Flanges Types, Classes and Assembly

Engineering Encyclopedia Saudi Aramco DeskTop Standards

FLANGES: TYPES, CLASSES AND ASSEMBLY

Note: The source of the technical material in this volume is the Professional Engineering Development Program (PEDP) of Engineering Services. Warning: The material contained in this document was developed for Saudi Aramco and is intended for the exclusive use of Saudi Aramco’s employees. Any material contained in this document which is not already in the public domain may not be copied, reproduced, sold, given, or disclosed to third parties, or otherwise used in whole, or in part, without the written permission of the Vice President, Engineering Services, Saudi Aramco.

Chapter : Mechanical File Reference: MEX-101.04

For additional information on this subject, contact PEDD Coordinator on 874-6556

Engineering Encyclopedia

Piping, Pipelines & Valves Flanges: Types, Classes and Assembly

Section

Page

INFORMATION ............................................................................................................... 5 INTRODUCTION ............................................................................................................. 5 FLANGE ASSEMBLY...................................................................................................... 6 FLANGE TYPES ............................................................................................................. 7 Flange Attachment Types .......................................................................................... 7 Threaded Flanges................................................................................................. 7 Blind Flanges ........................................................................................................ 8 Socket-Welded Flanges........................................................................................ 9 Slip-on Flanges ........................................................................................................ 10 Lapped Flange ......................................................................................................... 12 Welding-Neck Flanges ............................................................................................. 13 Flat-Faced Flanges .................................................................................................. 14 Raised-Face Flanges ............................................................................................... 16 Ring-Joint Flanges ................................................................................................... 16 GASKET TYPES ........................................................................................................... 18 Spiral-Wound Gaskets ............................................................................................. 18 Metal Ring-Joint Gaskets ......................................................................................... 20 Sheet Gaskets.......................................................................................................... 21 Sample Problem 1: Flange Type.............................................................................. 23 Solution............................................................................................................... 23 FLANGE STANDARDS ................................................................................................. 24 ASME B16.5 Flanges ............................................................................................... 25 API 605 Flanges....................................................................................................... 26 MSS Flanges............................................................................................................ 26 ASME B16.47........................................................................................................... 27 Saudi Aramco Flanges ............................................................................................. 28 DETERMINING THE MATERIAL GROUP FOR ASME FLANGES AND FLANGED FITTINGS ...................................................................................................................... 31 The Materials Specification Table ............................................................................ 31 Material Groups .................................................................................................. 31 Product Forms .................................................................................................... 32 Saudi Aramco Practice ....................................................................................... 32 Selection Procedure of the Material Group for ASME Flanges and Flanged Fittings32

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FLANGE RATING CLASS ............................................................................................. 34 Guidelines for Determining the Flange Rating Class................................................ 35 Flange Dimensions ............................................................................................. 37 Sample Problem 2: Flange Material and Class ........................................................ 38 Solution............................................................................................................... 38 FLANGE MAXIMUM ALLOWABLE OPERATING PRESSURE (MAOP)....................... 39 SAFETY OF FLANGED JOINTS ASSEMBLY............................................................... 41 Sample Problem 4.................................................................................................... 42 Solution............................................................................................................... 42 SUMMARY .................................................................................................................... 43 ADDENDUM.................................................................................................................. 44 ADDENDUM A .............................................................................................................. 46 ADDENDUM A .............................................................................................................. 46 ADDENDUM B .............................................................................................................. 47 ADDENDUM C .............................................................................................................. 52

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LIST OF Figures

Figure 1. Typical Flange Assembly ................................................................................... 6 Figure 2. Threaded Flanges ............................................................................................. 8 Figure 3. Blind Flange ..................................................................................................... 9 Figure 4. Socket-Welded Flange ..................................................................................... 10 Figure 5. Slip-on Flange .................................................................................................. 11 Figure 6. Lapped Flange Assembly and Typical Lap Flanges with the Stub Ends. ........ 12 Figure 7. Welding-Neck Flange Facing Types ................................................................. 14 Figure 8. Flat-Faced Flange ............................................................................................ 15 Figure 9. Raised-Faced Flange ....................................................................................... 16 Figure 10. Ring Joint Flange ............................................................................................ 17 Figure 11. Collection of Various Types of Gaskets .......................................................... 18 Figure 12. Typical and Cross-Section of Spiral-Wound Gasket. ...................................... 19 Figure 13 Metallic Ring Gaskets ....................................................................................... 20 Figure 14 Sheet Type Gaskets ......................................................................................... 22 Figure 15. Typical Forging and Manufacturing Process of ASME of Flanges.................. 24 Figure C-1. Stud Bolt Tightening Sequence 64

LIST OF TABLES Table 1. Standard Drawings for Flanges ......................................................................... 29 Table 2: Flange Material Selection Guide ......................................................................... 33 Table A-1. Industry Standards for Flanges and Flanged Fittings ..................................... 46 Table B-1. List of Material Specifications .......................................................................... 48 Table B-2. Pressure/Temperature Ratings for group 1.1 material (All Classes) .............. 49 Table B-3. Pressure/Temperature Ratings for group 2.1 material (All Classes) .............. 50 Table B-4. MSS SP-44 Steel Pipe Line Flanges ............................................................... 51 Table C-1. Friction Factors for Different Lubricants .......................................................... 55 Table C-2. Torque Value for A193 B7 and B7M Stud Bolts .............................................. 56 Table C-3. Torque Values for Isolating Gaskets ............................................................... 57

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Table C-4. Class 150:Torque Value for A193 B7 and B7M Stud Bolts ............................. 58 Table C-4. Class 300 Torque Value for A193 B7 and B7M Stud bolts ............................. 59 Table C-4. Class 600:Torque Value for A193 B7 and B7M Stud Bolts ............................. 60 Table C-4. Class 900:Torque Value for A193 B7 and B7M Stud Bolts ............................. 61 Table C-4. Class 1500:Torque Value for A193 B7 and B7M Stud Bolts ........................... 62 Table C-4. Class 2500:Torque Value for A193 B7 and B7M Stud Bolts ........................... 63

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INFORMATION INTRODUCTION The previous modules discussed calculation of the required wall thickness for straight pipe and some overall piping system design considerations. However, there is more to the pressure boundary of a piping system than just straight sections of pipe. These straight pipe sections must be connected to each other and to valves and equipment, have changes in direction, and be interconnected between systems. This is accomplished by using flanges and fittings. Selecting a flange or fitting requires the engineer to: •

Know the types of flanges and fittings that can be used based on Saudi Aramco and industry standards.

•

Select a material specification, material group and class, given design pressure, temperature, and pipe material.

This module discusses the different types of flanges and fittings and how to select the correct type when designing a piping system.

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FLANGE ASSEMBLY A flange is used to connect a pipe section to a piece of equipment, valve, or another pipe in a way that will permit relatively simple disassembly. Such disassembly may be required for maintenance, inspection or operational reasons. Figure 1 shows a typical flange assembly. Flange assembly is normally used for pipe sizes above 38 mm (1-1/2 in.) NPS.

Figure 1. Typical Flange Assembly A flange assembly consists of: •

Two flanges.

•

A gasket to provide a seal between the flanges.

•

Bolting to keep the assembly together.

One flange is attached to each of the items being joined. For example, a flanged valve may be installed in a piping system, and the pipe ends on each side of it also will have flanges. A gasket is a resilient material that is inserted between the flanges and seated against the portion of the flanges called the “face” or “facing”. The gasket provides the seal between the fluid in the pipe and the outside, and thus prevents leakage. Bolts compress the gasket to achieve the seal, and hold the flanges together against pressure and other loading. There are several types of flanges, flange attachment methods, flange facings, and gasket types. Saudi Aramco DeskTop Standards

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FLANGE TYPES This section describes the various flange types that are used in Saudi Aramco piping systems. We can divide the flanges into two categories. They could be either conventional (standard) or specialty flanges. There are several standard types of pipe flange. Two items must be specified to completely define a flange type. Flange Type = Attachment Method + Face Type A flange type is specified by stating the type of attachment and face. For example, "A weld-neck flat-faced flange." The type of attachment defines how the flange is connected to a pipe section or piece of equipment (such as a pressure-vessel nozzle). The type of flange face or facing defines the geometry of the flange surface that contacts the gasket.

Flange Attachment Types From an attachment criteria, the conventional types are either one of the flowing: 1. Threaded Flanges 2. Blind flange 3. Socket-welded flange Threaded Flanges A threaded flange has pipe threads machined into its bore as shown in Figure 2. The flange is screwed to matching threads on the pipe end. Threaded flanges are used only for small-diameter piping systems, up to 50 mm (2 in.) NPS (nominal pipe size), at locations where pipe disassembly may be required for maintenance, field modifications, or to match specialty fittings and valves. For hazardous services, a threaded flange may only be used up to 38 mm (1-1/2 in.) NPS. However, based on Saudi Aramco Engineering Standard SAES-L-009, Metallic Flanges, Gaskets, and Bolts, welded slip-on-type flanges are preferred over

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threaded flanges in screwed piping systems. Threaded flanges, and threaded piping systems in general, are not employed in larger diameters because of the increased difficulty of obtaining sufficient and uniform thread engagement. The preference for slip-on rather than threaded flanges is based on the greater likelihood of having a leak in a threaded-flange attachment joint.

Figure 2. Threaded Flanges Blind Flanges A blind flange, as shown in Figure 3, is a flat metal plate that is used to block flow in a piping system. A blind flange is included here for completeness. However, it is not attached to the pipe, but bolted to a mating flange. It is used when a pipe end or equipment nozzle must be blocked from flow, but there still must be an easy means of internal access.

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Figure 3. Blind Flange Socket-Welded Flanges A socket-welded flange has an oversized bore that is partially machined into the end opposite the face, as shown in Figure 4. The pipe is inserted into this "socket" and the flange fillet is welded to the pipe OD. The section of this module that discusses socket-welded fittings describes socket-welded attachments in more detail. Based on Saudi Aramco Engineering Standard SAES-L-010, Limitations on Piping Joints, the maximum size of socketwelded joints in hazardous services shall be 38 mm (1-1/2 in.) NPS for new construction. A maximum 50 mm (2 in.) NPS may be used for maintenance, minor field modifications of existing systems, and when needed to match existing equipment connections. However, as with threaded piping systems, SAESL-009 indicates that welded slip-on-type flanges are preferred over socket-welded flanges in socket-welded piping systems. Here again, this preference is based on the assumed greater reliability of a slip-on versus a socket-welded-type flange attachment.

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Figure 4. Socket-Welded Flange

Slip-on Flanges A slip-on flange, as shown in Figure 5, has an oversized bore. It is slipped over the pipe OD and projects slightly beyond the pipe end. The flange is then fillet welded to the pipe OD, and also between the flange bore and the pipe end. Slip-on flanges are typically a lower cost alternative to the welding-neck-type flange that will be described below. This is because a slip-on flange is lighter (i.e., uses less material) and requires less welding to attach it to the pipe. However, a slip-on flange is not suitable for high-temperature, cyclic, high-pressure or high external loading situations.

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Figure 5. Slip-on Flange Based on SAES-L-009, Saudi Aramco requires that an ASME Code Section VIII, Division 1 flange analysis be performed if a slip-on flange is used for any of the following cases: •

Severe cyclic conditions (i.e., large and frequent temperature fluctuations, or vibration-prone services).

•

Design temperature greater than 230°C (450°F).

•

ASME Class 400 or higher rating.

•

Pipe size over 600 mm (24 in.).

The flange analysis must consider thermal and other external piping loads, and must demonstrate that the flange will not be over stressed. Because of this extra analysis requirement, it is unlikely that a slip-on-type flange will be used in these services because its economic attractiveness will be reduced.

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Lapped Flange A lapped flange, as shown in Figure 6, is not physically connected to the pipe. It is slipped over a pipe stub that has a flared end, and the pipe stub is welded to the major pipe section. The flared pipe end has a machined face where the gasket is seated. The bolting holds the flanges and gasket joint together.

Figure 6. Lapped Flange Assembly and Typical Lap Flanges with the Stub Ends.

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Their use is also limited to special applications such as: No part of a lapped flange contacts the process fluid. Therefore, in high-alloy piping systems, a lapped flange may be made from less costly carbon steel material. To avoid welding dissimilar materials. To facilitate lining up the bolt holes in underwater flanged joints. The nature of a lap-joint flange allows it to be easily rotated to facilitate bolt hole alignment because it is not permanently attached to the pipe. A lapped-flange assembly is less able than other attachment types to absorb loads from a piping system because there is no connection between the flange and the pipe. Therefore, the capability to absorb loads must be considered in the overall system design. The use of lap-joint flanges is the exception rather than the rule. The main advantage of a lapped flange is cost, and then only in high-alloy piping systems. Based on SAES-L-009, Saudi Aramco prohibits the use of lap-joint flanges in severe cyclic conditions.

Welding-Neck Flanges A welding-neck flange, as shown in Figure 7, is the strongest of the standard flange attachment types. The end of the flange is butt-welded to the end of the pipe. The flange bore is sized to match the pipe bore. A welding-neck flange is the most widely used in refinery services because of its greater strength and ability to be used at high temperature and in cyclic service. However, it is the most expensive of the various flange attachment types because it is the heaviest (i.e., uses the most material) and requires the most welding to attach to the pipe end. Based on SAES-L-009, this is the preferred flange type in metallic piping systems, 50 mm (2 in.) NPS and above.

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Figure 7. Welding-Neck Flange Facing Types The area of a flange where the gasket is positioned is called the face or facing. The three primary flange facings are the flat face, raised face and ring joint. Any of the flange attachment types that were described above, except for the lapped flange, may use any of these facings. The facing for a lapped flange is located on the flared pipe stub end, not on the flange. The primary three type of flange facing will be discussed.

Flat-Faced Flanges In the flat-faced flange shown in Figure 8, the area where the gasket is located is at the same elevation as the surrounding flange surface. There is no change in elevation in proceeding from the flange inside diameter to its outside diameter. This provides uniform flange contact with the gasket over a large surface, and limits local flange bending that is caused by bolt load.

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Figure 8. Flat-Faced Flange A flat face is typically used only for cast or ductile iron flanges, with relatively low-strength material, or when a steel flange must mate to such a flange. Minimization of flange bending is necessary for cast iron, ductile iron, or other relatively lowstrength materials, but not for steel flanges. Therefore, there are few applications for flat-face flanges in refinery or petrochemical services because there are relatively few applications where such low-strength flange materials are acceptable. Sheet-type gaskets that extend from the flange inside diameter to the outside diameter (i.e., full face) typically are used with flat-face flanges. Based on SAES-L-009, a flat-faced flange with a full-face gasket shall be used when one or both of the mating flanges are cast iron, aluminum, plastic, or any other material that could be overstressed by the bolt load. Also, the are used foe highly corrosive service where contact of fluid with flange facing must be avoided.

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Raised-Face Flanges A raised-face flange is shown in Figure 9. The area where the gasket is located is higher than the surrounding flange surface, typically by 1.5 mm (1/16 in.). This raised-face portion of the flange has a specially machined, serrated finish that is suitable for the typical gasket types used in process plant applications. Any gasket type, other than a ring type, may be used with a raised-face flange. The raised face results in much less contact area and higher gasket contact stresses as compared to a flat face. The gasket is compressed and sealed only in the area of the raised face. A smooth machine finish, 3.2-6.4 micrometer AARH (arithmetic average roughness height), should be specified for use with spiral-wound gaskets. A raised-face flange is used for a very broad range of services, and is the most common type.

Figure 9. Raised-Faced Flange

Ring-Joint Flanges A ring-joint flange face, as shown in Figure 10, consists of a groove that is machined into the flange end. The sealing surfaces of the groove are smoothly finished to 63 micro inch surface roughness, and are free of any detrimental ridges or tool marks. The presence of such surface defects will result in a Saudi Aramco DeskTop Standards

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leaking joint, since a very smooth contact surface is required to achieve a leak-proof, metal-to-metal seal. A solid metal ringtype gasket is inserted in the groove. The ring-joint flange is used for the most severe service applications where the other possible flange face and gasket combinations will not provide acceptable performance. Typically, these are high-pressure and/or high-temperature services. Based on SAES-L-009, a ring-joint flange is required for steel flanges of Class 900 and higher, for design temperatures over 480°C (900°F), or for underwater pipelines in Class 300 and higher.

Figure 10. Ring Joint Flange

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GASKET TYPES The gasket provides the seal in a flange assembly. The three general gasket types that are typically used in pipe flanges for process plant and pipeline applications are:

Sheet.

Spiral wound.

Solid metal ring

Insulation gaskets

Figure 11. Collection of Various Types of Gaskets

Spiral-Wound Gaskets A spiral-wound gasket is manufactured by alternately winding strips of metal and soft filler material around a mandrel. This is illustrated in Figure 12. Most spiral-wound gaskets that are used for piping applications are supplied with an outer metal guide or retaining ring. The retaining ring outside diameter is typically sized to just contact the flange bolts, and thus serves as a gasket alignment aid. The retaining ring also acts as a compression limit stop to prevent over-compressing the gasket material during flange bolt-up. Sometimes, an inner retaining ring is also supplied, as

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shown in Figure 12. The inner ring improves stability for either larger gasket sizes or for weaker filler materials, such as Teflon. The standard spiral-wound gasket employs Type 304 stainless steel metal windings with asbestos filler. However, other winding and filler materials are available to suit particular service needs. Spiral-wound gaskets are the standard for use with raised-face flanges. Specially sized spiral-wound gaskets are also available for retrofit into ring-joint-type flanges when there is such a need. Spiral-wound gaskets tend to be used at higher temperatures and pressures than sheet gasket materials because they are stronger.

Figure 12. Typical and Cross-Section of Spiral-Wound Gasket.

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Spiral-wound gasket selection requirements are based on SAES-L-009 as follows: •

Spiral-wound Type 316 stainless-steel gaskets with a flexible graphite filler and a carbon steel guide ring are used with raised-faced flanges in most services. This includes most process hydrocarbon and steam services. In an oxidizing environment, the maximum use temperature is limited to 454°C (850°F).

•

For operating temperatures below -45°C (- 50°F), the guide ring shall be Type 304 stainless steel.

Metal Ring-Joint Gaskets Metal ring gaskets come into two basic shapes, an oval crosssection and an octagonal cross-section. The octagonal ring seals by surface wedging contact with the flange groove, and the oval ring seals by line contact. Therefore, the oval ring is somewhat more tolerant of slight flange misalignments than the octagonal ring, and still provides a tight seal. In addition, the same bolt load will result in a higher local gasket contact stress and thus a potentially tighter joint with an oval ring. Also, an octagonal ring cannot fit into older ring-joint flanges that have a round bottom groove.

Figure 13 Metallic Ring Gaskets Ring-joint gaskets are typically softer than the flange grooves. Therefore, the gasket, rather than the groove, will deform slightly under the applied bolt load. A variety of ring materials

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are available to suit the particular service needs. The most common materials are iron or soft steel, 4-6% chrome, and stainless steels. A solid metal ring-type gasket is used only with ring-joint-type flanges. Ring-joint gasket selection requirements are based on SAES-L-009 as follows: •

Soft iron, octagonal ring-joint gaskets shall be used with ASME B16.5, MSS-SP-44, or Saudi Aramco standard ringjoint flanges.

•

For ASME B16.5 ring-joint flanges in corrosive services, a low-carbon steel, and octagonal ring-joint gasket with a Buna-N rubber inner V-Type guard and outer molded-on ring guard shall be used.

•

For API 6A flanges, low-carbon steel, octagonal, pressure energized ring-joint gaskets in accordance with API 6A Type RX shall be used.

Sheet Gaskets The most common material used for sheet gaskets is compressed asbestos. However, there has been increasing concern regarding the ultimate availability of sheet asbestos gaskets due to potential worker health and materials disposal issues. Asbestos gaskets will no longer be available within several years, and the use of asbestos should be avoided whenever a suitable substitute is available. Several alternative sheet gasket materials have been introduced in recent years as shown in Figure 14. Many of these use synthetic fibers rather than asbestos, along with an elastomeric binder. The binder is a larger percentage of the sheet material in these synthetic fiber gaskets, and thus is a more significant factor in determining acceptable applications. Non asbestos sheet gaskets that utilize synthetic fiber with a binder will typically have a lower maximum operating temperature than a compressed asbestos gasket. Of equal importance is that they will have much less fire resistance than an asbestos gasket, so that greater flange leakage could be expected should a fire occur in the vicinity of a flange with a synthetic fiber she

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Figure 14 Sheet Type Gaskets Another non asbestos sheet-gasket material is composed of flexible graphite. The best flexible graphite sheet-gasket-types also employ a stainless steel sheet insert with the flexible graphite for increased strength. This gasket material has exhibited excellent corrosion resistance in most process plant applications, and has provided good performance at elevated temperatures. Sheet gaskets may be used with flat or raised-face flanges. Sheet gasket selection requirements are based on SAES-L-009 as follows: •

Compressed synthetic fiber sheet gaskets with an oilresistant binder, 1.6 mm (0.063 in.) thick, may be used for Class 150 flanges in non hazardous services up to 230°C (450°F). An example of their use is in lube oil piping.

•

Synthetic rubber gaskets, ASTM D1418 Class CSM, shall be used for all acid services except nitric acid and oleum. For nitric acid and oleum, ASTM D1418 Class FKM elastomer shall be used for flat-face flanges.

•

Elastometric material, 3 mm (1/8 in.) thick, with a Shore A durometer hardness of between 50 and 60, shall be used for full-face gaskets for plastic flanges. For wet chlorine or hypochlorite services, the elastomer shall be ASTM D1418 Class CSM.

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Sample Problem 1: Flange Type It is necessary to install a new pressure vessel at an existing Saudi Aramco plant. The flange and facing type and the gasket must be specified for this application. The necessary design information is as follows: The pressure vessel is carbon steel and is in a dangerous hydrocarbon service at a design temperature of 371°C (700°F). The design pressure is 3,448 kPa (500 psig), an ASME Class 300 carbon steel flange is required, and the pipe size is 200 mm (8 in.). Solution Since the material is not low strength, such as cast iron, a flatface flange is not required. The service conditions are not severe enough to require a ring-joint flange. Therefore, a raisedface flange should be used. The choices for flange attachment type are immediately narrowed down to slip-on or weld-neck types due to the 200 mm (8 in.) pipe size. Because the design temperature exceeds 232°C (450°F), a weld-neck flange should be used to avoid the flange analysis required by SAES-L-009. Since the design temperature exceeds 232°C (450°F), and the ASME Class exceeds 150, and this is a dangerous hydrocarbon service, sheet gaskets cannot be used. Because the flanges are raised face, ring-joint gaskets cannot be used. Therefore, spiral-wound gaskets with Type 316 stainless-steel windings, a flexible graphite filler, and a carbon steel guide ring are required, based on SAES-L-009. The complete solution to this problem is to use raised-face weld-neck flanges with a spiral-wound gasket that has Type 316 stainless-steel windings, a flexible graphite filler, and a carbon steel guide ring.

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FLANGE STANDARDS Saudi Aramco uses industry standards to define which flanges are used in Saudi Aramco piping systems. Piping is typically sized and purchased to meet standard diameters. Because standard pipe sizes are used, it is practical to have standard flange sizes and dimensions to assist manufacturer to reproduce qualified flanges. Figure 15 illustrates typical process of manufacturing forged flanges. There are four industry standards, a Saudi Aramco Engineering Standard, and a Saudi Aramco Material System Specification that cover flanges: •

ASME B16.5 flanges.

•

API-605 flanges.

•

MSS flanges.

•

ASME B16.47 flanges.

•

Saudi Aramco Special Flanges, as specified by standard drawings listed in SAES-L-009 and 02-SAMSS-011.

Figure 15. Typical Forging and Manufacturing Process of ASME of Flanges Saudi Aramco DeskTop Standards

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ASME B16.5 Flanges ASME B16.5, Pipe Flanges and Flanged Fittings, provides flange dimensional details and pressure/temperature ratings for standard pipe sizes from 13 through 600 mm (1/2 through 24 in.). This Standard covers a wide range of material types, and will typically be the flange standard used for process plant applications. The pressure/temperature ratings that are contained within ASME B16.5 specify the combinations of pressure and temperature that are acceptable for given flange sizes and dimensions. The term class is used to designate groupings of acceptable pressure/temperature combinations contained within ASME B16.5. ASME B16.5 contains seven classes designated as classes 150, 300, 400, 600, 900, 1500, and 2500. As the number of the class increases, the strength of the flanges within it increases. Therefore, higher flange classes can withstand higher pressure/temperature combinations. Determination of the appropriate flange class will be discussed later in this module. Saudi Aramco Engineering Standard SAES-L-009, Metallic Flanges, Gaskets and Bolts, contains the following requirements regarding the use of ASME B16.5 flanges: •

ASME B16.5 classes 150, 300, 600, 900 and 1500 shall be used for carbon and alloy steel flanges in 13 through 600 mm (1/2 through 24 in.) nominal pipe sizes. It shall be used for Class 2500 in nominal sizes 13 through 300 mm (1/2 through 12 in.).

•

Class 400 carbon steel flanges shall not be used for nominal sizes of less than 750 mm (30 in.).

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API 605 Flanges API 605 encompasses raised-face carbon steel welding-neck flanges in 650-1,500 mm (26-60 in.) nominal pipe sizes with pressure ratings corresponding to classes 75, 150, 300, 400, and 600. It also includes a class 900 for welding-neck flanges in 650-1,200 mm (26-48 in.) nominal pipe sizes. Finally, it also specifies flanges that are cast or forged as the integral ends of valves, fittings, or nozzles for classes 75, 150, or 300. API 605 begins where ASME B16.5 stops in terms of pipe size. However, it does not reach the maximum pressure/temperature ratings of ASME B16.5, nor does it cover material other than carbon steel. Based on SAES-L-009, API-605 flanges may be used for only class 75 in sizes of 650-900 mm (26-36 in.) in 50 mm (2 in.) increments, and sizes 1,050-1,500 mm (42-60 in.) in 150 mm (6 in.) increments.

MSS Flanges MSS standards are developed and revised by the Manufacturers Standardization Society of the Valve and Fittings Industry. MSS-SP-44, Steel Pipe Line Flanges, originally was developed to establish uniform flange dimensions for use with high-pressure pipelines of 650 through 1,500 mm (26 through 60 in.) size in pressure classes of 300 through 900. It later was revised to include sizes down to 300 mm (12 in.) and Class 150. The flange designs are intended primarily for use with API 5LX line pipe, and they are proportioned accordingly. Their design reflects also the higher design stresses that are permitted in pipeline service. There is a basic difference between ASME B16.5 and MSS-SP44 flanges. ASME B16.5 flanges originally were designed for attachment to relatively thick-walled pipe. However, the larger diameter SP-44 flanges have hubs that specifically are designed for attachment to relatively thin-walled, high yield-strength pipe. The "x" grades of the API 5L pipe material specification have relatively high yield strengths. Special attention should be paid to situations where an ASME B16.5 flange is attached to a thinwalled pipe operating near the maximum atmospheric temperature/pressure rating of the flange, or where an SP-44

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flange is attached to a relatively thick-walled pipe. The stress at the flange-hub attachment point should be checked in each of these cases to ensure that it is not excessive. MSS-SP-44 flanges may be used within the following limitations, in accordance with SAES-L-009: •

Classes 150, 300, 400, 600, and 900 for nominal pipe sizes of 300-600 mm (12-24 in.) for welding-neck flanges with single-taper hub only.

•

Classes 400 and 600 for pipe sizes of 1,250-1,500 mm (5060 in.), welding-neck and blind flanges, raised face only.

•

Class 900 for pipe sizes 650 through 1,200 mm (26 through 48 in.) welding-neck and blind flanges.

ASME B16.47 ASME B16.47, Large-Diameter Steel Flanges, is essentially a combination of the API 605 and MSS SP-44 flanges. ASME B16.47 covers pipe flanges in 650 through 1,500 mm (26 through 60 in.) nominal sizes in ratings corresponding to classes 75, 150, 300, 400, 600 and 900. MSS SP-44 flanges are designated as Series A flanges, and API 605 flanges are designated Series B. The materials that are covered by ASME B16.47 are the same as those in ASME B16.5, except that nickel-base alloys are excluded. Pressure/temperature ratings are consistent with ASME B16.5. 02-SAMSS-011, Forged Steel Weld-Neck Flanges for Low - and Intermediate-Temperature Service, permits the use of ASME B16.47 flanges, Series B, Class 75 for sizes that are not covered by Saudi Aramco Standard Drawings.

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Saudi Aramco Flanges SAES-L-009 specifies standard flange material specifications based on design temperature and strength requirements, as outlined in Work Aid 1. The use of ASTM A105 and A694 flange materials is restricted due to their poor experience in Saudi Aramco. Flange material specifications for pipeline applications are selected to be of comparable strength to that of the connected pipe. For example, if the pipe material that is used has a 290 MPa (42,000 psi) SMYS, the flange material has an F42 strength designation. SAES-L-009 also lists standard Saudi Aramco drawings that provide mandatory dimensional standards for specific size ranges, ratings, flange types, and facings. These standard flanges must be used as applicable within their defined scopes, even if API-605, MSS-SP-44, or ASME B16.47 has the same designations. These standard drawings are as follows:

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Table 1. Standard Drawings for Flanges

NPS Range

Class

Type

Facing

Standard Drawing

26-60

150

WN

RF

AD-036634

26-60

300

WN

RF

AD-036991

26-48

300

WN

RJ

AC-036484

54-60

300

WN

RJ

AC-036437

30-48

400

WN

RF

AD-036698

26-48

600

WN

RF

AD-036673

26-48

600

WN

RJ

AC-036442

26-48

300

Lap

RJ

AC-036486

54-60

300

Lap

RJ

AE-036438

26-48

600

Lap

RJ

AC-036443

54-60

75

Blind

RF

AD-036696

Where: WN: Weld neck.

Lap: Lapped flange

RF: Raised face.

Blind: Blind flange

RJ: Ring joint. 02-SAMSS-011, Forged Steel Weld-Neck Flanges for Intermediate-Temperature Service, provides Saudi Aramco purchase requirements for forged steel weld-neck flanges in low- and intermediate-temperature services. Services that have design temperatures above 425°C (800°F) or below -60°C (75°F), or those that require the use of higher alloy pipe material, Saudi Aramco DeskTop Standards

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are not covered by this SAMSS and must be handled as special cases. 02-SAMSS-011 was first issued in February 1994 and supersedes Standard Drawing AB-036028. It expands upon the flange material selection requirements that are specified in SAES-L-009 and the requirements that are specified in the relevant industry standards. These additional Saudi Aramco requirements are meant to ensure higher overall flange material quality based on past experience, and to minimize the probability of experiencing problems during piping system fabrication and operation. 02-SAMSS-011 adds additional restrictions on material usage, and further requirements in the following areas: •

Flange manufacturing details.

•

Maximum hardness limitations.

•

Heat treatment.

•

Material chemistry.

•

Mechanical strength testing.

•

Impact testing.

•

Hardness testing.

•

Nondestructive examination.

•

Repairs.

•

Markings.

•

Painting and shipping.

Participants are referred to 02-SAMSS-011 for specific details.

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DETERMINING THE MATERIAL GROUP FOR ASME FLANGES AND FLANGED FITTINGS The next step in specifying a flange or flanged fitting is to select the material specification and group number, which are needed to select the class or rating of the flange or flanged fitting. This section discusses the selection of flange materials specification and material group number. Flange material specifications are listed in Table 1A of ASME B16.5. A portion of this Table is reproduced as Addendum B-1. Material selection for threaded, socket-welded, and butt-welded fittings is not as involved but also will be discussed. Work Aid 1 summarizes the flange material selection process, the use of SAES-L-009 in selecting flange material specifications, and how to use the Materials Specifications Table.

The Materials Specification Table The Materials Specification Table is divided into two sections: •

Material groups.

•

Product forms.

Material Groups Material specifications are grouped within specific Material Group Numbers in this table. These groupings have been made to provide compatible flanged-joint ratings for materials that are likely to be used together. The lowest strength material in each group was used to determine the pressure rating for that group at a given temperature. Therefore, the ratings of some materials within a group are conservative.

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Product Forms This table also indicates three different product forms that are possible for flanges and flanged fittings: forging, castings, and plates. The relevant ASTM specifications are specified for these product forms. Most material groups have representative specifications in each of the product forms. However, some material chemistries within a material group might not be represented in each product form. For example, carbon steel in Group 1.1 can be found in all three product forms. However, CMn-Si steel in Group 1.1 can be plate only. ASME B16.5 specifies that plate may be used only for blind flanges, and certain sized reducing flanges where a blind flange is used. Saudi Aramco Practice Refer to Work Aid 1 for a procedure to select the appropriate material specification and Material Group Number. Saudi Aramco typically will use ASTM A 350, Grade LF2 forged carbon steel flanges for most process plant applications. Referring to Figure 20, A350, Grade LF2 is in Material Group No. 1.1.

Selection Procedure of the Material Group for ASME Flanges and Flanged Fittings The following procedure may be used to select the correct flange material and Material Group Number. 1. Identify the material chemistry (such as carbon steel, 1 1/4 Cr - 1/2 Mo) that is being used for the connected piping. 2. Identify the design temperature. 3. For pipeline applications, identify the Specified Minimum Yield Stress of the pipe material that is being used. 4. If the piping material is not carbon steel, refer to Table 1A in ASME B16.5 (Addendum-B-1), and continue in this step. If it is carbon steel, go to Step 5. a. Select the appropriate material specification that corresponds to the identified material chemistry and

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product form. The product form for flanges will almost always be a forging. b. Identify the Material Group Number that corresponds to the material specification. 5. If the material is carbon steel (or a low-alloy specification that is identified in SAES-L-009 and 02-SAMSS-011), refer to SAES-L-009 and Table 1 of 02-SAMSS-011 to select the appropriate flange material specification. The most common carbon steel flange material specifications for plant piping systems are summarized below. a) Identify the Material Group Number that corresponds to the material specification, from Table 1A in ASME B16.5 (Addendum-B-1). Material Group 1.1 corresponds to the above specifications. 6. Refer to SAES-L-009 and 02-SAMSS-011 for additional requirements and conditions that are not included, and for pipeline applications. Table 2: Flange Material Selection Guide Flange Material

Limitations

ASTM A 105

Restricted to non hydrocarbon service (except flare lines), -18 to 425°C (0 to 800°F).

ASTM A 105 N (normalized)

Can be used for hydrocarbon service , -18 to 425°C (0 to 800°F).

ASTM A 350 Gr. LF 2

-30 to 345°C (-20 to 650°F).

ASTM A 350 Gr. LF 2 LO TEMP -45 to 345°C (-50 to 650°F). Impact testing required.

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FLANGE RATING CLASS After the Material Group has been determined, the next step in the selection process for flanges and flanged fittings is to select the appropriate class. The class is based on pressure and temperature, and is determined by using pressure/temperature rating tables, the Material Group, design metal temperature, and design pressure. Selecting the class sets all the detailed dimensions for flanges and flanged fittings. The objective is to select the lowest class that is appropriate for the design conditions. This section will discuss the appropriate pressure/temperature rating classes for flanges and flanged fittings. The following will deal only with ASME B16.5 because this is the most widely used and broadest flange standard. The classes of API 605, MSS-SP-44, and ASME B16.47 flanges are identical to those that are contained in ASME B16.5 for the same number designations. API 605 is limited to carbon steel material. Pressure/Temperature Rating Tables •

The class accounts for the required flange design temperature and pressure.

•

ASME B16.5 contains seven classes designated Classes 150, 300, 400, 600, 900, 1500, and 2500.

•

Each class specifies the design pressure and temperature combinations that are acceptable for a flange having that designation.

•

As the number of the class increases, the strength of the flanges increases. Therefore, higher flange classes can withstand higher pressure/temperature combinations.

•

As the number of the class increases, the cost of the flanges also increases because more material is being used to make the higher class stronger. Therefore, there is an economic incentive to use the lowest class that will meet the design requirements.

•

Each of the material group has a table in ASME B16.5 that provides the ratings for all classes, Addendum B-2 and B-3 are extracts for material group 1.1 and 2.1 respectively.

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For MSS Sp-44 flanges there is only one table of flange rating which is extracted in Addendum-B-4. •

ASME B31.3 and B31.4 permit higher pressures than are indicated in the rating table for conditions that exist for shorter duration. These will be discussed in a later section.

•

A general flange class selection procedure is outlined next.

Guidelines for Determining the Flange Rating Class Use the following procedure to determine the Class for ASME B16.5 flanges and flanged fittings. Fill in the blank lines as required. Given: •

Generic pipe material________________ (such as Carbon Steel, C-1/2 M, 3-1/2 Ni)

•

Design Pressure, kPa (psig)__________________________

•

Design Temperature, °C (°F)_________________________

•

Nominal Pipe Size, mm (in.)__________________________

•

Pipe material SMYS (pipeline applications), MPa (psi)______________________

Selection Procedure: 1. Review SAES-L-009 and 02-SAMSS-011 for carbon and low alloy steel flange requirements. (a) Saudi Aramco Requirement_______________________ 2. Determine the required flange product form (forging, casting, and plate). Most pipe flanges are forging. a) Product Form____________________________

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3. Proceed to Table 1A of ASME B16.5 to select Material Group No., considering the required material and product form. Flange material is to have comparable chemistry to pipe material (except possibly lapped flanges), and meet SAES-L-009 and 02-SAMSS-011 requirements. a) Material Group Number_________________________ 4. Proceed to Table 2, ASME B16.5, for the appropriate material group to determine the flange class. For the specified design temperature, determine the maximum allowable operating pressure (MAOP) proceeding from lower to higher classes. Class

150

300

400

600

900

1500 2000

For ASME B31.4 and B31. 8 piping systems, you must note that flanges shall not be derated for temperature. The design pressure for –20 to 100 Deg. F is acceptable up to 250 Deg. F. For temperature higher than 250 Deg. F but not more than 450 Deg. F, the derating factors per MSS SP-44 should be used for carbon steel material AS SHOWN IN Addendum B-4. Complete this table only until the MAOP for a class exceeds the design pressure. The required flange class is the lowest one whose MAOP exceeds the design pressure. a) Required Class __________________________

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Flange Dimensions ASME B16.5, which provides dimensions for all flange classes. The flange geometry is completely specified by the dimensions given in this table. The flange dimensions for a given class are the same for all possible flange materials. Therefore, variations in material strength are accommodated by changes in acceptable temperature/pressure combinations within a given class, rather than changing flange dimensions. A similar table is contained in ASME B16.5 for each class, but the flange dimensions differ in each class. For the same pipe sizes, flanges become thicker, heavier, and stronger as the class increases.

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Sample Problem 2: Flange Material and Class A new piping system will be installed at an existing Saudi Aramco plant designed and constructed to ASME B31.3. It is necessary to determine the ASME class that is required for the flanges. The following design information is provided: •

Pipe Material: carbon steel

•

Design Temperature: 371°C (700°F).

•

Design Pressure: 3,448 kPa (500 psig).

All the needed ASME B16.5 tables are contained in the Work Aid section of this module. Solution •

Determine the Material Group Number for the flanges by referring to ASME B16.5 Table 1A. Find the carbon steel material in the Nominal Designation Steel column. The material specification for forged flanges would be A105 or A350 Gr. LF2, and the corresponding material Group Number is 1.1.

•

Refer to Table 2 for material group 1.1. Read the allowable design pressure at the intersection of the 371°C (700°F) design temperature. Class 150 gives lower working pressure than the design.

For class 300, the working pressure is 535 psig which is higher than the required design 500 psig. Therefore class 300 is acceptable. •

The required flange class is 300.

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FLANGE MAXIMUM ALLOWABLE OPERATING PRESSURE (MAOP) An engineer may be asked to check the maximum allowable operating pressure (MAOP) for a flange or fitting when there are changes in the piping design conditions, such as an increase in pressure. This section discusses how to determine the MAOP of the flange/fitting for a given temperature, given a flange/fitting class. Previous discussions showed how the required class is determined for flanges and flanged fittings, and threaded and socket-welded fittings. They also described how the pressure/temperature limitations of wrought steel butt-welded fittings are determined. In each case, it is a relatively simple matter to work backwards to determine the MAOP for a particular flange or fitting. Work Aid 3 provides a procedure for determining MAOP. Conditions Beyond Normal Design Conditions Previous sections described how to determine the maximum allowable long-term operating pressure for flanges and fittings. The ASME B31 Codes permit an allowance for occasional excursions above this long-term design pressure. However, the codes differ regarding the permissible extent of these excursions. In ASME B31.3 piping systems, it is permissible to exceed the pressure rating or the allowable stress for pressure design at the temperature of the increased condition by not more than: •

33% for no more than 10 hours at any one time and no more than 100 hours/year, or

•

20% for no more than 50 hours at any one time and no more than 500 hours per year.

Referring to the Class 300 flange in Sample Problem 2 at 371°C (700°F), the pressure could rise to 758 psig (1.33 x 570) or 684 psig (1.2 x 570) during a short-time excursion, depending on the duration of the excursion. The ASME B31.4 and ASME B31.8 transportation piping codes differ from B31.3 and from each other with regard to conditions beyond normal design conditions. ASME B31.4 will permit a

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10% increase over the rated pressure for variations from normal operation, such as those caused by liquid surges. It does not contain any details covering the maximum duration or number of these variations. ASME B31.8 does not contain any permissible allowance for pressure increases above the normal maximum rated pressure.

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SAFETY OF FLANGED JOINTS ASSEMBLY Though it seems flanged joint assembly is very straightforward and simple, petrochemical industries have experienced tragic incidents due to failures of flanged joints. The main requirements and factors to achieve reliable flanged joints are the following: ƒ

Flange type, material and rating.

ƒ

Gasket material, type and quality.

ƒ

Appropriate surface finish of the flange rating

ƒ

Right bolting procedure is followed

ƒ

Good workman ship by the people assembling the flanges.

ƒ

Careful inspection during the above stages as required.

Generally, the flange has very high safety margins in its design. Over the years of experience, it has been found that the human factor is the main reason for failures in the flanged joints. There are standards and acceptable practices that should be carefully followed to insure safety around the flanged joints. The latest revision of SAES-L-050, 1999, has outlined such procedures in the Appendix-A which has been extracted for importance into this module as Addendum-C. Following are common workmanship mistakes found during assembly of flanges that could lead to leakage: 1) Improper surface finish of the flange facing. 2) Gasket is not centered. 3) Uneven bolting torque. 4) Torque value are either under minimum required or way over to the point that gasket is completely not functional. 5) Installing the wrong gasket, type or rating.

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Sample Problem 4 An existing piping system currently has a design temperature of 149°C (300°F) and a design pressure of 1,482 kPa (215 psig). The flange material is carbon steel, ASTM A350, Grade LF2, and Class 150 flanges are used. Process engineers have determined that it would be advantageous if the design pressure could be raised to 1,689 kPa (245 psig) at the same design temperature. Can this be done using the existing flanges? Solution •

Refer to ASME B16.5, Table 1A, in Addendum B-1. Locate the ASTM A350, Grade LF2 flange material. This corresponds to Material Group 1.1.

•

Refer to ASME B16.5 Table 2 for Material Group 1.1 in Addendum B-2. At a design temperature of 149°C (300°F) for Material Group 1.1, the maximum allowable operating pressure is 1,586 kPa (230 psig). This exceeds the current design pressure, but is not enough for the proposed design pressure. Therefore, the Class 150 flanges are not acceptable.

•

Refer to Table 2 for Class 300 in Work Aid 2. Class 300 flanges are acceptable for the new service by a wide margin. Therefore, the flanges and flanged fittings must be changed to Class 300 to be suitable for the proposed increase in design pressure. Note that the existing pipe wall thickness will also need to be checked for the new design conditions.

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SUMMARY A flange assembly consists of two flanges plus a gasket and bolting. Saudi Aramco requirements specify the flange and gasket types that must be used based on specified service conditions. Industry requirements specify standard flange dimensions and acceptable pressure/temperature combinations, which may be used with these. Fittings are used to make some change in the geometry of a piping system, and may be attached to the connected pipe by threading, socket welding, or butt-welding. Acceptable pressure/temperature combinations for fittings are based on comparisons with comparable seamless pipe.

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ADDENDUM

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Index of Addendum

Page(s)

ADDENDUM .......................................................ERROR! BOOKMARK NOT DEFINED. ADDENDUM A ................................................................................................... 46 ADDENDUM A ................................................................................................... 46 ADDENDUM B ................................................................................................... 47 ADDENDUM C ................................................................................................... 52

List of Figures Figure C-1. Stud Bolt Tightening Sequence ................................................................ 64 list of tables Table A-1. Industry Standards for Flanges and Flanged Fittings ................................ 46 Table B-1. List of Material Specifications ................................................................... 48 Table B-2. Pressure/Temperature Ratings for group 1.1 material (All Classes) ........ 49 Table B-3. Pressure/Temperature Ratings for group 2.1 material (All Classes) .......

50

Table B-4. MSS SP-44 Steel Pipe Line Flanges ......................................................... 51 Table C-1. Friction Factors for Different Lubricants ...................................................... 55 Table C-2. Torque Value for A193 B7 and B7M Stud Bolts ......................................... 56 Table C-3. Torque Values for Isolating Gaskets ........................................................... 57 Table C-4. Class 150:Torque Value for A193 B7 and B7M Stud Bolts ......................... 58 Table C-4. Class 300 Torque Value for A193 B7 and B7M Stud .................................. 59 Table C-4. Class 600:Torque Value for A193 B7 and B7M Stud Bolts ......................... 60 Table C-4. Class 900:Torque Value for A193 B7 and B7M Stud .................................. 61 Table C-4. Class 1500:Torque Value for A193 B7 and B7M Stud Bolts ....................... 62 Table C-4. Class 2500:Torque Value for A193 B7 and B7M Stud Bolts ....................... 63

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ADDENDUM A Table A-1. Industry Standards for Flanges and Flanged Fittings Standard

Title

ASME B16.1

CAST IRON PIPE FLANGES AND FLANGED FITTINGS, CLASS 25, 125, 250, AND 800.

ASME B16.5

PIPE FLANGES AND FLANGED FITTINGS.

ASME B16.47

LARGE-DIAMETER STEEL FLANGES, NPS 26 THROUGH NPS 60.

API 605

LARGE-DIAMETER CARBON STEEL FLANGES.

MSS SP-44

STEEL PIPE LINE FLANGES.

API 6A

WELLHEAD EQUIPMENT.

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ADDENDUM B Table B-1. List of Material Specifications (Excerpt) Source Addendum B-1 ASME B16.5

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Table B-1. List of Material Specifications (Excerpt – Continued) Source Addendum B-1 ASME B16.5

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Table B-2. Pressure/Temperature Ratings for group 1.1 material (All Classes) Source Addendum B-1 ASME B16.5

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Table B-3. Pressure/Temperature Ratings for group 2.1 material (All Classes) Source Addendum B-1 ASME B16.5

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Table B-4. MSS SP-44 Steel Pipe Line Flanges (Pressure-Temperature Ratings Maximum Allowable Non-Shock Working Pressures in Pounds Per Square Inch - Gage) TEMP. F

CLASS 150 CLASS 300

CLASS 400

CLASS 600

CLASS 900

-20 TO 250

285

740

990

1480

2220

300

275

715

955

1430

2145

350

265

690

925

1380

2070

400

255

665

890

1330

2000

450

245

640

860

1285

1925

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ADDENDUM C SAES-L-050 Flanged Joints Assembly Procedure A-1

Scope

A-2

This procedure defines minimum requirements for flanged joints assembly including bolts tightening. Contractor shall be responsible to assure that proper leak proof joints are achieved.

A-3

Pre-assembly Inspection A-3.1 Bolts shall be visually checked for proper size, dimension and for any physical damage to shanks or threads which would interfere with bolt assembly or performance. Also, check the suitability of the stud bolts for service temperature. A-3.2 The flange facing, particularly the seating area, shall be visually examined for cleanness and insure that no damage, such as scratches exist. A-3.3 The gasket shall be verified for correct type, rating, and dimension. Also, it shall be free from any damage particularly in the seating element. Insure that spiral wound gaskets are stored flat specially for large sizes, 24” inch and larger. A-3.4 Verify that proper lubricant is used. Lubricant for bolts and nuts shall be Jet-Lube SS-30 or other acceptable lubricants listed in Table A.1. A-3.5 Tightening tools shall be checked for adequacy, performance and calibration.

A-4

Torque values vary according to flange rating, bolt size, type of gasket, and friction factor of the lubricant. The torque values are specified in Tables A-2 and A-3. Table A-2 applies to all gasket listed in SAES-L-009, except for isolating gaskets, based on a friction factor of 0.12, using Jet-Lube SS-30. Table A-3 applies to isolating gaskets (e.g. Pikotek), based on a friction factor of 0.10. Table A-4 are torque values for various flange ratings, bolt sizes and friction factors.

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A-5

Torquing Tools: A-5.1 There are various types of tools available to achieve the proper torque value. Selection of the proper tool depends on the stud bolt size, physical location of the flagged joint, and criticality of the flange. Identifying the proper tools shall be resolved between Contractor, SAPMT, Proponent and Inspection prior to commencing the erection of the piping. A-5.2 The manufacturer's instructions shall be followed for the operation, limitation and maintenance of all torque wrenches used to perform flange bolts tightening. A-5.3 Torque wrench calibration shall be performed in accordance with manufacturer’s recommendations, or as required by the inspector after consultation with Piping Specialist in Consulting Services Department.

A-6

Stud Bolt Tightening Procedure Step 1: Align flanges and gasket. Clamp securely in place. Step 2: Apply lubricant to stud threads over length and nut engagement and to face of nut which contacts flange. Insure that the nuts run freely down the thread of the studs. Step 3: Install all studs and nuts hand tight, insure that studs pass freely through the flange holes. Center studs between nuts so that equal number of threads project at each end. Step 4: Number each stud according to its position in the flange as shown on Figure A.1. Stud Bolt Tightening Sequence. Step 5: Tightening studs per Stud Bolt Tightening Sequence with an appropriate tool such as air impact wrench or equal. Step 6: For joints containing RTJ or Spiral Wound Gaskets, repeat step 5. Step 7: Tighten the stud bolts in stages to obtain the final required torque from the appropriate torque table. The first stage should not be more than 30% of the final torque. Apply the torque evenly to each stud following the stud bolt tightening sequence. The final torque must be within ± 5 percent of the required values per paragraph A-4. A.7

Stud Bolt Additional Tightening Procedure Where Leaks Occur During Pressure Testing.

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Step 1: Re-torque stud bolts to maximum torque value shown on table. Step 2: If leak does not stop after re-torquing has been performed, disassemble the flange joint and inspect as follows: a.

Inspect stud bolts and nuts for defects or damage to threads or improper cleaning of threads. Commentary Note: Do not use wire brushes to clean threads.

b.

Inspect flange faces for damage, misalignment, or,

c.

Inspect gasket for damage or defects.

Step 3: After all defective and damaged items have been repaired or replaced, reassemble the flange joint using a new gasket and tighten the bolts using the maximum torque values.

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Table C-1. Friction Factors for Different Lubricants Lubricants

Friction Factors

Torque Correction Factor

Moly Graphite

.06

0.67

Tool Joint Compound

.08

0.8

Graphite and Oil

.10

1.0

Aerocote #4

.11

1.1

KOPR-KOTE

.11

1.1

EL-PRO C5A

.11

1.1

FEL-PRO C100

.11

1.1

FEL-PRO C102

.11

1.1

Jet Lube SS-30

.12

1.2

API Bul. 5A2

.13

1.3

Light Machine Oil as shipped

.15

1.5

Dry Bolts

.2

2

(used as the base line for torque values in Table A-2)

(commonly called Anti-Seize)

Thread Compound

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Piping, Pipelines & Valves Flanges: Types, Classes and Assembly

Table C-2. Torque Value for A193 B7 and B7M Stud Bolts with A194 2H and 2HM Nuts

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22.

Stud Bolt Size inch 1/2 9/16 5/8 3/4 7/8 1 1-1/8 1-1/4 1-3/8 1-1/2 1-5/8 1-3/4 1-7/8 2 2-1/4 2-1/2 2-3/4 3 3-1/4 3-1/2 3-3/4 4

Torque Minimum Ft-Lb 30 43 60 107 170 256 374 524 709 934 1201 1515 1879 2296 3311 4151 6150 8033 10,253 12,872 15,901 19,356

Torque Maximum Ft-Lb 34 49 68 120 190 287 420 590 798 1051 1351 1704 2113 2583 3724 5155 6918 9037 11,545 14,481 17,888 21,775

Note (1): Torque values based on 0.10 Average Friction Factor. A combination of various elements such as the conditions of the threads, the condition of the flange to the nut bearing surface and the type of lubricant used, makes up the friction factor which can vary from .04 to .20 or as much as 500 percent.

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Piping, Pipelines & Valves Flanges: Types, Classes and Assembly

Table C-3. Torque Values for Isolating Gaskets (Pikotek) on ASME B16.5 and ASME B16.47 Series A & B, Class 150 Through Class 2500 Flanges 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

Stud Bolt Size inch 1/2 5/8 3/4 7/8 1 1-1/8 1-1/4 1-3/8 1-1/2 1-5/8 1-3/4 1-7/8 2 2-1/4 2-1/2

Torque Minimum Ft-Lb 30 60 100 160 245 355 500 680 800 1100 1500 2000 2200 3180 4400

Note (1): Torque values based on 30,000 psi tension load and 0.15 Friction Factor from API-5A2 thread compound. See Table A-2 for other factors. Commentary Notes: (a) For ASME Class 900 through Class 2500, API-6B and API-6BX Class 2000 through Class 15000, and RTJ Flanges, the maximum compressive stresses induced during installation should not exceed 25,000 psi. Design to 12,500 psi when possible. (b) Calculations for compressive stresses applied during torque-up procedures must account for ring joint grooves, gasket seal grooves, raised face diameters, and gasket inside diameter. (See PIKOTEK Gasket User's manual) (c) Bolt tensioning equipment such as HYDRATIGHT may be used for class 900 and above resulting in a minimum residual bolt stress of 30000 psi and a maximum of 50000 psi. Refer to PIKOTEK Gasket User's manual for specific bolting instructions.

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Piping, Pipelines & Valves Flanges: Types, Classes and Assembly

Table C-4. Class 150:Torque Value for A193 B7 and B7M Stud Bolts with A194 2H and 2HM Nuts Nominal Pipe Size (in)

Number Of Bolts

Dia. Of Bolts (in)

1/2

4

1/2

27

33

35

38

41

46

60

3/4 1 1 1/4 1 1/2 2 2 1/2 3 4 5 6 8 10 12 14 16 18 20 24 26 28 30 32 34 36

4 4 4 4 4 4 8 8 8 8 12 12 12 16 16 16 20 20 24 28 28 28 32 32

1/2 1/2 1/2 1/2 5/8 5/8 5/8 5/8 3/4 3/4 3/4 7/8 7/8 1 1 1 1/8 1 1/8 1 1/4 1 1/4 1 1/4 1 1/4 1 1/2 1 1/2 1 1/2

27 27 27 30 53 60 66 60 93 104 116 148 167 248 220 320 320 445 445 445 445 785 785 785

33 33 33 37 64 72 80 72 112 126 140 179 201 299 266 387 387 540 541 541 541 958 958 958

35 35 35 40 69 78 86 78 121 137 152 194 218 325 289 421 421 588 589 589 589 1044 1044 1044

38 38 38 43 75 84 93 84 131 147 164 209 236 351 312 455 455 636 636 636 636 1131 1131 1131

41 41 41 46 80 90 100 90 140 158 176 225 253 376 335 489 489 684 684 684 684 1217 1217 1217

46 46 46 52 91 102 113 102 160 179 199 225 287 428 380 556 556 779 780 780 780 1390 1390 1390

60 60 60 67 118 132 147 132 207 233 259 332 374 556 495 725 725 1018 1019 1019 1019 1821 1821 1821

Saudi Aramco DeskTop Standards

Required Torque (Ft.Lbs) For Different Coefficient Of Friction For Lubricant Selection Refer To Table 3-A 0.08 0.10 0.11 0.12 0.13 0.15 0.20

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Table C-4. Class 300 Torque Value for A193 B7 and B7M Stud bolts with A194 2H and 2HM Nuts, (Continued)) Nominal Pipe Size (in)

Number Of Bolts

Dia. Of Bolts (in)

1/2 3/4 1 1 1/4 1 1/2 2 2 1/2 3 4 5 6 8 10 12 14 16 18 20 24

4 4 4 4 4 8 8 8 8 8 12 12 16 16 20 20 24 24 24

1/2 5/8 5/8 5/8 3/4 5/8 3/4 3/4 3/4 3/4 3/4 7/8 1 1 1/8 1 1/8 1 1/4 1 1/4 1 1/4 1 1/2

Required Torque (Ft.Lbs) For Different Coefficient Of Friction For Lubricant Selection Refer To Table 3-A 0.08 0.10 0.11 0.12 0.13 0.15 0.20 27 33 35 38 41 46 60 53 64 69 75 80 91 118 53 64 69 75 80 91 118 53 64 69 75 80 91 118 93 112 121 131 140 160 207 53 64 69 75 80 91 118 93 112 121 131 140 160 207 93 112 121 131 140 160 207 104 126 137 147 158 179 233 104 126 137 147 158 179 233 104 126 137 147 158 179 233 167 201 218 236 253 287 374 248 229 325 351 376 428 556 360 436 474 512 550 626 816 360 436 474 512 550 626 816 500 608 662 715 769 877 1145 500 608 662 715 769 877 1145 500 608 662 715 769 877 1145 883 1078 1175 1272 1369 1564 2049

26 28 30 32 34 36

28 28 28 28 32 32

1 5/8 1 5/8 1 3/4 1 7/8 1 7/8 1 1/2

1006 1131 1422 1761 1761 1907

Saudi Aramco DeskTop Standards

1229 1382 1740 2157 2157 2339

1340 1508 1899 2356 2356 2555

1452 1633 2058 2554 2554 2771

1563 1759 2217 2752 2752 2987

1787 2010 2535 3149 3149 3149

2345 2638 3331 4141 4141 4500

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Piping, Pipelines & Valves Flanges: Types, Classes and Assembly

Table C-4. Class 600:Torque Value for A193 B7 and B7M Stud Bolts with A194 2H and 2HM Nuts, (Continued) Nominal Pipe Size (in)

Number Of Bolts

Dia. Of Bolts (in)

1/2 3/4 1 1 1/4 1 1/2 2 2 1/2 3 4 5 6 8 10 12 14 16 18 20 24 26 28 30 32 34 36

4 4 4 4 4 8 8 8 8 8 12 12 16 20 20 20 20 24 24 28 28 28 28 28 28

1/2 5/8 5/8 5/8 3/4 5/8 3/4 3/4 7/8 1 1 1 1/8 1 1/8 1 1/4 1 3/8 1 1/2 1 5/8 1 5/8 1 7/8 1 7/8 2 2 2 1/4 2 1/4 2 1/2

Saudi Aramco DeskTop Standards

Required Torque (Ft.Lbs) For Different Coefficient Of Friction For Lubricant Selection Refer To Table 3-A 0.08 0.10 0.11 0.12 0.13 0.15 0.20 27 33 35 38 41 46 60 53 64 69 75 80 91 118 53 64 69 75 80 91 118 60 72 78 84 90 102 132 104 126 137 147 158 179 233 60 72 78 84 90 102 132 93 112 121 131 140 160 207 104 126 137 147 158 179 233 185 223 243 262 281 319 415 275 332 361 390 418 475 618 248 299 325 351 376 428 556 399 484 526 569 611 695 907 500 608 662 715 769 877 1145 500 608 662 715 769 877 1145 674 821 894 968 1041 1188 1554 883 1078 1175 1272 1369 1564 2049 1131 1382 1507 1633 1756 2010 2637 1131 1382 1507 1633 1756 2010 2637 1761 2157 2356 2554 2752 3149 4141 1761 2157 2356 2554 2752 3149 4141 2146 2632 2876 3119 3362 3894 5065 2384 2925 3195 3465 3736 4276 5628 3075 3779 4131 4484 4836 5540 7301 3416 4199 4590 4982 5373 6156 8112 4237 5215 5704 6194 6683 7662 10108

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Piping, Pipelines & Valves Flanges: Types, Classes and Assembly

Table C-4. Class 900:Torque Value for A193 B7 and B7M Stud Bolts with A194 2H and 2HM Nuts, (Continued) Nominal Pipe Size (in)

Number Of Bolts

Dia. Of Bolts (in)

1/2 3/4 1 1 1/4 1 1/2 2 2 1/2 3 4 5 6 8 10 12 14 16 18 20 24 26 28 30 32 34 36

4 4 4 4 4 8 8 8 8 8 12 12 16 20 20 20 20 20 20 20 20 20 20 20 20

3/4 3/4 7/8 7/8 1 7/8 1 7/8 1 1/8 1 1/4 1 1/8 1 3/8 1 3/8 1 3/8 1 1/2 1 5/8 1 7/8 2 2 1/2 2 3/4 3 3 3 1/4 3 1/2 3 1/2

Saudi Aramco DeskTop Standards

Required Torque (Ft.Lbs) For Different Coefficient Of Friction For Lubricant Selection Refer To Table 3-A 0.08 0.10 0.11 0.12 0.13 0.15 0.20 93 112 121 131 140 160 207 93 112 121 131 140 160 207 148 179 194 209 225 255 332 167 201 218 236 253 287 374 248 299 325 351 376 428 556 148 179 194 209 225 255 332 220 266 289 312 335 380 495 185 233 243 262 281 319 415 360 436 474 512 550 626 816 500 608 662 715 769 877 1145 394 484 526 569 611 695 907 674 821 894 968 1041 1188 1554 749 912 994 1075 1157 1320 1727 749 912 994 1075 1157 1320 1727 982 1198 1306 1413 1521 1737 2277 1257 1536 1675 1814 1954 2233 2930 1956 2397 2618 2838 3058 3499 4601 2385 2925 3195 3466 3736 4277 5628 4239 5218 5707 6197 6686 7665 10113 5678 6998 5659 8319 8979 10300 13601 7387 9115 9979 10843 11707 13435 17755 7387 9115 9979 10843 11707 13435 17755 9425 11640 12748 13856 14964 17180 22719 11807 14595 15989 17383 18777 21565 28534 11807 14595 15989 17383 18777 21565 28534

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Table C-4. Class 1500:Torque Value for A193 B7 and B7M Stud Bolts with A194 2H and 2HM Nuts, (Continued) Nominal Pipe Size (in)

Number Of Bolts

Dia. Of Bolts (in)

Required Torque (Ft.Lbs) For Different Coefficient Of Friction For Lubricant Selection Refer To Table 3-A 0.08

0.10

0.11

0.12

0.13

0.15

0.20

1/2

4

3/4

93

112

121

131

140

160

207

3/4

4

3/4

104

126

137

147

158

179

233

1

4

7/8

167

201

218

236

253

287

374

1 1/4

4

7/8

185

223

243

262

281

319

415

1 1/2

4

1

275

332

361

390

418

475

618

2

8

7/8

185

223

243

262

281

319

415

2 1/2

8

1

275

332

361

390

418

475

618

3

8

1 1/8

399

484

526

569

611

695

907

4

8

1 1/4

556

675

735

795

855

974

1273

5

8

1 1/2

982

1198

1306

1413

1521

1737

2277

6

12

1 3/8

749

912

994

1075

1157

1320

1727

8

12

1 5/8

1257

1536

1675

1814

1954

2233

2930

10

12

1 7/8

1956

2397

2618

2838

3058

3499

4601

12

16

2

2385

2925

3195

3466

3736

4277

5628

14

16

2 1/4

3073

3777

4129

4481

4833

5537

7279

16

16

2 1/2

4239

5218

5707

6197

6686

7665

10113

18

16

2 3/4

5677

6998

7658

8318

8978

10299

13600

20

16

3

7387

9115

9979

10843

11707

13436

17756

24

16

3 1/2

11806

14593

15987

17380

18774

21561

28529

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Table C-4. Class 2500:Torque Value for A193 B7 and B7M Stud Bolts with A194 2H and 2HM Nuts, (Continued) Nominal Pipe Size (in)

Number Of Bolts

Dia. Of Bolts (in)

Required Torque (Ft.Lbs) For Different Coefficient Of Friction For Lubricant Selection Refer To Table 3-A 0.08

0.10

0.11

0.12

0.13

0.15

0.20

1/2

4

3/4

104

126

137

147

158

179

233

3/4

4

3/4

116

140

152

164

176

199

259

1

4

7/8

185

223

243

262

281

319

415

1 1/4

4

1

303

366

397

429

460

523

680

1 1/2

4

1 1/8

439

532

579

625

672

765

997

2

8

1

303

366

397

429

460

523

680

2 1/2

8

1 1/8

399

484

526

569

611

695

907

3

8

1 1/4

612

743

809

874

940

1071

1400

4

8

1 1/2

1080

1317

1436

1555

1674

1911

2505

5

8

1 3/4

1579

1932

2109

2285

2462

2815

3698

6

8

2

2385

2925

3195

3466

3736

4277

5628

8

12

2

2385

2925

3195

3466

3736

4277

5628

10

12

2 1/2

4709

5759

6341

6885

7429

8517

11237

12

12

2 3/4

6308

7775

8509

9242

9976

11443

15111

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Piping, Pipelines & Valves Flanges: Types, Classes and Assembly

Figure C-1. Stud Bolt Tightening Sequence

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