Exp Mn Sm090 En R0 Seals fa3f

MECHANICAL MAINTENANCE SEALS

TRAINING MANUAL COURSE EXP-MN-SM090 Revision 0

Field Operations Training Mechanical Maintenance Seals

MECHANICAL MAINTENANCE SEALS CONTENTS 1. OBJECTIVES ..................................................................................................................4 2. INTRODUCTION .............................................................................................................5 3. MECHANICAL SEALS.....................................................................................................8 3.1. FIELD OF USE..........................................................................................................9 3.2. MULTIPLE APPLICATIONS....................................................................................10 3.3. SEVERE OPERATING CONDITIONS ....................................................................11 3.4. SEALS ARE BECOMING MORE AND MORE INGENIOUS...................................12 3.5. PRECAUTIONS TO BE TAKEN..............................................................................12 3.5.1. During installation............................................................................................12 3.5.2. When starting the installation ..........................................................................13 3.6. INSTALLING A SEAL..............................................................................................14 4. SEALING RINGS...........................................................................................................17 4.1. GENERAL ...............................................................................................................17 4.2. DESCRIPTION OF THE LIP RINGS .......................................................................19 4.2.1. Production materials........................................................................................20 4.3. SHAFT RUNOUT AND WOBBLE ...........................................................................21 4.3.1. Runout.............................................................................................................21 4.3.2. Shaft wobble....................................................................................................22 4.4. LUBRICATION AND FRICTION..............................................................................22 4.5. SEALING-RING CONFIGURATION........................................................................23 4.6. TROUBLESHOOTING ............................................................................................25 5. PACKING GLAND .........................................................................................................28 5.1. DEFINITION............................................................................................................28 5.2. ADVANTAGES OF PACKING GLANDS .................................................................29 5.3. BRAID STRUCTURE ..............................................................................................29 5.3.1. Dual diagonal-interlock braid ...........................................................................29 5.3.2. Triple diagonal-interlock braid .........................................................................29 5.3.3. Quadruple diagonal-interlock braid..................................................................30 5.3.4. Braid-on-braid packing ....................................................................................30 5.4. CHOICE OF BRAID ................................................................................................30 5.4.1. Packing ring specifications ..............................................................................31 5.4.2. Different assembly configurations ...................................................................31 5.5. TROUBLESHOOTING ............................................................................................33 5.5.1. One or more rings missing from the housing...................................................33 5.5.2. Pieces of packing protruding between the shaft and flange. ...........................33 5.5.3. Smaller radial thickness than during assembly................................................33 5.5.4. Unequal ring radial thickness. .........................................................................34 5.5.5. Shrinkage of the axial faces. ...........................................................................34 5.5.6. The bottom rings are OK but the top rings are damaged.................................34 5.6. PACKING GLAND REPAIR ....................................................................................35 5.6.1. Preparing the packing gland............................................................................35 5.6.2. Installing the rings ...........................................................................................37 Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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5.7. PACKING GLAND INSPECTION ............................................................................39 5.7.1. On a valve .......................................................................................................39 5.7.2. On a pump.......................................................................................................39 5.8. THE DIFFERENT TYPES OF BRAIDED PACKINGS .............................................40 5.8.1. Vegetable fibre braided packing impregnated with PTFE................................40 5.8.2. Synthetic fibre braided packing impregnated with PTFE .................................42 5.8.3. Carbon fibre braided packing ..........................................................................44 5.8.4. Pure PTFE braided packing ............................................................................46 5.8.5. Soft PTFE packing ..........................................................................................48 5.8.6. PTFE packing with graphite.............................................................................50 5.8.7. PTFE packing with Kevlar-reinforces corners..................................................52 5.8.8. Kevlar packing.................................................................................................54 5.8.9. Gland packing .................................................................................................56 6. FIGURES.......................................................................................................................58 7. TABLES .........................................................................................................................60

Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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1. OBJECTIVES This course summarises the information which a technician must know to master the various sealing processes used on an oil industry site.


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2. INTRODUCTION In engineering there are often clearances between the parts. These clearances generate ages through which the drive fluid or lubricating fluid can escape. A mechanical seal is a device which provides the sealing between a shaft's rotational or translational movement and a stationary housing.

Figure 1: Seal on a moving shaft The main function of a seal is to prevent the fluid escaping from its receptacle or housing, or to prevent the ingress of contaminants. When the seal consists of several elements with different functions, we call it a "sealing system". Many sealing applications involve systems in movement. The seal must provide long-term efficiency and be adapted to the environment. The seal's lifetime depends on a large number of parameters. It will only meet the requirements if these parameters are taken into during its design, assembly and operation. There are several types of shaft seal available (and many variants of these different types): Mechanical seal Braided packings Sealing rings


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Figure 2: Conventional mechanical seal

Figure 3: Packing gland with braided packing

Figure 4: Packing gland with lip seal There are a very large number of different sealing devices to meet the wide variety of requirements in the best possible conditions. There are several dynamic sealing systems available.


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They are designed to provide the sealing between a rotating shaft and a fixed housing (pump, agitators, compressor, etc.) rolled rings: it is used to control leaks according to the ring thickness and the clearance between the fixed and rotating parts. labyrinth seal: seal providing a greater control of the leak segmented rings: with this system there is a leak rate of around one drip (segmented busting). lip seal: they are frequently used as bearing seals and can have single or multiple lips. gland with braided packing: one of the most common sealing systems but which requires surveillance and interventions. swivel couplings: seal for rotating fluid transfer systems mechanical seal: mechanical seals are made from high-precision engineered components and based on the manufacturers' expertise. Sealing problems are complex. For example, a rotating shaft transmits power to a propeller, a wheel, etc. by ing through a wall designed to separate two fluids from each other. One of the fluids is generally the atmosphere, the other is the product to be sealed. The pressures and/or temperatures of each fluid are different. There must therefore be a dynamic sealing system between this shaft and the static part of the machine.


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3. MECHANICAL SEALS A mechanical seal consists of two subassemblies: A static part A rotating part Figure 5: Seals (static and rotating components) The components forming these seals are made from high-precision engineered components and based on the manufacturers' expertise. Different materials are used for the design of the rings and O-rings of mechanical seals.

Figure 6: Rings and O-rings The parts forming a mechanical seal can be classified into four groups: Friction faces Secondary seal (seals, diaphragms, bellows, etc.) Elastic element (spring, bellows, etc.) Other components combining the 2 subassemblies (sleeve, cover, etc.) When static, these two subassemblies are maintained in by the action of the elastic element. This elastic element can be: incorporated in the static subassembly or the rotating subassembly immersed in the fluid to be sealed protected from this fluid. Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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Figure 7: Detail view of a mechanical seal Whatever the forces acting on the seal and the rotation defects, the subassembly containing the elastic element (spring) must be able to move into all directions so that the faces are permanently in . It is said to be "semi-dynamic". The secondary seal in this subassembly is subjected to the low or even very low amplitude reciprocating axial movements and is therefore called a secondary semi-dynamic seal.

3.1. FIELD OF USE Extraction, transfer, refining, onshore and offshore: Severe service conditions Difficult maintenance Marine environment and small size are two important criteria. Figure 8: Seal in a hostile environment Due to its technology, this type of seal can solve most problems. It provides an almost total seal for both static and dynamic use. Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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The mechanical seal is constantly being developed due to the diverse demands of the market. Figure 9: Mechanical seals The permanently changing technological and economic requirements of the industrial world result in a more and more generalised use of dynamic sealing by mechanical seals. Mechanical seal technology is continually improving and thus provides maximum sealing reliability for the most diverse products in increasingly severe operating conditions.

3.2. MULTIPLE APPLICATIONS The sealing systems meet the requirements of all sectors of activity in industries such as: chemicals, automobile, petrochemicals, oil, paper, transformation, food, textiles, pharmaceuticals, etc. They are used in many industrial, scientific or domestic applications where rotating components must be sealed. A very wide range of products require seals: clear or charged products mixtures syrups bitumens paper pulp cements powders liquefied or non-liquefied gases, etc. They can just as easily be used for water, wine, phosphoric acid, hydrocarbons, automobile coolant and helium as for abrasive products. Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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3.3. SEVERE OPERATING CONDITIONS Two technologies have been developed which provide almost total sealing which is both static and dynamic: mechanical seals less mechanical seals (called "gas seals"). Mechanical seals provide the sealing for rotating shafts. The increased operating constraints has led to the development of gas seals operating without face , separated by a very thin film of fluid. The friction between the seal's rings and therefore the wear are prevented.

Figure 10: Gas seals In the first case the sealing is between two faces moving relative to each other (rotation), lubricated by a liquid film. This film is provided either from the fluid carried by the machine, or by an auxiliary fluid. However, dry seals are sometimes used where there is an actual between the faces.

Figure 11: Dry seal Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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The wide variety of fluids and the specific requirements of the s have led the manufacturers to develop components using an extremely wide range of materials. Graphite, carbon, aluminium, stainless steel and ceramics are used, and also tungsten carbide, nickel stainless steel alloys, molybdenum chrome, porous silicon carbide, various types of elastomers as well as radiation-resistant materials, for example. We can see that the applications require a very high level of competence in very varied disciplines.

3.4. SEALS ARE BECOMING MORE AND MORE INGENIOUS Mechanical seal technology is continually improving and thus provides maximum sealing reliability for the most diverse products in increasingly severe operating conditions. The pressures exceed 450 bars, the temperatures are in excess of 400°C, the speeds accelerate to over 10,000 rpm and the diameters can be greater than 500 mm. The mechanical seal rings have to meet very specific criteria, in particular: High hardness High rigidity Good sliding properties High thermal conductivity Low thermal expansion The expected lifetimes can reach several thousands of hours of operation. Therefore we must be very vigilant when installing mechanical seals.

3.5. PRECAUTIONS TO BE TAKEN 3.5.1. During installation Incorrect storage can prevent the seal from functioning correctly. Before using a mechanical seal we must check that non of its parts are missing and that it is in good condition. Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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Carbon, silicon carbide or ceramic parts can break if dropped. Seals can become fragile due to initial invisible cracking which breaks during the first few hours of operation. The rotating surfaces of the friction faces are flat due to the running in. This ground face must not be laid down just any old how on any surface. (Important: the workstation surface roughness can damage the ground face). The assembly instructions must be strictly respected. Before installation on the machine, the machine must be inspected: Shaft surface roughness Runout check where necessary Clearance (axial and radial) During installation, special care must be taken to: Avoid impacts between the surface and the machine The machine must be very clean (shaft part) Do not twist the O-rings Take care when installing the O-rings over splines or grooves (sharp edges) Do not leave finger marks on the mating faces Check that the oil supply ducts are facing the right way (fluid flow direction) Lightly lubricating the seal may make it easier to install; in this case use a lubricant compatible with the application concerned.

3.5.2. When starting the installation Certain measures must be taken before starting an installation whose seal has been changed. By default, all the systems are removed (valves open), the machine will have been spun by hand (to check that the shaft rotates freely) and no rough spots must have been detected.


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Before entry into service and when a new seal has been fitted a leak rate of around a drip is permissible. This leak must disappear after the face running in period. Once the machine is running, check that there are no (major) leaks at the seal, no vibrations or unusual noises, and that the seal does not heat up too quickly. When the machine has been running for some time, check that the slight leak tolerated when the systems were put into service has disappeared.

3.6. INSTALLING A SEAL Before installing a mechanical seal, carefully read the installation instructions. The following instructions must be strictly respected when installing a mechanical seal: A mechanical seal is a fragile precision component. Keep the seal in its original packaging until the moment of installation Check that the seal has not been damaged during storage or transport Never touch the sliding surfaces with your fingers Be careful not to damage the seal during installation. Never lay down the rings on their sliding surface Work in a clean environment Keep your hands and tools clean. Microscopic particles left on the surfaces of seals can cause a leak. Figure 12: Wash your hands If the seal has a lubrication system ensure that the lubrication ducts are unobstructed Clean the shaft and the seal housing, check them for damage (can cause leaks at the O-ring or incorrect ring ). Figure 13: Clean the shaft and seal housing


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Teflon (PTFE) O-rings can be easily damaged during installation. It may be necessary to lightly lubricate the parts (depending on the use of the seal >> food products, etc.). If oil is unsuitable, use clean water.

Figure 14: Lubricate the O-ring and shaft Special tools: it is easier to install a mechanical seal if a tapered guide bush is used during assembly. This covers the sharp edges of the shaft and thus considerably reduces the risk of damaging the seal during assembly.

Figure 15: Special tapered assembly guide bush A mechanical seal does not normally require maintenance. If there are no problems, it should not be removed (don't take it out just to have a look!!!). When removed, it will almost always be necessary to replace the mechanical seal. During normal running, if there a drip of pressurised liquid from the mechanical seal, this indicates that it is damaged and must be replaced. Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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Do not reinstall mechanical seals which have been removed. The seal surfaces will wear creating matched grooves on each of them. If the seal is reinstalled the grooves will no longer be matched.

Figure 16: Worn seal


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4. SEALING RINGS 4.1. GENERAL Sealing rings are seals designed for rotating shafts. They are manufactured in a wide variety of shapes and materials to adapt to the operating conditions. They are commonly called "spi seals" by motor mechanics. The term designates a radial sealing ring for rotating (crankshaft, etc.) or slidings parts (e.g. motorcycle forks). This term comes from the German SPI company which was the first to manufacture this type of seal. These are some of the most commonly used seals, particularly for rotating shafts and where there are low pressure differences. The basic profile of the ring used today (fig.1) consists of the following: a metal reinforcement (A) which gives it rigidity and facilitates its installation and attachment, a seal lip (B), which is the only part subjected to the relative movement and therefore liable to wear, a spring (C), which keeps the lip constantly in with the shaft, and finally, a diaphragm (D), which is the main element of the assembly since the whole of the rotating shaft is subject to small but constant vibrations.

Figure 17: Detail view of a conventional sealing ring Once the pressure between the lip and shaft is obtained due to the spring which allows the lubricant film to form, these vibrations can, from time to time, increase the thickness of this film till it reaches values sufficient to create an oil leak.


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The only way of avoiding this leak is to maintain the film thickness more or less constant, therefore the diaphragm must be sensitive enough to "follow" the shaft's vibrations. For optimum sealing the sealing rings must meet certain criteria. The dynamic sealing and the static sealing (when stopped) are obtained by a radial pressure exerted by the seal lip. Two fundamental factors must be taken into : Seal lip diameter (it must be smaller than the nominal shaft diameter). Spring force (different tensions can be obtained by modifying the spring length). The shape and choice of the material are important. The bearings must be protected from dust and external contamination, and the oils and greases used to lubricate the mechanisms and bearings must be prevented from leaking. A good lubricating oil forms a film which is difficult to eliminate and which adheres to the gear wheels, bearings and shafts. The function of the sealing ring is to retain the oil or grease and prevent the ingress of dust and contamination. A lubricant film is formed under the sealing ring due to the rotation of the shaft. This film forms during the first few moments of the ring's operation due to capillary effect. The thickness of this film depends on the rotation speed, the oil temperature, the oil viscosity, the pressure and the shaft roughness.

Figure 18: Formation of the lubricant film


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4.2. DESCRIPTION OF THE LIP RINGS A lip ring is made up of three different parts: A metal reinforcement (generally an L-shaped ring) A rubber part, which itself consist of three elements Cover Diaphragm Sealing lip A helical spring

Figure 19: Detail view of a sealing ring


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4.2.1. Production materials 4.2.1.1. Nitrile Nitrile rubber has good mechanical properties and a high wear resistance. It is the most commonly used material for producing seals. It is chemically compatible with oils, vegetable and mineral greases, water and most fluids. Nitrile resists temperatures between -30 °C and 100 °C. This material is mostly used when there are no specific requirements on the sealing ring.

4.2.1.2. Viton® Viton® has an excellent resistance to high temperatures, mineral oils, fuels, synthetic hydraulic fluids, oxygen, ozone, etc. It is resistant to most fluids and lubricants which attack nitrile or silicone. Viton® resists temperatures between -15 °C and 200 °C.

4.2.1.3. Silicone Silicone has a very good resistance to high and low temperatures. It is a good insulator, it resists bad weather and is nontoxic. Silicone resists temperatures between -60 °C and 200 °C.

4.2.1.4. PTFE Polytetrafluorethylene or PTFE has exceptional mechanical properties and exceptional chemical resistance. It has a very low friction coefficient which means that it can be used at high speeds. PTFE resists temperatures between – 50 °C and 270 °C. There are different international standards which form the basis of sealing ring design. See the table of sealing ring equivalences (below) for the most common brands.


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ISO 6194

DIN 3760

Description

1

A

Elastomer exterior

R

IE

C

BA

WA

SC

CB

4

AS

Elastomer exterior with dust lip

RST

IEL

BASL

WAS

TC

CC

2

B

Metal exterior

M

EE

M

B1

WB

SB2

BB

5

BS

Metal exterior with dust lip

MST

EEL

MP

B1SL

WBS

TB2

BC

3

C

Double metal outer cage

GV

M2

B2

WC

SA2

AB DB

6

CS

Double metal outer cage with dust lip

GVS T

M2P

B2SL

WCS

TA2

DC

Most common equivalences

Table 1: Lip ring production materials

4.3. SHAFT RUNOUT AND WOBBLE 4.3.1. Runout The centreline of the shaft and the centreline of the housing must perfectly coincide. The sealing ring diaphragm can only compensate for a small misalignment.

Figure 20: Ring/shaft runout


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4.3.2. Shaft wobble The wobble of the shaft with respect to the sealing ring must not exceed a certain value. The maximum deviation A, at the sealing lip, is the difference between the shaft centreline and the housing centreline. Value A is determined by the rotation speed, the elastomer used and the design of the sealing ring. Figure 21: Shaft wobble

4.4. LUBRICATION AND FRICTION Sealing ring must never operate dry. The lubrication must be continuous, not only during running, but right from the moment the ring is fitted. Therefore the ring and shaft must be lubricated before assembly to simplify installation and provide the initial lubrication. For fluids with a low lubricating ability, two rings may be used. The space between the two rings will be filled with lubricant. Figure 22: Dual-ring configuration If there is only space for one single sealing ring, the space between the two lips must be packed with grease. The rings must be fitted so that adding grease does not create an overpressure. Friction results in a power loss which is inevitable since this is linked with the sealing ring operating principle. This power loss is determined by the following elements: Ring materials Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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Shaft surface roughness Formation if a lubricant film Pressure Sealing lip preload Operating temperature The oil used Figure 23: Single-ring configuration

4.5. SEALING-RING CONFIGURATION To ensure that the ring operates correctly, particular attention must be given to the following points: Examine the ring to ensure it is clean and has no irregularities. Apply grease to the ring lip. If it has a scraper ring, pack the space between the two lips with grease. Check that the spring is correctly positioned in its housing. Examine the shaft and eliminate all roughness, machining deposits and generally all impurities on its surface. The edges must be rounded or bevelled. If this is not the case, use an assembly sleeve with rounded edges which has an external diameter slightly greater than the shaft diameter. Figure 24: Assembly sleeve Special care must be taken to ensure the lip is not damaged during installation. Any small cut in the lip during installation will inevitably result in a leak in service.


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The ring must be positioned without stress. It must be installed in its housing using a uniform pressure around the whole circumference. Care must also be taken to insert it perpendicular to the shaft. Assembly tools are available and these must be used where possible to install the rings. Otherwise a packing tool must be manufactured locally.

Figure 25: Installation tools

Figure 26: Assembly tools Do not forget to lubricate the external diameter of the ring to make it easier to insert. Sealing rings are generally available for shaft diameters from 4 mm to 560 mm.

Figure 27: Different ring profiles Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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4.6. TROUBLESHOOTING The sealing ring rotates at the same time as the shaft. The sealing ring's external Ø is less than the internal Ø of the bore. Choose a ring with the correct dimensions. The sealing ring moves axially along the shaft. The ring's external Ø is less than the internal Ø of the bore The overpressure is causing the ring to move axially. Choose a ring with the correct dimensions. The sealing ring is distorted. The internal Ø of the bore is too small. Check the bore dimensions. Choose a ring with the correct dimensions. The ring housing is damaged. Ill-adapted tools used during installation. Use the correct tools Take the necessary precautions during installation. Sealing ring external Ø deteriorated. Ring incorrectly installed. Incorrect bore surface roughness. Incorrect preparation of parts before installation. Check that the parts are clean. Check the bore surface roughness. Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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Check the condition of the bevel. High level of wear on the sealing lip. Insufficient lubrication. Excessive pressure. Ensure that the lubrication is sufficient. Check the runout. Use a pressure-resistant ring. Partial wear on the external Ø of the lip. The sealing ring is not centred with respect to the shaft in the bore. Centre the ring in the bore using a suitable tool. Axial tears on the lip. Excessive temperature, pressure, rotation speed. Insufficient lubrication. Chose a ring of the correct type. Ensure that the lubrication is sufficient. The sealing lip is swollen. Incorrect elastomer. Chose a ring of the correct type. The sealing ring is scratched. Rough shaft surface. Incorrect tools used. Ring incorrectly installed. Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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Check the shaft surface roughness. Use the correct tools. Use the best installation method. Sealing lip bent over. Ring incorrectly installed. Excessive fluid pressure. Lubricate the sealing lip and the shaft before installation. Choose a ring adapted to the overpressure. Tears in the diaphragm. Excessive fluid pressure. Impacts on the flexible part. Choose a ring adapted to the overpressure. The spring has come out of its slot. Ring incorrectly installed. Spring slot not deep enough. Choose a spring adapted to the ring.


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5. PACKING GLAND 5.1. DEFINITION Packing is a nonwoven fibrous by-product from the hemp and flax industries. This by-product has always had a variety of uses: It was used In the construction of wooden boats to pack the seams between the planks to make the vessel waterproof and prevent leaks (this operation is called caulking) Packing was also used to fabricate gun "match cords", also known as "slow matches" (impregnated wicks used for firing early matchlock muskets, cannons, etc.). In a similar manner to shipbuilding, packing was used to seal the points where parts through walls and housings. The name "packing gland" (also known as "gland seal") is still used for a wide range of sealing systems designed to provide a minimum of mechanical to cables, tubes or rods ing through a wall or bulkhead whether sealed or not.

Figure 28: Packing gland


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5.2. ADVANTAGES OF PACKING GLANDS Sealing by gland packing is a very old principle which, however, is still used today due to the continuous development of new high-quality materials for the sealing technology. Gland packing is very widely used due to its multiple advantages over other types of seals. Packing gland housing (also known as "stuffing box") is of simple construction and does not require a high precision. Relatively low price. Easy to install and maintain. Robust sealing material, even in severe operating conditions with abrasive and contaminated fluids. Easily adjustable leak. Long lifetime with very low friction coefficients due to the modern composition of the materials.

5.3. BRAID STRUCTURE 5.3.1. Dual diagonal-interlock braid Twisted braiding. Relatively rough surface. For braid cross-sectional areas of 3-5 mm (with cores) Figure 29: Dual diagonal-interlock braid

5.3.2. Triple diagonal-interlock braid Uniform braiding with high volumetric stability. For braid cross-sectional areas of 6-7 mm (with 12 cores) and 8 mm (with 15 cores). Figure 30: Triple diagonal-interlock braid Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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5.3.3. Quadruple diagonal-interlock braid Uniform braiding with higher than average volumetric stability. Wear resistant, smooth, high elasticity surface. For braid cross-sectional areas of 10-16 mm (with 24 cores) and from 18 mm (with 36 cores).

Figure 31: Quadruple diagonal-interlock braid

5.3.4. Braid-on-braid packing Uniform core, wound or braided, covered with one or more braid-on-braid layer . Very fine and uniform surfaces with excellent adaptation ability. For cross-sectional areas of 3-16 mm (with 16 cores), and 16 mm and above (with 36 cores).

5.4. CHOICE OF BRAID If a packing's elasticity is highly affected by an imbalance, a misalignment or a high rpm, in this case choose a braid with larger cross-sectional area. For valves and fittings which are not affected by the problems mentioned above, a smaller cross-sectional area can be used, i.e. in the lower range. The choice of the packing's crosssectional area (h) and the number of turns used (H) will depend on the size of the packing housing. Figure 32: Housing size


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5.4.1. Packing ring specifications If a packing gland overheats, use a distance ring to reduce the number of packing rings. The highest wear on the sealing rings and shaft is normally to be found just after the packing gland follower. The follower pressure can be evenly distributed by preloading each ring. The preload values are values based on experience.

Figure 33: Number of turns (and compression)

5.4.2. Different assembly configurations 5.4.2.1. Standard configuration The rings are stacked one after the other in the housing and then compressed by the follower.

Figure 34: Standard configuration Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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5.4.2.2. Configuration with anti-extrusion washers The PTFE washers between the packing rings prevent the packing or lubricant being forced out.

Figure 35: Anti-extrusion washers

5.4.2.3. Configuration with top and bottom compression washers The top and bottom compression washers prevent the flexible sealing rings from being forced out.

Figure 36: Top and bottom compression washers

5.4.2.4. Configuration with flushing Protection of the packing arrangements by flushing. Figure 37: Flushing

5.4.2.5. Cooling, control of leak rate, flushing, lubrication Use of lantern ring for cooling, flushing and lubrication. The compressibility of the packing must be taken into consideration.

Figure 38: Cooling lantern ring


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5.5. TROUBLESHOOTING Problems with a seal's operation are not always easy to understand. However, the reason will often be obvious after a close examination of the rings. The problems described below are especially concern pumps, etc. For valves, the problems will be more easily corrected (tightening the follower or changing the packing).

5.5.1. One or more rings missing from the housing. The clearance between the shaft and the packing gland housing is too great, thus increasing the likelihood of the packing being forced out into the fluid circulation system. Install top and bottom compression washers. Figure 39: Excessive clearance between shaft and housing

5.5.2. Pieces of packing protruding between the shaft and flange. The clearance between the shaft and the follower is too great. Fit anti-extrusion washers to correct the problem. Figure 40: Clearance between follower and shaft

5.5.3. Smaller radial thickness than during assembly. The incorrect mechanical operation, particularly of a bearing, or a probable runout results in a widening of the packing due to the shaft imbalance. Check for probable shaft runout. Check the bearings. Figure 41: Shaft runout


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5.5.4. Unequal ring radial thickness. An axial misalignment between the shaft and the packing gland housing due to an irregular oscillation causes high packing wear. Correct the axial misalignment problem Figure 42: Shaft axial misalignment

5.5.5. Shrinkage of the axial faces. One or more rings have been cut too short. Therefore the following ring is pressed into the space formed. Cut the rings to the correct length. Figure 43: Ring shrinkage

5.5.6. The bottom rings are OK but the top rings are damaged. Due to the incorrect assembly of the bottom rings, the follower pressure necessary for the sealing is not evenly distributed over all the rings. Fit the bottom rings correctly during assembly. Figure 44: Bad distribution of forces


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5.6. PACKING GLAND REPAIR 5.6.1. Preparing the packing gland Before installing the new packing rings the old packing must first be removed from the packing gland. Remove the worn packing and clean the packing gland housing correctly (using compressed air). An examination of the removed rings may allow you to determine the cause of a possible problems (if the packing rings are not too damaged during removal). To easily remove the rings, use an extractor designed for this purpose or a sharp scriber.

Figure 45: Packing extraction method

Figure 46: Extractors and scriber Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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Recommendation: before fitting the new packing rings, check that they have been cut correctly and that they are the correct size. To obtain rings of the correct length with matching ends you will find a ring cutter or "guillotine" very useful.

Figure 47: Packing ring cutter

If there is no packing ring cutter available on the site, there is a manual cutting method.

Figure 48: Manual cut

Figure 49: Straight cut and bevelled cut From experience, a bevelled cut should be used in preference to a straight cut. This will make the ring easier to install.


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5.6.2. Installing the rings Most existing packings are braided in such a way that the pattern forms an arrow. During assembly, ensure that the direction of the arrow on the braid points anticlockwise to obtain a hydrodynamic reflux effect. Figure 50: Direction of assembly

Once cut (to the correct length), the rings must be fitted on the shaft by a lateral twisting movement.

Figure 51: Fitting the rings

Figure 52: Method of twisting the rings Each packing ring must be separately pressed into the bottom of the packing gland housing using the follower or, where necessary, a metal sleeve. Figure 53: Fitting the packing rings (1) If it is difficult to insert the packing rings into the housing, roll a metal tube on Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

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them using a certain amount of force to reduce their cross-sectional area by a few tenths of a millimetre so that they can be inserted in the housing more easily.

Figure 54: Rolling the packing rings to reduce their diameter The packing rings must be assembled so that the cuts are offset from each other. This offset will be 90° or 180° depending on the number of rings.

Figure 55: Offsetting the cuts

Figure 56: Bevelled cuts


Page 38 / 60


5.7. PACKING GLAND INSPECTION 5.7.1. On a valve Tighten the follower until the packing exerts a slight resistance to the spindle movement.

Figure 57: Valve packing gland

5.7.2. On a pump When all the rings have been inserted in the housing the packing gland follower must be tightened slightly using a spanner, then slackened again until the shaft moves freely. The follower is then fully tightened manually. Start the pump (all the circuits correctly configured). It is absolutely necessary that the seal leaks during this phase. If this is not the case, the pump must be immediately stopped to prevent the packing overheating. When the packing gland has cooled down, restart the pump, without slacking the packing gland follower, until a slight leak appears. When the leak appears, allow the pump to run for 10 minutes in this condition. The leak will be reduced by slowly tightening the follower until the pump manufacturer's recommended leak rate is obtained.

Figure 58: Pump packing gland


Page 39 / 60


5.8. THE DIFFERENT TYPES OF BRAIDED PACKINGS 5.8.1. Vegetable fibre braided packing impregnated with PTFE

Figure 59: Vegetable fibre braided packing

5.8.1.1. Operating limits

P (bar)

25

T (°C) V (m/s)

130 + 120

10

2

Table 2: Vegetable fibre braided packing operating limits

5.8.1.2. Composition Vegetable fibres impregnated fibre by fibre with pure PTFE dispersion and treated with a special chemically neutral lubricant. Highly elastic, flexible and with a very low friction coefficient. Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

Page 40 / 60


Braided packing resistant to most fluids (fuels, oils, water and seawater).

5.8.1.3. Fields of use In the petrochemical industry, in marine technology, nuclear power stations, refineries, paper industry and agricultural technology.

5.8.1.4. Dimensions and weights Crosssectional area mm

Crosssectional area inches

4

1

5

3

6

Weight g/m

/8

25

/16

40

¼

60

8

5

/16

100

10

3

/8

170

12

½

245

14

9

/16

340

16

5

/8

460

18

11

/16

585

20

¾

720

22

7

/8

870

24

61

/64

1040

1

1130

25

Table 3: Dimensions and weights of vegetable fibre braided packing


Page 41 / 60


5.8.2. Synthetic fibre braided packing impregnated with PTFE

Figure 60: Synthetic fibre braided packing


P (bar)

20

T (°C) V (m/s)

60

80

- 40 to + 260 8

2

Table 4: Synthetic fibre braided packing operating limits

5.8.2.2. Composition Universal interbraided packing with a combination of synthetic fibres impregnated with PTFE. Its advantages over standard braided packing are: Higher durability Constant elasticity Protects the shafts Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

Page 42 / 60


5.8.2.3. Fields of use This braided packing is used both for axial and radial movements, and for valves and fittings. It covers most of the uses for axial and radial movements in the paper, mining and chemical industries and also in the petrochemical industry.

5.8.2.4. Dimensions and weights Crosssectional area mm 5 6

Crosssectional area inches 3

Weight g/m

/16

31

¼

67

8

5

10

3

/8

126

12

½

225

/16

86

14

9

/16

276

16

5

/8

347

18

11

/16

412

20

¾

481

22

7

/8

532

1

680

25

Table 5: Dimensions and weights of synthetic fibre braided packing


Page 43 / 60


5.8.3. Carbon fibre braided packing

Figure 61: Carbon fibre braided packing


P (bar)

20

T (°C) V (m/s)

60

100

+ 350 15

1.5

2

Table 6: Carbon fibre braided packing operating limits

5.8.3.2. Composition Carbon fibres treated fibre by fibre with pure graphite powder. This braided packing is resistant to most fluids such as chemicals, hydrochloric acid and heat transfer oils (except sulphurised oil, fuming nitric acid and fluorine).


Page 44 / 60


5.8.3.3. Fields of use Pumps, valves, agitators.



4

1

5

3

6

Weight g/m

/8

15

/16

25

¼

35

8

5

10

3

/8

110

12

½

160

/16

60

14

9

/16

215

16

5

/8

280

18

11

/16

355

20

¾

440

22

7

/8

540

24

61

/64

640

1

690

25

Table 7: Dimensions and weights of carbon fibre braided packing


Page 45 / 60


5.8.4. Pure PTFE braided packing

Figure 62: PTFE braided packing


P (bar)

15

T (°C) V (m/s)

200 - 200 to + 280

7

0.5

Table 8: Pure PTFE braided packing operating limits

5.8.4.2. Composition Diagonally braided pure PTFE fibres treated fibre by fibre with PTFE dispersion, high density for the cross-sectional area and compact structure, very reliable friction coefficient. Good resistance to water, steam, alkaline liquors and highly concentrated acids, solvents, oil, fatty acids, degreasing agents, corrosive products, hydrogen and heat transfer oil.


Page 46 / 60


5.8.4.3. Fields of use Valves, centrifugal pumps, piston pumps, mixers, agitators, in thermal power stations, and in the food and chemical industries.



4

1

5

3

6

Weight g/m

/8

25

/16

40

¼

60

8

5

/16

110

10

3

/8

170

12

½

245

14

9

/16

315

16

5

/8

410

18

11

/16

520

20

¾

640

22

7

/8

775

24

61

/64

920

1

1000

25

Table 9: Dimensions and weights of pure PTFE braided packing


Page 47 / 60


5.8.5. Soft PTFE packing

Figure 63: Soft PTFE packing

5.8.5.1. Composition Soft PTFE with graphite (black packing) or without graphite (pure and white) with lubricant material, very high density for the cross-sectional area and excellent sliding properties. Resistant to water, process water, acids, solvents, oils, degreasing agents, adhesives and lacquers.

5.8.5.2. Fields of use Universal usage, excellent deformation ability, efficiently protects shafts, pumps, mixers, kneading machines, valves (top and bottom compression washers are required).


Page 48 / 60




4

1

5

3

6

Weight g/m

/8

25

/16

40

¼

70

8

5

/16

100

10

3

/8

150

12

½

230

14

9

/16

300

16

5

/8

400

18

11

/16

500

20

¾

600

22

7

/8

750

24

61

/64

870

1

940

25

Table 10: Dimensions and weights of soft PTFE packing


Page 49 / 60


5.8.6. PTFE packing with graphite

Figure 64: PTFE packing with graphite


P (bar)

25

T (°C) V (m/s)

250

250

- 200 to + 280 20

2

2

Table 11:Operating limits of PTFE packing with graphite

5.8.6.2. Composition Made of PTFE with graphite and containing a lubricant material, very highly improved thermal conductivity, volumetric stability, low friction coefficient and no fragilisation or ageing. Resistant to hot and cold water, oils, greases, gas, steam, acids, concentrated alkaline liquors, solvents, hydrocarbons and heat transfer oils (unsuitable for highly oxidising fluids such as oleum, fuming nitric acid, gaseous fluorine, etc.). Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

Page 50 / 60


Also available with graphite PTFE fibres (high graphite content), diagonally braided, without lubricant for use in the presence of oxygen.

5.8.6.3. Fields of use Universal usage.



4

1

5

3

6

Weight g/m

/8

25

/16

40

¼

60

8

5

/16

110

10

3

/8

160

12

½

230

14

9

/16

310

16

5

/8

400

18

11

/16

490

20

¾

600

22

7

/8

730

24

61

/64

865

1

940

25

Table 12: Dimensions and weights of PTFE packing with graphite


Page 51 / 60


5.8.7. PTFE packing with Kevlar-reinforces corners

Figure 65: Corners reinforced with Kevlar fibres


P (bar)

30

T (°C) V (m/s)

30

250

- 100 to + 280 2,0

2

2

Table 13: Operating limits of PTFE packing reinforced with Kevlar

5.8.7.2. Composition Pure PTFE packing, corners reinforced with aramide (Kevlar) fibres, impregnated fibre by fibre with a PTFE dispersion and with an added lubricant. Resistant to practically all fluids. For universal usage (except for liquid metal alkalis or use in the presence of oxygen).


Page 52 / 60


5.8.7.3. Field of use Specially for piston pumps in the high pressure domain.



Weight g/m

/16

40

¼

60

8

5

/16

105

10

3

/8

160

12

½

230

14

9

/16

315

16

5

/8

410

18

11

/16

520

20

¾

640

22

7

/8

780

24

61

/64

920

1

1000

25

Table 14: Dimensions and weights of PTFE packings reinforced with Kevlar


Page 53 / 60


5.8.8. Kevlar packing

Figure 66: Kevlar packing


P (bar)

25

T (°C)

100

400

- 100 to + 280

V (m/s)

2

2

2

Table 15: Kevlar packing operating limits

5.8.8.2. Composition Diagonally braided aramide synthetic fibres (Kevlar) impregnated with PTFE. Resistant to hot and cold water, wastewater, oils, grease, gas, acids, process water and abrasive fluids.


Page 54 / 60


5.8.8.3. Fields of use Pumps and valve in the chemical and petrochemical fields, water treatment plants and the paper industry.



4

1

5

3

6

Weight g/m

/8

25

/16

40

¼

55

8

5

10

3

/8

145

12

½

210

/16

95

14

9

/16

280

16

5

/8

360

18

11

/16

455

20

¾

560

22

7

/8

680

24

61

/64

810

1

875

25

Table 16: Dimensions and weights of Kevlar packing


Page 55 / 60


5.8.9. Gland packing

Figure 67: Gland packings


P (bar)

290 + 480

T (°C) + 650 (*) V (m/s)

1 Table 17: Gland packing operating limits

(*): in steam

5.8.9.2. Composition Braided packing with expanded pure graphite fibres, reinforced with a thin steel core.


Page 56 / 60


5.8.9.3. Fields of operation This packing combines the advantages of standard braided packing with the exceptional sealing properties of pressed expanded pure graphite packing rings.



Weight g/m

/16

29

¼

65

8

5

10

3

/8

115

12

½

185

/16

83

14

9

/16

213

16

5

/8

370

18

11

/16

400

20

¾

417

22

7

/8

556

1

769

25

Table 18: Dimensions and weights of gland packing


Page 57 / 60


6. FIGURES Figure 1: Seal on a moving shaft .........................................................................................5 Figure 2: Conventional mechanical seal ..............................................................................6 Figure 3: Packing gland with braided packing......................................................................6 Figure 4: Packing gland with lip seal....................................................................................6 Figure 5: Seals (static and rotating components).................................................................8 Figure 6: Rings and O-rings.................................................................................................8 Figure 7: Detail view of a mechanical seal...........................................................................9 Figure 8: Seal in a hostile environment................................................................................9 Figure 9: Mechanical seals ................................................................................................10 Figure 10: Gas seals..........................................................................................................11 Figure 11: Dry seal ............................................................................................................11 Figure 12: Wash your hands..............................................................................................14 Figure 13: Clean the shaft and seal housing......................................................................14 Figure 14: Lubricate the O-ring and shaft ..........................................................................15 Figure 15: Special tapered assembly guide bush ..............................................................15 Figure 16: Worn seal .........................................................................................................16 Figure 17: Detail view of a conventional sealing ring .........................................................17 Figure 18: Formation of the lubricant film...........................................................................18 Figure 19: Detail view of a sealing ring ..............................................................................19 Figure 20: Ring/shaft runout ..............................................................................................21 Figure 21: Shaft wobble .....................................................................................................22 Figure 22: Dual-ring configuration......................................................................................22 Figure 23: Single-ring configuration ...................................................................................23 Figure 24: Assembly sleeve...............................................................................................23 Figure 25: Installation tools ................................................................................................24 Figure 26: Assembly tools..................................................................................................24 Figure 27: Different ring profiles.........................................................................................24 Figure 28: Packing gland ...................................................................................................28 Figure 29: Dual diagonal-interlock braid ............................................................................29 Figure 30: Triple diagonal-interlock braid...........................................................................29 Figure 31: Quadruple diagonal-interlock braid ...................................................................30 Figure 32: Housing size .....................................................................................................30 Figure 33: Number of turns (and compression) .................................................................31 Figure 34: Standard configuration......................................................................................31 Figure 35: Anti-extrusion washers .....................................................................................32 Figure 36: Top and bottom compression washers .............................................................32 Figure 37: Flushing ............................................................................................................32 Figure 38: Cooling lantern ring...........................................................................................32 Figure 39: Excessive clearance between shaft and housing .............................................33 Figure 40: Clearance between follower and shaft..............................................................33 Figure 41: Shaft runout ......................................................................................................33 Figure 42: Shaft axial misalignment ...................................................................................34 Figure 43: Ring shrinkage..................................................................................................34 Figure 44: Bad distribution of forces ..................................................................................34 Figure 45: Packing extraction method ...............................................................................35 Training course: EXP-MN-SM090-EN Last revised: 17/03/2008

Page 58 / 60


Figure 46: Extractors and scriber.......................................................................................35 Figure 47: Packing ring cutter ............................................................................................36 Figure 48: Manual cut ........................................................................................................36 Figure 49: Straight cut and bevelled cut ............................................................................36 Figure 50: Direction of assembly .......................................................................................37 Figure 51: Fitting the rings .................................................................................................37 Figure 52: Method of twisting the rings ..............................................................................37 Figure 53: Fitting the packing rings (1) ..............................................................................37 Figure 54: Rolling the packing rings to reduce their diameter ............................................38 Figure 55: Offsetting the cuts.............................................................................................38 Figure 56: Bevelled cuts ....................................................................................................38 Figure 57: Valve packing gland..........................................................................................39 Figure 58: Pump packing gland .........................................................................................39 Figure 59: Vegetable fibre braided packing .......................................................................40 Figure 60: Synthetic fibre braided packing.........................................................................42 Figure 61: Carbon fibre braided packing............................................................................44 Figure 62: PTFE braided packing ......................................................................................46 Figure 63: Soft PTFE packing............................................................................................48 Figure 64: PTFE packing with graphite ..............................................................................50 Figure 65: Corners reinforced with Kevlar fibres................................................................52 Figure 66: Kevlar packing ..................................................................................................54 Figure 67: Gland packings .................................................................................................56


Page 59 / 60


7. TABLES Table 1: Lip ring production materials ................................................................................21 Table 2: Vegetable fibre braided packing operating limits .................................................40 Table 3: Dimensions and weights of vegetable fibre braided packing ...............................41 Table 4: Synthetic fibre braided packing operating limits ...................................................42 Table 5: Dimensions and weights of synthetic fibre braided packing.................................43 Table 6: Carbon fibre braided packing operating limits......................................................44 Table 7: Dimensions and weights of carbon fibre braided packing ....................................45 Table 8: Pure PTFE braided packing operating limits........................................................46 Table 9: Dimensions and weights of pure PTFE braided packing......................................47 Table 10: Dimensions and weights of soft PTFE packing ..................................................49 Table 11:Operating limits of PTFE packing with graphite ..................................................50 Table 12: Dimensions and weights of PTFE packing with graphite ...................................51 Table 13: Operating limits of PTFE packing reinforced with Kevlar ...................................52 Table 14: Dimensions and weights of PTFE packings reinforced with Kevlar....................53 Table 15: Kevlar packing operating limits ..........................................................................54 Table 16: Dimensions and weights of Kevlar packing........................................................55 Table 17: Gland packing operating limits ...........................................................................56 Table 18: Dimensions and weights of gland packing .........................................................57


Page 60 / 60

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