bronze award

• INTRODUCTION TOAESSEAL®

• MECHANICAL SEALHISTORY

• WHAT IS A MECHANICALSEAL?

• SEAL BALANCE

• SHAFT FRETTING

• THE CARTRIDGE SEALRANGE

• CHOOSING THE CORRECTMATERIALS

BRONZEMechanical SealTraining Course

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© Copyright 2002 AESSEAL plc All Rights Reserved.L-UK/US-AWARD-B-06

AESSEAL®

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ISSUE 06 - 01/2002

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CONTENTS

PAGE

Bronze AwardMechanical Seal Training Course

Contents PageSection Description Page Number

Introduction to AESSEAL® ................................................................4

The Market: ......................................................................................6

Mechanical Seal History: ..................................................................9

What is a Pump?: ............................................................................10

What is a Mechanical Seal?: ..........................................................14

Types of Mechanical Seals: ............................................................16

Seal Balance: ..................................................................................22

Primary Seal Face Flatness: ..........................................................26

Shaft Fretting: ..................................................................................27

The AESSEAL® Modular Sealing System: ......................................28

The Cartridge Seal Range:..............................................................34

Elementary Environmental Controls: ..............................................39

Choosing the Correct Materials: ......................................................42

Seal Application Form: ....................................................................46

Glossary of Seal Terms: ..................................................................49

All seal sales are made in accordance with AESSEAL plc standard conditions of sale 2969L.ame Issue5 dated 6th June 2000 Document Ref (IN 4506). In particular we would like to emphasise clause 9.2,which follows:

The sole obligation of AESSEAL plc under this Limited Warranty shall be to repair or replace or haveits Authorised Distributor repair or replace any defective products within forty-five business days of acomplaint communicated in writing to AESSEAL plc.AESSEAL plc SHALL NOT BE LIABLE FOR THE BREACH OF ANY WARRANTY, EXPRESS OR

IMPLIED, INCLUDING WITHOUT LIMITATION ANY WARRANTY OF MERCHANTABILITY OF

FITNESS FOR A PARTICULAR PURPOSE, OR FOR ANY DAMAGES OR OTHER LIABILITY ARISING

OUT OF OR IN CONNECTION WITH CUSTOMERS’ USE OF SUPPLIER PRODUCTS OR AESSEAL plc OR

THE AUTHORISED DISTRIBUTOR DESIGNING, MANUFACTURING OR SELLING SUPPLIED

PRODUCTS. IN NO EVENT SHALL AESSEAL plc BE LIABLE FOR DIRECT, SPECIAL, INCIDENTAL OR

CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION LOST SALES OR PROFIT, LOST

PRODUCTION OR OUTPUT, INJURY TO PROPERTY OR REPUTATION, OR ANY OTHER DAMAGES

WHETHER ARISING IN CONTRACT OR TORT OR OTHERWISE (WHETHER OR NOT ATTRIBUTABLE

TO THE FAULT OR NEGLIGENCE OF AESSEAL plc). UNDER NO CIRCUMSTANCES SHALL ANY

RECOVERY OF ANY KIND AGAINST AESSEAL plc BE GREATER IN AMOUNT THAN THE PRICE OF

THE PRODUCT TO THE END USER.

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© Copyright 2002 AESSEAL plc All Rights Reserved. L-UK/US-AWARD-B-06

AESSEAL®

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ISSUE 06 - 01/2002

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INTRODUCTION TO

AESSEAL®

The Company, originally called Aurora Packings & Seals Limited, was formed in 1974 to sellMechanical seals, Compression packings, Hydraulic seals, Sheet jointing and Maintenance products.

In 1979, the Company was purchased by the present Managing Director and re-named A.E.S.Engineering Ltd., since when considerable expansion plus further acquisitions have taken place.

The Head Office and main manufacturing centre (center) of AESSEAL® is at the Global TechnologyCentre, Mill Close, where the design, testing, assembly and distribution of seals also takes place.

Introduction to AESSEAL®

Other units are at:

• Mangham Road, Rotherham, South Yorkshire,where specialist machining and the productionof the metal bellows range takes place.

• Bradford, where large diameter mechanicalseals are manufactured.

• Derby, a Mechanical Seal Service Centre(center) and regional sales office.

• Derby, Component seal division.

• Peterborough, a regional sales office,Mechanical Seal Service Centre and PumpRefurbishment Centre (center).

• Middlesbrough, regional sales office.

• Scotland, regional sales office.

• AESSEAL SE plc, Essex, regional sales office.

• AESSEAL SE plc, Pontypridd, regional salesoffice.

• AESSEAL (MCK) Ltd. Lisburn, EngineeredSystems Division.

• AESSEAL (MCK) Ltd. Co. Cork, regionalsales office.

• Knoxville Tennessee, Seal Refurbishing andAssembly Plant for the North Americanmarket.

• Seneca Falls, New York, USA, regional salesoffice.

• AESSEAL Eastman Site, Kingsport,Tennessee, regional sales and service office.

• AESSEAL ESP LLC, Cedar Rapids, Iowa,

• AESSEAL Deutschland AG. Germany,regional sales office.

• AESSEAL Italia, Italy, regional sales office.

• AESSEAL Pty Ltd, South Africa, regionalsales office.

• AESSEAL Pty Ltd, Confluid Branch, SouthAfrica, regional sales office.

• AESSEAL Malaysia SDN. BHD. regionalsales office.

• AESSEAL Nederland, regional sales office.

• AESSEAL (Iberica S.L.) regional sales office.

• AESSEAL Danmark, regional sales office.

• AESSEAL France s.a.r.l., regional sales office.

• AESSEAL Turkiye, Istanbul, Turkey, regionalsales office.

• AESSEAL Canada Inc., regional sales office.

• AESSEAL China Ltd, with branches inNingbo, Shanghai and Nanjing.

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INTRODUCTION TO

AESSEAL®

There is a fast growing distributor network covering the rest of the world. Current production ofmechanical seals is the AESSEAL® range of cartridge mechanical seals, plus internally and externallymounted seal ranges. There are also ranges of large and high pressure ‘special’ mechanical sealsdesigned and built to meet specific customer or market requirements. AESSEAL® provides a full‘customized’ mechanical seal Design and Manufacturing service to meet any market needs.AESSEAL® takes pride in it’s Design and Technical Resource capability, backed by completeDynamic and Static Test facilities, including Finite Element Analysis and Volatile Organic Emissiontesting.

Great emphasis is placed on ensuring that all products of AESSEAL® reflect the latest technologyavailable, both in Design and Production, with Quality and Customer Service second to none in theIndustry.

The Company has patents on products unique to itself and is Quality Assured to ISO 9001 (BS 5750,Pt 1). Certified by LRQA (Lloyds Register Quality Assurance)

In 1994 the company gained the Investors in People award in addition to the Rotherham Winners inBusiness Award, for its commitment to training.

The professionalism of AESSEAL® has been recognized nationally four times within twelve years bybeing awarded the most coveted Queens Award.

1988: The Queens Award for Technological Achievement.

1993: The Queens Award for Export Achievement.

1995: The Queens Award for Export Achievement.

2000: The Queens Awards for Enterprise, International Trade.

In addition to the Queens Award won in 2000, the company was the winner of the prestigiousNatWest Sunday Times “Company of Tomorrow” Award and the IMECHE MX 2001 award forcustomer focus from the Institute of Mechanical Engineers.

AESSEAL® is totally committed to customer service with the key objective being to provide a 24hour delivery lead time on standard seals. As part of this commitment, the company provides acomprehensive technical support service, including a CD-ROM seal selection and site surveydatabase, and a range of training courses available to employees and customers.

The company operates globally in such growth areas as:

Chemical and Pharmaceutical IndustryPulp and Paper IndustryOil and PetrochemicalsSteel ManufacturingDefenceMiningWater and Waste TreatmentElectricity GenerationShipping

In January 2002 the company name was changed to AESSEAL plc in the UK and AESSEAL Inc. inthe US to make brand and company name the same.

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THE SEALING

MARKET

The MarketThe mechanical motion that drives today’s industry is a rotary one, although not to the total exclusionof the reciprocating action.

Some claims are made that ‘special’ mechanical seals exist for sealing the reciprocating motion. This isnot true. The ‘primary seal’ in a mechanical seal is a rotating one. The mechanical seal can only beused on rotating machinery.

Probably the claims made are referring to mechanically-aided compression packings or Chevron rings.Several such arrangements exist, but they are not what is known as a mechanical or rotating seal face.

So the mechanical seal is only used in rotating machinery. Excluding the electric motor, the rotatingpump, in all its design variations, is the most common piece of machinery used in industry today.Pumps have to be sealed. Add to this other pieces of rotating machinery that need to be sealed, such asMixers (top, side and bottom entry), Compressors and all the rest of the rotating equipment inindustrial use and one immediately realizes that there is a large market. An estimate of the existingU.K. market for mechanical seals in 2000 was US $110m. The worldwide market size is around US$2.3billion dollars.

Wherever there is industry, production or service, there is rotating machinery. Wherever there isrotating machinery there are requirements for mechanical seals.

This market in simple categorization can be split into two sectors:

• O.E.M. (Original Equipment Manufacturer)

• End-User

The O.E.M. refers to the manufacturers of rotating equipment requiring sealing.

The End-User is where the rotating equipment is installed.

Both market sectors must be the object of any mechanical seal manufacturers sales force.

MARKET CHARACTERISTICS

There are a number of characteristics unique to the mechanical seal market that make it particularlyattractive. Let us consider some of these:

• Cushioned against economic trends. As it has been said that mechanical seals are used in allindustrial sectors, then if one or more sectors is depressed the other less affected sectors provide aconsiderable market.

• Affected by weather. Perhaps not so obvious but if there are any doubts, ask a long-time PlantEngineer.

Rotating equipment, unless specially designed, does not like cold weather. Cold weather causesbreakdowns (for a number of reasons) and breakdowns often provide opportunity for mechanical sealreplacement or conversion.

In fact, it can be said that the whole of the industrial sealing market benefits from hard winters.

• Good replacement or after market.

Although very reliable, if correctly selected and installed, no mechanical seal will last for ever. Also, ifthere is any problem with any other component of the machine, e.g. impeller nut loosens, bearingbreakdown, etc., this will damage the mechanical seal. In fact, in many instances mechanical sealfailure often indicates that there is a more major problem and many times it gives warning before morecostly damage occurs.

The big seal companies claim that when a mechanical seal comes to the end of its useful life, the sparesit has used will be six times the value of its original cost. Recently, the advent of readily-available,more robust materials, primarily Silicon Carbide, have reduced this figure but it must still be four timesor more.

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THE SEALING

MARKET

• Market still rising. The world is becoming even more industrialized. More reliable and effective sealperformances are required by established industry, mainly for reasons that could be categorizedunder the headings of Efficiency, Health and Safety etc. All these are achievable only by moreeffective, more complete seal arrangements.

The Glandless pump and the Magnetically Driven pump will, of course, have an effect on reducingthe total mechanical seal market, but these are expensive, have application limitations and are verycostly to repair, so, yes they will affect the overall market, but in a finite manner and the overallsituation will still be as a rising curve.

• Not a ‘me too’ product. Many of the products in the industrial sealing market are ‘me too’, e.g.Compression packings, Jointings, Gaskets, ‘O’ rings etc. Identical products are available from anumber of different manufacturers. Mechanical seals do not come into this category. Some, ofcourse, are similar and indeed some international standards encourage this, but various designs andtypes have advantages one over the other, which becomes more apparent as the application becomesmore complicated.

• Understanding. A mechanical seal provides a service. It is a piece of auxiliary equipment in a pieceof capital equipment. To market this piece of auxiliary equipment one must have productknowledge, equipment knowledge and application knowledge. The better these understandings, themore successful will be the product in the market place.

One might continue on this theme, but enough, and one hopes that sufficient has been said to indicatethe attractiveness of the mechanical seal market.

The biggest competitor to the mechanical seal is still Compression packing, albeit not as significant asprevious. There is still a lot of machinery sealed with Compression packing for no other reason than itwas originally supplied by the O.E.M., so let us consider one against the other.

For:

• Inexpensive, although some of the modernmaterials of construction have reduced thisnoticeably.

• Adjustable in operation. Yes, but often wasdangerous practice and no longer allowedunder ISO 9000 Code of Practice.

• Maintainable without dismantling the pump.Yes, but gland has to be pulled back andremoving packing rings from within thestuffing box can be difficult.

• Wide range of proven materials for multipleapplications. Yes, but less than for amechanical seal.

Against:

• Requires copious lubrication so obviousleakage. Yes but can be overstated.Compression packing has to leak forlubrication, otherwize it will burn out, but withmodern materials, correct installation andattention this can be quite minimal.

• Constant monitoring and adjustment required.Agreed.

• Adjustment not precise, which can lead to wearof pump components. Agreed.

• High power consumption - capital cost ofdriver. Agreed.

PACKING

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THE SEALING

MARKET

MECHANICAL SEALS

Added Advantages of a Cartridge Seal

For:

• Reduced leakage - practically zero. Yes, but allseals leak something or the faces will burn out.However, this is extremely slight and usually isin vapour form.

• Reduced power consumption, this is oftenconsiderable.

• Factory pre-set, no adjustment needed. True.

• No wear of pump components. True, if sleeve-mounted; not always so if mounted direct onshaft, depends upon type of seal.

Against:

• Sensitive to mishandling during fitting, not ifnormal care is taken.

• Alignment is critical, run out, vibration and endfloat tolerances are small. Can be overstated,and alignment problems can be catered for byusing a self-aligning seat.

IN CONCLUSION

The mechanical seal market is a good one to be in and currently there seems no change in industrialattitude that will hinder the growth of the cartridge seal sector within it, in fact, quite the contrary.Into the future one only sees hardening of the all powerful rulings that will only bring moresophistication and continued overall growth.

It must be said that cartridge seal assemblies have been around for many years, but these were usuallyspecially made to order. They varied - large, small, complex, simple - from mere gland plate and sleeveassemblies to giant total seal, environmental equipment and bearing modules.

The object was for a module design that could be removed as a unit and taken away for repair.

In recent years several changes in industrial attitudes, brought about by legislation or situation, havebrought the cartridge seal into much greater focus. Some of these being:

• Health and Safety Legislation.

• Move away from packed stuffing boxes - no continuous leakage.

• Economies - people - wasted product - cost money.

• Greater use of off-site Maintenance Contractors.

• Shortage of trained installers.

So, the cartridge seal became an increasingly preferred arrangement as a way to meet what is required,but what does it offer:

• A ready to install module containing all parts of a total sealing assembly, shaft sleeve, seal glandplate etc.

• Ease of fitting - minimum skills only.

• Its gland plate bolting design is such that it will fit onto the majority of stuffing boxes, located on theexisting gland follower arrangements.

• Designed to fit into most stuffing box dimensions.

• Ease of conversion from compression packings or shaft mounted seals.

• Ease of removal for off-site refurbishment.

• Easier installation in less accessible locations.

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MECHANICAL SEAL

HISTORY

Mechanical Seal HistoryA true history of the mechanical seal has never been documented, nor probably ever will or can be,but some facts give us indication.

Prior to the industrial revolution the ‘power’ sources which drove industry such as it was, were:

• Human - Direct (rotary or reciprocating)- Treadmills

• Beast - Direct rotation- Treadmills

• Water - Water wheels

• Wind - Windmills

The piece of machinery that drove the Industrial Revolution was the steam engine and the basicmotion a reciprocating one. These did not give way to any great degree until the advent of the electricmotor when gradually the rotating motion took over.

Where required, sealing of reciprocating machinery and mechanisms, was and still is accomplishedby means of compression packing or improvements upon the compression theme such as chevronrings. The materials used were all natural, such as leather, cotton, hemp, etc.

What is left of the reciprocating motion is still sealed in very much the same manner, althoughsynthetic materials have now superseded the natural ones.

The earliest form of fluid transportation in quantity was by gravitational force and many early postindustrial revolution plants were still built on natural inclines to provide this and if a waterwayexisted at the bottom of this incline as a means of transportation so much the better.

Gradually however, for a number of reasons, apart from lack of natural locations, the pump came intoprominence as a means of fluid transportation first with reciprocating, then a rotary motion.

The original form of rotary pump packing was compression packing, which is still with us today.

However, by the 1930s pump manufacturers and compression packing manufacturers had started toexperiment with the idea that a fluid seal could be created by a rotating disc being moved against astationary one and eventually the mechanical seal was born.

Pump manufacturers were first thought to have developed a practical mechanical seal and certainlyPulsometer Pumps of Reading were using their own developed one prior to the 1939-45 war.

Although visually appearing crude the design of the earliest mechanical seal is immediatelyrecognizable in its sophisticated successor today. The basic principle and component parts beingfunctionally similar. Materials were either bronze or brass.

The 1940s and 50s saw great strides being made in the Oil, Chemical and Petrochemical industriesand demands on machinery increased accordingly, with sealing ever more a consideration. So themechanical seal was developed to keep pace, but this development is more the story of the materialsof construction than design.

So we have the mechanical seal of today, truly an extremely important and sophisticated piece ofmachinery equipment, with its function growing ever more essential particularly due to environmentalconsiderations.

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WHAT IS

A PUMP?

What is a Pump?A pump is a machine that takes the energy of the prime mover (electric motor, combustion engine,etc.) and converts it into energy contained within the media being pumped. This energy can be:

a. A velocity energy

b. A pressure energy

c. A combination of (a) and (b)

There are a number of basic designs of pumps, but there are also many variations on these designsresulting in a long classification, that in the main is unnecessary and confusing.

The most accepted definition of what type a pump is, is by its motion and basically these are:

• Reciprocating

• Rotary

• Centrifugal

If we extend these types of motion to their individual types by design we will find a classification asfollows:

Reciprocating: Piston, Plunger, Diaphragm.

Not suited to Mechanical Sealing

Rotary: Gear, Screw, Vane, Lobe, Progressive cavity.

Centrifugal: Radial Flow, Mixed Flow, Axial Flow.

Designation by design of impeller

All these designs of pumps and variations on them have a shaft sealing device, by far the mostcommon being either:

• A mechanical seal

• Compression packing

The use of reciprocating pumps these days is relatively uncommon compared to the other two.Nevertheless for certain specific duties this is still the most effective design. Shaft sealing is usuallyeffected by compression packings or a sophistication of this, such as chevron rings and for thesereasons centrifugal and rotary will only be considered, centrifugal being by far the most versatile andtherefore most common.

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WHAT IS

A PUMP?

CENTRIFUGAL PUMPS

There are quite a number of ways to illustrate the effect of centrifugal force as applied to pumping.We will stay with the two most usually quoted.

BTC Fig 5.1

Now if we were to put a belt around this shaft and so rotate the pan, the straight line level of the fluidwould become dished and eventually slop over the edges of the pan.

It is centrifugal force that lifted the liquid to a height of ‘H’. In crude terms this can be called‘pumped’.

A bucket with a hole in its bottom is filled with fluid and a rope attached to its handle. The bucket isthen whirled around via the rope over one’s head. Once whirling has started no fluid will be lost out ofthe top of the bucket but the water will be thrown out of the hole for a distance all around. The fasterthe rotation the further the distance and the sooner the bucket will be emptied. Again in crude terms thefaster the rotation the more fluid is ‘pumped’ to a greater distance or ‘head’.

A pan mounted on a centrally located vertical shaft, as shown is partly filled with liquid. The differencebetween the liquid level and edge of pan we will call ‘H’.

Example A

Example B

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WHAT IS

A PUMP?

A simple horizontal centrifugal pump comprizes a rotating element, called an impeller (1) containedin a casing (2). The impeller is mounted on to the end of a rotating shaft (3). Fluid enters the center or‘eye’ (4) of the impeller and is rotated by means of the impeller vanes (5). Centrifugal force thenthrows the fluid from the center of the impeller to its periphery with considerable velocity andpressure. Inside the casing is a volute shaped passage (6) of increasing cross sectional area, thiscollects the fluid and converts some of its velocity into more pressure energy. The volute shapedpassage finishes at the discharge port flange (7). The sketch below should help in understanding thisexplanation.

CENTRIFUGAL PUMPS

BTC Fig 5.2

ROTARY PUMPS

Compared to the centrifugal pump the principle of the rotary pump is simple.

A rotary pump comprizes gears, lobes, vanes, single/double/triple screws, etc. Operating in a closefitting casing it is a positive displacement machine.

Instead of spinning the fluid as it enters the casing as the centrifugal pump does the rotary traps theliquid in its rotating elements and forces it around the inside of the casing and expels it through thedischarge.

There follows three drawings illustrating the principle of operation of a rotary lobe pump and a rotaryvane pump. These are among the most common rotary pump designs in use today.

The drawings and attached brief notes should indicate clearly how these pumps work, so simple istheir operation.

1

4

5

7

6 23

MOTOR

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WHAT IS

A PUMP?

THE ROTARY LOBE PUMP

Principle of Operation

As the rotors start to rotate (Figure 5.3.1) an expanding cavity is formed creating a partial vacuum atthe inlet port which draws product into the pumping chamber. Each rotor well is consequently filled(Figure 5.3.2) and positively displaced, thereby sealing itself against the internal faces of the casing.Finally, the product is forced out of the discharge port. (Figure 5.3.3)

BTC Fig 5.3.1 BTC Fig 5.3.2

BTC Fig 5.4

BTC Fig 5.3.3

VANE PUMP


The shaft rotates and the vanes arethrown out on to the inner surface ofthe casing (a) (Figure 5.4). Thiscreates a partial vacuum at pump inlet,drawing fluid into pump chamber andfilling voids between individualvanes. As fluid is carried round byvanes it is compressed and pressurizedand exits at the pump outlet.

INLETOUTLET

DIRECTION OFROTATION

CASING (a)CASING (a)

DIRECTION OFROTATION

PROGRESSIVE CAVITY


A metallic helical rotorrevolves inside a rubberstator which also has a helicalform inside it. The rotor is aninterference fit inside thestator and as it rotates formsa continuously moving cavitypushing fluid towards thedischarge.

BTC Fig 5.5

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WHAT IS A

MECHANICAL SEAL?

What is a Mechanical Seal?THE BASICS

A mechanical seal consists of twocomponents, one stationary, the otherrotating against it, to achieve a sealwith minimal leakage (Figure 6.1).

STATIONARYROTATING

AXIAL FORCE

LEAK PATH

BTC Fig 6.1DESIGN

The simplest practical design of a mechanical seal has seven components (Figure 6.2):

1. Stationary component, commonly called ‘the seat’.

2. Stationary component sealing member.

3. Rotating component.

4. Rotating component sealing member.

5. Spring.

6. Gland Plate.

7. Clamp Ring.

5

7

32

6

14

BTC Fig 6.2 OHP Ref: Slide 10

A mechanical seal has four main sealing points:

1. The seal between the rotating (3) and stationary faces (1). This is known as the primary seal.

2. The seal between the stationary member (1) and stuffing box face, ie: Gasket (2).

3. The seal between the rotating member and shaft or shaft sleeve(4). This is known as the secondaryseal and may be an ‘O’-Ring as shown, a ‘V’-Ring, a ‘wedge’ or any similar sealing ring.

4. The seal between the gland plate and stuffing box, this is usually a gasket (2) or ‘O’-Ring.

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WHAT IS A

MECHANICAL SEAL?

SEALING POINTS

Three of the four main sealing points of a mechanical seal need little explanation, but number one,between the rotating and stationary members needs a little more consideration. This ’primary’ seal isthe basis of all mechanical seal design and is what makes it work.

The surfaces of both rotating and stationary components that ‘rub’ together are extremely flat, in fact,they are usually lapped within two light bands (an optical method of measuring flatness). Thisflatness minimizes leakage to a degree where to all intents and purposes it is non-existent.

In fact, there is leakage between these faces but it is minute and (for immediate consideration)appears as a vapor.

FLUID FILM AND VAPORIZATION

If the rotating components of a mechanical seal rotated against each other without some form oflubrication they would soon wear out due to face friction and the heat it generates.

So lubrication is required and at this stage of our considerations this is supplied by the liquid beingsealed. This is known as the fluid film and maintaining its stability is of prime importance, if the sealis to give satisfactory service. Fluid film has been and still is the subject of much deliberation andresearch and becomes more interesting as one progresses in the subject of mechanical seals but fornow assume a situation exists as in the following sketch. Product being pumped forms a stable fluidfilm across the two mating faces. Frictional heat can increase product temperature causing avaporization of the liquid between the faces.

If vaporization occurs and there is no stable fluid film between the faces, rapid wear takes place andthe seal fails.

RETURNING TO DESIGN

The rotating component rotates with the shaft and is usually driven by a spring. Spring compression,provides initial face pressure usually 1 to 2 barg. This pressure is maintained when the seal is at restvia the springs thus preventing leakage between the mating faces.

The stationary component is held firmly in the gland plate and is usually slotted or bored to take ananti-rotation pin fitted into the gland plate - an important requirement on larger sizes.

Various spring drive arrangements exist between both shaft and spring, and rotating member andspring.

BTC Fig 6.3

ROTATINGCOMPONENT

STATIONARYCOMPONENT

PIN

SPRING

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TYPES OF

MECHANICAL SEALS

Types of Mechanical SealsDefining mechanical seals by type initially mayseem somewhat complex but in reality is quitesimple and soon becomes so with a littleexperience. Of course it can be madecomplicated but this is totally unnecessary.

We will define mechanical seals, five basicways but a definition may contain two, three,four or even five in combination.

• Rotating or stationary

• Balanced or unbalanced

• Horizontally or vertically mounted

• Design feature

• Arrangement

ROTATING OR STATIONARY

As we know a mechanical seal has two basic components, the unit or seal and the seat, as shown below.

SPRINGS

RotaryMember


In the arrangement shown (Fig 7.1) the unit orseal is located on to the shaft, thus it rotates withthe shaft and is called a rotating seal (the rotarymember contains the springs). This is by far themost common of these two arrangements.

Similarly if the positions of the two componentsare reversed and the unit or seal (which containsthe springs) is held stationary in the gland plateit is called a stationary seal. (See BTC Figure7.2)

When do we move from rotatingto stationary unit location?Primarily when rotating speedsare approaching or above 25m/sec(5000 f.p.m). At such speeds,dynamic forces exceed thelimitations of a rotary unit withsprings. A stationary seal preventsexcessive secondary sealmovement, maintains satisfactoryprimary seal component trackingand handles the high torquesinvolved. At these speeds, if theunit were rotating, its greaterweight than that of the seataccentuates any shaft movementsor distortion.

This face rotates withthe shaft or sleeve

In a stationaryseal the springsare behind thestationary face.(The springs donot rotate)


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TYPES OF

MECHANICAL SEALS

BALANCED OR UNBALANCED

Mechanical seals are referred to as either balanced or unbalanced. More correctly, this should behydraulically balanced or hydraulically unbalanced.

Let us consider the following diagram which represents in simplest form a rotating unit mechanicalseal with stationary seat.

S’BOX PRESSURE

Atmospheric Pressure

The stuffing box pressure (plus spring pressure) tends to push the faces of the unit and seat together.However, there is a fluid film between these faces, which is subject to a hydraulic pressure gradientbetween stuffing box pressure and atmosheric pressure. The pressure gradient is assumed to be lineartherefore the net average pressure within the film is 50% of the stuffing box pressure. This in factcreates a wedge shaped force attempting to push the faces apart as shown below:

PRESSURE GRADIENT

PRESSUREGRADIENT

BTC Fig 7.4

As the stuffing box pressure increases, the resulting pressure acting over the sealing area of the facesincreases, the wedge becomes less effective until eventually the wedge fluid film breaks down andthere is no lubrication. The faces destroy each other and the primary seal has failed.

The maximum pressure an unbalanced seal can withstand is dependent upon shaft diameter, speed,face materials and nature of fluid being sealed, but is always less than that for a balanced seal.

Having considered the unbalanced seal, we will now consider the same seal in a balancedconfiguration. Stuffing box pressure remains the same and we will use it to reduce face pressure.

BTC Fig 7.3

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TYPES OF

MECHANICAL SEALS

In the above figure we have provided the shaft with a reducing diameter step. All hydraulic conditionsremain as for the unbalanced consideration.

The difference is that the rotating unit is subject to equalising pressure beyond diameter ‘D’ and thereis hydraulic balance in this area. Stuffing box pressure now acts on area ‘A’ of the seal between theshaft ‘B’ and diameter ‘D’. Since the face area remains the same, the face load is reduced.

Simply this relates to the working position of the mechanical seal in the piece of rotating equipment itis part of, e.g. if the pump is a horizontal one it has a horizontal shaft and therefore the seal isdescribed as horizontally mounted. Similarly if the pump is a vertical one, the seal is described asvertically mounted.

In mixing or agitating machinery, the more common arrangements are vertical (shaft top entry),horizontal (shaft side entry). The third mounting in this type of machinery is another vertical one(shaft bottom entry).

This usually either relates to:

• Whether the primary seal stationary force is either by single spring, multi-spring or bellows.

• Whether the secondary seal is a ‘wedge’ or similar or an ‘O’ ring.

• Removal of the metallic section of the seal from the product.

• A combination of the first three.

STUFFING BOX PRESSURE

UNIT

SHAFT

SEATB I.D

.

D

a

BALANCED OR UNBALANCED

HORIZONTALLY OR VERTICALLY

MOUNTED

DESIGN FEATURE

A

BTC Fig 7.5

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TYPES OF

MECHANICAL SEALS

SINGLE SPRINGS

Usually cheap to buy, especially in the smaller sizesand relatively easy to fit (not always the case). Canonly be used on low pressure up to 80 p.s.i.maximum and at low shaft surface speed when inits usual unbalanced design. The single spring has ahigh and low pressure area bearing on the face,giving UNEVEN face wear. Can sometimes only berotated in one direction, dependent on design.

MULTIPLE SPRINGS

Can take higher shaft speeds and greater pressuresthan the single spring version. Gives even faceloading. Will rotate in either direction. Usuallyeasier to balance hydraulically. Limitations -temperature limits of the elastomer. Can be morecostly to buy.

NON-METALLIC

SEAL

Designed so as to remove any metallic componentfrom the fluid and prevent chemical attack. UsuallyCarbon or Teflon-faced, also known as theChemical or external seal.

ALL-METAL SEAL

Usually of Metal Bellows design. Developed forthe Oil and the Oil-related industries. If used athigh temperature, can be “as stated” all metal as theelastomer may be replaced with a mechanicalclamp to the shaft. Commonly found with ‘O’ ringsto seal and therefore replaceable with ‘O’ ringpusher-type seals. May clog easily and if theBellows splits, then large product loss occurs.

ARRANGEMENT

So far we have only considered single seals but health and safety and the considerations of theenvironment increasingly demand that measures be taken to ensure that seal leakage does not escapeinto the atmosphere or is suitably contained or diluted

To accomplish this there are various additions to a single seal arrangement that will suit and these willbe discussed later. For now let us consider arrangements comprising more than one seal.

There are basically three seal arrangements that comprize double seals:

• Double back to back • Double face to face • Tandem seals

It is arguable that there is a fourth arrangement, the cartridge but strictly speaking this is a selfcontained unit and can contain seals in single, double (even triple) and tandem arrangement.

Whatever is the opinion, AESSEAL® is a volume supplier of this product and as such it forms themajor part of our seal range.





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TYPES OF

MECHANICAL SEALS

DOUBLE BACK TO BACK

A typical outline sketch of this arrangement is shown in Fig 7.10. As its name implies in thisarrangement two seals are mounted back to back in the stuffing box.

PRODUCTFLUID

INBOARD OUTBOARD

BTC Fig 7.10

PUMPED PRODUCT

BTC Fig 7.11

DOUBLE FACE TO FACE

TANDEM Arrangement as shown in Fig 7.12.

BTC Fig 7.12

In this arrangement the inner seal acts exactly as a single seal, so the duty must be suitable for a singleseal. Barrier fluid pressure is lower than sealed pressure and the outboard seal again acts as a singleseal to seal the barrier fluid pressure.

Like most double seal arrangements the tandem seal is usually a safety one and is used to seal toxic,volatile, carcinogenic and similar hazardous media. It eliminates icing of fluids when applicable (thebuffer fluid is an anti-freeze). It also is a 100% back up seal. Should the inboard seal fail the outboardseal takes over until the piece of rotating equipment can be shut down for maintenance. Pressurealarm systems can be incorporated in the auxiliary sealant system to give warning of inboard sealfailure.

The seal design requires a large installation length and this may cause radial run-out problems due tolarge overhang from bearings.

(Separate unit seals) This arrangement is typically as shown in Fig 7.11. The double face to face sealarrangement is not very common and is primarily an alternative to the back to back arrangementwhere stuffing box depth is too shallow to accommodate it.

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TYPES OF

MECHANICAL SEALS

In more recent years several changes in industrial attitude brought about by legislation or situationhave brought the cartridge seal into much greater focus. Some of these being:

• Health and Safety legislation.

• Move away from packed stuffing boxes - no continuous leaks.

• Economy.

• Wasted product cost money.

• Reduction in plant maintenance personnel.

• Growth of off-site sub-contractors.

So the cartridge seal became increasingly a preferred arrangement and manufacturers produced rangesof standard designs to suit and meet the market demand.

What does a cartridge seal offer?

• A ready to install module containing all parts of a total sealing assembly, shaft sleeve, seal and glandplate, etc.

• It is easy to fit - minimum skills only required.

• Its gland plate bolting design is such that it will fit onto the majority of stuffing boxes, located on theexisting gland-follower arrangements.

• Design also allows fitting into existing stuffing box dimensions.

• Ease of conversion from packed glands.

• Ease of removal for workshop off-site refurbishment.

• Easier installation in less accessible locations.

Currently there seems no change in industrial attitude that will hinder the growth of the cartridge sealmarket, in fact, quite the contrary. Off-site maintenance, sub-contractors, ease of replacement,minimum down-time and so on are all considerations gaining momentum, not slackening.

ADVANTAGES/DISADVANTAGES COMPAREDWITH A BASIC MECHANICAL SEAL

The advantages have been sufficiently dealt with under ‘Concepts’.

Arguably the only disadvantages are those of cost but even then when one considers the benefitsbought by these, the true disadvantage is questionable. Nevertheless, the cartridge seal is initiallymore expensive than a basic seal comprising seal unit and seat, but the difference is not as high asperhaps one imagines as it may be assumed that the seal unit and seal comprize some 60% of the totalcost. Beyond this any marginal price considerations are really not worth mentioning.

THE CARTRIDGE MECHANICAL SEAL

Concepts

Cartridge mechanical seal assemblies have beenaround for many years. These vary from simplesmall diameter combinations of shaft sleeve, sealand endplate, to very large complex onesincluding everything, even bearings.

The objective whether large or small, simple orcomplex, was for a module design that could beremoved as a unit, replaced by a similar one ortaken away for workshop repair.

The industries specifying such seal assemblieswere basically the process ones and usually theywere individually designed to meet the special requirements of a user or contractor engineer.


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SEAL

BALANCE

Let us look at the main forces acting on a mechanical seal:

Seal Balance

Static

Wp=Force due to product pressure

Ws=Force due to springs

Wf=Force within fluid film

Wo=Opening force

From Figure 8.1, WF is representing a fluid film. It is known that on the stuffing box side of the sealfaces, 100% of the pressure in the stuffing box is seen, and on the atmospheric side of the seal faces 0%of the pressure is seen. It is unknown however, what happens in-between, although a minute amount ofproduct crosses the faces to lubricate and cool them. If this did not happen, then excessive heat wouldbuild up due to friction and seal failure would result.

FvFc

Wp

W oWs Wf

It is important to fit balanced mechanical seals to pumps. The effect of balance is to reduce the effectof the pressure in the stuffing box by reducing the area of the seal it acts upon.

Dynamic

Fv = Viscous Forces

Fc = Centrifugal Forces

ROTARY FACE

STAT FACE

ROTARY FACE

STAT FACENO FLUID FILM-RESULT DRY FACE CONTACT. RAPID WEAR & OVERHEATING DUE TO HIGH FRICTION.

FLUID

FLUID

STABLE FLUID FILMNECESSARY FOR SEALFACE LUBRICATION.

BTC Fig 8.1

BTC Fig 8.2

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SEAL

BALANCE

We also know from our physics that pressure acts equally in all directions - see Figure 8.3.

Pressure acts on the rear area of the seal down to the sliding diameter and to the outside of the faceline. Other forces above that are cancelled out by opposite forces.

Imagine a lady in no shoes. Her weight is spread over the area of the sole of her feet.

Then put her in high heel shoes and her weight is then loaded onto a tiny area, putting a higher forceonto the ground (dinting cork tiles and putting holes in your lawn).

Put the same lady in snow shoes and her weight is distributed over a large area and she would be ableto walk on very soft snow without sinking in.

Let us apply the same load-spreading principles to physics.

{A {A

{A {A

REDUCTIO AD ABSURDUM


The diagram below (Figure 8.4) is that of a cone. If we load the top surface with200 lbf on the given area of 4 square inches. The reversing pressure will be:

2004

When this is transmitted to the bottom surface, which is reduced in area, theresulting pressure is still a load of 200lbf, but acting on only 2 square inches,therefore the resulting pressure is:

The pressure is increased!

Pressure on top surface = 50 Ibf / in

Pressure on bottom surface = 100 Ibf / in

2

2

200 IbfCircular section, 4 sq. in.

Circular section, 2 sq. in.




2002

= 100lbf/in2.

= 50lbf/in2.

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© Copyright 2002 AESSEAL® All Rights Reserved.

SEAL

BALANCE

Figure 8.5 illustrates a pyramid. If we load thetop surface with 200lbf on the given area of 4square inches. Again, the pressure on thatsurface will be

= 50lbf/in2.2004

Transmitting the load in this solid to the bottomface we have the same 200 lbf, but an area of 8square inch, therefore the resulting pressure is

= 25 lbf/in2.

The pressure is reduced!

2008

Pressure on bottom surface = 25 Ibf / in

Pressure on top surface = 50 Ibf / in2

2

200 IbfCircular section, 4 sq. in.





{ } BA

SLI

DIN

G D

IAM

ET

ER

SLI

DIN

GD

IAM

ET

ER

Let us put these principles into mechanical seals.


Figures 8.7 & 8.8 show ways in which area A is reduced thereby decreasing the seal interface force.

BTC Fig 8.7 OHP Ref: Slide 20 BTC Fig 8.8

As you see, the area seeing the stuffing box pressure (area A) is much larger than that of the seal faces(area B), therefore the load on the seal by the fluid is increasing the pressure on the seal faces.

If a discharge valve in the pump pipework was to be closed in this instance, the resulting pressurespike could well cause the seal to fail due to excess pressure.

L-UK/US-AWARD-B-06

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SEAL

BALANCE

At this basic level the only really important things to remember are the advantages ofbalanced seals compared to unbalanced seals.

ADVANTAGES OF BALANCED SEALS

General

•Can operate in higher pressures

•Less heat generated

•Reduced face wear

•Higher shaft speeds

•Less face distortion

•Less torque

•Less power consumption

•Wider range of face materials

•Less need for internal / external controls

•Versatility

•Allows for Overloads / System malfunctions

•Vacuum sealing

AESSEAL Seals

•No additional sleeves required

•No damage to shafts or sleeves

L-UK/US-AWARD-B-06

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PRIMARY SEAL

FACE FLATNESS

Primary Seal Face FlatnessThe primary seal is the basis of all mechanical seal design. As we know this seal consists of two flatfaces, one fixed, one rotating, running against each other, with a liquid film between them providinglubrication.

The width or thickness of the lubricating film is dependent upon a number of variables but thedistance between the two faces is constant in that this has the greatest influence, the closer these aretogether, the thinner the fluid film and the least likelihood of leakage across the faces. It thereforefollows that the flatter these surfaces are within practical manufacturing constraints, the better. Theprocess of achieving face flatness adopted by the mechanical seal industry is called lapping.

In this process a lapping machine is used, which provides one or a number of rotating ‘plates’ on towhich the face or seat of a mechanical seal is placed. The surface to be finished is in contact with thelapping plate.

Following lapping the workpiece surface is then polished to a reflective finish.

Final surface finish must be polished to a degree of light reflection, sufficient for its flatness to bechecked.

The degree of face flatness is checked by what is known as the optical interference fringe method.Here an optical flat (a quartz or pyrex disc, with surface/s finished to within 0.000001/0.000005"-0.025/0.125 microns) is placed over the lapped and polished face and placed under a helium lightsource, from this a pattern of fringe interference is produced. This pattern is then translated into ameasurement of flatness by comparison of the pattern obtained with various patterns (usually in chartform) which indicate the flatness accuracy.

Figure 9.1 shows a helium light source (wave length approximately 0.0006mm/0.00002") hitting theoptical flat (A) it then passes through the optical flat. When it reaches the other side, some is reflected(Point B) and the rest reflects from the specimen (Point C). When the light hits the optical flat again(Point D) it passes back through the optical flat. The two reflections (E and F) can then be observedfrom above the optical flat.

Flatness is measured in light bands, one light band = 0.000011 or 0.0003mm. There are 85 light bandsto one thousandth (0.001") of an inch.

Small diameter seal faces (< 4” Diameter.) are lapped to two light bands or less, larger (> 4”Diameter.) faces less than five light bands. The additional sheet shows how face patterns areinterpreted, the process is similar to reading the contours on a map. Figure 9.2 shows a typically flatsurface, a series of straight, parallel equi-shaped lines shows that a face is flat to within one lightband.

BTC Fig 9.1 BTC Fig 9.2

1 LIGHTBAND

FACEWIDTH

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SHAFT

FRETTING

Shaft FrettingThis phenomena is also known as shaft corrosion or shaft erosion and occurs in the area of secondaryseal and shaft (or sleeve) contact.

It is caused by excessive shaft axial movement beyond that specified by the seal manufacturer.Machinery vibration, shaft run out or deflection are also contributing factors. The situation can alsobe aggravated where the primary seal wear debris can migrate under the secondary seal, so providinga very efficient grinding media.

It is more prevalent when the secondary seal is manufactured from P.T.F.E. or similar semi-rigidmaterials rather than an elastomer, as the more flexible elastomer is better able to accept the shaftdisplacements.

The softer elastomer will also absorb certain amounts of primary seal debris better than P.T.F.E.

SHAFT FRETTING

The movement of the secondary seal on the shaft or sleeve eventually removes the oxide coatingproviding protection from corrosion. A resultant ‘groove’ is worn around the shaft diameter in thesecondary seal contact area, appearing pitted or shiny. Eventually the secondary seal locates itself inthis groove beyond the capability of the primary seal closing force. Primary seal wear can no longerbe taken up and leakage occurs.

Shaft fretting remedial actions are expensive, usually meaning sleeve replacement or shaft coating inarea of secondary seal slide with a hard material such as chrome or aluminium oxide. An even moreexpensive solution is of course to eliminate the causes of the excessive movement. ‘The better longterm solution is to replace the ‘shaft fretting’ type seal with a different design’.

Secondary Seal

MOVEMENT


All multi-spring AESSEAL® mechanical seals are guaranteed not to fret shafts or sleeves

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AESSEAL® MODULAR

SEALING SYSTEM

The AESSEAL®

Modular Sealing SystemMinimum component parts mean maximumproduction efficiency and minimum inventoryholdings. This results in minimum productionand storage costs, that are eventually reflectedin improved final price and lead times.

The AESSEAL® Modular System is so designedas to make maximum use of the minimumnumber of components throughout the entireranges of seals, yet still maintaining availabilityof all materials and elastomers.

1

2

34

5 &6 (Secondaryseal shown)

7


1) A sleeve.

2) A cast gland plate, drilled and tapped forflush and quench connections as required.

3) A stationary or self aligning stationary,mounted into the gland plate.

4) An internal seal.

5) External restrictor bushing, throttle bushing,lip seal or secondary seal, as required.

6) An external seal when required.

7) Sealing elastomers and clamp gland gasket.

Sleeves are manufactured in 316L ST.ST asstandard, with an elastomer seal on the shaft andgrubscrew (set-screw) located, outside thestuffing box.

Gland plates are cast 316 Stainless Steel andwith flush and quench connections drilled NPT.

Stationary and self aligning stationary -discussed separately.

The internal seal - discussed separately.

All standard bushings are carbon, although othermaterials may be available.

The secondary seal - discussed separately.

Sealing elastomers, standard materials areViton®, although E.P.R., Zalek®., Aflas®, andKalrez® are available.

Gland plate gasket material is either C.A.F. oran asbestos free alternative.

STATIONARY SEATS

There are four basic designs of stationary seat:

The DIN stationary. See BTC Fig 11.2 / OHP Slide 61

The ‘L’ stationary. See BTC Fig 11.3 / OHP Slide 22

The ‘T’ stationary. See BTC Fig 11.4 / OHP Slide 32

The ‘R’ or boot mount stationary. See BTC Fig 11.5 / OHP Slide 14

The basic components in the ranges of cartridge seals are:

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AESSEAL® MODULAR

SEALING SYSTEM

THE DIN STATIONARY

Designed to fit stuffing boxes to DIN EN 12756standard.

‘O’ Ring mounted, pin located.

Materials: 99.5% aluminium oxide ceramic,solid silicon carbide.

The DIN stationary is also supplied completewith gland plate, this is designated CDG/SDG.

DIN STATIONARY


THE ‘L’

STATIONARY

Clamp mounted.

Materials: 99.5% alumina ceramic.

Both faces lapped for differing installationlengths.



THE ‘T’

STATIONARY

Clamp mounted.

Materials: 99.5% alumina ceramic.

Both faces are lapped for reversal when theduty face wears (theoretically).

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AESSEAL® MODULAR

SEALING SYSTEM

THE ‘R’ OR BOOT MOUNT STATIONARY

The ‘DIN’ seat is pin located as an anti rotationdevice, and is ‘O’ ring mounted. In this designthe flexibility of the ‘O’ ring is utilized toreduce shock transfer and the distortionassociated with clamped types.

Because the ‘L’ and ‘T’ seats are both clampedin position they will not rotate, but can easily bedistorted due to excessive clamping.

The ‘R’ seat is cup mounted giving a degree offlexibility, but this also allows a simple squaresection shape to be utilized for costconsiderations.


Although ‘L’, ‘T’ and ‘R’ seat are available in ceramic as the standard material, othermaterials can be supplied as specials. Gaskets are in CAF or an asbestos free alternative.

Cup mounted.

Materials: 95% Alumina Ceramic

SELF ALIGNING SEATS

AESSEAL® have developed two designs of selfaligning seats, the USL and the USI but why andwhat are the advantages of this design over otherseat designs?

Self aligning seats will take up angularmisalignment at the primary seal.

Misalignment between the rotating andstationary faces can be caused by a number ofreasons:

1) The shaft is misaligned because the bearinghousings have been machined out of true withthe center line of the shaft.

2) The pump is distorted by the way it isclamped to the pump bed.

3) The motor is misaligned to the pump body.

4) The face of the stuffing box and the glandfollower are not at 90˚ to each other.

5) Corrosion or dirt in the stuffing box face.

6) Pipe strain: During its working life thepipework ‘relaxes’ when valves or pumpsetcflanges and pump flanges are no longer atthe same attitude to each other and by forcing

them together can cause pipe strain causingmis-alignment. This may not be obvious butusing highly sophisticated viewinginstruments the pump can be seen to be understress and actually looks as if it is bent.

7) Coupling mis-alignment will cause manyshaft mis-alignment problems due to thegyroscopic effect of the coupling whenrotated at speed.

Whatever the reason angular misalignment ofthe primary seal faces is a problem, it will causealmost instantaneous leakage, severe fretting ofcomponent ultimately resulting in severecatastrophic failure due to component fatigue.However, this can be a accomodated by the useof the AESSEAL® PATENTED UNIVERSALSELF ALIGNER.

Each rotation of the shaft will generate springmovement, twice for each revolution of theshaft. The number of times misalignment occursin machinery suffering this problem is often notfully appreciated but at a synchronized driverspeed of 1500 r.p.m. this is over 4,000,000spring deflections during a 24 hour operation. Itis considerable. In addition to excessive wear ofthe rotating face occuring, damage is also causedto other seal unit components, e.g. primary seal,‘O’ rings, drive pins, etc.

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AESSEAL® MODULAR

SEALING SYSTEM

SELF ALIGNING SEATS

There are two basic types of self aligningstationary designs available:

• Spring activated, where a wave spring isutilized behind the stationary member to giveflexibility.

• Universal joint activation of the stationarymember. This is the AESSEAL® patenteddesign.

The spring in the spring activated design willresist the movement of the stationary member.This causes excessive wear of the primary seal,in time the spring effectiveness will deteriorateand there is always a danger of breakage.

In the universal joint design the stationarymoves into position freely, unrestricted andwith no compensating forces acting on itsmovement, and stays there.

There is often an initial misconception aboutself aligning seats as it is assumed they are incontinuous movement when in action. This isof course not true. At start-up the self aligneradopts a set position accommodating the planeof the rotating member face, caused bymisalignment.

The AESSEAL® self-aligning seat designs havemade a major contribution to the success of thecartridge seal range.

THE USI SELF-ALIGNING SEAT AND

VARIATIONS

In this design the universal joint principle isachieved by gimble location.

Face materials are Chrome Oxide on StainlessSteel or Solid Tungsten Carbide.

The design not only overcomes misalignment

problems but also prevents face distortioncaused by clamp plate over-tightening.

Another option of USI the is available with adifferent body diameter designated the USL\A.

THE USI SELF-ALIGNING SEAT AND

VARIATIONS

This is a development of the USL and one piecestationary members, i.e. not in Stainless Steelcarriers. This was necessary as in the originaldesign two pins located into the back of thestationary face. For Silicon Carbide and Ceramicmaterials this was not possible and the USIdesign eliminates this requirement.

This seat is used with the SAI rotary unit.

AESSEAL® manufacture a range of cartridgemechanical seals with the USL stationary,however, these have been replaced by the presentrange, although AESSEAL® will continue tosupport there furbishment/replacement of them inthe field.


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AESSEAL® MODULAR

SEALING SYSTEM

THE SAI ROTATING UNIT


The standard externally mounted seals in the AESSEAL® Modular System are now the NCE™ andthe CS™ range formerly the SE™.

Both seals are similar, the main differences being that the CS™ has none of its metal componentsexposed to the media being sealed while the NCE™ has metal parts in contact with the fluid. Whenthe NCE™ is installed in the cartridge seal design and acting as a double seal, barrier fluids areusually non-corrosive, so it is not important that metal parts in the NCE™ are in contact with thebarrier fluid.

THE NCE™ AND CS™ ROTATING UNIT

The standard rotary unit in the AESSEAL®

modular system is the SAI™ - see sketch.

Features of the SAI™ are:

• An internal seal unit.

• Hydraulically balanced.

• Multi spring.

• Springs and drive lug are positioned out of themedia being sealed.

• Short length - 15/16" (33mm).

• Small radially.

• Dynamic ‘O’ ring located on integral barreland is so positioned as to minimize hang-uppossibilities.

• Bi-direction rotation.

• Polished smooth profile inner and out barrelsprevent clogging, minimize germ traps andmaximize sterilization effects on hygienicduties.

• Static ‘O’ ring in contact with shaft or sleeve.

Face materials are Carbon, Solid TungstenCarbide, Solid Silicon Carbide.

The very compact dimensions of this seal,enables it to fit the vast majority of stuffingboxes without modification and therefore makesit ideal for conversion from compressionpackings.

The SAI™ is available in imperial sizes and inmetric sizes conforms to BSEN 12756.

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AESSEAL® MODULAR

SEALING SYSTEM

The CS™ Seal is a balancedseal with its metal parts notin contact with the mediabeing sealed.

It is used in its own right as asingle externally mountedseal, with typical applicationsin the chemical industry.

It is balanced, ‘O’ ringmounted, non shaft fretting,with grubscrew (set-screw)drive. Carbon face isstandard but it is alsoavailable in P.T.F.E. in sizesranging from 0.625” - 2.625”(20mm - 65mm) as standard,however larger sizes areavilable. Silicon Carbide andCeramic hard faces areavailable in limited sizes.

The NCE™ Seal is an external seal with its metal components in contact with the media beingpumped. Can be used as a single externally mounted seal. It is balanced ‘O’ ring mounted, non shaftfretting, with grubscrew (set-screw) drive.

This seal was designed to accommodate all the AESSEAL® range of face materials, a feature notavailable in the CS™. Thus the full hard face options are available when required.

This is the external seal unit used to create a CDSA™.

BTC Fig 11.8


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THE CARTRIDGE

SEAL RANGE

The Cartridge Seal Range

• The ‘old’ range utilizing the U.S.L. selfaligning seat.

The basic seals in the old range being:

• CSAI™

• CAPI™

• CAPO™

• CMDS™

• SCI™

• The ‘new’ range utilizing the U.S.I. selfaligning seat.

The basic seals in the ‘new’ range being:

• CURC™

• CRCO™

• CDSA™ and Bi-Metal CDSA™

• CURE™

• SCUSI™

Fundamentally there were two ranges of cartridge seals:

Both ranges are size compatible.

Although the ‘old’ range has been superseded by the ‘new’, it will continue to be servicedby AESSEAL®.

THE CURC

Comprizes the SAI™ rotary on a sleeve, withthe USI stationary in a cast glandplate assembly,restriction bushing and clamp ring.

It is a balanced, ‘O’ ring seal, non-shaft frettingand is positively located by centering clips. TheCURC™ has multiple springs which are not incontact with the product.

Quench, Flush and Drain connections areincorporated into the gland plate. These can beused to control the environment in which theseal works.

THE CRCO

Identical to the CURC™ except that the carbonrestriction bush is replaced by an oil seal.

The maximum barrier fluid pressure is 10 p.s.i.(This is due to limitations of oil seals.)

BTC Fig 12.1 OHP Ref: AW 0003


Centering Clips notshown

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THE CARTRIDGE

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THE CURE™

The next development from the CRCO™. Bychanging the oil seal for a set of low pressureseal faces, the inherent problem of oil sealfailure and sleeve wear are overcome.

THE CDSA™

This is a cartridge mounted double seal. TheSAI™ rotary is mounted on to the cartridgesleeve running against a USI™ self-aligningseat located into the gland plate. A secondUSI™ is also mounted outboard of the first andan NCE ™ is mounted on the sleeve runningagainst it.

The maximum barrier fluid pressure is 250 p.s.i.(16.5 bar) but normally this will be 1 bar (15p.s.i.) above stuffing box pressure.

THE BI METALCDSA™

This is a CDSA™ adapted for use in corrosiveduties where 316 Stainless Steel is not suitable.This adaption is achieved by manufacturing allmetal parts ‘wetted’ by the media being sealedin applicable corrosion resistant metals. Othermetal parts remain as standard, thus the Bi-metal CDSA™ avoids the expense of total sealmanufacture in high cost metals. Standardmetals available are Alloy 20, Titanium andAlloy 276. Others can be obtained to order.Elastomer material is selected accordingly. U.S.patent allowed, U.K. patent pending.

THE SCUSI™

A short external length seal comprising ofSAI™/USI™ components. Gland platethickness is kept to a minimum thus achievingminimum protrusion from the stuffing box tonearest obstruction. ‘Flush’ environmentalcontrol tapping only. No restriction bushing isincluded and clips set the installation positionfor the seal.

ANSI ‘BIG BORE’

The CURC™ and CDSA™ cartridge seals areavailable suitably adapted to meet ANSI PlusPump Specifications for large bore stuffingboxes, by using a big bore gland plate. Againthe Bi-metal version of the CDSA™ isavailable. A Flow-Inducer may be used in theCDSA™ - called the FI-CDSA™ - to createbarrier fluid circulation. This is possible due tothe increased radial clearance in the stuffing box.

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THE CARTRIDGE

SEAL RANGE

Although AESSEAL® is justifiably best known for its ranges of cartridge seals, where in the U.K. it isthe market sector leader, it must not be forgotten that the internal and external mechanical seals usedin the cartridge seal modular concept are complete single seals in their own right. They are equal ifnot better pieces of engineered sealing equipment than anything offered by competition in theirrespective performance class.

We have discussed the SAI™, NCE™ and SE™ and must now add to these the SMS™, CSWIB™,RDS™ and Convertor II™.

THE SMS™

The SMS™ is an internal, balanced, ‘O’ ring seal, grubscrew (set-screw) located.

It was designed as a competitor to the small diameter single spring design of competition.

It is a clean profile seal, non-shaft fretting, with its springs sealed off from the media.

It is usually run against the ‘R’ ceramic stationary seat and is available in increments of 1/8" from 1/2"to 1” carbon faced only.

BTC Fig 12.8

THE CSWIB™

CSWIB™ is an abbreviation for “Cartridge Seal With Internal Bearing”, it performs the dual functionof seal and support bearing and therefore, although strictly speaking is included in the cartridge sealcategory, is somewhat different.

The CSWIB™ is designed to overcome excessive shaft radial movement or ‘run out’, which whenpresent makes acceptable seal life impossible to achieve.

The CSWIB™ comprizes a shaft sleeve, SAI™ seal and barrel running against an ‘O’ ring mountedstationary seat. The seat is mounted into a robust gland plate outboard of which is also mounted asealed for life single deep groove ball bearing. The seal unit is grubscrew (set-screw) located onto theshaft and bolted through the gland plate on to the stuffing box face.

Radial ‘run out’ is contained by the gland plate being pilot located into the stuffing box I.D.

The CSWIB™ is available with or without quench and drain tappings in the gland plate, in the latteralternative a grease connection is also provided. A flush may also be installed.

SAISEAL

SLEEVE

INTERGRATINGBEARING

‘O’ RING MOUNTEDSTATIONARY

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THE CARTRIDGE

SEAL RANGE

Another excellent piece of engineered sealing technology designed and manufactured by AESSEAL®

is the range of radially divided seals, known in abbreviation as the RDS™ range.

Radially divided or better known in the industry, split seals, are not new in the market and in fact havebeen available for many years in various design forms which operated with varying and mostlyunacceptable degrees of success.

The name split seal originated from the practice of breaking or splitting the two primary seal faces, socracking them in two halves. Even with the strictest of manufacturing procedures this cracking cannotbe fully controlled and very often in practice results in the establishment of a leak path.

In the AESSEAL® approach, 50% of this potential leak path is eliminated. Although the stationarycarbon remains a split component, the rotary has lapped matching faces of its halves. It must be addedthat the stationary is split to such a high degree of control that a better description is probably‘fractured’.

The attraction of the divided seal design is that it can be maintained without disturbing the shaftcoupling or driver. This might not be so relevant in small diameter shaft machinery wheremaintenance can be accomplished manually, nevertheless, drive re-location and re-aligning is stillnecessary. However once shaft diameters have increased to where manual effort is no longer possibleand machinery such as a crane is required, the task of conventional mechanical seal maintenancebecomes a long and expensive one.

Initially the most attractive applications for the RDS™ seal will be as a mechanical seal conversionfrom conventional compression packing, where the ease of installation reasoning in the previousparagraph is equally relevant.

The RDS™ seal is a unitary design and requires no adaptor plate between it and the stuffing box face.It has been designed to keep its number of components to a minimum and to the very highestengineering standards. It is as effective a leak free radially divided mechanical seal as is possiblewithin acceptable commercial restraints.

Other engineered design features of the RDS™ are its stationary seal unit design, non-shaft frettingcharacteristic, ‘flush’ environmental control tapping and correct installation and wear device.

The RDS™ has been designed to seal cold, aqueous-based liquids.


THE RDS™

Lapped Rotary half

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THE CARTRIDGE

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THE CONVERTOR II

The Convertor II is intended as a low cost cartridge seal directly to replace compression packings orsingle component mechanical seals.

It is balanced.

Manufactured from AESSEAL® standard seal components.

Face materials - Carbon/Ceramic as standard or any of the face materials held in stock.

Rotary seal.

‘O’ ring mounted seat.

Sizes from 1.000" to 4.000" (24mm to 100mm) diameter.

Glandplate thickness - Finite Element assisted, designed and tested.

20 bar pressure rating.

4000 feet per minute speed limit. (20 m/s)

-40˚ C (-40˚F) to 200˚ C (400˚F) temperature rating, dependent upon elastomers used. Viton® isstandard.

Non-asbestos gasket, raised flange located.

Factory repair and replacement spares kits available.


L-UK/US-AWARD-B-06

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ENVIRONMENTAL

CONTROLS

Flush is the term given for the arrangement in a mechanical seal assembly that allows the mediabeing sealed (or an external one compatible with it) to be introduced into the area of the matingfaces. It’s main functions being:-

a. To cool.

b. To prevent deposits at the seal faces.

c. To exclude abrasive media from seal face area.

Elementary EnvironmentalControls

THE FLUSH CONNECTION

As pump discharge pressure is usually higher than that in the stuffing box, it is common practice totake the flush from this.

If an external flush is introduced, it must be at least one bar higher than the pressure being sealed.

As well as cooling the seal area and preventing deposit build-up in the seal chamber, temperaturecontrol can be achieved by the introduction of coolers or heaters into the flush line.

Separators or strainers can be fitted to remove solids etc., if so required. By these means the correct“environment” for the seal’s successful operation is established and maintained.

Flush Fluid:(Pressure must be higherthan the product pressure)

The diagram below shows a typicalflush arrangement.

BTC Fig 13.1 OHP Ref: AW 0003

ProductPressure

L-UK/US-AWARD-B-06

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ENVIRONMENTAL

CONTROLS

The term quenching in mechanical seal terminology means immersing the atmospheric side of a sealassembly in water, other fluids, steam or any other acceptable media.

Since the quenching media is usually required to flow through the atmospheric side of a sealassembly, it is said to drain away, hence quench and drain.

Another definition of a quench is to say that it supplies an external sourced fluid, vapor or gas to amechanical seal’s primary seal on the atmospheric side.

The quench is retained within the mechanical seal by some form of outboard auxiliary seal, such as athrottle bush, lip seal or another mechanical seal, selection of which is dependent upon the nature andrequired pressure of the quenching media.

A mechanical seal with quenching facilities can often be considered as a partway arrangementbetween a single and full double installation.

The diagram below shows a typical Quench & Drain arrangement.

THE QUENCH AND DRAIN FUNCTION

In this arrangement someleakage of the quench fluidwould occur at this point


Some of the services provided by the quencharrangement are:

• Removal of leakage across the primary seal ofthe mechanical seal

• Lubrication of the primary seal via its I.D.

• Exclusion of air. When sealed media leakagereacts unfavourably when coming into contactwith the atmosphere.

• Protection against dry running, which for anyreason this might occur.

• Stabilization of the fluid film between theprimary seal faces. Vacuum or close tovaporization applications.

• Cooling.

• Heating.

Vapor and gas quenching will be discussed later.

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ENVIRONMENTAL

CONTROLS

Barrier Fluid Entry

BARRIER FLUID

The diagram below is that of a fully operating double seal.

An external liquid is provided between the inboard and outboard seal faces.


LOW PRESSURE BARRIER

When used at a lower pressure than the stuffing box condition, the barrier fluid can serve as acoolant, provide lubrication for dry running conditions or help to prevent the build up of crystallizedparticles at the internal seal faces.

A barrier fluid pressure which is higher than the stuffing box pressure, prevents the pumped productfrom entering the barrier fluid system and ultimately leaking to atmosphere. A High Pressure Barrieralso means that the internal face film is barrier fluid rather than product.

HIGH PRESSURE BARRIER

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CHOOSING THE

CORRECT MATERIALS

METALLURGY

Along with the rest of the Mechanical Seal Industry, AESSEAL® has standardized on 316L StainlessSteel for its metal parts.

As a guide to the suitability of 316 Stainless Steel to the media being sealed, if the pipework on theinstallation is of Steel, Iron, Brass, Bronze or Stainless Steel, then it will be compatible.

Some media that will attack 316L Stainless Steel include:

• 98% Sulphuric acid, above ambient temperature. 50% to 85% at 60˚ C (140˚F) will destroy 316LStainless Steel.

• Caution with Acetic acid as in certain conditions it will attack Molybdenum.

• Hydrofluoric acid is totally unacceptable, use Alloy 276, but check with Rotherham.

• Hydrochloric acid, check with Rotherham.

• Fuming Nitric acid, check with Rotherham.

• Sulphuric acid, use Alloy 20, but check with Rotherham

• Chlorine Dioxide, use Titanium, but check with Rotherham.

• Temperature rises drastically increase the corrosion rates of acids.

If 316L Stainless Steel is not suitable, then the Bi-metal exotic alloy seal or the SE seal should beconsidered.

For the Bi-metal exotic alloy seal, Alloy 20, Alloy 276 and Titanium wetted inboard seal componentsare inventoried in popular sizes.

Alloy 20 is a grade of Stainless Steel having greater corrosion resistance than 316L Stainless Steel.

Alloy 276 is a nickel-based alloy with Molybdenum, Chrome, Manganese, Copper and Iron added. Itscorrosion resistance is amongst the highest of all metals. Alloy 276 is the material used byAESSEAL® for its springs, as in addition to its corrosion properties its ‘spring force’ is 25% more thanfor a Stainless Steel spring material such as 302. Also, it does not suffer from Chloride stresscorrosion as Stainless Steel might do when exposed to Chloride containing media, especially in thinsection forms such as springs.

Springs in the AESSEAL® range of seals have been tested by an independent test facility for 10million deflections with no breakages.

Titanium is one of the best corrosion-resistance materials commercially available. It is resistant tosuch aggressive media as Nitric acid and Chlorine Dioxide.

The CS™ seal is designed as an external seal and is so designed that none of its metal parts are incontact with the media being sealed. Wetted components are of Ceramic (seat) and Carbon (face), bothof which have extreme corrosion resistance qualities.

The flange gasket can be of P.T.F.E. and the secondary seal would be an elastomeric ‘O’ ring, whichcan be corrosion resistant to virtually all aggressive media and gases.

Choosing the CorrectMaterials

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To be more accurate, the standard Carbon used by AESSEAL® as with the rest of the mechanical sealindustry, is an artificial one produced from Coke, Graphite, Carbon black and Anthracite incombination with binding agents such as Coal Tar, Pitch or Synthetic Resin.

The AESSEAL® grade of Carbon is described as triple-resin impregnated. Its maximum operatingtemperature is 200˚ C (400˚F). above which the resin boils out of the Carbon. It will then fall out of its316L Stainless Steel carrier and eventually disintegrate.

Carbon is compatible with a very extensive range of chemicals -see Appendix ‘Compatibility SheetNumber D.220/1’.

In addition to its chemical compatibility qualities, Carbon has excellent sliding characteristics, and isthe preferred material for the rotating member of the primary seal.

More qualities of Carbon are its lubricity, excellent heat dissipation and hard-wearing properties.Carbon is porous (about 8%) hence the need for vacuum impregnation to seal this porosity. Phenolicresin is usually the material used for this purpose.

Good Carbon performance is determined by the type, composition and grain of its base materials andthe binder used. Impregnation exerts a secondary influence.

Viton® is the most widely used ‘O’ ring material in the Mechanical Seal Industry. Viton® is aFluorocarbon Rubber (FPM) and Viton® is the trade name for FPM, used by DuPont Dow Elastomers.

A number of grades of viton are available, the one selected by AESSEAL® for its standard is E60C,which in addition to being the best grade to resist compression set also has good chemical resistance.

Viton® is not really a low temperature elastomer, with a typical minimum of -20˚ C (-4˚F), itsmaximum being 200˚ C (400˚F). The Shore Hardness is 75, which gives good wear characteristics.Maximum temperature in high pressure hot water applications is 80˚ C (180˚F).

E.P.R. - Ethylene Propylene Rubber, Typical temperature range is - 40˚ C (-40˚F). to 150˚ C (300˚F).

E.P.R. has a Shore Hardness of 75 and has better recovery but less stable compression setcharacteristics than Viton®. It is normally used only in hot water and caustic/alkali solutions.

E.P.R. has the best resistance to radioactive environments.

F.E.P. - Fluorinated Ethylene Propylene, ‘O’ rings are constructed by placing a heat sealed tube ofF.E.P. over a core of rubber. The core is usually Silicone rubber although Viton® is also available.

F.E.P. has excellent resilience and recovery characteristics. It has almost the same chemical resistanceas Teflon. Temperature range is typically - 60˚ C (-75˚F). to 205˚ C (400˚F). Great care should betaken when handling and fitting F.E.P. rings. In particular make sure that any burrs or sharp edges arerounded off and smoothed.

Although available from inventory AES never recommend the use of F.E.P. ‘O’ rings in their range ofmechanical seals.

Kalrez® - Grade 4079 is the AESSEAL® standard grade. This gives a chemical resistance similar toTeflon and is thermally stable up to 316˚ C (600˚F). For extreme hot water and steam applications,Grade 3018 should be used.

Aflas® - thermally stable up to 200˚ C (400˚F). Particularly relevant in the Pulp and Paper Industry onliqueur (liquor) duties, also in high temperature hot water and caustic applications.

CARBON

‘O’ RING MATERIALS

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CHOOSING THE

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Carbon/Ceramic

• Widely used combination.

• Ceramic is hard (2500 Vickers Hardness).

• It is chemical resistant.

• The higher the Alumina content, the greater its resistance to heat check. The higher the percentage,the better the quality. The grade used by AESSEAL® is 99.5%, or superfine grade.

• Ceramic has extremely poor heat dissipation qualities, is also brittle and suffers from a phenomenaknown as heat checking.

Carbon/Chrome Oxide

• Chrome Oxide has much better heat dissipation qualities than Ceramic.

• It has the chemical resistance of 316 Stainless Steel.

• Not suitable for extreme acid or alkaline applications which may attack the stainless steel and causedetachment of the Chrome Oxide layer.

• Excellent general purpose face material for aqueous-based media.

• Metal to metal drive can also extend seal life.

• Good in alkali environments.

• Not to be used at pH < 2.5.

Solid Tungsten Carbide/Solid Tungsten Carbide

• Not as hard as Ceramic (~75 Rockwell C).

• A tough material, mechanically good.

• Good shock characteristics.

• Very good heat dissipation qualities.

• Cannot be used in dry running situations under any circumstances.

Carbon/Solid Tungsten Carbide

• Good high temperature hot water combination or any similar ‘close to vaporization’ applications.

• Generally as for STC/STC.

• Not as good on abrasive application, but has better ‘sliding’ properties.

Carbon/Silicon Carbide

• Very good chemical compatibility.

• Extremely good heat dissipation qualities.

• Very hard.

•Very brittle.

Solid Tungsten Carbide/Silicon Carbide

• Generally the preferred combination for abrasive duties or certain high pressure applications.

Silicon Carbide/Silicon Carbide

• Should only ever be used in extreme acid duties (where Solid Tungsten Carbide would be attacked).

PRIMARY SEAL MATERIALCOMBINATIONS

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CHOOSING THE

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Choosing the CorrectMaterials

Vickers Hardness Rockwell C

3000 HV

2500 HV

2000 HV

80 C (max)

1500 HV 75 C

1000 HV69 C

500 HV49 C20 C (min)

0 HV

Shore A

100

50

SILICON CARBIDE (REACTION BONDED)

SILICON CARBIDE (SINTERED)CERAMIC

TUNGSTEN CARBIDE (COBALT BONDED)TUNGSTEN CARBIDE (NICKEL BONDED)

CHROME OXIDE

STELLITE

316 STAINLESS STEEL

NI RESIST

CARBON

PTFE

VITON

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SEAL APPLICATION

FORM

Seal Application FormThis form (see pages 47 & 48) must be completed every time a salesman fits a mechanical seal to apump:

a) Which he / she has not fitted a seal to before.

b) In which a seal meets a new application.

c) If the customer is new to your company.

d) If you want any technical help from AESSEAL®

e) If the application is known but the size is different or the pump is different than previously used.

Looking at the sheet the top portion needs to be noted by yourselves so that you can readily identify ifthe customer calls whether it is a new or previously experienced application he / she is talking about.Should your company not want us to have this information about the customer, be prepared to acceptthat any enquiries (inquiries) are bound to be extended. Any further information required will have tobe sought by yourselves or the salesman concerned, as we cannot contact the customer directly.

The more details you can fill in on the form the less time it will take for a reply to any queries youmay make to AESSEAL® Rotherham.

The next sections must be filled in full, any gaps will be treated as unknowns and we will ask forclarification on those spaces on the form.

Incomplete or inaccurate answers will lead to more mechanical seal failures.

For any specials AESSEAL® will undertake a technical and commercial appraisal, please fill in thefirst section on the back page fully.

REMEMBER:

AESSEAL® restricts its warranty to defects in materials and workmanship, except where a mechanicalseal is sold by its own direct salesforce. Where a distributor makes the sales profit it is theirresponsibility to meet any warranty claims. Almost all mechanical seal failures are caused by factorsbeyond our control. That is why we pressure test every mechanical seal prior to shipping from ourfactory.

HEALTH & SAFETY

All mechanical seals are wearing parts, with a finite life expectancy. All purchasers of mechanicalseals should make adequate provision to control and monitor the product being sealed, to ensurepersonnel safety once the effective life of the seal is over.

For safety reasons, all potentially hazardous products should be sealed with a full double facedmechanical seal. A properly installed, selected and controlled double seal gives greater chances ofadvance warning of impending failure. Even double seals will eventually fail. Advance user planningto control the resultant product leakage, careful installation, adequate monitoring and proper productselection are essential to ensure (insure) Health and Safety at Work.

All mechanical seals last longer on well maintained equipment.

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SEAL APPLICATION

FORM

Date................. Seal Application Eng...............Code........... ORDER / ENQUIRY

AESSEAL plcMill Close, Bradmarsh Business Park,Templeborough, Rotherham, S60 1BZ.

Telephone: 01709 369966 Facsimile: 01709 720788

CUSTOMERCompany..................................................................................................

Plant..................................Location...............................Contact................................Telephone.................................. Facsimile...................................

D1 DIA...................................SLEEVE/SHAFT

D2 DIA..............................................................

PCD 3...............................................................

D4 THREAD.....................................No...........

BOLT PATTERN...............................................

L1.....................................................................

L2.....................................................................

L3.....................................................................

PUMP DETAILS

Manufacturer.....................................................Size / Type........................................................Serial No...........................................................Speed...............................................................Max Gland O/D.................................................Pump Modifications..............................................................................................................................................................................................Axial Movement (max)......................................Radial Movement (max)...................................S’Box Recess Dia.............................................S’Box Outside Dia............................................API Plan No......................................................

PRODUCT DETAILS

Product.............................................................Chemical Composition / Concentration..........................................................................................................................................................................................................................................Temperature °C................................................p.H....................................................................Pressure in S’Box.............................................Abrasive Content ? YES / NOMax Particle Size..............................................Flush Available ? YES / NOFlush Fluid........................................................Dry Running? YES / NO

For official use only SEAL SUGGESTION

SIZE TYPE FACE MATERIAL (S) O-RING MATERIAL (S)

QUANTITY....................... PRICE..................................... DELIVERY.....................................

Ref: IN 3992 Issue: F 01 January 2002

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SEAL APPLICATION

FORM

INFORMATION FOR NON-STANDARD DESIGNS

ESSENTIAL information for non-standard designs - to aid in a technical andcommercial evaluation by AESSEAL® management.

1) What is the Customer currently using in the proposed application?

a) Packing type :-b) Seal type :-c) Seal Faces :-

i) Inboard - ................................... ii) Outboard - ...................................d) Elastomers :-

i) Inboard - ................................... ii) Outboard - ...................................

2) What is the current cost to the customer of the existing sealing device?.......................................................................................................................

3) Please indicate what your customer expects to pay you for the applicationsolution?.......................................................................................................................

4) How many identical units does the customer expect to seal, if the first itemproves successful?.......................................................................................................................

5) What is the total anticipated value of business after solving this problem at our price to the customer?

i) Within 12 months? ....................................................................................ii) 12 to 24 months?......................................................................................

6) Any additional information you feel AESSEAL®. might find helpful. (e.g. Details of Operation Systems, Barrier Fluid or Flush System, etc.)...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................

For official use onlyRequested...............................................................Date.........................................LOGGED ON SYSTEM

Signed.......................................Date..........................Enquiry No............................

Ref: IN 3992 Issue: F 01 January 2002

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GLOSSARY OF

SEAL TERMS

A

ANSI/ASME: American National Standards Institute/American Society ofMechanical Engineers.

Anti-Rotation Device: A device usually a pin used to prevent the rotation of one component ofthe primary seal relevant to the other.

API: American Petroleum Institute.

API Piping Plan: Piping plans recommended by the API for the auxiliary equipmentrequired in a mechanical seal application.

Asperities: Minute imperfections (peaks & troughs) in either face of the primaryseal which are present following normal lapping procedures.

Auxiliary Equipment: Additional equipment used with a mechanical seal, usually to create ormaintain a favourable environment around it and so ensure (insure)reliable service.

Axial Movement: Movement along the axis parallel to the center line of the shaft.

B

Back to Back Seals: See double seals.

Balance Holes: Holes through the hub of an impeller, providing pressure equalizationbehind the impeller with that of the suction pressure and so reduce thestuffing box pressure.

Balanced Seal: A mechanical seal so designed as to reduce the effect of the fluid’shydraulic pressure upon the primary seal face loads.

Balance (Hydraulic): Is the ratio of two areas. The area of the sealing face which is boundedby the balance diameter and the inside diameter of the sealing face andthe area which is bounded by the outer and inner diameters of thesealing face, normally referred to as a percentage, e.g. 70%, or ratio e.g.70/30, or decimal e.g. 0.7.

Bedding In: Running in.

Bellows: Bellows component of a bellows seal, usually of elastomeric, PTFE ormetal construction. Elastomeric bellows are a moulded (molded)design, with Viton® being the most popular elastomer. PTFE bellowsare machined. Metal bellows are constructed from a series of metaldiscs, welded together alternatively at O.D. and I.D. Metal bellows arealso available constructed via hydraulic and rolled techniques.

Bi-Directional Seal: A seal which is designed to seal equally well in clockwise or counter-clockwise rotation.

Blistering: A term used to describe damage to carbons usually caused inHydrocarbon applications.

Boot Seal: A seal in which the primary member is a bellows or some otheraccordion shape. It is attached to both members between which sealingis required and is therefore only capable of sealing, oscillating,reciprocating or angular motions.

Bore Seal: A device who’s O.D. surface mates with a bore surface.

It provides sealing between these two surfaces.

Boundary Lubrication: Situation where both primary seal members are in contact, relying onabsorbed fluid for lubrication.

Glossary of Seal Terms

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GLOSSARY OF

SEAL TERMS

Bubble Point: The temperature at constant pressure which produces a bubble in aliquid.

Buffer Fluid (Barrier fluid): In double seal arrangements, the fluid introduced between the seals toisolate the arrangement from both the fluid being sealed and theatmosphere. In this arrangement, the pressure of the buffer fluid ishigher (1 or 2 bar) (15-30 p.s.i.) than that of the sealed fluid.

In tandem seal arrangements, the object is the same as for double seals,but buffer pressure is lower than that of the sealed fluid.

By-Pass Flush: Flush taken from the pump volute or H.P. side of the system.

C

Carbonization: A reduction of Hydrocarbons resulting in a carbonaceous residue.

Carrier: That component of a mechanical seal which carries a face (eitherstationary or rotating) of the primary, either by shrink fit, by othermechanical means or adhesive.

Cartridge Seal: A complete mechanical seal assembly with gland plate. Sleevemounted, only needing bolting onto the stuffing box.

Cavitation: A condition in which vapour (vapor) or gas bubbles occur locally inliquids (normally in an area where pressure decreases suddenly). Thesubsequent collapse of the bubbles causes high local impact pressurewhich may result in seal wear.

Cavity also Chamber: The annular area between a bore and a shaft, into which a mechanicalseal is fitted.

Clamp Plate: A plate bolted to the stuffing box carrying the ‘seat’. Also seal plate.

Clearance Seal: A seal which limits the leakage between a rotating or reciprocatingshaft and a stationary housing by means of a controlled annularclearance between the two.

Closing Force: Pressure of sealed fluid plus spring pressure.

Coking: Formation of carbonaceous deposits on the atmospheric side of amechanical seal arrangement.

Composite Seal: A seal which is composed of two or more materials of differingflexibility or hardness. The materials are usually bonded together, e.g.the John Crane type 10 family of PTFE seals.

Compression Set: The thickness difference between a gasket or static seal prior and postto compression, usually expressed as a percentage of the totalcompression.

Controlled Leakage Seal: A mechanical seal so designed to allow leakage across the primary seal.

Coolant: A cool liquid, introduced to a mechanical seal arrangement from anexternal source to facilitate cooling.

Crystalliztion: Formation of crystals on the atmospheric side of a mechanical sealarrangement.

Cyclone Separator: A piece of ancillary equipment, fitted in a pumped fluid recirculationline to remove solids. A Hydrocyclone.

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GLOSSARY OF

SEAL TERMS

D

Dead Ended: A stuffing box arrangement where the buffer fluid or sealing fluid doesnot circulate within it.

Diaphragm Seal: A seal, the secondary seal of which consists of a flexiblediaphragm.Differential Pressure: The difference in pressure betweentwo points in a system, e.g. one upstream of a mechanical seal and onedownstream of it.

DIN: Deutches Institut Für Normen E/German Engineering StandardsInstitute.

Double Balance: The feature of a mechanical seal design (special) that allows it to workunder a given reverse pressure.

Double Seal: A seal arrangement where two seals are used, back to back or face toface and buffer fluid passed between them.

Dry Running: A condition where there is no liquid present between the faces of theprimary seal, in a mechanical seal, when it is in operation.

Dynamic Seal: A seal which has rotating, oscillating or reciprocating motion betweenits sealing components.

E

Elastomer: An elastic material, compounded with fillers, release agents andsimilar.

End Plate: A plate which holds the non-rotating part of a mechanical seal andconnects it to the seal chamber, also gland plate.

Extrusion: The displacement of a part of an ‘O’ ring or similar seal into a gapwhen subjected to pressure or movement.

Eye: The circular inlet of an impeller.

F

Face Width: The radial dimension of the narrower face of the primary seal.

Film Thickness: The distance between the two members of the primary seal in amechanical seal.

Film Transfer: When a film of material off the softer of the two members of theprimary seal is deposited onto the harder one.

Flash: Extrusions on an elastomer (‘O’ ring) formed in its moulding(molding).

Flashing: Rapid vaporization of a fluid.

Flatness: The comparison of the flatness of a mechanical seal face or seat to aperfect plane. Expressed in Helium light bands, 1 light band =0.0000116” (0.29 microns).

Flinger: Disc device shaft mounted to impart radial movement to mechanicalseal leakage, so keeping it away from bearings, etc, also slinger.

Fluid Film: The film of sealed media separating and lubricating the primary seal.

Flush: An amount of fluid introduced into the seal chamber in close proximityto the I.D. of the primary seal of the mechanical seal.

Free Length: The uncompressed axial length of a mechanical seal assembly. Thisterm is also applicable to -springs or bellows.

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GLOSSARY OF

SEAL TERMS

G

Gasket: A device used between two static (usually) surfaces to prevent leakage.

Gland: Stationary part of a mechanical seal often fixed to the pump/mixer.

Gland Follower: The axially moveable part of a stuffing box which is forced against thesealing members by means of manual adjustment, resulting in anincrease in radial sealing force.

H

Hang-Up: A condition where the secondary seal in a mechanical seal arrangementdoes not take up primary seal wear.

Header: A rigid ring used to prevent axial movement of a seal(s) within a gland.

Heat Check: Fine radial cracks, in the harder of the two primary seal numbers,caused by thermal stress. Dry running, cold quenching.

Housing: A rigid structure which supports and locates the seal assembly withrespect to the shaft.

Hydraulic Load: The axial load resulting from fluid pressures only. Also applicable topneumatic load.

I

Icing: Formation of ice on the atmospheric side of mechanical sealarrangement.

Injection: See flush and quench.

Interface: Region between the two faces of the primary seal.

L

Labyrinth Seal: A clearance type of seal where the fluid being sealed must traverse atortuous path in order to escape. There are many designs of labyrinthused in this type of seal.

Leakage Rate: The quantity of fluid passing through a seal in a given length of time.

M

Magnetic Seal: A seal which uses magnetic material instead of springs or bellows toprovide the closing force.

Mechanical Load: The load applied to a seal to ensure (insure) contact between the matingfaces, excluding fluid pressure.

Minimum Compressed Length: The length of a mechanical seal assembly which has been loaded to itssolid length. Also applicable to springs and bellows.

N

Neck Bush: Close clearance bushing at bottom of stuffing box, restricting flow ofsealed fluid into seal chamber.

O

Operating Length; The axial distance of a mechanical seal from the primary seal locationto a reference point or plane. The term also applies to the dimensionalrange within which a bellows can be safely operated.

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GLOSSARY OF

SEAL TERMS

Optical Flat: A transparent disc, usually of fused quartz, lapped and polished towithin 0.1 light band flatness on one or both faces. It is used to measureflatness in conjunction with a Monochromatic Light Source.

Outside Mounted Seal: A mechanical seal with its unit/head mounted outside the containerholding the fluid to be sealed.

P

Pitting: Voids in surfaces of the primary seal faces usually caused bymechanical erosion, chemical corrosion or cavitation.

Primary Seal: The seal between the rotating and stationary members of a mechanicalseal.

Pumping Ring: A simplified impeller within a chamber which circulates fluid through aclosed loop for cooling purposes.

Pusher-Type Seal: A mechanical seal in which the secondary seal is pushed along the shaftor sleeve to take up face wear of the primary seal.

PV Factor: An arbitrary term which is the product of face pressure and relativesliding velocity. The term is considered to provide some sort ofmeasure as to the severity of service and thus is relative to seal life.

Q

Quench: A neutral fluid which is introduced into the atmospheric side of a sealassembly.

R

Running Torque: The torque required to sustain a shaft in rotary motion.

S

Scuffing: A mild degree of galling which results from the welding of asperitiesdue to frictional heat. The welded asperities break causing surfacedegradation.

Seal: A device designed to prevent the movement of fluid (or other media)from one area to another, or to exclude contaminates.

Seal Assembly: A total two-part seal.

Seal Bushing: A seal type consisting of a close fitting sleeve within which the shaftrotates. Leakage is controlled by the clearance between the shaft andthe bushing. The bushing O.D. is usually press fitted and locked into ahousing.

Seal Cavity Pressure: The pressure on the product side of a mechanical seal assembly.

Seal Envelope: The external dimensions of a mechanical seal.

Seal Head: The assembly of parts comprising the complete functional unit of theaxially moveable part of a mechanical seal. Also called the unit.

Seal Housing: A structure which supports and locates the primary seal.

Seal Nose: The part of the rotating member of the primary seal coming in closestproximity to the face of the mating member.

Seal Unit: That part of a two piece mechanical seal assembly containingsecondary seal, springs, etc.

Secondary Seal: A device, such as ‘O’ ring or bellows, which allows axial movement ofthe primary seal of a mechanical seal without leakage.

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GLOSSARY OF

SEAL TERMS

Shaft Eccentricity: The radial distance which the geometric center of a shaft is displacedfrom the axis of its rotation.

Shaft Runout: Twice the distance which the center of a shaft is displaced from its axisof rotation, i.e. twice the eccentricity.

Slinger: A disc-like device which is mounted close to the gland plate andimparts radial movement to a liquid in order to prevent it entering anarea where it will cause damage.

Spiral Wound Gasket: A device formed by winding a metal and suitable filler layer into aspiral. It is usually ‘V’ shaped and seals statically.

Split Seal: A seal which has its primary sealing members split in a plane parallelto the axis of a shaft, thus they are each two semi-circles. Other sealmembers may be divided according to individual designs.

Spring: A machine element capable of storing energy and releasing it asrequired. In mechanical seal engineering springs are primarily used tomaintain pressure on the primary seal when there is no hydraulicclosing force present.

Spring Force: The axial force exerted by a spring to overcome dynamic force and anysecondary seal friction force.

Spring Pressure: The face pressure between the members of the primary seal of amechanical seal resulting from its spring load only.

Spring Rate: The force, independent of initial tension, which is required to extendthe working length of a spring/ unit distance.

Starting Torque: The torque required to initiate rotary motion.

Starved Lubrication: Insufficient or total lack of lubrication.

Stator: The stationary part of a two piece mechanical seal.

Stick-Slip: A friction phenomenon which perhaps is best described as a ‘jerky’motion usually resulting when one surface is being dragged overanother as in non or boundary lubricated primary seal conditions.

Stuffing Box: A cylindrical cavity and the enclosing stationary parts surrounding ashaft, designed to accept a packing for the purpose of preventingleakage along the shaft.

Surface Finish: The smoothness of a metallic surface, e.g. shafts, sleeves, etc.

T

Tandem Seal: A two seal arrangement, one mounted after the other, with units andseats orientated in the same direction.

Torque: (As applied to mechanical sealing). A resistance to shaft rotationcaused by the frictional drag of the primary seal in a mechanical seal.

Torsion Vibration: A vibration having a circumferential or angular sense such as isgenerated by stick-slip action of the primary seal.

Track: The mark made by a seal on the surface with which it mates, alsotracking pattern.

U

Unbalanced Seal: A mechanical seal so designed that 100-150% of the hydraulic pressureof the sealed fluid acts to close the primary seal.

Unitized Seal: A seal assembly in which all the components are retained in a singlepackage, e.g. cartridge seal.

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GLOSSARY OF

SEAL TERMS

V

Vaporization: When a liquid changes state to a vapour or gas.

Vapour (Vapor) Pressure: The pressure below which a liquid becomes a vapour or gas, at a giventemperature.

Vent Connection: A connection in the gland plate outboard of the seal through whichleakage may be vented or fluid passed.

Volute: The part of a centrifugal pump within which the impeller operates.

W

Water Hammer: The sound of concussion, when a flowing liquid is suddenly stopped.

Wave Spring: A disc type of spring, deformed to have a multiple wave pattern in aplace perpendicular to its axis. It utilizes little axial space and istherefore used in seal designs requiring minimum length.

Wear Rate: The amount of seal surface wear worn in a given amount of time.

Wedge Type Seal: A mechanical seal where the secondary seal is of wedge shape crosssection, e.g. John Crane type 109.

Weepage: A minute amount of liquid leakage across the primary seal. There is nodefinition of ‘minute’ but it is often considered as less than one dropper minute.

Wildback Seal: A helically grooved liner, usually installed on a shaft which operatesthrough a clearance and lowers leakage by means of its pumping actionresulting from the transfer or momentum to the fluid. Also Helix seal,Screw seal, Viscoseal.

Wipe: Excessive radial movement of the primary seal faces across each other.

AESSEAL plc, Rotherham, U.K. Telephone: +44 (0) 1709 369966

AESSEAL plc, Derby, U.K. Telephone: +44 (0) 1332 366738

AESSEAL plc, Peterborough, U.K. Telephone: +44 (0) 1733 230787

AESSEAL plc, Scotland, U.K. Telephone: +44 (0) 1698 849808

AESSEAL plc, Middlesbrough, U.K. Telephone +44 (0) 1642 245744

AESSEAL plc, Essex, U.K. Telephone: +44 (0) 1708 256600

AESSEAL plc, Pontypridd, U.K. Telephone: +44 (0) 1443 844330

AESSEAL (MCK) Ltd., Lisburn, U.K. Telephone: +44 (0) 28 9266 9966

AESSEAL (MCK) Ltd., Co. Cork, Ireland. Telephone: +353 (0) 214 633477

AESSEAL Inc., Knoxville, Tennessee, USA. Telephone: +1 865 531 0192

AESSEAL Inc., Seneca Falls, New York, USA. Telephone: +1 315 568 4706

AESSEAL Inc., Kingsport, Tennessee, USA. Telephone: +1 423 224 7573

AESSEAL ESP LLC, Cedar Rapids, Iowa, USA. Telephone: +1 319 393 4310

AESSEAL Deutschland AG. Telephone: +49 (0) 60 74 881293

AESSEAL Italia SRL. Telephone: +39 (0) 33 197 0556

AESSEAL Pty Ltd., Gauteng, South Africa. Telephone: +27 (0) 11 466 6500

AESSEAL Pty Ltd., Confluid Branch, Amanzimtoti, South Africa. Telephone: +27 (0) 31 903 5438

AESSEALMalaysia SDN. BHD. Telephone: +603 8062 1233

AESSEAL Nederland. Telephone: +31 (0) 76 564 9292

AESSEAL Ibérica S.L. Telephone: +34 977 55 43 30

AESSEAL Danmark, Køge, Denmark. Telephone: +45 56 64 14 00

AESSEAL France S.A.R.L. Telephone: +33 (0) 3 2017 2850

AESSEAL Turkiye, Istanbul, Turkey. Telephone: +90 (0) 212 237 40 47

AESSEAL Canada Inc. Telephone: +1 807 624 2727

AESSEAL China Ltd. Telephone: +86 574 8770 1888

web: http://www.aesseal.com email: [email protected]

AESSEAL® produces components of the highest quality,for demanding customers across the world. To achieve

customer satisfaction, upon which the future ofAESSEAL® depends, we need employees who are totally

equipped to handle every aspect of our business.

The Company is, therefore, committed to the Investor inPeople standard. We have undertaken, as part of this

initiative, to train and develop all employees to thestandard necessary to achieve company objectives.

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