gasket manual Final 20100512

Date: 11-05-2010 Rev-0 Ref: MMT-3.2.9

KARACHI NUCLEAR POWER COMPLEX Mechanical Maintenance Training Centre

GASKET TRAINING MANUAL

Prepared By:

_______________________

RIZWAN AHMED Senior Engineer

Checked By: Approved By:

_________________ ____________ Syed Sarwar Ali, P.E Shahab Mukhtar H (MMTC) SM (MMD)

KARACHI NUCLEAR POWER PLANT Mechanical Maintenance Training Centre

Ref: MMT-3.2.7 Subject: Gasket Training Manual Date: 31-03-2010 Rev-0 Sheet 1

INDEX

S.No. Description Page No. 1.0 Section I - Introduction 03 1.1 Definitions 03 1.2 Why Gasket is used? 03 1.3 How does it work? 04 2.0 Section II – GASKET SELECTION 05 Types of Gasket 05 2.1 Non-Metallic Gasket 06 2.1.1 Rubber Gasket 06 2.1.2 Graphite Sheet Gasket 09 2.1.3 Asbestos, Non-asbestos Compress Joint Sheet Gasket 09 2.1.4 PTFE Gasket 10 2.1.5 Non Metallic Gasket Selection 11 2.2 Semi-Metallic Gasket Materials 12 2.2.1 Spiral Wound Gasket 12 2.2.2 Types of Spiral Wound Gasket 13 2.2.3 Selection of Gasket According to Flange type 15 2.2.4 Available Spiral Wound Gasket Materials 16 2.2.5 Temperature Limits for common Metal and Filler Materials 16 2.2.6 Space and Clearance for Gasket 17 2.2.7 Compression Thickness of Gasket 18 2.2.8 Maximum Bore of ASME B16.5 Flanges 18 2.2.9 Gasket Characteristics 19 2.2.10 Gasket Identification Guide 20 2.3 Jacketed Metal Gaskets 21 2.4 The Standard Shapes for Heat Exchanger Gaskets 23 2.5 Metallic Gasket 24



2.5.1 Ring Joint Gasket 24 2.5.2 Metallic Gasket Materials for Ring Joint 25 2.5.3 Corrugated Gasket 27 2.5.4 Serrated Gasket 28 2.5.5 Flat Metal Gasket 30 2.5.6 Metallic O-Ring 30 2.6 Example: Gasket selection 31 2.6.1 How to Order Gasket 32 2.6.2 Application Data Form 32 2.7 Gasket Material and Contact Facing 33 3.0 Section III –Gasket Installation 35 3.1 Before installation 35 3.2 Gasket Installation Procedure 35 3.3 Bolting Sequence 37 3.4 Bolt Torque 38 3.5 Bolting Data Recommended Minimum size 39 4.0 Section IV –Trouble Shooting 40 Annexure-A: Codes and Standards For Gasket A1 - Metal Jacketed Gasket for ASME B16.50 Flanges 41 A2 - Metal Jacketed Gasket for ASME B16.47 Flanges 42 A3 - Non-Metallic Flat Gasket for ASME B16.50 Flanges 43 A4 - Non-Metallic Flat Gasket for ASME B16.47 Flanges 44 Annexure -B: Comparison Table by Manufacturer B1 - Semi-Metallic Gaskets (Spiral Wound) 45 B2 - Metal Jacketed Gaskets 46 B3 - Metallic & Non-Metallic Gaskets 47 Annexure -C: Chemical Resistance of Materials C1 - Chemical Resistance of Metals 48 C2 - Chemical Resistance of Non-Metals 51



1. Introduction 1.1 Definitions

A gasket is a mechanical seal that fills the space between two mating surfaces may also be called a seal, generally to prevent leakage from or into the joined objects while under compression.

Gaskets save money by allowing "less-than-perfect" mating surfaces on machine parts which can use a gasket to fill irregularities. Gaskets are commonly produced by cutting from sheet materials, such as gasket paper, rubber, silicone, metal, cork, felt, neoprene, nitrile rubber, fiberglass, or a plastic polymer such as PTFE (polychlorotetrafluoroethylene).

The gasket material selected must be capable of sealing mating surfaces, resistant to the medium being sealed, and able to withstand the application temperatures and pressures.

1.2 Why Gasket is used?

Gaskets are used to create a static seal between two stationary members of a mechanical assembly and to maintain that seal under operating conditions which may vary dependent upon changes in pressures and temperatures. If it were possible to have perfectly mated flanges.

If it were possible to maintain an intimate contact of these perfectly mated flanges throughout the extremes of operating conditions, a gasket would not be required. This is virtually an impossibility because of:

• the size of the vessel and/or the flanges. • the difficulty in maintaining such extremely smooth flange finishes during

handling and assembly. • corrosion and erosion of the flange surfaces during operations.

As a consequence, relatively inexpensive gaskets are used to provide the sealing element in these mechanical assemblies. In most cases, the gasket provides a seal by external forces flowing the gasket material into the imperfections between the mating surfaces.



1.3 How Does It Work?

A seal is effected by the action of force upon the gasket surface. This force which compresses the gasket, causes it to flow into the flange macro and micro imperfections. The combination of contact stress, generated by the applied force between the gasket and the flange, and the densification of the gasket material, prevents the escape of the confined fluid from the assembly.

Flange Imperfections

On seating, the gasket must be capable of overcoming the macro and micro imperfections. Macro defects are imperfections such as flange distortions, non-parallelism, scoring, troughs, while superficial imperfections such as minor scratches and minor scores are considered micro imperfections.

Forces on the Gasket

In order to ensure the maintenance of the seal throughout the life expectancy of the assembly, sufficient stress must remain on the gasket surface to prevent leakage. The residual bolt load on the gasket should at all times be greater than the hydrostatic end force acting against it.

The hydrostatic end force is the force produced by the internal pressure which acts to separate the flanges.



2. GASKET SELECTION

Gaskets can be clearly defined into three main categories, non-metallic, semi-metallic and metallic types. The mechanical characteristics and performance of a gasket will vary extensively, depending upon the type of gasket selected and the materials, from which it is manufactured. Mechanical properties are an important factor when considering gasket design, but the primary selection of a gasket type is influenced by the following factors;

• Temperature of the media to be contained • Pressure of the media to be contained • Compatibility with Fluid • Criticality of the application

TYPES OF GASKET

NON- METALLIC Usually composite sheet materials for low pressure class applications. They are suitable for a wide range of general and corrosive chemical services and are supplied in both non-asbestos and asbestos materials.

Types: Elastomers, Compressed Asbestos Fiber (CAF) Sheets, Non asbestos Fiber Sheets, PTFE gaskets, Insulating Gaskets, Graphite Sheet Products.

SEMI-METALLIC A composite gasket consists of both non-metallic and metallic materials. The metal generally provides the strength and resilience of the gasket. These gaskets are suitable for both low and high temperature/pressure applications. A wide range of materials are available.

Type : Metal Jacketed Gaskets, Spiral Wound Gaskets.

METALLIC

It can be fabricated from one metal or a combination of metallic materials, in a variety of shapes and sizes depending on high temperature/pressure applications. High loads are required to seat metallic gaskets, relying on the deformation of the material into the flange imperfections.

Type : Ring Type Joints, Lens Rings, Delta Rings, Bridgeman Rings, Serrated Gaskets, Corrugated Gaskets.



2.1 NON-METALLIC GASKET MATERIALS

2.1.1 RUBBER GASKETS

NATURAL RUBBER (NR)

Natural rubber has good resistance to mild acids and alkalies, salts and chlorine solutions. It has poor resistance to oils and solvents and is not recommended for use with ozone. Itstemperature range is very limited and is suitable only for use from -70°F to 200°F.

STYRENE-BUTADIENE RUBBER (SBR)

SBR is a synthetic rubber that has excellent abrasion resistance and has good resistance to weak organic acids, alcohols, moderate chemicals and ketones. It is not good in ozone, strong acids, fats, oils, greases and most hydrocarbons. Its temperature limitations are approximately -65°F to 250°F.

CHLOROPRENE RUBBER (CR) Neoprene®

Chloroprene is a synthetic rubber that is suitable for use against moderate acids, alkalies and salt solutions. It has good resistance to commercial oils and fuels. It is very poor against strong oxidizing acids, aromatic and chlorinated hydrocarbons. Its temperature range would be from approximately -60°F to 250°F.

ACRYLONITRILE-BUTADIENE RUBBER (NBR)

Buna-N is a synthetic rubber that has good resistance to oils and solvents, aromatic and aliphatic hydrocarbons, petroleum oils and gasolines over a wide range of temperature. It also has good resistance to caustics and salts but only fair acid resistance. It is poor in strong oxidizing agents, chlorinated hydrocarbons, ketones and esters. It is suitable over a temperature range of approximately -60°F to 250°F.

FLUOROCARBON RUBBER (FKM) Viton®

Fluorocarbon elastomer has good resistance to oils, fuel, chlorinated solvents, aliphatic and aromatic hydro-carbons and strong acids. It is not suitable for use against amines, esters, ketones or steam. Its normal temperature range would be between -15°F and 450°F.



CHLOROSULFONATED POLYETHELENE RUBBER (CSM) Hypalon®

This material has good acid, alkali and salt resistance. It resists weathering, sunlight, ozone, oils and commercial fuels such as diesel and kerosene. It is not good in aromatics or chlorinated hydrocarbons and has poor resistance against chromic acid and nitric acid. Its normal temperature range would be between -50°F and 275°F.

SILICONE RUBBER (VMQ)

Silicone rubbers have good resistance to hot air. They are unaffected by sunlight and ozone. They are not, however, suitable for use against steam, aliphatic and aromatic hydrocarbons. The temperature range would be between -65°F to 500°F.

ETHYLENE PROPYLENE DIENE RUBBER (EPDM)

This synthetic material has good resistance to strong acids, alkalies, salts and chlorine solutions. It is not suitable for use in oils, solvents or aromatic hydrocarbons. Its temperature range would be between - 70°F and 350°F.



2.1.2 GRAPHITE SHEET GASKET

Flexible graphite is a distinctive sheet material with the high temperature and chemical resistance of graphite and the additional characteristics of flexibility, compatibility, conformability, and resilience. These characteristics differentiate flexible graphite make it a superior high performance packing and gasketing material. Because of its unique properties, flexible graphite gaskets and packing are particularly well suited for high and low temperature and corrosive fluid sealing applications.

SPECIAL FEATURES 1. Unsurpassed leak tight sealability over extended periods of time and service temperature 2. Non-asbestos and non-fibrous 3. High temperature creep and blow-out resistant. 4. Exceeds the most stringent sealability regulations for VOC or hazardous emissions. 5. Chemically compatible with a wide range of fluids and gases. 6. Adequate for most refinery, petrochemical and industrial service requirement.

2.1.3 ASBESTOS, NON-ASBESTOS COMPRESSED JOINT SHEET GASKET

Gaskets for specific applications may contain asbestos. It is usually desirable that the gasket be made from a material that is to some degree yielding such that to withstand high compressive loads and is able to deform and tightly fills the space it is designed for, including any slight irregularities.

One of the more desirable properties of an effective gasket in industrial applications for compressed fiber gasket material is the ability. Most industrial gasket applications involve bolts exerting compression well into the 14 MPa (2000 psi) range or higher. Generally speaking, there are several truisms that allow for best gasket performance. One of the more tried and tested is: "The more compressive load exerted on the gasket, the longer it will last". There are several ways to measure a gasket material's ability to withstand compressive loading. The "hot compression test" is probably the most accepted of these. Most manufacturers of gasket materials will provide or publish these results.

The use of Asbestos have restricted because of health problems. In order to replace the Asbestos sheet, many makers in the world have manufacturing the non-asbestos joint sheet to replace the asbestos sheets. The non-asbestos sheet gasket provides superior heat resistance and excellent sealing in low pressure services. So, It is widely used in industry and chemical lines.



2.1.4 PTFE GASKET

Where extreme resistance is required to seal against toxic and highly corrosive media, PTFE is used almost totally chemically insert. It is only attacked by molted alkali metals and certain fluorine compounds at elevated temperatures. However, the use of virgin PTFE sheet as a sealing material is limited, since the material suffers extensively from creep and cold flow when subjected to compressive loadings, even at ambient temperature. This can result in excessive stress on the gasket surface and subsequent leakage. In order to overcome sealing problems associated with virgin PTFE, a range of PTFE composites are available with enhanced creep and cold flow resistance.

The PTFE resin is filled with approximately 15 ~ 25% glass fibre or carbon. The addition of glass or carbon fibre improves the creep resistance of the material and reduces the cold flow characteristics, making it more suitable for use as a sheet gasket material. The glass or carbon fibre addition gives an significant effect on the chemical resistance of the material

TYPES AND SHAPE



2.1.5 NON METALLIC GASKET SELECTION



2.2 SEMI-METALLIC GASKET 2.2.1 Spiral Wound Gasket (Semi-metallic)

Spiral wound gaskets are to be constructed as alternate plies of preformed metal windings (hoof) and plain fillers that are spirally wound when compressed between two flanges. A "v" and "w" shaped crown centered in the metal strip acts is a spring, giving gaskets greater resilience under varying conditions. Filler and strip (hoof) materials can be changed to accommodate different chemical compatibility requirements. If the load available to compress a gasket is limited, gasket construction and dimensions can be altered to provide an effective seal.

A spiral wound gasket may include a centering ring, an inner ring or both. The outer centering ring enters the gasket within the flange and acts as a compression limiter, while the inner ring provides additional radial strength. The inner ring also reduces flange erosion and protects the sealing element.

Resilience and strength make spiral wound gaskets an ideal choice under a variety of conditions and applications. Widely used in refineries and chemical processing plants, spiral wound gaskets are also effective for power generation, aerospace, and a variety of valve and special applications.



2.2.2 TYPE OF SPIRAL WOUND GASKET

A) BASIC TYPE

Basic construction type, inner and outer diameters are reinforced with several piles of metal without filler to give greater stability and better compression characteristics.

- Suitable for tongue and groove, male and female or grooved to flat face flange assemblies.

B) INNER RING TYPE

Solid inner metal ring acts as a compression stopper. To prevent accumulation of solids, reduce turbulent flow of process fluids and minimize erosion, damages of gasket between flange bore and the inside diameter, the annular space is filled

up by solid inner metal ring.

- Suitable for male and female pipe flanges.

C) CENTER RING TYPE

Solid centering ring accurately locates the gasket on the flange face to give the additional radial strength to prevent the gasket blowout and acts as a compression limiter. In case of installing the centering ring, it is very easy to



install the gasket to flange face because the end of centering ring will touch at bolts

- Suitable for use with flat face and raised face flanges.

For class 900 and above an internal ring is recommended.

D) INNER RING & CENTER RING TYPE

A inner ring and centering ring type gasket will give an additional compression limiting stopper for gasket inner and outer side. It will prevent the corrosions on flange face at annular space.

- Suitable for use with flat face and raised face flanges and specified for high pressure / temperature service

- Class 900 and above or where corrosive or toxic media are present.

E) LSS (Low Seating Stress) TYPE

The type LSS spiral wound gasket type use to provide an alternative to sheet gaskets in Class 150 and Class 300 service. In case of required low load for seating, Type LSS gaskets can give the solutions for inherent strength, resiliency



and blowout resistance of spiral wound gaskets. They are manufactured with high purity flexible graphite filler or PTFE filler for optimum seating.

- Suitable for the full range of standard class 150 and class 300 flanges, as well as other non-standard low pressure flanges.

2.2.3



2.2.4 AVAILABLE SPIRAL WOUND GASKET MATERIALS

2.2.5 TEMPERATURE LIMITS FOR COMMON METAL & FILLER MATERIALS



2.2.6 Space and clearance for gasket

The width of spiral wound gasket, when it is compressed, tends to expand and a space for the expansion is to be taken into account in design of flanges or joints.

(1) Flat or raised face is widely employed for pipe flanges and machinery joints as a gasket seating face. Spiral wound gasket with centering ring or with centering/inner rings is normally used on such flanges or joints. The following space is ideal for the gasket and it is desired to be taken into account when design new machinery and equipments.

(2) Tongue-and-groove or male-and-female flange is sometimes employed in pressure vessels and valve bonnets. Basic type spiral wound gasket (without ring) is normally used for the former case and spiral wound gasket with inner ring for the latter case. It is desired to have the following clearance for the mentioned gaskets.



The Value of W’ is normally regarded as the width of gasket sealing element. The gasket contact area W° can be obtained in the following way.

• in case of nominal gasket thickness 6.4 mm W° = W’ - 2.0mm • in case of nominal gasket thickness 4.5 mm W° = W’ - 1.5mm • in case of nominal gasket thickness 3.2 mm W° = W’ - 1.0mm

The depth(f4) of tongue-and-groove or male-andfemale flange must be more than 5 mm if nominal gasket thickness is 4.5mm.

2.2.7 Compression Thickness of Gasket

Recommendable compression thickness of spiral wound gasket is as listed in the following table:

2.2.8 MAXIMUM BORE OF ASME B16.5 FLANGES FOR USE WITH SPIRAL- WOUND GASKETS (ASME B16.20-2000)



2.2.9 GASKET CHARACTERISTICS



2.2.10 GASKET IDENTIFICATION GUIDE



2.3 JACKETED METAL GASKETS (Semi-Metallic)

The internal part of gasket is composed of an non-asbestos or glass wool or graphite millboard and the outside is jacketed by the various thin metallic material. Various available shape are such as round, oval, non-circular, etc.

- Up to Class 900, steam, water, hot water, hydrocarbon, cryogenic line, low temperature gas, LPG

The inside of jacketed metal gasket is composed of various soft filler material which is excellent in heat resistance, and the out side of it is jacketed

with steel sheet material. The soft filler provides for adequate sealing, the outside steel makes it suitable for high pressure and temperature. The surface of jacketed metal can be fabricated with corrugated shape or flat. To improve the sealing function, the surface of jacket can be treated with pure graphite sheet.



2.4



2.5 METALLIC GASKET

2.5.1 RING JOINT GASKET

Solid-metal gaskets with oval and octagonal cross sections provide the pressure-proof joints for high-pressure and high temperature lines. Ring joint gaskets are identified by R, RX, or BX number that relates to flange size, pressure class, the appropriate flange standard. Irregular type ring joint gaskets such as Bridgeman ring, delta ring, double cone ring, round ring are also available with regard to customer's request.

- Up to Class 20,000 psi , oil field on drilling, petroleum equipment.

Ring joint gaskets were initially developed for use in the petroleum industry, where high pressure/ temperature application requires the need for high integrity seal. They are mainly used in the oil field on drilling and completion equipment. Ring type joints are also usually used for valves and pipe work assemblies, along with some high integrity vessel joint.

TYPES AND SHAPE



2.5.2



2.5.3 CORRUGATED GASKET

In order to give better surface contact, in which the spring effect of metal is present, the metal corrugated gasket is used in low pressure applications that require a thin line contact because of space or weight limitations or where available bolt loads are low.

The corrugated metal gaskets are excellent sealing effects in gas.

- These are widely used in class 150 and 300 valve caps and pipe flanges.

Corrugated types are widely used in gaskets for Valves bonnet from ANSI class 150 to 300 pounds. The corrugated gaskets have used in gas sealing application because of excellent sealing effect. It has used the various types such as round, oval, etc. To give the better performance, the surface of corrugated gaskets will be covered with pure graphite sheets or PTFE.



2.5.4 SERRATED GASKET

Serrated gasket are manufactured using a metallic base ring machined which concentric grooves at an appropriate angle and depth, then covered with a soft sealing element. and give the advantages of reducing the bolt load required to effect a seal.

- These gaskets are used for high pressure/temperature steam, gas line.



Serrated gasket is composed of various metal and thickness plates, which are in serrated form on both faces just as numerous concentric circle. It is used when bolting force is not sufficient to seal a flat gasket because the peak points of serrated parts contact effectively on the flange surfaces. It is commonly used on valve bonnet and flanges attached to equipment. 3 types of cross section are available. The angle between the mountains can be used in either 60° or 90°. But the below tables are based on 90° angle.



2.5.5 FLAT METAL GASKET

The flat surface metal gasket of simple type provides pressure proof joints for high pressure and temperature lines. The flat metal gaskets require more bolt loads than the corrugated and serrated gasket.

- These gaskets are used for high pressure/temperature steam, gas line, valve caps and pipe flanges, heat exchangers.

2.5.6 METALLIC O-RING

The metallic O-Ring Seals are used when elastomers and other non-metallic seals will not seal properly or do not offer the required reliability for the application, usually as a result of temperatures, pressures, or the environment. Metallic O-Ring Seals are long lasting seals and unlike non-metallic seals, they are not subject to failure due to incompatibility with the environment, out gassing or from deterioration due to age. Metallic O-Ring Seals are generally fabricated from tubing consisting of stainless steel or high temperature alloys such as Inconel. These materials are frequently used because they offer resilient properties that enable the seal to "Spring-Back".

APPLICATIONS

For sealing gases or liquid -250 °C or 1000 °C, vacuum to 2000Kg/cm2. Aerospace, Nuclear, Chemical /Plastics, Vacuum Processing/Research

SHAPED SEALS

Metallic O-Ring Seals can be produced in various shapes. The availability of shaped O-Ring permits the design engineer to select the shapes. However, we recommend contacting our Technical Service staff for design assistance of seal and groove.



2.6 EXAMPLE: GASKET SELECTION GASKET SELECTION CRITERIA

1. Flange Type and Dimensions 2. Number of Bolts and Size 3. Bolt Material 4. Pressure (Operating/Design) 5. Temperature (Operating/Design) 6. Gasket Materials 7. Surface Finish

GASKET PROPERTIES

Following properties are desired by using gasket:

1. Seals system fluid. 2. Chemically resists the system fluid to prevent serious impairment of its physical

properties. 3. Deforms enough to flow into the imperfections on the gasket seating surfaces to

provide intimate contact between the gasket and the seating surfaces. 4. Withstands system temperatures without serious impairment of its performance

properties. 5. Is resilient and resists creep enough to maintain an adequate portion of the

applied load. 6. Has sufficient strength to resist crushing under the applied load, and maintain its

integrity when being handled and installed. 7. Does not contaminate the system fluid. 8. Does not promote corrosion of the gasket seating surfaces. 9. is easily and cleanly removable at the time of replacement.



2.6.1 HOW TO ORDER GASKET?

When ordering Gasket Example

Gasket Style Style CGI Spiral Wound Gasket Nominal Pipe size (NPS) 4”

Pressure Rating Class 900 Gasket Standard ASME B16.20 Winding Materials 316L

Outer Ring Material Carbon Steel Inner Ring Material 316L



2.7 Gasket Materials and Contact Facings



Effective Gasket Width



3. GASKET INSTALLATION

3.1 BEFORE INSTALLATION

1. Remove old gasket and clean flange surface of all debris. For best result, use a

metal flange scraper and aerosol gasket remover and a wire brush, then inspect the flange for damage. Be sure surface finish and flatness are satisfactory.

2. Composition gaskets (non-asbestos, asbestos) become dried out and brittle so that they do not always provided an effective seal when reused.

3. Bolted joints and flanges are designed for use with the particular type of gasket specified. Substitution of a gasket of different construction or improper dimensions may be result in leakage and damage to gasket surfaces.

4. Metal or metal jacketed gaskets, when compressed initially, flow to match their contact surfaces.

5. In so doing they are work hardened and if reused, may provided an imperfect seal or result in deformation and damage to the gasket contact surfaces of the equipment.

6. When metal jacketed type gaskets are used with a tongue groove joint without nubbin. The gasket should be installed so that the tongue bears on the seamless side of the gasket jacket. When nubbin is used, the nubbin should bear on the seamless side.

3.2 GASKET INSTALLATION PROCEDURE It is important that all bolted joints be tightened uniformly and in a diametrically staggered pattern, as illustrated in below figure, except for special high pressure closures when the instructions of the manufacturer should be followed.

1. Inspect the gasket. It is important that the correct gasket has been chosen for the

bolted flange connection. Verify that the material is as specified and visually inspect the gasket for any obvious defects or damage.

2. Center the gasket on the flange. This is extremely vital where raised faces are involved. Note : Standard ANSI ring gaskets, when properly cut, Should center themselves when the bolts are in place.

3. Use a torque wrench and well-lubricated fasteners with hardened flat washers to ensure correct initial loading.

4. Inspect the gasket seating surfaces. Look for tool marks, cracks, scratches, or pitting by corrosion. Radial tool marks on a gasket seating surfaces are virtually impossible to seal regardless of the type of gasket used. Therefore, every attempt should be made to minimize these.



5. Use only new studs or bolts, nuts and washers. Make sure they are of good

quality and appropriate for the application. 6. Lubricate all thread contact areas and nut facings. The importance of proper

lubrication cannot be overstated! A proper lubricant will provide a low coefficient of friction for more consistent achieved bolt stress. An anti seize compound, when used as a bolt and nut lubricant, will facilitate subsequent disassembly.

7. Loosely install stud bolts. With Raised face and flat face installation, loosely install the stud bolts on the lower half of the flange. Insert the gasket between the flange facing to allow the bolts to center the gasket on the assembly. Install the remaining bolts and nuts and bring all to a hand-tight or snug condition. In a recessed or grooved installation, center the gasket midway into the recess or groove. (If the joint is vertical, it may be necessary to use a minimum amount of cup grease, gasket cement, or some other adhesive compatible with the process fluids, to keep the gasket in position until the flanges are tightened.) Then, install all bolts and nuts to a hand-tight or snug condition.

8. Identify the proper bolting sequence and number bolts accordingly. See charts for recommended bolting sequences. Each bolt should be numbered so that bolt torque sequences can be easily followed. Failure to follow proper bolt torque sequences can result in cocking flanges. Then, regardless of the amount of subsequent torquing, they cannot be brought back to parallel. This can contribute heavily to a leaky joint.

9. Torque the Bolts. Bolts should be torqued in a proper bolting sequence, in a minimum of four stages as specified in Steps 8, 9, 10, and 11.

10. Torque the bolts up to a maximum of 30% of the final torque value required following the recommended bolt torque sequence.

11. Repeat Step 8, increasing the torque to approximately 60% of the final torque required.

12. Repeat Step g, increasing the torque to the final torque value. 13. Retorque all studs. All studs should be retorqued using a rotational pattern of

retorquing to the final value of torque until no further rotation of the nuts can be achieved. This may require several retorquings as torquing of one stud causes relaxation in adjacent studs. Continue torquing until equilibrium has been achieved.

14. Some flange joints should be retightened just before being put in operation, to account for bolt and gasket relaxation. Success has also been reported with heat exchangers, with certain gasket types* and flange facings, when bolting is retightened during initial heat up, before loss of lubricant (or bolt seizing).



3.3 Bolting Sequence



3.4 Bolt Torque



3.5 BOLTING DATA-RECOMMENDED MINIUM SIZE



4. Troubleshooting



Annexure (A-1)

CODES AND STANDARDS FOR GASKET



Annexure (A-2)



Annexure (A-3)



Annexure (A-4)



Annexure (B-1)

COMPARISON TABLE BY MANUFACTURER ITEM : SEMI-METALLIC GASKET (Spiral Wound)



Annexure (B-2)

COMPARISON TABLE SEMI-METALLIC GASKET (Spiral Wound) Continued…..



Annexure (B-3)



Annexure (C-1)



Annexure (C-2)



Annexure (C-2



Annexure (C-2)



Annexure (D-1)

SPIRAL WOUND GASKET IDENTIFICATION AND SELECTION



Annexure (D-2)



Annexure (D-3)

gasket manual Final 20100512

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