138645938 Valve Selection Types and Classes

Engineering Encyclopedia Saudi Aramco DeskTop Standards

VALVE SELECTION: TYPES AND CLASSES

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-101.06

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

Engineering Encyclopedia

Piping, Pipelines & Valves Valve Selection: Types and Classes

Section .....................................................................................................................Page INFORMATION ............................................................................................................... 5 INTRODUCTION............................................................................................................. 5 DESCRIBING VALVES IN TERMS OF THEIR FUNCTIONS, TYPES, AND COMPONENTS............................................................................................................... 6 Gate Valves .......................................................................................................... 7 Function................................................................................................................ 7 Major Gate Valve Components............................................................................. 9 Body Pattern......................................................................................................... 9 Gates.................................................................................................................. 10 Bonnets .............................................................................................................. 11 Trim .................................................................................................................... 13 Stems ................................................................................................................. 13 Stem Packing System ........................................................................................ 15 End Connections ................................................................................................ 16 Seats .................................................................................................................. 17 Ball Valve............................................................................................................ 18 Function.............................................................................................................. 20 Major Ball Valve Types and Components........................................................... 20 Types.................................................................................................................. 20 Body ................................................................................................................... 21 Ball ..................................................................................................................... 22 Seats .................................................................................................................. 23 Ball Supports ...................................................................................................... 24 Plug Valve .......................................................................................................... 24 Function.............................................................................................................. 25 Major Plug Valve Types and Components ......................................................... 26 Types.................................................................................................................. 26 Body ................................................................................................................... 27 Plug Styles and Seating Mechanisms ................................................................ 27 Plug Support....................................................................................................... 28 Seats .................................................................................................................. 28 SELECTING THE TYPE AND SIZE OF A VALVE THAT IS SUITABLE FOR PROCESS APPLICATIONS .......................................................................................... 30

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Step 1: List the Data Required........................................................................... 31 Valve Sizing........................................................................................................ 31 Step 2: Identify Suitable Valve-Types and Components.................................... 32 Step 3: Determine Valve-Type Limitations for Suitable Valves through Saudi Aramco Engineering Standard SAES-L-008, Selection of Valve ............ 33 Step 4: Finalize Valve Selection by Considering Other Factors......................... 39 Standardization................................................................................................... 39 Inventory............................................................................................................. 39 Experience.......................................................................................................... 39 Cost .................................................................................................................... 40 Delivery Time...................................................................................................... 40 Materials ............................................................................................................. 40 Dimensions......................................................................................................... 40 Step 5: Provide a Full Description...................................................................... 40 Sample Problem 1: Part A. ................................................................................ 45 Solution: Part A.................................................................................................. 46 Sample Problem 1: Part B ................................................................................. 48 Solution: Part B.................................................................................................. 49 Locations "A" and "B" ......................................................................................... 49 Location "C"........................................................................................................ 49 Location "D"........................................................................................................ 50 Location "D"........................................................................................................ 50 Location "E" ........................................................................................................ 50 Determining the Required Valve Class and Associated MAOP .......................... 51 Pressure/Temperature Ratings........................................................................... 56 IDENTIFYING VALVE INSPECTION AND TESTING REQUIREMENTS ..................... 57 Minimum Inspection Requirements for New Valves ........................................... 58 Surface Examination .......................................................................................... 58 Dimensional and Component Checks ................................................................ 59 Shell Test............................................................................................................ 60 Back Seat Test ................................................................................................... 60 Low-pressure Closure Test................................................................................. 61 High-pressure Closure Test................................................................................ 61 Fire safe Test...................................................................................................... 62 Other Inspection Considerations ........................................................................ 63

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SUMMARY.................................................................................................................... 64 WORK AIDS.................................................................................................................. 65 WORK AID 1: STEPS FOR SELECTING VALVES AND VALVE COMPONENTS ...... 65 WORK AID 2: Procedure for Determining Valve Class, MAOP, and Appropriate Test Type ........................................................................................ 69

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LIST OF FIGURES Figure 1. Full-Port Gate Valve......................................................................................... 8 Figure 2. Solid-Wedge Gate.......................................................................................... 10 Figure 3. Flexible-Wedge Gate ..................................................................................... 11 Figure 4. Bolted Bonnet................................................................................................. 12 Figure 5. Screwed Bonnet............................................................................................. 13 Figure 6. Rising Stem with Outside Screw (OS&Y) ....................................................... 14 Figure 8. Stem Packing System with Lantern Ring ....................................................... 16 Figure 9. Integral Seat................................................................................................... 18 Figure 10. Full-Bore Ball Valve...................................................................................... 19 Figure 11. Seat Rings................................................................................................... 22 Figure 12. Multi-Segment Plug Valve ........................................................................... 25 Figure 13. Pump Rising System ................................................................................... 45 Figure 14. List of Material Specifications...................................................................... 53 Figure 15. Typical Pressure/Temperature Limits for Gate and Ball Valves ................. 56 Figure 17. Mandatory Tests for Valve Types (Based on API 598 and 04-SAMSS-048).................................................................................... 70

LIST OF TABLES Table 1. Information on Valve Sizes, Ratings and Standards ...................................... 43 Table 2. Standard Class Ratings for Group 1.1 Materials ............................................ 54 Table 3. Special Class, Working Pressure by Classes, psi .......................................... 54 55

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INFORMATION INTRODUCTION An engineer will often be asked to participate in the design of a piping system by evaluating a contractor's technical proposal, auditing a contractor's work, performing a screening study for cost estimating purposes, or actually designing and managing pieces of the project. The previous module discussed branch connections where two sections of pipe come together. This module discusses another step in designing a piping system, valve selection. Valves are necessary for the basic function of a piping system. This module reviews how to specify the appropriate type of valve for a particular application, and how to determine the appropriate pressure rating. When a plant is designed, the types of valves and their location within a piping system are selected. After the type of valve is determined, the engineer and/or contractor must refer to Saudi Aramco Engineering Standards for valve engineering requirements. He must also refer to the Saudi Aramco Materials System Specifications, (SAMSS's), for design requirements for specific valve-types in order to complete the purchase order. MEX 101.02 discussed piping system material selection, which included valve material requirements. Valve material selection will not be discussed in this module. Over 95% of the valves that are used in process plant and pipeline applications will be one of the types that are discussed in this module. A number of other specialty-type valves are also used in specific applications. These include clamp or pinch valves, diaphragm valves, needle valves, and ram-type sampling valves. Specialty-type valves will not be discussed.

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DESCRIBING VALVES IN TERMS OF THEIR FUNCTIONS, TYPES, AND COMPONENTS The engineer must know the possible functions of a valve before being able to select the appropriate valve for a particular application. Fluid flows through a pipe, and valves are used to control the flow. A valve may be used to block flow, throttle flow, or prevent flow reversal. The following describes the basic valve functions. The block-flow function provides completely on or completely off flow control of a fluid in a piping system, generally without throttling or variable control capability. It might be necessary to block flow in order to take a piece of equipment out of service for maintenance, while the rest of the unit remains in operation, or to separate two portions of a single system to accommodate various operating scenarios. To throttle flow in a piping system may increase or decrease the amount of fluid flowing in the system and can also help control pressure at points within the system. It might be necessary to throttle flow in order to regulate the filling rate of a pressure vessel, or to control unit operating pressure levels. In some cases, it might be necessary to automatically prevent the reversal of flow beyond the valve location and not allow fluid to reverse its direction during sudden pressure changes or system upsets. Preventing reverse flow might be necessary to avoid damage to a pump or a compressor, or to automatically prevent backflow into the upstream part of the system due to process reasons. Various types of valves may be used for each function. The gate valve is the type that is most commonly used to block flow in a process plant. The ball-, plug-, butterfly-, diaphragm-, and globe-type valves are used to block flow to a lesser extent. The globe valve is the type most commonly used to throttle flow in a refinery. Butterfly and diaphragm valves are also used to throttle flow. The check valve is the only valve-type that is used to prevent flow reversal. There are three kinds of check valves: swing, ball, and lift.

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The engineer must know the various types of valves because some valves have advantages over others in particular applications. For example, numerous valve-types will block flow. The gate valve is most commonly used; however, the ball valve may be a better choice based on the particular application. This section discusses types of valves and their major components, and their suitability for the various functions. Saudi Aramco Engineering Standard, SAES-L-008, Selection of Valves, and the 04-SAMSS-series of Saudi Aramco Material System Specifications provide specific design and service limitations for valve-types and components. These will be discussed further in subsequent sections of this module.

Gate Valves About 75 percent of all valves in process plants are gate valves. Most valves in process plants function as block valves. Block valves are required only to fully shut off or fully turn on flow. The gate valve is an optimum engineering and economic choice for this on or off service. The gate valve is available in the full range of pipe sizes, ASME/ANSI B16.34 pressure/temperature ratings, and materials that are encountered in process plant applications. The gate valve is not suitable to throttle flow because it will pass the maximum possible flow while it is only partially open, and the valve seating surfaces can erode rapidly from fluid flow when the valve is not in the fully open or fully closed position. Function The off/on flow control of a gate valve is achieved by moving a gate into or out of the fluid-flow stream. When the full-port gate valve is in the open (on) position, it provides a full line size, unobstructed, straight through flow passage, and thus results in a minimum-flow pressure drop. In reduced-port and Type-type gate valves, the flow area is smaller than the line size, causing slightly higher-pressure drops than a full-port valve. The gate valve shuts off flow by forcing the gate against the valve body seating surfaces, which creates a pressure-tight seal in both directions.

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Figure 1. Full-Port Gate Valve

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Major Gate Valve Components The typical process plant gate valve consists of 20 or more components, as shown in Figure 1. The design of most of these components is standardized, but can vary in detail according to purchaser preference. Seven of these components (the body, gate, bonnet, stem, stem packing system, end connections, and seats) are especially significant and can be obtained in a variety of designs. The selection of a particular component design and/or material depends on both the service conditions and the economics for the application. Body Pattern Most standard gate valves are available in either cast or forged steel body construction up to about 100 mm (4 in.) NPS. Body castings are usually supplied for larger gate valves because of the cost and difficulty associated with forging the relatively complex shapes of gate valves in the larger sizes. There are three types of body patterns: full-port, venturi-port, reducedport. Full Port –The line size flow area and resulting minimum pressure drop of the full-port valve, shown in Figure 1, make it suitable for all process plant applications where a gate valve is required. Its use is mandatory for systems where pipe scrapers must be employed. However, a full-port valve is usually not the most economical selection, since reduced-port- and venturi-type valves are less expensive. Per API 600, Steel Gate Valves Flanged and Butt-Welding Ends, full-port is specified for all flanged valves. Venturi- or Reduced-Port – In the venturi- or reduced-port valve, the seat opening is one or more pipe sizes less than the valve size. This reduces the valve cost due to the overall smaller valve casting size. However, the reduced seat size increases valve pressure drop, reduces its strength to absorb loads from the piping system, and does not permit use of pipe scrapers. Reduced-port valves are available only up to 100 mm (4 in.) in size and are the normal choice in small diameters. A reduced-port is specified for valves that are specified to meet API 602, Compact Steel Gate Valves.

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Gates There are several different gate designs. The solid- and flexible-wedge gate are the most common. 04-SAMSS-001 defines gate-type requirements for different valve sizes and ratings. For example, a flexible wedge is required for valves 100 mm (4 in.) NPS and larger in ASME/ANSI classes 150 through 600. Solid-Wedge Gate – The solid-wedge gate, shown in Figure 2, is the lowest cost and most widely used gate-type in process plants. Solid-wedges are of one-piece construction and the seating surfaces are precision machined with a wedge taper. A precision-dimensional match between the gate and the body seating surfaces is required to obtain a tight a seal. The solidwedge gate is favored for its strong, simple design, but it is prone to sticking when used in services where extreme temperature changes or gradients [∆T> 194°C (350°F)] cause the valve body to contract more than the gate.

Figure 2. Solid-Wedge Gate

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Flexible-Wedge Gate – The flexible-wedge gate shown in Figure 3 is the second most widely used type. Although similar to the solid wedge, the flexible wedge contains a deep annular groove in the gate, midway between the two seating surfaces. This groove reduces the rigidity of the gate and allows slight relative flexing between the seating surfaces. This flexing allows the disc seating surfaces to accommodate some thermal movement or dimensional misalignment between the gate seats and the body seats. For this reason, the flexible-wedge gate is more suitable than the solid-wedge gate for high-temperature applications and is less prone to gate sticking.

Figure 3. Flexible-Wedge Gate Bonnets The valve bonnet is a pressure-retaining component that supports the valve stem and operating mechanism and contains the stem-to-bonnet packing gland seal system. The bonnet joint provides a pressure-tight closure between the process fluid and atmosphere at the junction between the bonnet and the valve body. The primary bonnet types include bolted, welded, pressure-seal, seal-welded, threaded, union, and screwed. Bolted and screwed are the most common bonnet types. Bolted Bonnet – A typical bolted bonnet is shown in Figure 4. The bolted bonnet uses flanged construction to permit its removal from the valve body, thus giving complete access to the valve stem, gate, and body seat for maintenance. Because of the bolted-flange gasket detail, this design is subject to the same potential leakage problems as a normal pipe flange. Saudi Aramco DeskTop Standards

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Therefore, the bonnet should be treated in the same manner as a pipe flange with regard to bolting and gasket selection. The bolted bonnet is the most practical and commonly used design for process plant gate valves, and is available in all sizes and ASME/ANSI pressure/temperature ratings.

Figure 4. Bolted Bonnet Screwed Bonnet – The screwed-in bonnet, as shown in Figure 5, is threaded externally and screwed into an internally threaded valve body. An alternative design is the screwed-on bonnet, where the bonnet is internally threaded and screwed onto an externally threaded body. Although of low cost and simple design, the screwed bonnet has several disadvantages. First, the threaded joint is susceptible to loosening when subjected to vibration or through the application of stem torque on the gland. Second, screwing the bonnet firmly to the body neck tends to distort the body neck or bonnet. It is therefore more difficult to achieve and maintain a tight seal with a screwed bonnet valve than with the other types. Therefore, this type of bonnet should be considered for use only in small [50 mm (2 in.) or less], low rating (Class 150 or less), bronze and steel valves in clean, noncorrosive, utility-type services.

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Figure 5. Screwed Bonnet Trim API 600, Steel Gate Valves, Flanged and Butt-welding Ends, defines gate valve trim as the stem, the body seat surface, the gate seat surface, the bushing or weld-deposit used for the backseat and stem hole guide, and small internal parts that normally contact the service fluid, excluding the pin used in making a stem-to-gate connection (the pin is specified to be an austenitic stainless steel). Trim material is selected to prevent galling or metal wear of surfaces in sliding contact with each other, and to minimize corrosion and erosion effects. API 600 lists 16 different nominal trims by composition of seating materials and their associated hardness. Saudi Aramco trim material requirements were discussed in MEX 101.02. Stems The stem raises and lowers the gate. It is designed to withstand the forces that are generated during movement of the gate, which creates compression and tension in the stem. However, the stem is not designed to resist the fluid forces that act on the disc. A loose stem-to-gate connection is provided to permit the fluid forces that act on the gate to be transmitted to body gate guides, which are provided for that purpose. The stem is provided with some form of threading, which, upon turning, causes it to drive the gate up or down.

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Rising Stem with Outside Screw – As shown in Figure 6, the valve stem rises, along with the gate, from the closed to open position, and the stem threads remain outside the valve body. This is called a rising stem/outside screw design, and is commonly referred to as an OS&Y design. An important advantage of this design is that the stem threads never contact the contained fluid. Therefore, they are not subject to corrosion or erosion and are not susceptible to the accumulation of sediment deposits, which could lead to damage or jamming of the stem screw. In addition, the stem mechanism is readily accessible for lubrication and maintenance. Another advantage of this stem design is extended packing life; a result of the stem not rotating as it moves the gate. Because the stem rises above the hand wheel or operator, it automatically indicates the approximate gate position.

Stem Screw

Stem Screw

Figure 6. Rising Stem with Outside Screw (OS&Y) Rising Stem With Inside Screw – The rising stem/inside screw, shown in Figure 7, positions the gate by an internal, stem-screw mechanism. Because the hand wheel and stem move together, their position indicates the gate position. This stem type is available only on valves 100 mm (4 in.) and smaller in diameter. Because the stem screw is internal, it is only suitable for noncorrosive services.

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Figure 7. Rising Stem with Inside Screw Stem Packing System A stem packing system provides a seal between the stem and the valve bonnet. The system, as shown in Figure 8, consists of a stuffing box, packing (with or without lantern ring), gland follower, and packing gland bolts and nuts. The seal that is formed when the packing is simultaneously forced against the valve stem and bonnet prevents leakage. This is accomplished by tightening the packing gland nuts that force the gland follower down and compresses the packing. A lantern ring is sometimes used where a condensing chamber, injection of sealant, or purging into the stuffing box is required.

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The packing system consists of several rings of resilient, pliable material installed in the stuffing box. The most often used rings consist of braided asbestos containing lubricants and corrosion inhibitors. Wire is inserted in some packings to increase their ability to resist extrusion, and to serve as a sacrificial electrode to prevent depletion of valve stem chrome content or stem pitting that can occur when packing areas are not completely dry. SAES-L-008 specifies Saudi Aramco packing requirements, as discussed in MEX 101.02.

Figure 8. Stem Packing System with Lantern Ring End Connections The valve ends connect the valve to the associated piping. The specific type of end connection that is employed is dictated by the service requirements and usually is the same type as used for pipe connections to equipment. The available valve-end connections are flanges, butt-welds, socket-welds, and threads.

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Seats The extent to which tight shutoff is accomplished depends directly on the sealing ability of the seating surfaces, consisting of body seats and gate seats. The ability of two contacting surfaces to form a seal is a function of the degree of surface conformability between them. Perfect contact, (i.e., no voids), gives zero leakage, but this cannot be achieved in practice since an absolutely smooth surface with 100% conformability cannot be attained. The problem therefore is to achieve sufficient conformability to keep the leakage rate within acceptable limits. There are two general categories of valve seats: the hard seat with metal-to-metal contact, and the soft seat with a metal-tononmetal primary contact. Hard Seats – Hard seats are more economical, can be used at higher pressures and temperatures, and are the most common seat design used in gate valves. The body-seating surface may be designed as a separate seat ring, which is threaded or welded into the valve body, or be integral with the valve body. Figure 9 illustrates the integral seat design. Integral seats will typically be used only for small size valves. 04-SAMSS-001, Gate Valves, specifies seat ring design requirements. Soft Seats – Soft seats provide better shutoff, approaching zero leakage. However, the soft seat materials that are used (such as Teflon or Viton) limit the maximum-use temperature of the valve to a level that is much lower than the valve ASME/ANSI pressure class. When a soft seat is used in a gate valve, the soft seat material will typically be inserted into a groove that has been machined into the valve body-seating surface.

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Integral Seat

Body-to-Gate Seat Interface

Figure 9. Integral Seat

Ball Valve Ball valves usually function as block valves to fully shut off or fully open flow. Ball valves are well suited for conditions where quick on/off and/or bubble-tight service are required. The ball valve is available in the full range of pipe sizes and materials that are needed in process plant applications, and most softsealed models are suitable for double-block and bleed applications. However, it is important to note that pressure/temperature ratings for ball valve soft seats, above ambient temperatures, are usually lower than the ASME/ANSI ratings for steel valves. This is because of the lower physical properties of the soft-seat materials. Soft-sealed ball valves are not normally used for throttling service because the valve softseats are subject to erosion or distortion/displacement caused by fluid flow when the valve is not in the fully open or fully closed position.

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The soft-sealed ball valve is a good choice as a block valve when used within the limitations previously mentioned and when bubble-tight shutoff, double-block and bleed capability, or the quick on/off feature is required. Where such capabilities are not required, the ball valve is usually not the best choice in most sizes, because of its higher cost relative to gate valves.

Figure 10. Full-Bore Ball Valve

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Function The ball valve is quick-opening and requires only a quarter-turn from full open to full closed. A ball is used to permit or block flow. A hole, provided through one axis of the ball, connects with the inlet and outlet ports of the valve body. With the ball in the open position, straight-through flow is accomplished. When the ball is turned 90°, flow is blocked. In the closed position, tight shutoff is obtained by resilient, seat-to-metal ball-sealing contact, and to a lesser degree, by metal-to-metal contact in metal-seated models.

Major Ball Valve Types and Components The following describes some major ball valve types and components that directly influence function or differentiate ball valves from other valves. Refer to Figure 10. Types Most ball valve models have soft-sealed body seat designs, but are frequently of a non-fire safe-type that is generally unsuitable for process service. There are two basic seating types for process service applications: the nonresilient, seated- (metal, carbon-graphite, etc.) and the soft-sealed, fire safe-type. Only the soft-sealed, fire safe design will be discussed, since that is the type that is required most often. Fire safe ball valves utilize a narrow-band primary-seal ring of a soft, resilient material (such as Teflon) in the body seats to prevent leakage through the annulus between the ball and body cavity. Fire safe ball valves also include a secondary, metal-tometal seal (see Figure 11) to assure a positive shutoff capability in the event of fire or other damage to the soft seals. They also require high-temperature stem packings, cover gaskets, and external bolting materials to minimize external leakage in a fire situation.

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Body The body of a ball valve contains and supports the ball, stem, and operating mechanism. There are several body designs available, but all fall into the two basic categories of one-piece or multi-piece designs. Multi-piece Body – In the multi-piece body design, the valve body is circumferentially divided into pieces, thereby permitting the ball and seats to be installed or removed by disassembling the body. This is illustrated in Figure 10. The body segments are fastened together by flanging, screwing, or with long through-bolts. However, the exposed through-bolt arrangement is not recommended for fire safe valve applications, as directflame impingement can cause bolt relaxation and substantial external joint leakage. The multi-piece body is acceptable for use in all utility services, but must be certified fire safe for use in hydrocarbon services. The vendor should certify that the body joint(s) are capable of withstanding full-pipe stresses with no resultant joint leakage. One-piece Body – There are three basic one-piece body designs: the end-entry, top-entry and sealed (welded) designs. In the end-entry-type, the ball and seats are installed axially and retained by an axial retaining ring. One desirable feature of this design is the ability to eliminate one external leakage path by eliminating one body joint, usually required on other types for ball and seat installation. However, this configuration has a safety hazard in that faulty retention of the ball could result in blowout when the downstream flange of the valve is disconnected under pressure, unless the retaining ring design can be locked in. In the top-entry body-type, the ball and seats are fit into the top of the valve and retained by a cover or bonnet. This body construction permits inline maintenance of the valve to the extent of replacing the ball or seats. This is a particular advantage for valves that are butt-welded, seal-welded, or socket-welded into the line.

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The sealed-body design uses welded construction. The ball and seats are positioned in the body before welding the body seams. While sealing a valve by welding eliminates external leakage, it restricts inspection and maintenance of the valve internals, in that cutting and re-welding of the valve body would be required to provide internal access. Ball The ball is the mechanism that either permits or prevents flow. A hole bored through one axis of the ball connects the inlet and outlet ports of the body as shown in Figures 10 and 11C. By rotating the ball 90°, it is possible to fully shut off or permit flow through the valve. The port opening in valves of the same size may vary significantly among manufacturers. For example, in the 6 mm through 50 mm (1/4 in. through 2 in.) sizes, the port size can vary up to 13 mm (1/2 in.) for a given size. Therefore, when a particular type of port, i.e., full- or reduced-, is required for a specific application, it should be specified.

Figure 11. Seat Rings

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Seats The ability of a ball valve to provide tight closure depends on the sealing capability of the ball and body seat contact surfaces. In a ball valve, there is a metal-to-metal or metal-to-nonmetal primary-contact interface. The metal seating surface is always on the ball while the nonmetallic seating surface, if any, is always on the body seat rings. Two varieties of soft-seat rings are used in ball valves. In one variety, a metallic seat ring contains the soft-seat material. In the other type, the ring is fabricated entirely of nonmetallic material. The following paragraphs describe these rings, service-related selection considerations, and fire safe features. Soft-Seat (Metallic Seat Ring) – The metallic seat ring, containing a nonmetallic insert, usually requires application of a mechanical force, such as provided by springs, to provide the required bearing pressure to achieve a tight seal. For example, the spring in Figure 11C is mounted on the stem and as wear of the seats occurs, the ball and seats are continuously pressed together. Another arrangement is shown in Figure 11B, where the springs are mounted in back of the seats. Designs that contain springs should not be used in highly corrosive services unless the spring material has been evaluated and judged suitable for the service. Also, the ability of the spring material to withstand the high temperature of a fire is questionable and makes this design type less suitable for fire safe designs. Soft-Seat (Nonmetallic Seat Ring) – The nonmetallic seat ring is fabricated from an elastomeric material, such as Teflon. The ring may be held firmly against the ball by an insert that is screwed into the end port, or it may be installed in a recess in the valve body and held in place by the clamping force between the three parts of the valve.

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Any of these designs are acceptable for use in utility services. However, for a fire safe design, a secondary metal-to-metal seating arrangement is required to limit leakage in the event that the soft-seat material is lost during a fire. This is accomplished by including a metal retention lip on the valve body or insert as shown in Figures 11A. Upon loss of the soft seat, the line pressure forces the ball against this metal retention lip (secondary seat) to effect a tight closure. Ball Supports There are two basic designs for supporting the ball within the valve body: the seat-supported, and the trunnion-supported designs. In the seat-supported design, the ball is supported by the seat rings. In the trunnion design, the ball is supported by a trunnion that is attached to the bottom of the ball. The trunnion fits into a recess in the bottom of the valve body where it is supported and guided when the ball is rotated. Plug Valve Plug valves usually function as block valves to fully shut off or fully open flow. They are well suited for conditions where quick on/off and/or bubble-tight shutoff are required. Most plug valve styles are available in the full range of pipe sizes and materials that are needed in process plant applications. Soft-sealed styles with full cylindrical plugs are suitable for double-block and bleed applications. The soft-seal-types, however, may have lower temperature/pressure ratings than those given in ASME/ANSI B16.34 for steel valves, because of the lesser physical properties of the soft-seat materials. Soft-seal plug valves are not normally used for throttling service, since the soft seals are subject to erosion or distortion/displacement caused by fluid flow when the valve is not in the fully open or closed position. A plug valve is a good choice as a block valve when used within the limitations noted above, and when bubble-tight shutoff or quick on/off operation is required.

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Figure 12. Multi-Segment Plug Valve Function The plug valve utilizes a cylindrical and usually tapered plug to provide quarter-turn operation from fully open to fully closed. A hole is provided through one axis of the plug, connecting the inlet and outlet ports of the valve body for straight-through flow when in the open position, and completely blocking flow when rotated 90° to the closed position. In the closed position, tight shutoff is obtained either by sealant injected into the plug/body cavity interface, or by resilient, seat-to-metal seat-sealing contact (as in a soft-seated ball valve).

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Major Plug Valve Types and Components The following describes some major plug valve components and types that directly influence function or differentiate plug valves from other valves. Refer to Figure 12. Types There are three basic plug valve-types: the lubricated, nonlubricated, and soft-sealed fire safe. Nonlubricated, nonfire safe plug valves have few applications in process plants and will not be discussed. Lubricated Plug Valve – A lubricated plug valve depends on injection of a sealant to prevent leakage around the plug through the interface between the plug and the body cavity. The sealant is injected through a pressure fitting into the body cavity and distributed across all seating surfaces via grooves in the plug. The sealant material must be compatible with the process fluid, resist breakdown at maximum design temperature, and retain its fluidity and lubricating properties at minimum design temperature. Lubricated plug valves can provide good long-term performance if adequate maintenance attention can be ensured. With its substantial secondary metal-to-metal seating and capacity for restoring tight shutoff by sealant injection, this valve-type is inherently fire safe with respect to through-leakage. However, appropriate high-temperature stem packings, gaskets, and supplementary seals must be provided to ensure fire safe integrity against external leakage. Soft-Sealed, Fire safe Plug Valve – Fire safe plug valves use a narrow-band primary-seal ring of a soft, resilient material (such as Teflon) in the annulus between the plug and body cavity to prevent leakage. A fire safe soft-sealed plug valve also has a secondary metal-to-metal backup seal. This assures positive shutoff capability if the soft seal is damaged by fire. The maximum temperature limit of the valve is limited by the softseal material.

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Body Plug valves are typically of the one-piece body design, with top or bottom entry. Body styles include the short pattern, regular (reduced-port) pattern, venturi pattern, and the round-port fullbore pattern. The short pattern design has the same face-to-face dimensions as Classes 150 and 300 flanged steel gate valves. This pattern is advantageous when replacing existing gate valves or when there are space restrictions. Regular pattern (reduced-port) designs have a smaller plug-port area than do full-bore valves, are less expensive, and represent the most commonly available style. They may be used in cases where pressure drop is not critical and the service application does not require scraping or rodding. Venturi-pattern designs provide maximum weight and cost savings, because they have the smallest port area for a given nominal valve size. Their use restrictions are the same as for regular pattern valves. The round-port full-bore pattern is the most expensive for a given nominal size, but is required where pressure drop is critical or where scraping or rodding will be required. Plug Styles and Seating Mechanisms The plug opens or closes the flow path through the valve. A full- or reduced-bore hole through one axis of the plug permits straight-through flow when aligned with the longitudinal valve axis and flow is blocked when the plug is rotated 90° to the closed position. Common plug configurations are the full cylindrical (usually tapered), and eccentric-cylindrical segment styles. The most common style is the full-cylindrical tapered plug, with sealant grooves for the lubricated-type valve or resilient-seat inserts for the soft-seal-type valve. This configuration is best suited to the constant wedge- seating mechanism used with lubricated plugs and to the lift-off, turn and reseat design used for some nonlubricated types.

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In the lift-off turn and reseat plug design, as the hand wheel is rotated from the fully open or fully closed position, the stem guide arrangement causes the plug to rise slightly out of the body seat taper, rotate 90°, then reseat with a final downward thrust. This feature minimizes operating torque and seat wear, since there is no contact with the body seats during plug rotation, and the plug/body seating surfaces are shielded from the process fluid for both the open and closed positions. Another plug style is the eccentric-mounted cylindrical segment. The metal plug is equipped with resilient-seat inserts or a full resilient facing for bubble-tight shutoff, or is all metal faced for high-temperature applications where tight shutoff is not required. The eccentric mounting of the plug causes a radial thrust into the seats when the plug is rotated to the closed position. This affords tight shutoff by seat compression but avoids the frictional seat wear that accompanies plug rotation when plugs and body seats are mounted concentrically. This plug style may not be used in double block and bleed applications, since there is only a single (downstream) sealing face. Plug Support There are two basic methods of plug support: floating (or seat) support, and trunnion support. These are analogous to the support designs that are used in ball valves. Seats The degree of closure afforded by a plug valve depends on the sealing capability of the plug and body seats. Where tight closure is required, lubricated or soft-seal fire safe plug valves may be used within the temperature limits of the lubricant or soft-seal material. For lubricated plug valves, the sealant provides the seal. The second style uses metal seats with resilient inserts, required for fire safe applications. Sealant Seating (Lubricated Plugs) – For lubricated plug valves, the sealant is the sealing mechanism as well as the lubricant for the metal-to-metal seating interfaces. Bubble-tight shutoff can be obtained when sealant is initially injected. However, sealant pressure will dissipate with time via slow

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leakage through the seating interface and periodic sealant injection is required to maintain tight shutoff, particularly at higher temperatures. The sealant must be chemically compatible with the process fluid and have appropriate viscosity for the intended operating temperature. Combined Soft-Seal and Metal-to-Metal Seating, Fire safe Design – The usual configuration for this seal-type is the inclusion of a resilient material, such as Teflon or Viton, in a retaining groove that is machined in the valve plug. The softseal material must be chemically compatible with the process fluid and adequate for the maximum design temperature. Teflon is inert to most process fluids and has a maximum temperature limit of 232°C (450°F). Viton is more resilient than Teflon, but is less resistant to some process fluids and has a 204°C (400°F) temperature limit. Other resilient seals are available, but their temperature limits are generally lower. This seal-type is suitable for fire safe service applications, due to its back-up metal-tometal seating in the case of fire damage to the soft seals. However, a fire safe design must also incorporate appropriate stem seals, cover gaskets, and cover bolting materials to minimize external leakage, as well.

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SELECTING THE TYPE AND SIZE OF A VALVE THAT IS SUITABLE FOR PROCESS APPLICATIONS Selecting the appropriate valve depends on the fluid in a piping system, the system's design conditions, the service application, the functions and types of valves (as discussed earlier in this module), and the applicable SAES and SAMSS requirements. Other considerations for selecting valves are discussed in further detail in this section. SAES-L-008 and the 04-SAMSS-series provide requirements and limitations for valve selection. The valve selection procedure, as described below and summarized in Work Aid 1, is a guide for selecting the appropriate valve for the three primary functions discussed earlier. However, it is important to understand that selecting valves may simply be a matter of duplicating valves from a system that has provided good performance. Similarly, good experience with a particular valve model in one service often justifies using the same model elsewhere in an essentially identical service.

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Step 1:

List the Data Required Basic piping system design and valve application data are required before a valve can be selected. Data Required

1.

Where to Find Data

Fluid service. (Such as steam, crude oil)

Design Specifications.

2.

Valve function. (Block, throttling)

By knowledge of function desired.

3.

Design temperature and pressure.

Design Specifications.

4.

Material and corrosion allowance.

Design Specifications, SAES-L-008.

5.

Application. (Such as isolation, product segregation)

By knowledge of function desired.

6.

Special features desired. (Such as quick on/off, bubble-tight shutoff).

Design Specifications; process engineer, operating experience.

7.

Size.

Design Specifications.

Refer to service categories summarized in SAES-L-008.

Review of the data that is collected will begin to narrow the choices of potentially suitable valves. For example, if a block valve is needed, all the check valve-types are immediately eliminated from consideration. Valve Sizing In most cases, valve size is identical to pipe size. In some cases, a valve must be larger than the pipe in order to pass the required flow-rate due to pressure drop across the particular valve-type being used. In other cases, it might be advantageous for a valve to be smaller for economic reasons. When fluid is flowing steadily in a long, straight pipe of uniform diameter, the flow pattern assumes a certain characteristic form. Any disruption, such as due to friction, will cause a drop in pressure. Valves also disrupt the flow pattern and, therefore,

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cause a pressure drop in the piping system. The loss of pressure produced by a valve consists of: •

The pressure drop within the valve itself.

•

The pressure drop in the upstream and downstream piping that exceeds what would normally occur if there was no valve in the line.

Equations are used to calculate the pressure drop across a valve, based on the flow characteristics of the particular valvetype. It must be determined whether the pressure drop is acceptable for the process design requirements. Since the pressure drop caused by valves can affect the size of the valve, it can also influence the selection of one valve-type over another, since different valve-types have different pressure-drop characteristics. It is also normally the process design engineer who determines whether the system pressure drop is acceptable. Further discussion of pressure drop across valves is beyond the scope of this course.

Step 2:

Identify Suitable Valve-Types and Components Based on the required valve function and other applicable data, numerous valve-types may be suitable for a particular service. The previous section on valve-types discussed the suitability of valve-types for particular functions. A chart included in Work Aid 1 matches valve functions with suitable types. This information is then combined to develop a list of the valve types suitable for the application. At this point in the process, there may still be multiple candidates, in which case the following should be considered: •

A gate valve will be used for most block valve applications.

•

A globe valve will be used for most throttling applications.

•

A swing check valve will be used for most flow-reversal prevention applications.

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Step 3:

Determine Valve-Type Limitations for Suitable Valves through Saudi Aramco Engineering Standard SAES-L-008, Selection of Valves Saudi Aramco Engineering Standard SAES-L-008, Selection of Valves, provides limitations on the use of specific valve-types for particular applications. It also contains materials requirements for the valve body, trim and packing. SAES-L-008 discusses: •

The limitations on the selection of all valves normally classified under the 04-SAMSS-series. Where applicable, this standard supplements the requirements of the ASME/ANSI B31 Codes for pressure piping.

•

General design limitations for major valve components. These include: Bonnets − Pressure-seal bonnets shall only be used in steam or other clean, noncorrosive services. A pressure-seal bonnet valve relies on a metal-to-metal seal to prevent external leakage at the bonnet. Corrosive- or highfouling-type services could affect the long-term reliability of this metal-to-metal seal. − Welded bonnet valves are limited to a 50 mm (2 in.) maximum size. They are generally also not permitted in wet, sour service except where severe vibration is expected. A welded bonnet valve does not permit easy internal access. Therefore, their use is limited to low-cost valves (i.e., small size) where they will be discarded rather than maintained. They are generally not used in wet, sour service since a higher degree of maintenance could be expected. − Screwed bonnet or body valves must have a locking pin or be tack-welded to the valve body for all hydrocarbon or hazardous services. The concern here is that the threaded joint may become loose and leak during operation.

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− Union bonnet valves are not permitted in any hydrocarbon or hazardous services. Here again, the concern is that the connection may loosen and leak during operation. End Connections − Valve end connection requirements and limitations are generally identical to those of other pipe and fittings, as specified in SAES-L-010. − If valves have soft seats, and have either threaded ends with seal welds or are socket-welded, the soft seats must be removed before welding or the valves supplied with factory-installed nipples. The concern here is that if field welding is done too close to the valve seats, the welding heat will damage the seats. Ratings − The ratings for soft-seated valves must be suitable for the design conditions and consider any limitations of the softseat material. The maximum permitted temperature for a soft-seat-type valve is typically in the range 93-232°C (200-450°F), depending on the soft-seat material used. − In hydrocarbon services, the minimum rating for threaded- and socket-welded-type valves 50 mm (2 in.) NPS and smaller in size must be Class 800 per API 602. This ensures a basic strength in these small valves to withstand mechanical or physical abuse, not just the design pressure/temperature. Stem Packing − Isolation valves 75 mm (3 in.) NPS and larger in hydrocarbon services shall not have stem packing or seals that are pure polymer or elastomer, unless the valves are qualified as being firesafe. The concern here is that in the event of a fire in the vicinity, these packing materials would be destroyed and significant leakage from the packing gland would make the fire worse. Stems − Inside screw/rising stem (ISRS) and nonrising-stem (NRS) valves 38 mm (1 1/2 in.) NPS and smaller shall not be used in corrosive hydrocarbon services. The

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concern here is that the stem threads could corrode and thus hinder valve movement. •

Specific valve-type limitations. These include: Ball Valves − Stems must be blowout-proof. This is required to permit loosening the packing gland and repacking the valve while the system is under pressure. − Welded-body-type ball valves cannot be used in services where damage to the soft seats during commissioning and/or operation cannot be avoided and must be anticipated. Internal maintenance on this valve-type is difficult, since the valve body must be cut open for access. Therefore, it should not be used where seat damage can be anticipated. Butterfly Valves − Concentric butterfly valves are permitted only in nonhydrocarbon, noncritical applications. Such a valve design cannot have firesafe capability, so it could not be used as a block valve for other than these services. − High-performance butterfly valves in hydrocarbon service are limited to ASME/ANSI Class 300. They must meet API 609, Lug- And Wafer-Type Butterfly Valves, and have an offset-seat construction, be firesafe, generally have a full-lug design, and not have a preferred flow direction. These requirements permit using this potentially lower-cost valve option for the lower ANSI Classes, while ensuring a high-quality valve is obtained (API 609 and firesafe), and that it will seal against flow from either direction. Check Valves − Dual- and single-plate wafer check valves shall not be used in pulsating services, such as in reciprocating pump or compressor systems. The concern here is that the pressure pulsations will cause the valve discs to continually open and shut, and lead to eventual fatigue failure of the closure springs or plates. − Nonslam-type check valves must be installed in the discharge lines of pumps or compressors that are installed in parallel. In such an arrangement, the

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equipment is spared and will be periodically switched in operation. This will lead to a flow-reversal situation which is part of normal operation, rather than being an upset. Thus a nonslam-type check valve (i.e., one without spring-assisted closure) would be less prone to disk failure resulting from repeated operation. •

Specific service limitations. These include: Low-temperature Service − The requirements of Saudi Aramco Material System Specification 04-SAMSS-003, Additional Requirements for Low-Temperature Valves, must be met for services between -45 and 0°C (-50 and 32°F). These requirements are meant to prevent brittle fracture of the valve body. − Valves for services less than -45°C (-50°F) must be austenitic stainless steel and meet 04-SAMSS-003. Again, this is for brittle fracture prevention. − All valves in services below -100°C (-150°F) must have extended bonnets. An extended bonnet valve is equipped with bonnet/stem extensions, with the packing gland located at the top. This provides an insulating gas column to moderate the temperature in the packing gland region. This avoids excessive packing shrinkage and iceup around the stem, which can cause external leakage or valve cycling problems, respectively. Underwater Valves − Isolation valves must be ball-type per 04-SAMSS-051, Ball Valves, and have a minimum rating of ASME/ANSI Class 300. The quick-shutoff capability of a ball valve is desirable in underwater applications. The Class 300 provides a minimum degree of mechanical strength for use in underwater applications, even if Class 150 would be sufficient based on pressure/temperature considerations alone. Isolation Services − Only gate, ball, or plug valves may be used as isolation valves in pressure-relief valve inlet and discharge piping, flare systems, or for emergency isolation. These are critical, plant safety-related applications, and these valvetypes are felt to be the most reliable.

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− Gate valves used around pressure-relief valves or in flare systems must be installed with the stem installed either horizontal or sloping down, away from the valve. These valves will normally be full-open when the unit is in operation to permit unimpeded flow through the safety systems. It is essential from a safety standpoint that these lines remain unobstructed. Mounting gate valves as specified ensures that the flow passage will remain open if the stem fails. If gate valves are mounted otherwise, a stem failure could permit the gate to fall shut, thus blocking the safety-relief path. This concern does not exist for either ball or plug valves, since a stem failure would not cause movement of their closure components. − Soft-seated emergency isolation valves are to be certified firesafe in accordance with specified industry standards. Isolation valves are often needed to segregate sections of a plant during a fire, so they must be able to perform this function even if the soft seat is damaged. − Emergency shutdown (ESD) valves must be ball valves with a suitable power actuator. These valves must fully close in the shortest possible time, thus leading to the use of ball valves. − Flangeless valves shall not be used as the first block valve against storage tanks or vessels that contain hazardous materials. A flangeless valve is mounted between two pipe flanges, with gaskets on each side of the valve and long studs that span the flanges and valve. This results in two, gasketed joints being held tight by one set of studs. The concern with such a valve in the stated applications is in a fire situation. Thermal expansion of the long studs due to the heat of a fire could cause the gasketed joints to loosen and significant external leakage to occur. Thus the closed block valve would be ineffective in keeping the large volume of hazardous material from adding to the emergency. •

Materials limitations. These include: − Valves with bodies of cast or ductile iron, or low meltingpoint alloys such as brass or bronze, shall not be used in hydrocarbon services. In the event of a fire in the vicinity, valves made of these relatively low-strength materials could easily fail and add more fuel to the fire.

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− Valves with either steel or ductile iron bodies must be used in several specified applications. However ductile iron still cannot be used in hydrocarbon services, as previously stated. The specified applications are: + The first valve on all tanks and vessels if valve failure could result in personnel or fire hazard, or a large monetary loss. + Isolation valves on main utility lines entering a plant area, where the operating and shut-off valves are cast iron or nonferrous construction. + In hazardous areas where it is essential that the valve do not fail in a fire, as in aboveground firewater-system block valves. The valve applications identified are critical from a safety standpoint. Therefore, these requirements ensure that lowstrength body materials are not permitted. − Minimum valve material requirements are specified based on fluid service. Asbestos gaskets and packing are not to be used whenever there is a technically acceptable nonasbestos product available. SAES-L-008 also provides tables that provide service and application requirements. •

Table I, Service and Application Requirements, Valve Body and Trim Material, must be referred to for all valve applications. It specifies acceptable valve body and trim materials based on the fluid environment, concentration, and design temperature. The main focus of this table is gate valves, but its requirements are also to be applied to other valve-types as applicable.

•

Table II, Alternate Stem and Spring Materials, provides acceptable alternatives for situations in which a different material from the trim specified in Table I is desirable for a valve stem or spring. This might be necessary for fabrication, availability, or cost reasons.

•

Table III, Service & Application Requirements, Plastic/Elastomeric Components, must be referred to for soft-seated-type valves. It specifies acceptable materials for nonmetallic valve components based on the fluid environment.

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Step 4:

•

Table IV, Metallic Materials Designations, defines the abbreviations that are used in the standard.

•

Table V, Packings, must be used to specify packing material based on fluid service and design temperature.

•

Table VI, Gaskets, must be used to specify valve-bonnet gaskets. This table is used in conjunction with Tables I, III, and V, and the gasket-type being used for piping.

Finalize Valve Selection by Considering Other Factors When two or more valves are found to be suitable for a specific service, several additional factors must be evaluated before making the final selection.

Standardization There may be strong preferences for certain valve types for particular applications or at certain sites. This information can be found in the piping specifications, material inventory, maintenance department office, or purchasing department notes. Inventory Certain valves may be available, avoiding the need for new purchases. Experience Good or bad experience with certain valve-types in similar situations may influence the final selection. Data may be available from operations or maintenance departments.

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Cost Sometimes two valves can be suitable, but one may be less expensive. Data should be obtained from a cost estimating manual, vendors, or the purchasing department. Delivery Time Valves of large size, alloy, or high-pressure class may have a delivery time of six months to two years. This should be checked if there is a possibility of hampering project completion. Materials Substitution of a different but acceptable material may permit cost or delivery time credits. SAES-L-008 and the 04-SAMSSseries provide material requirements. Dimensions Replacement valves should have the same face-to-face dimensions as the original valves. After evaluating all the criteria, it may be found that none of the valve types being considered is ideal. At this point, consideration must be given to using less stringent criteria. For example, can a higher cost be justified to gain greater service reliability?

Step 5:

Provide a Full Description A full description of a valve-type requires the engineer to specify additional information, as summarized in Work Aid 1. The 04SAMSS-series provides additional design requirements for specific valve-types. These include: •

References to appropriate industry standards and other Saudi Aramco requirements.

•

Modifications to industry standards to make a valve suitable for Saudi Aramco applications.

•

Specific design, materials, testing, inspection, marking, and shipping requirements that are appropriate for Saudi Aramco applications. These typically go beyond what is already

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specified in an industry standard, make selections where options are available, or provide coverage where none is available and Saudi Aramco does not wish to accept the valve manufacturer's standard design. The following summarizes the SAMSS's that relate to valves: •

04-SAMSS-001 - Gate Valves.

•

04-SAMSS-002 - Globe Valves.

•

04-SAMSS-003 - Additional Requirements for LowTemperature Valves.

•

04-SAMSS-005 - Check Valves, Swing-Type.

•

04-SAMSS-035 - General Requirements for Valves.

•

04-SAMSS-041 - Expanding Plug Valve.

•

04-SAMSS-042 - 4-Way Diverter Valve.

•

04-SAMSS-048 - Valve Inspection and Testing Requirements.

•

04-SAMSS-049 - Inspection and Testing Requirements for API 6A 10,000 psi Valves.

•

04-SAMSS-050 - Gate Valves, Through-Conduit-Type, API 6D.

•

04-SAMSS-051 - Ball Valves, API 6D.

•

04-SAMSS-052 - Ball Valves, API 6A.

Note that several of the valve-types that are included in the listed SAMSS's were not discussed. These are beyond the scope of this course. It should also be noted that 04-SAMSS003 applies to all valves with a minimum design temperature between 0°C and -46°C (32°F and -50°F) regardless of type and 04-SAMSS-035 and 04-SAMSS-048 applies to all valve types. Thus, they should also be included in the valve purchase order.

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Since the requirements of 04-SAMSS-035 apply to all valves, several items contained within it are highlighted below: •

The valve vendor must submit detailed drawings for Saudi Aramco review and approval.

•

For drains, vents, and other body fittings:

•

Threaded and socket-welded connections are limited to a maximum of 38 mm (1 1/2 in.) NPS. − The minimum body rating is to be Class 800 per API 602.

•

Buried double-block and bleed valves are to have their vent and drain connections, and any supplied sealant injection fittings, extended aboveground in accordance with specified requirements.

•

Material requirements are specified for carbon steel buttwelding end valves, hard facing material, austenitic stainless steel valves, and bonnet or packing gland bolting.

•

Plating requirements are specified.

•

Bolting requirements are specified.

•

Valve operator and actuator requirements are specified.

•

Quality assurance, painting and coating, preparation for shipment, and marking requirements are specified.

The 04-SAMSS-series of valve specifications generally reference industry valve standards to use as base design documents where such standards exist for particular valvetypes. There are also industry standards for valve-types for which there are no 04-SAMSS specifications. Table 1 summarizes the currently available industry standards for valves, and the general extent of their coverage. It should again be noted that Saudi Aramco has computerized the SAMSS’s requirements, as discussed in MEX 101.02. Therefore, once a particular valve-type has been selected, a complete purchase description can be obtained, along with acceptable vendors and a Saudi Aramco stock number.

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Table 1. Information on Valve Sizes, Ratings and Standards VALVE TYPE

BODY MATERIAL

APPLICABLE VALVE STANDARD & SIZE (6)

SIZE (1) AVAIL, in.

RECOM SIZE LIMIT

RATING AVAILABLE

Gate

Steel

API 600,1-24

1-24

≥2

150-2500

Gate

Steel

API 602,1/4 -4

1/4-2