING THE LIFE OFPACKING

There are many factors thatinfluence the life of packing, some todo with the design, others with the waythey are used and maintained. Manyof these factors can be influenced andimproved upon by just simply lookingat a different or enhanced method toinstall packing.

With a conventional flushed packingsystem there are a number of issues:

● The distribution of the gland loadtransfer to radial load between eachpacking ring is very inefficient after thefirst three rings● The amount of sealing (radial load)reduces dramatically as thecompressive load decreases● The last two rings have a minimalradial load causing pulp to leakbetween the packing and sleevecausing sleeve and packing damage● After a few adjustments thelubricants are washed out of these lasttwo rings and lose volume. Thisrequires gland adjustments to maintainproper loading.● Increasing gland load to maintainadequate compressive load on thebottom rings creates higher radialloads on the top rings causing sleevedamage and packing glazing orburning●In addition the lantern ring dislocatesand may even obstruct the flush flowcompletely.

This way of installing packing ismaintenance intensive and leads toshort life, heavy sleeve wear (as seenbelow) and uncontrolled leakage.

Figure 9: SpiralTrac™ keeps the sealchamber free of abrasives● Vents the seal chamber. ● Actively and constantly removesabrasives without the need for flushing. ● Improves seal cooling by providing better circulation and effective fluidexchange. ● Increases life of the seal. ● Eliminates the need of a flush orreduces the flush rate by 90%

Figure 10: Factors that reduce packing life● Loss of lubricants. ● Heat damage to fibres. ● Erraticflush water systems. ● Damaged fibres due to abrasives. ● Extrusion. ● Lack of break-in. ● Chemical attack

Figure 11: Conventional Flushed Packing System● Gland load transfer is inefficient and gland loads arereduced drastically past the lantern ring. ● Radial load isinsufficient and allows stock to penetrate underneath thepacking causing wear

Figure 8: Best Practice For Agitators● Utilise third generation split seals ● Install SpiralTrac™; - use with 90% reduced flush.

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FLUSH WATER REDUCTION

By utilising the SpiralTrac™Environmental Controller andChesterton’s advanced mechanicalpacking technology, it has been proventhat only three rings of packing areoptimal for sealing mixers, pumps,agitators, and other critical equipment.

The patented SpiralTrac™ designremoves abrasive particulates from thestuffing box, replaces the bottom tworings of packing (in a standard

configuration), and extends packinglife. Figure 13 below shows anexample of the SpiralTrac™ Version Pand three rings of Chesterton packing(The Superset).

Consult your local ChestertonSpecialist for assistance specifying thecorrect packing style and quantity aswell as a SpiralTrac™ EnvironmentalController for your most challengingapplications today.

WORLD PULP&PAPER 44

Bottom of Stuffing Box

Lantern Ring Position

Bottom of Stuffing Box

Advantages of SpiralTrac™ Version P ● Fewer rings of packing required● Fewer gland adjustments after installation● Easier packing removal and repacking● less time consuming packing removal and repacking● Increase MTBR● Less sleeve wear● Lowers flush rate 60% to 90%

Figure 13: Chesterton SuperSet includes SpiralTrac™ VersionP with mechanical packing

Figure 12: Conventional Flushed Packing System: After a few adjustments1 Lubricants and blocking agents washed out; packingbecomes hard and lifeless. 2 Lantern ring dislocates,obstructing flush flow and causing excessive anduncontrolled leakage. 3 High sleeve wear

1 2 3

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