fluido barrera seleccion

5/26/2018 Fluido Barrera Seleccion

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Supply media formechanical seals

Rely on excellence


2/202

Introduction

Selection of the correct sealing system requires the

choice of a suitable supply medium. The question ofwhich supply medium is the right one is thereforeimportant, but not always easy to answer. The fact isthat unsuitable supply media may significantly reducethe life time of seals and have a negative effect on theprocess stream.

For the operator of the production plant, it is often noteasy to find the right product. This brochure will helpto evaluate the effects of supply media on the life timeof seals, and to choose a suitab le medium taking intoaccount the most important criteria.

On the following pages, basics, terms, and thepurposes of supply media are explained. This leads tothe properties of the ideal supply medium. Finally,standard supply media are discussed and selectedproblematic cases are described.

Generally, it is not possible to make a global statementon the basis of this brochure as to whether or not asupply medium is suitable for a mechanical seal. Butthe consequences and effects may be more easilyevaluated, and an increase of the seals l ife time maybe achieved in specific applications.


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If mechanical seals are used in pumps or other

machines like mixers or dryers, often a supply systemwith a suitable medium is necessary to cool and/orlubricate the seal or to avoid deposits. The externalmedium is named with the umbrella term supplymedium and performs diverse tasks dependent on theapplication.

Supply systems may be used in combination withsingle and multiple seals.

The supply system takes over the heat removal orcooling in cases of high process temperatures, or hightemperatures at the seal due to the dynamic fric tion ofthe seal faces.

If the process medium itself is not suitable forlubrication of the seal because of bad lubricationproperties, or other reasons, for example high solidcontents, then the supply medium takes over thelubrication.

If the operating temperature is near the vapour pointof the process medium, then there is an increased riskof evaporation in the sealing gap, and as aconsequence dry running and destruction of the seal.

The application of a supply medium can avoid this.

Supply media are also used if process media with a

high solid content have to be sealed. Part icles mayenter the sealing gap which can lead to a destructionof the seal faces. Beyond this, solids may depositinside the seal chamber thus blocking the o-rings andthe springs movabili ty.

Deposits at the atmospheric side of the seal occur ifthe process medium for example tends to crystallizeor due to crack residues from oils.

In a lot of applications the process medium has to becompletely separated from the environment. Possiblereasons are, environmental hazards caused by theprocess medium, threat to safety in the workplace, orthe process medium may not come into contact withoxygen.

Also heating of the seal by a supply medium may benecessary if the process medium has a high meltingpoint. Otherwise the process medium would harden atthe atmospheric side and therefore lead to damagesat the seal.

Purposes and function

Technical term

(according to API 682*)

Descripton Possible purposes

Quench Introduction of an external medium on the atmospheric side of

the mechanical seal.

nnnnnnnn

Flush Introduction of the process medium itself or an external medium

into the stuffing box chamber in the area of the seal faces.

nnnnn

Buffer medium Introduction of an external medium between two mechanical

seals whereas the pressure of the buffer medium is below the

pressure to be sealed.

nn

Barrier medium Introduction of an external medium between two mechanical

seals whereas the pressure of the buffer (barrier) medium is

above the pressure to be sealed.

nnnnnnn

n Cooling of the sealn Lubrication of the seal faces and therefore prevention of dry runningn Pressure increase in the sealing gap

(increase of P to the vapour curve)n Prevention of seal face destruction e.g. by solid particlesn Prevention of deposits in the area of the seal facesn Prevention of deposits at the atmospheric side of the sealn Complete separation of the process medium from the environmentnHeating of the seal due to process media with high melting point

*) Standard of the American Petroleum Institute for refineries and similar applications.

The most important applications for supply media and their purposes.

Seal supply system in operation


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Modes of operation and supply systems

Depending on the design and the arrangement of the

mechanical seal, and the required functions of thesupply system for the specific application, differentmodes of operation are possible or necessary. Theplans for the auxiliary systems are based on the API682.

Quench

A quench according to API P lan 51 or 62 means thatmostly water or a gaseous medium like steam ornitrogen is used as supply medium at atmosphericpressure.

Flush

Flushing serves ei ther to lower the temperature or toprevent deposits in the area of the seal faces. Theflushing medium may be the process medium itself oran external medium. The most common API plans are11, 21, 31 and 41. If an external medium is used thenit is called API plan 32.

The flushing pressure has to be always higher than the

pressure to be sealed. To restrict the flow of the flushinto the process medium the flushing medium shouldbe sealed against the impelle r. This can be achievedby using a flow rate restrictor (thrott le). The flowspeed in the throttle gap should be between 1.0 and2.5 m/s. Thus it is avoided that soiled product comesbetween the seal faces.

Plan 61: Plugged connectionsPlan 62 / 61

Plan 32

Plan 52 / 53A

Plan 74

API Plan 62 / 61

API Plan 32

API Plan 52 / 53A

API Plan 74

Buffer and barrier medium

If an external medium is introduced between twomechanical seals two different pressure conditionsare possible:

p3< p1: If the pressure of the supply medium (p3) islower than the pressure to be sealed (p1), then it isnamed a buffer medium (equivalent to API Plan 52) ora buffer gas (equivalent to API plan 72).

p3= p0: If the pressure of the buf fer medium isatmospheric pressure then we talk about anunpressurized operation.

p3> p1: In case of a pressurized operation accordingto API plan 53 or 54 the supply medium is calledbarrier medium or barrier gas with API plan 74.

In most cases it is recommended that the barrierpressure should be 2-3 bar higher than the highestpressure to be sealed. In cases with operatingpressures p1> 20 bar the barrier pressure should be10 % higher than the pressure to be sea led.

Different values should be seriously challenged and

matched with the relevant experts, if necessary. Incase of vacuum operation higher differential pressuresmay be required after consulting EagleBurgmann.

If a quench or a buffer medium is used due to thepressure conditions, the quench medium is enrichedwith the process medium in the course of time. Incase of a flush according to API plan 32, or apressurized operation according to API plan 53 or 54,the pressure of the barrier medium is a lways higherthan the operation pressure of the process medium tobe sealed. The result is that the barrier medium is

introduced into the process medium in a certainamount.

In a lot of cases a circulation of the supply medium isrequired. This can be provided by a natural ci rculationby the thermosiphon effect, or by forced circulationusing an integrated pumping device inside the seal, ora circulation pump. The circulating volume isdependent on different parameters like the type ofcirculation, the rotational speed, or the viscosity of theused supply medium.

Further information about the API isavailable in the brochure Sealingsystems according to API 682 whichwill be sent to you on request.


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SPS

N 2

SPN

Mechanical seal

SPU

SPI

1

2

m

(Option)

(Option)

(Option)

IN

INOUT

OUT

SPS

Orifice

SPN

Mechanical seal

SPU

SPI

1

2

m

Flare stack

(Option)

(Option)

IN

OUT IN

OUT

Pressurized thermosiphon system fornatural or forced circulation.

SPS - Level control unitSPI - Measuring unitSPU - Circulation pumpSPN - Refill pumpN2- Nitrogen

Pressureless thermosiphon system fornatural or forced circulation.

5

Supply systems

Supply systems can be divided into pressureless andpressurized systems. Examples for such systems aredisplayed on this page.

During the installation some genera l things have to beconsidered: Assembly and operating manual of the supplysystem.

The installation of the supply system shouldprovide an easy operation, monitoring and

maintenance. The tank should be positioned above themechanical seal (approximately 1 2 m) to allowa natural circulation of the supply medium. Thedistance may be shorter if the circulation issupported by a pumping device inside the seal or acirculation pump. The piping of the supply system loop should bemade of stainless steel and the dimensions shouldbe according to the assembly and operatingmanual. The pipe sections are normally connectedby screwed joints.

The arrangement of the piping should be as shortand streamlined as poss ible. To avoid air pocketsthe pipes should be installed steadily rising. Tochange the direction, only pipe bends and for shut-offs, ball valves with full bore should be used. In principle the outlet pipe of the mechanical sealhas to be connected with the lateral connec tion ofthe supply system tank. Please carry out thefollowing instructions for the connection: Mechanical seal OUT has to be connected withsupply system IN, Supply system OUT has to be connected withmechanical seal IN.

EagleBurgmann TS2000 seal supply system, displayed withcirculation pump SPU 5000. Equipped with all necessary

connections for additional measuring units.


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The ideal supply medium

The demands on the ideal supply medium are

sophisticated and it is difficult to always fulfill allcriteria. Therefore each decision is characterized bysetting priorities and making compromises. Mainly thefollowing criteria are important to select a suitablesupply medium:

High lubrication capacity High heat capacity Free of solids No tendency to deposit High resistance of the used materials High ageing resistance Suitable viscosity Good compatibility with the process medium No classification as hazardous substance High ignition temperature and high flash point Suffic ient distance between the boiling point andthe process temperature No tendency to foam Good availability and low costs

Cartex-DN double mechanical seal withconnections and integrated pumping device.The viscosity of the supply medium isrecommended to be max. ISO VG 5.

General demands

One of the primary tasks of a supply medium is thelubrication of the seal faces consequently the supplymedium should have a high lubrication capacity. Inmost cases the lubricity of water is sufficient. Also, ahigh heat capacity has advantages if the supplymedium is used for cooling the seal, because the heatcapacity is proport ional to the heat removal. The heatcapacity of the supply medium has to be consideredduring the dimensioning of the supply system tocalculate the required circulation rate for example.

The supply medium may neither contain solids nortend to build up deposits. Deposi ts or smears mayoccur, for example, due to crack residues of oils, ordue to residue building additives in oils, particularlyzinc or phosphor additives or silicates. For this reasonalso media which tend to crystallize should not beused.

The materials of the supply system have to beresistant against the supply medium. For example ifEPDM elastomers are used, no oil may be used assupply medium.

Important is also the high ageing resistance whichmeans the supply medium should not change itsproperties even after time. This may happen by theinfluence of temperature or shear stress, by contactwith air (oxidation reactions, cracking, formation ofacids, polymerisation) or humidity (hydrolysis,formation of acids).

Heat capacityspec. heat capacity at 20 C

[kJ/(kgK)]Thermal conductivity at 20 C

[W/(mK)]

normal water 4.3 0.6

30 % propylene glycol/70 % water 3.95 0.47

oil ~2 ~0.1

silicone oils 1.45 ~0.15

glycerine 2.4 0.3

ethanol 2.4 0.17

air 1 0.026

nitrogen 1 0.026

Oil and other hydrocarbons have about half of the heat capacity of water.

Specific heat capacities and thermal conductivities of typical media


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Viscosity

Low viscosity fluids are generally more suitable to beused as supply medium than fluids with a highviscosity. The higher the operational demands on theseal regarding rotating speed and heat generation thelower the viscosity has to be. (In exceptional caseshigher viscosities may be required. This has to bechecked on an individual basis.

The viscosity is dependent on temperature anddecreases with increasing temperature and vice versa.Therefore the viscosity index of the supply mediumshould be as high as possible, which means thetemperature dependence of the viscosity should be aslow as possible. In general synthetic oils have a higherviscosity index than mineral oils. Independent of theoperation mode of the mechanical seal, the followingrecommendations regarding the optimal viscosity ofthe supply medium can be given. Preferably i t shouldbe observed within the whole operating temperaturerange.

Natural circulation: 0.5 to 5 mm/s;

Forced circulation by a pumping device inside themechanical seal: 0.5 12 mm/s;

Forced circulation by an external circulation pump:0.5 15 mm/s.

A pumping device inside a mechanical seal may be apumping screw or a pump ring. Here the performancecurve has to be considered because it is dependent onthe viscosity. Seals with different pump devices likethe EagleBurgmann Cartexhave to be examinedseparately.

If an external pump is used for the c irculation itsdesign data has to be observed. For example, i f anEagleBurgmann SPU500 is used the maximumallowable viscosity is 15 mm/s.

If a gear pump is used in an EagleBurgmann SPA, apressurized barrier fluid system, the viscosity withinthe whole operating temperature range has to be12 mm/s minimum.

In exceptional cases, for example, with compressorsor agitators, higher viscosities (up to 68 mm/s) maybe used. But this always has to be checked with the

relevant experts.

The viscosity describes the thickness of liquids and melts, but alsoof suspensions. It is a measure of the fluids internal resistance to

flow and is defined by the frictional resistance with which a fluid

responds to deformation by compressive or shear stress. The higherthe viscosity the thicker the fluid and the lower the capability of

flow.

There are two related measures of fluid viscosity known as

dynamic and kinematic viscosity.

The dynamic viscosity is the ratio of shear stress and the velocity

gradient vertical to the flow direction. It can be defined by the forceF to move 2 parallel planes with the velocity v against each other. In

most cases it is measured with rotation viscometers.

V F

d

A

Graphical illustration of the dynamic viscosity.Source: Rmpp Lexikon

The current unit of dynamic viscosity is mPas. In earlier times theunit P (Poise) or cP (Centi poise) was used.

1 cP = 1 mPas. Water has a viscosity of 1 mPas at 20 C.

The kinematic viscosity is a measure of the internal friction in a

fluid. It is measured for example with a capillary or falling sphere

viscometer, or it is calculated by dividing the dynamic viscos ity by the

density of the liquid: = /

Today the common unit of the kinematic viscosity is mm/s. In

earlier times the unit St (Stokes) or cSt (centi Stokes) was used.

1 cSt = 1 mm/s.

Specialities regarding the viscosity are non-Newtonian fluids. In

contrast to Newtonian fluids these fluids change their viscosity with

the applied strain rate. As a result, non-Newtonian fluids may nothave a well-defined viscosity. Examples for non-Newtonian fluids are

blood, cement glues, quicksand, sand-water-mixtures, starch-water-

mixtures, lubricants, polymer melts, ketchup and pudding. Dependingon their properties change by the applied shear rate, non-Newtonian

fluids may be divided into pseudoplastic fluids (v iscosity is reduced

with shear rate) and dilatants (viscosity is increased with shear rate).

Non-Newtonian fluids should not be used as supply medium for

mechanical seals because their properties change when shear forces

are applied. This may have negative effects on the life time of the

mechanical seal.

Viscosity


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The ideal supply medium

Compatibility with theprocess medium

The compatibility of the supply medium with the

process medium has to be checked together with theend user in each case. The supp ly medium should beinert against the process medium, which means noreaction can take place between the supply mediumand the process medium at the correspondingoperating conditions.

Also the quality of the process medium must not benegatively influenced by the supply medium. This is ofparticular importance with end products such as, food,cosmetics and pharmaceuticals.

If necessary specific regulations like the germanRegulation about the use of extraction solvents andother auxiliary materials in the production of food, thegerman food and commodities act Lebensmittel- undBedarfsgegenstndegesetz (LMBG) and specificCodes of federal regulations (CFR) of the food &drug administration (FDA) has to be considered. Theevaluation whether a medium can be used as supplymedium in the food and pharmaceutical industry hasto be done by the operator of the seal.

On the strength of past experience supply mediawhich are certified according to USDA-H1 or NSF/H1(USDA = United States Department of Agriculture,NSF = National Sanitary Foundation) can be used.

Probably media which are approved according to CFR172: Food additives permitted for direct addition tofood for human consumption or CFR 178: Indirectfood additives: adjuvants, production aids, andsanitizers may also be used.

Security aspects

In principle the evaluation of the supply mediumregarding environmental hazard, health hazard andsecurity aspects (safety in the work place) has to bedone by the operator of the seal. The used supplymedium should not be classified as a hazardoussubstance, thus it should neither be harmful to healthnor to the environment.

The ignition temperature of the supply medium shouldbe significantly higher than the maximum operatingtemperature. Low flammability is a further criterion:the flash point should be significantly higher than the

maximum operating temperature. The formation ofexplosive or ignitable mixtures with air has to beavoided in all cases.

The maximum operating temperature should be atleast 40 C lower than the boiling point of the supplymedium. If the seal is only low stressed, which meanslow pressure, low sliding velocity and low temperature,a lower temperature difference of e.g. 20 C may besufficient. This has to be clarified on an individualbasis.

Documents to evaluate the supply medium with

regard to environmental hazard, health hazard and

security aspects (safety in workplace):

Material safety data sheet Technical instructions on air quality control TA-Luft

GESTIS database on hazardous substances (Information system

on hazardous substances of the German Social Accident

Insurance) List of hazardous substances of the German Institute for

Occupational Safety and Health. It contains the classification and

the labelling of substances according to the EC-directive 67/548/EWG, Appendix I List of hazardous substances, and the TRGS

905 Directory of carcinogenic, mutagenic or reproduction toxic

substances. European chemical Substances Information System (ESIS) Regulation (EC) No. 1272/2008

Ignition temperature and flash point

The ignition temperature is the lowest temperature of a hot surface

at which substances self ignite. According to this, the ignitiontemperature is the lowest temperature which flammable gases,

vapours, dusts or finely dispersed solids must have in the most

ignitable mixture with air to initiate the combustion or the explosion.It is not a material constant but dependent on the test conditions.

The flash point is the lowest temperature, corrected to a pressure of

101,3 kPa (760 Torr), at which the vapours can be ignited by anignition source under specified test conditions.

Source: Rmpp Online Lexikon


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Gas solubility, foaming

Increased gas content in the supply medium has anegative impact on the seal and has to be avoided.

Also foaming is problematic in combination with asupply medium.

Generally the gas solubility of liquids increases withrising pressure and decreasing temperature. Dissolvedsalts decrease the solubility of gases. Due to thelower density and the centrifugal forces the dissolvedgas (e.g. air, nitrogen) accumulates at the smallestdiameter and thus can not escape . This may lead to aring of gas in the seal gap and thus leads to dryrunning and destruction of the seal faces.

The degassing of the medium may be mainly aproblem in pressurized operation with the usage of athermosiphon vessel where nitrogen is used to createthe pressure in the supply system: in this case

nitrogen can dissolve in the barrier fluid and degassesinside the seal. Therefore it is recommended to limitthe maximum barrier pressure in combination withthermosiphon systems to 20 bar.

Foaming of the supply medium may occur if airdegasses in a liquid but does not collapse at thesurface. This may have different reasons, e.g. highcontent of additives in oi ls, impurities or leak air.

0

2

4

6

8

0 20 40 60

Methanol 50 C

Methanol -25 C

Mineral oil* 100 CMineral oil* 20 C

Water 0 C

Water 90 C

Standardcmgas/gsolvent

Pressure [bar]*viscosity at 38 C: 34,9 mm 2/s

0,00

0,01

0,02

0,03

0,04

0,05

0,06

0,07

0,08

0,09

0,10

0 10 20 30 40 50 60 70 80

Solubilityingnitrogenperkgwater

5 bar 15 bar 20 bar 30 bar 50 bar

Temperature [C]

0,00

0,05

0,10

0,15

0,20

0,25

0,30

0,35

-80 -60 -40 -20 0 20 40 60 80

Solubility

in

g

nitroge

n

per

kg

liquid

Temperature [C]

Water 1-Propanol Ethanol Methanol Olive oil

Henrys law

ci= ij pi

ci = concentration of gas in liquid

pi = partial pressure of the gas above the liquidij = temperature dependent solubili ty coefficient of the gas i in liquid j

(= Bunsen absorption coefficient or Bunsen coefficient)

The amount of gas which is dissolved in a liquid is proportional to its partial pressure at the liquid

surface (at equilibrium). At equilibrium means the liquid is saturated. Only at high pressures there will bea difference in proportionality.

The solubility of nitrogen in water dependent on pressureSource: The solubility of nitrogen and air in liquids, J. Phys. Ref. Data, Vol. 13, No. 2, 1984

The solubility of nitrogen in liquids at atmospheric pressureSource: The solubility of nitrogen and air in liquids, J. Phys. Ref. Data, Vol. 13, No. 2, 1984

The solubility of nitrogen in liquids dependent on pressure


10/2010

In this chapter detailed information about standard

supply media is provided and existing problems aredescribed.

Supply media which are often used: Water Mixtures of water-glycol Alcohols Different oils like mineral oils, synthe tic oils, whiteoils or vegetable oils Gaseous media like nitrogen or steam

Water

In a lot of cases water is a suitable supply medium. Inmost of the cases demineralized water or distilledwater can be used. Because the lubricationcharacteristics of these water qualities are quite badthe suitability has to be checked with an expert fromEagleBurgmann in case of hard/hard seal facecombinations and high operational demands on theseal.

Make sure that the temperature at the seal outletdoes not exceed 60 C. On the one hand a sufficien tdistance to the boiling poin t has to be ensured and onthe other hand the deposition of calcium carbonateshould be kept on a low level.

The water should not contain any solids as they tendto deposit (calcium carbonate). The deposition ofcalcium carbonate is mainly problematic at theatmospheric side of the seal due to the vaporisation ofthe leakage. This may lead to clogging of the dynamicO-ring.

Standard supply media

Water with the following properties is

suitable as supply medium.

6.5 pH-value 7.5

25 S/cm conductivity 250S/cm

Total dissolved solids (TDS) 500mg/l

Hardness of water 100 ppm CaCO3( 5.6 dH) 60 mg/l CaCO3 Alkalinity 150 mg/l CaCO3

(ideal is between 80 and 120 mg/l CaCO3)

no solids

Turbidity < 5 NTU Chloride content < 250 ppm

0 LSI (Langelier saturation index) +0.5

Free of gas, which means 0.2 Ncm dissolved gas

per cm of water

In general distilled or demineralized water fulfill these criteria.

Effects of the water quality on the function of a mechanical seal

Product side (PS) Atmospheric side (AS)(e.g. air)

Turbidity

Clogging of springs,dyn. O-rings, micro-organisms block bores

Solid content

Clogging of springs, dyn.O-rings, Wear of slidingfaces in case of had-softsealface combinations

supply medium

Chloride-content

Pitting corrosion at O-ring seatDamage of springs

LSI (Langelier saturation index) to evaluatethe tendency to calcium carbonate deposition

calcification

Dissolved gas

At decompression from p3to p0dissolved gas degasses from the liquid

risk of dry running

pH -va lue Conducti vi ty Tota l di ssol ved sol ids(TDS)

Hardness of water


11/2011

The Langelier saturation index can be calcu lated on

the basis of a water analysis, e.g. with the LSI-calculator from EagleBurgmann.

LSI = pH - pHspHs= f (TDS, T, c(CaCO3), A)

TDS = Total dissolved solids in mg/l T = Temperature in C c(CaCO3) = Concentration of calcium carbonate(CaCO3) in mg/l A = Alkalinity (measured as CaCO3in mg/l) pH = pH-value of the water

The decision tree below can be used to evaluate the

quality parameters of water which should be used assupply medium. The surrounding conditions, mainlythe temperature play a decisive role.

Some of the parameters interact in their effects thus ifonly one parameter is given the evaluation of thewater quality is not possible. Therefore the saturationindex (also Langelier saturation index, LSI) wasestablished which describes the tendency of waterregarding calcium carbonate deposition.

Decision tree to evaluate the quality of water as supply medium

Demineralized water or distilled water available?yes

Usable in most cases. Pay attention with high loaded seals and

had-hard seal face combinations!

no

Organize parameters of the water

pH-Value Conductivity Total dissolved solids

(TDS)

Hardness of water Solid content Turbidity Dissolved gas Chloride

content

LSI (Langelier saturation index)

Evaluation of tendency to calcium carbonate deposition

O < LSI < +0.5 no < 5 NTU < 0.2 Ncm3gas/cm3 < 250 ppm

Restrictions on seal life time can occur, but water can still be used.

If the parameters of the water are above the limits, a significant reduction of the seal life time will occur.

The alkalinity describes the capacity of water to

neutralize acids. It is measured in mg calciumcarbonate per liter of water (mg/l CaCO3). If thealkalinity is not known the following assumption maybe made (However this is only an approximation andtherefore imprecise):

Alkalinity (mg/l CaCO3) = Carbonate hardness (mg/lor ppm) 0.7

Typically calcification occurs under the followingconditions:Hardness > 100 ppm CaCO3 5.6 dH 1 mmol/lTDS > 1000 ppm andpH > 7.5

However the temperature of the water plays a decisiverole and has to be considered. The tendency ofcalcium carbonate deposition increases withincreasing temperature. Indeed there are possiblemeasures to influence the calcification:

Demineralization by reverse osmosis, distillation orde-ionization. With the aid of these water treat-ment methods the dissolved minerals are removedfrom the water and thus the total dissolved solids

(TDS-value) will be reduced. Water softening by using additives or ionexchangers. Thereby the calc ium and magnesiumconcentration in the water will be reduced. Acidification of the water by using e.g. citric acid.The pH-value should not fall below 6. Avoidance of high temperatures

Comparative table for hardness values

If the total hardness is known but not the calcium hardness it can be assumed that the measured hardness comes from calcium carbonate

(worst case). Then calcium hardness = total hardness.

German degree of

hardness [d]

Alkaline earth

metal ions

[mmol/l]

Alkaline earth

metal ions

[mval/l]

Engl. degree of

hardness [e]

French degree of

hardness [f]

ppm CaCO3[US]

1 0.2 0.4 1.3 1.8 17.8

3 0.5 1.1 3.8 5.3 53.4

5 0.9 1.8 6.3 8.9 89.0

8 1.4 2.9 10.0 14.2 142.4

10 1.8 3.6 12.5 17.8 178.0

13 2.3 4.6 16.3 23.1 231.4

15 2.7 5.4 18.8 26.7 267.0

18 3.2 6.4 22.5 32.0 320.4

20 3.6 7.1 25.0 35.6 356.025 4.5 8.9 31.3 44.5 445.0

30 5.4 10.7 37.5 53.4 534.0

1 German degree of hardness [d] is equal to 10 mg CaCO 3per 1000 ml of water


12/2012


Water-glycol mixtures

are mixtures of water and ethylene or propyleneglycol. Further additives should not be used. Water

with cooling agents like antifreeze or corrosioninhibitors, heat transfer media and cooling brines arenot suitable.

Propylene glycol should be preferred becauseethylene glycol has a health hazard potential and issubject to the classification according to theEC-directive of hazardous substances.

Typically, mixtures of about 30 % glycol and 70 %water are used as supply medium. Mixtu res with aglycol content of more than 50 % should not be usedbecause the viscosity significantly increases withincreasing glycol content. The advantage of mixturesof water-glycol over water is the considerably lowerfreezing point.

0 10 20 30 40 50

Content of ethylene glycol, propylene glycol or glycerol [mass%]

Boiling

point[C

]

100

101

102

103

104

105

106

107

108

109

water-ethylene glycol water-propylene glycol water-glycerol

0 10 20 30 40 50


Freezing

point[

C]

0

-5

-10

-15

-20

-25

-30

-35

-40

water-ethylene glycol water-propylene glycol water-glycerol

0 10 20 30 40 50


Spec.

heatcapacity

[kJ/kg

K]

3,0

3,1

3,2

3,3

3,4

3,5

3,6

3,7

3,8

3,9

4,0

4,1

4,2

4,3water-ethylene glycol water-propylene glycol water-glycerol

Boiling points of water-ethylene glycol, water-propylene glycol and water-glycerol mixturesSource: Internet, pro Khlsole GmbH

Freezing points of water-ethylene glycol, water-propylene glycol and water-glycerol mixturesSource: Internet, pro Khlsole GmbH

Specific heat capacity of water-ethylene glycol, water-propylene glycol and water-glycerol mixturesSource: Internet, pro Khlsole GmbH


13/2013

-30 -20 -10 0 10 20 30 40 50 60 70 80

0,5

1

2

5

10

20

50

100

200

water20 % propylene glycol30 % propylene glycol40 % propylene glycol50 % propylene glycol

Temperature [C]

Dynamicviscosity[mPas

]

-30 -20 -10 0 10 20 30 40 50 60 70 80

0,5

1

5

100

10

20

50

2

water20 % ethylene glycol30 % ethylene glycol40 % ethylene glycol50 % ethylene glycol

Temperature [C]

Dynam

icviscosity[mPas

]

Dynamic viscosity ofwater-ethylene glycol mixturesSource: Internet, Glykosol N Data sheet, pro Khlsole GmbH

Dynamic viscosity ofwater-propylene glycol mixturesSource: Internet, Pekasol L Data sheet, pro Khlsole GmbH

Agitator seal withTS-system

Dynamic viscosity ofwater-glycerol mixturesSource: Ullmanns Encyclopedia of Industrial Chemistry, paper Glycerol

-30 -20 -10 0 10 20 30 40 50 60 70 800,1

12

5

0,5

1020

50

100

water30 % glycerol50 % glycerol

Temperature [C]

Dynamicviscosity

[mPas

]


14/20


15/2015


Synthetic oils

There are different types of base oils produced bychemical synthesis. The most important group are thesynthetic hydrocarbons with the polyalphaolefines(PAO) and the alkylated aromatics. They are mainlyused for the lubrication of refrigerating machines.Polyalphaolefines are saturated aliphatichydrocarbons. They have a high oxidation resistancewhich is comparable with that of minera l oils and theyhave a very good chemical stabil ity.

The polyglycols are an additional group of syntheticoils with their most important representativespolyethylene glycols and polypropylene glycols. They

have a high viscosity index, limited oxidationresistance and very good lubrication properties.

Carboxylic acid esters were originally developed foraircraft engines. Polyol esters and diesters belong tothis group. Polyol esters are mainly used for thelubrication of refrigerating machines. Both the polyolesters and the diesters have very good thermal andoxidation resistance and a high viscosity index, usuallybetween 160 and 180. But both groups aresusceptible to hydrolysis if they get in contact withwater.

The phosphoric acid esters or phosphate esters aretertiary esters of phosphoric acid. They have a lowviscosity index, a good oxidation resistance but only inneutral environment, a limited thermal stability andthey are susceptible to hydrolysis if they get in contactwith water. Fluorinated elastomers should be preferredas secondary sealing elements.

If the oils should be fast and completelybiodegradable, then either vegetable oils, polyethyleneglycols or carboxylic acid esters (diester or polyolesters) should be considered.

Compressor oils are an additional group of mineraloils which are often used as supply medium. They arehighly raffinated mineral oils and therefore of higherthermal stability than standard mineral oils. They are

used to lubricate fast running bearings and gearsinstalled in turbo compressors and steam turbines.Oils for this use are specified in the DIN 51515.However, compressor oils are not suitable for highsliding velocities (>100 m/s), because they formdeposits or smears on the sliding faces.

Good experiences exist with the oils Shell Morlina 5and 10 and Aral Vitam AC, which have proventhemselves as barrier fluids used on several test rigs.

A further recommendation is Klber Paraliq 12, aparaffin type mineral oil: Certi fied according to NSF-H1, which means that itmay be used in food and pharmaceuticalapplications Operating temperature range: -10 60C Kinematic viscosity: 17 mm/s at 40 C and 3.7mm/s at 100 C

Mineral oils

Often so called lubricating oils are used as supplymedia. They are composed of the high boil ing

fractions of the raw oil and are separated by vacuumdistillation, de-paraffinized and de-aromatized. At theend high quality products are treated with hydrogenunder pressure to eliminate impurities. Thus the baseoils are produced. The properties of the end product(motor oil, gear oil, electrical insulating oil, metalworking oil, hydraulic oil etc.) are adjusted by mixingof base oils with different properties and by selectingsuitable additives.

Lubricating oils are classified in viscosity classesaccording to the ISO-VG (International organisation forstandardization Viscosity Grade). The labeling showsthe viscosity at 40 C.Example: ISO VG 5 -> ~5 mm/s at 40 C

In many cases also hydraulic oils are used as supplymedium. These are operating liquids used forhydrostatic and hydrodynamic transmission of power.The labelling shows which additives were added.

Product group Code according to

DIN 51502

Code according to

ISO 6743, part 3

Hydraulic oils without additives H HH

Hydraulic oils with oxidation inhibitors and

corrosion inhibitorsHL HL

Hydraulic oils HL with additional wear

protection additivesHLP HM

Hydraulic oils HLP/HM with additional

viscosity index improversHVLP HV

Classification of the hydraulic oils based on mineral oilsSource: ABC der Schmierung, Castrol


16/2016


Properties Mineral

oils

Synthetic oils

Synthetichydrocarbons

Polyglycols Carboxylic ac idesters

Phosphoricacid ester

PAO Alkylated

aromatics

Diesters Polyol

esters

Rheological behaviour at low

temp.

0 ++++ ++ +++ ++++ ++++ 0

Viscosity at high temp. + +++ + ++++ ++++ ++++ 0

Oxidation resistance

(with additives)

+ ++++ ++ +++ ++ ++++ +

Resistance to hydrolysis ++++ ++++ ++++ +++ + + 0

Biodegradability 0 0 0 ++ +++ 0

Toxicity low low low low low low increased

++++ excellent, +++ very good, ++ good, + acceptable, 0 moderate, poor

Comparison between the properties of mineral and synthetic oilsSource: Industrie Report Synthetische Schmierstoffe, Mobil Schmierstoff GmbH, 1999

PAO PAO & esters Diesters Polyglycols

Klber Summit

HySyn FG 15

Klberoil 4

UH1-15 AF

Klber Summit

DSL 32

Klber Summit

PGS 10 A

General information Mineral oil free

compressor oil

Synthetic compressor

oil; high oxidation

resistance and thermal

stability;fast biodegradable

Synthetic compressor

oil; low solubility of gas

Approval regarding food /

pharmaceutical applications

USDA-H1 and

FDA CFR 178

USDA-H1 / NSF H1 and

FDA CFR 178

Operating temperature

range [C]

-45 to 135 -45 to 110 to 140 to 140

Kinematic viscosity at

40 C / 100 C [mm/s]

15 / 3.6 15 / 3.5 31 / 4.9 10 / 2.5

Synthetic oils which are suitable as supply medium(Recommendations by Klber Lubrication)

Perfluorinated polyethers are a further group ofsynthetic oils. They are special lubricants which arevery stable and as a consequence they are essentiallyinert against chemical and corrosive attacks. Beyondthis they are non-flammable, non-combustible andharmless for health and environment.

Typical applications are in processes with strongoxidants like oxygen (O2), ozone (O3), nitrogen oxides(NOx), sulfur oxides (SOx), halogens (e.g. F2,Cl2),hydrogen halides (e.g. HF, HCl, HBr) and uraniumhexafluoride (UF6).

4 % Alkylated aromatics

1 % Others50 % Polyalphaolefines15 % Polyglycols

25 % Esters5 % Phosphoric acid esters

Usage of synthetic base oils in lubricantsSource: Industrie Report Synthetische Schmierstoffe, Mobil Schmierstoff GmbH, 1999


17/2017

If dry air is used it has to be considered that noreaction takes place between the process medium andair and that no explosive mixtures may form.

In case of gaseous supply medium it has to beconsidered that the lower the dew point the dryer thegas and the worse the lubrication capacity. In case ofdew point is < -70 C the wear of the carbon sealfaces will be increased. Another common gaseoussupply medium is steam. It is mainly used as steam

quench to heat the atmospheric side of the mechanicalseal in case of process media wi th a high meltingpoint. Thus solidification of the leakage is avoided. Asteam quench may also be used to avoid the contact ofleakage with the atmosphere if an undesired reactionoccurs between the medium and the air. Steam is alsoused in food applications.

If a steam quench is used, i t has to be considered thatthe steam temperature is high enough to avoidcondensation of the steam within the mechanical seal.If condensation could not be avoided the condensate

has to be systematically discharged to avoiddisadvantages at the mechanical seal.

Gaseous supply media

Are used to operate gas lubricated mechanical sealsor as quench medium in combination with liquidlubricated single seals and the most often usedgaseous supply media is nitrogen (N2). This can beused for many reaction systems as inert gas. Nitrogenis easily available in most of the production plants viaan internal network. Most gas lubricated mechanicalseals apply nitrogen as the barrier medium. Nitrogen

can also be used as gas quench e.g. as icingprotection at operating temperatures significantlybelow 0 C. The Icing of the atmospheric parts of themechanical seal is avoided by gas injection in the sealcover.

Another typical application is the usage of N2as gasquench in combination with liquid lubricated singleseals to avoid a reaction of the product leakage withair. Thus contact with oxygen in the air is avoided andno oxidation reaction may occur.

Perfluorinated polyethers (PFPE)

Klberalfa YM 3-30 Klberalfa DH 3-100

General informat ion Ful ly syn thet ic , non -flammable

lubricants with good low temperature

behaviour

High temperature oil

Operating temperature

range [C]

-60 up to +100

(at 21 Vol% oxygen content)

-25 up to 180

-60 up to +60

(at 21 Vol% oxygen content)

Kinematic viscosity at

40 C / 100 C [mm/s]

25 / 5 100 / 12

Perfluorinated polyethers which are suitable as supply medium(Recommendations by Klber Lubrication)

White oils

Are a group of oils which are often used as supplymedium. They are high-value lubricants which aresynthesized out of paraffinic oils. You can differentiatebetween technical and extra high-quality medicalwhite oils.

Technical white oils are very stable regardingenvironmental influences and gum formation and they

do not get rancid. Medical white oils are used inpharmaceutical, food and cosmetic applications andhave to fulfil high quality standards regarding purityand compatibility. Therefore these medical white oilsare colourless, odourless and tasteless and they arearomatic and sulphur free.

Due to their limited temperature stability the maximumoutlet temperature of the supply medium isrecommended not to exceed 60 C.

Vegetable oils

The advantage of vegetable oils as supply medium istheir good biodegradability. Beyond this they are easyavailable and may be used in the food industry.However vegetable oils have a relatively lowresistance against hydrolysis and a low oxidationresistance caused by the polyunsaturated fatty acids.Therefore vegetable oils should only be used forprocess temperatures up to 60 C. Purity requirements on gaseous supply media

like air and nitrogen according to ISO 8573-1

Class Units

quantity and size of particles 2 100.000 particles0.1 d 0.5 m

humidity class 3 -50 C < dew point -20 C

oil content 1 0.01 mg/m3

EagleBurgmann GSS4016 gas supply system for gaslubricated mechanical seals. The main functions of theGSS are:

Filtering of the barrier or the flushing gas Pressure monitoring and control Flow monitoring

Leakage control and discharge


18/2018

Diesel

Low flammable fuel mixtures for diesel engines whichmainly consist of paraffines with different contents ofolefines, cycloalkanes and aromatic hydrocarbons.Their composition may differ and is mainly dependenton the production process. Normal ly they have aboiling point between 170 C 360 C and a flashpoint between 70 C 100 C.

Diesel should not be used as supply medium becauseit is subject to the classification according to theEC-directive of hazardous substances (R40: Limitedevidence of a carcinogenic effect).

Highly purified water

(pharmaceutical water, ultrapure water, HPW HighlyPurified Water, WFI Water For Injection).

Highly purified water in different qualities is mainlyused as supply medium in food and pharmaceuticalapplications and if aseptic operating conditions arerequired. The quality of highly purified water (HPW)and water for injection (WFI) is the same, whereas

WFI may only be produced by distillation processesand HPW may also be produced by using membraneprocesses.

The problem with highly purified water withconductivities of < 5 S/cm is the bad lubricationcapacity and the high corrosiveness. If highly purifiedwater is used it has to be considered that su itablematerials are used. Stainless steels with low ferritecontent are resistant whereas 1.4404 and 1.4435have proved for higher requirements. Beyond this thesurface quality has to be on a high level.

For the face materials SiC against SiC is used asstandard where specific qualities have particularlyproven. Because of the bad lubrication propertiesHS-grooves should be used . PTFE or EPDM may beused as elastomer materials.

Antifreeze agents for cars

(cooler protection)

Indeed these media are often based on ethyleneglycol but contain corrosion inhibitors or otheradditives like e.g. silicates which may lead to a highwear of the seal faces. Common trade names are e.g.Glysantin.

Lubricants for automatic transmissions,so called

They are also called ATFs (Automatic transmissionfluid) and commonly used in the USA because of theirgood availability and low viscosity. But some additivesmay cause wear problems at the seal faces. For thisreason they should not be used for applications withhigh operating demands (high pressures, hightemperatures, high rotating speeds etc.).

Silicon oils

Have a very good thermal stability, are essentiallychemically inert and have a high viscosity index but at

high operating demands in most of the cases not verystable. They may contain silicate additives or formsilicates at high shear stresses. These glassy particleslead to an increased abrasion or form deposits andwill block the movability of the dynamic O-ring.For this reason they should not be used forapplications with high operating demands.

Methanol

Is commonly used in low temperature applications

with temperatures lower than -40 C. It has a meltingpoint of -98 C and a boiling point of 64.5 C.Disadvantages of methanol are the bad lubricationproperties and the classification according to theEC-directive of hazardous substances as toxic.

In this chapter some examples for non recommended

supply media are described. Nevertheless they areoften used. These are:

Not recommendedsupply media

EagleBurgmann supply system SPA 2000.Pressurized barrier fluid systems type SPA in its basic versionprovide all four functions of a supply system which are necessaryfor the operation of double mechanical seals: barrier fluid circula-tion, cooling, pressure build-up in the sealing chamber and leakagecompensation.

PW

(Purified Water,

gereinigtes Wasser)

HPW

(Highly Purified Water,

hochreines Wasser)

WFI

(Water For Injection, Wasser

fr Injektionszwecke)

Process Distillation , ion exchange, or other

suitable processes

E.g. reverse osmosis combined with

ultrafiltration and ion exchange

Distillation

Conductivity < 4.3 S/cm at 20 C < 1.1 S/cm at 20 C < 1.1 S/cm at 20 C

Water qualities according to Pharm. Eur.


19/2019

Service notes

The supply medium should be changed regularly. It is

recommended to change the supply medium aftereach repair, each shut down or if the concentration ofthe process medium in the supply system is too high,but at least every 12 months. The most economicchange interval has to be determined by the operatorof the production plant himself dependent on hisexperience.

In case of acid or alkaline process media the pH-valuein the supply system may be taken as indicator whento change the supply medium. When the pH-valuediffers more than 2 units from the original value thenthe supply medium should be changed. Beyond this achloride concentration of 250 ppm should not beexceeded in a closed loop thermosiphon systembecause an increasing corrosion rate can be theconsequence.

If the pump is installed outside then the risk offreezing has to be considered. The supply mediummust not be frozen and also the change in viscosityhas to be taken into account (viscosity increases withdecreasing temperature). In critical cases heating forthe seal should be provided.

Critical process media and the usage of supply media

are for example highly concentrated acids and bases.If in this case water is used as the buffer medium (thesealed process pressure is lower than the pressure ofthe buffer medium) the supply system is enriched veryfast with the acid or base process which may lead toan increased corrosion. Therefore the flow-throughoperation mode or a flush with an external mediumshould be used in this case.

If pressurized operation (pressure of the barriermedium is higher than the sealed process pressure) incombination with water as barrier medium is used, i tmay produce a spontaneous and large heatdevelopment. Beyond this a chemical potentialequalization occurs despite the higher barrier pressureand therefore an equalization of the pH-value betweenthe process and the barrier medium takes place quitefast.

A concrete example is the sealing of concentratedsulfuric acid. For this application positive experiencesare available with isododecane as supply medium atoperating temperatures up to 50 C and the supplymedium Galden(perfluorinated polyether). Generallyspeaking perfluorinated polyethers seem to be

suitable for the application with concentrated sulfuricacid because of their high chemical inertness. Paraffinand silicon oils have been found unsuitable severaltimes because they were decomposed by the sulfuricacid.

The trend is that concentrated sulfuric acid will beeither hermetically sealed by using a magneticcoupling or sealed by using gas lubricated mechanicalseals.

Supply media forcritical process media

Mechanical seal, type SH for high pressures and high slidingspeeds for the usage in heavy duty pumps in power plants and inthe oil industry. The displayed double seal SHF4 is equipped with apumping device and a cooling flange.

Because of the variety of applications all technical statements can only be seen asguidance. A warranty in particular cases is only possible if the exact operating conditionsare known by EagleBurgmann and if this is confirmed in a specific agreement. In case ofextremely critical operating conditions we recommend requesting expert advice from ourapplication engineers. Subject to modifications.


20/20

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Aeussere Sauerlacher Strae 6-1082515 Wolfratshausen / GermanyTel.: +49 (0)8171 23 0Fax: +49 (0)8171 23 12 [email protected]

www.eagleburgmann.com

EagleBurgmann is one of the leading internat ional companies for industrial sealing technology.Our products are used everywhere that safety and reliability are important: In the oil and gasindustries, pe troleum refining, pharmacy, chemicals, energy, food, paper, water, marine applications,aerospace and mining. Every day, more than 5,270 employees contribute their ideas, solutionsand commitment to ensuring that customers all over the world can rely on our seals. Our modular sealserv ice, TotalSealCare, underlines our commitment to customer orientation and our provision of

tailor-made services for every application.

Rely on excellence

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