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1、 MSS SP-120-2006 www.mss-hq.org Standard Practice Developed and Approved by the Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. 127 Park Street, NE Vienna, Virginia 22180 (703) 281-6613 Email: infomss-hq.org Flexible Graphite Packing System for Rising Stem Steel Valves
2、 - Design Requirements MSS Copyright MSS Provided by IHS under license with MSS Not for ResaleNo reproduction or networking permitted without license from IHS MSSSTANDARD PRACTICESP-120 i This MSS Standard Practice was developed under the consensus of the MSS Technical Committee 308 and the MSS Coor
3、dinating Committee. The content of this Standard Practice is the result of the efforts of competent and concerned volunteers to provide an effective, clear, and non-exclusive specification that will benefit the industry as a whole. This MSS Standard Practice is intended as a basis for common practic
4、e by the manufacture, the user, and the general public. The existence of an MSS Standard Practice does not in itself preclude the manufacture, sale, or use of products not conforming to the Standard Practice. Mandatory conformance is established only by reference in a code, specification, sales cont
5、ract, or public law, as applicable. U.S. customary units in this SP are the standard; metric (SI) units are for reference only. Unless otherwise specifically noted in this MSS SP, any standard referred to herein is identified by the date of issue that was applicable to the referenced standard(s) at
6、the date of issue of this MSS SP. (See Annex A). Any part of this standard may be quoted. Credit lines should read Extracted from MSS SP-120, 2006, with permission of the publisher, the Manufacturers Standardization Society. Reproduction prohibited under copyright convention unless written permissio
7、n is granted by the Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. Originally Approved March 1997 Copyright 1997 by Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. Printed in U.S.A. Copyright MSS Provided by IHS under license with MSS No
8、t for ResaleNo reproduction or networking permitted without license from IHS MSSSTANDARD PRACTICESP-120 ii FOREWORD This Standard Practice was developed by a cooperative effort of representatives of valve and packing manufacturers. This Standard Practice is intended primarily to be an aid for the ma
9、nufacture and procurement of packing systems with design features for rising-stem steel valves that utilize flexible graphite packing. However, this does not preclude the use of these system features for other types of packing systems since this Standard Practice represents the consensus input from
10、a broad spectrum of industry applications. This Standard Practice shall not be construed to be effective for all pressures and types of services expected of ASME B16.34 valves. Special service applications such as low fugitive emissions control or toxic fluid may require additional or different desi
11、gn measures that are outside the scope of this Standard Practice. Copyright MSS Provided by IHS under license with MSS Not for ResaleNo reproduction or networking permitted without license from IHS MSSSTANDARD PRACTICESP-120 iii TABLE OF CONTENTS SECTION PAGE 1 SCOPE. 1 2 DEFINITIONS 1 3 PACKING ASS
12、EMBLY. 1 4 STEM 2 5 PACKING GLAND . 2 6 PACKING CHAMBER 2 7 PACKING WASHER OR VALVE BONNET 2 TABLE 1 Packing System Details (U.S. Units) 3 2 Packing System Details (Metric Units) 4 FIGURE 1 Packing System Details (U.S. Units). 3 2 Packing System Details (Metric Units) . 4 3 Stem/Bonnet Details (U.S.
13、 Units) . 5 4 Stem/Bonnet Details (Metric Units) . 6 5 Geometric Symbols Definitions . 7 ANNEX A Referenced Standards and Applicable Dates 8 Copyright MSS Provided by IHS under license with MSS Not for ResaleNo reproduction or networking permitted without license from IHS MSSSTANDARD PRACTICESP-120
14、1 FLEXIBLE GRAPHITE PACKING SYSTEM FOR RISING STEM STEEL VALVES - DESIGN REQUIREMENTS 1. SCOPE (1) 1.1 This Standard Practice establishes material and dimensional requirements for valve packing, packing chamber, packing gland, packing washer, bonnet, and stem as they relate to the total packing asse
15、mbly. 1.2 This Standard Practice applies to standard, special, and limited Class 150 through Class 4500 (including intermediate classes) ASME B16.34 type steel gate, globe, and angle valves designed with rotating/ rising and non-rotating/rising stems. 1.3 This Standard Practice applies to valves in
16、which a flexible graphite packing assembly is used as the primary stem-sealing system. 1.4 This Standard Practice does not apply to valves that include a lantern ring as part of its packing system nor to bonnetless valves with split glands. 2. DEFINITIONS 2.1 See MSS SP-96 for definitions of terms u
17、sed in this Standard Practice. 2.2 See Figure 5 for definitions of symbols used in this Standard Practice. 3. PACKING ASSEMBLY 3.1 The packing shall be composed of center and end rings or a cylinder of flexible graphite and end rings. A flexible graphite packing assembly that is NOTE: (1) This Stand
18、ard Practice is not intended to apply to valves developed for and predominantly used in instrument piping systems. (See MSS SP-99 and MSS SP-105) constructed with a braided carbon or braided graphite or metal-mesh that reinforces the flexible graphite may not require end rings. The end rings shall s
19、erve as wipers and anti-extrusion devices to keep the flexible graphite in the packing chamber during operation, including stroking, of the valve. Individual center rings may contain up to 2 splits per ring to facilitate valve packing installation. Braided end rings shall contain a maximum of 1 spli
20、t per ring and molded end rings shall contain a maximum of 2 splits per ring. The end ring properties shall be designed to deter the extrusion and/or erosion of the center flexible graphite rings during valve operation. Packing assemblies of flexible graphite without end rings may be used; however,
21、the diametrical clearance specified in Table 1 and Table 2 shall be reduced to a maximum of 50% of that required for higher than Class 300 valves. The packing shall also be qualified to the requirements of MSS SP-121. 3.2 The packing assembly shall contain a dispersed passive corrosion-inhibitor, a
22、dispersed embedded active corrosion-inhibitor, or a suitable combination of inhibitors, to minimize stem pitting caused by the galvanic corrosion phenomenon set up in a wet valve packing-chamber. Inhibitors in end rings are optional, unless otherwise specified by the purchaser. 3.3 The pre-installed
23、 density and dimensions of the flexible graphite packing shall be at the valve manufacturers option. The final adjusted density and dimensions of the packing assembly shall be capable of sealing with no visible leakage when the valve is tested at a pressure equal to the valves 100F pressure rating a
24、t ambient conditions. The as-shipped remaining packing and packing gland adjustment (packing gland tight) shall be greater than 10% of the minimum depth of the packing chamber listed in Table 1 and Table 2. Copyright MSS Provided by IHS under license with MSS Not for ResaleNo reproduction or network
25、ing permitted without license from IHS MSSSTANDARD PRACTICESP-120 2 6. PACKING CHAMBER 6.1 The dimensional tolerance of the packing chamber shall be such that the maximum diametrical clearance between gland or follower and the packing chamber (“A“) illustrated in Table 1 and Table 2 is not exceeded.
26、 The packing depth 4W or 5W illustrated in Table 1 and Table 2 refers to the equivalent of 4 or 5 square rings of packing which includes the top and bottom end rings. The packing chamber inside diameter surface finish shall be 125 Ra (microinch) (3.2 micrometers) or smoother, as illustrated in Figur
27、e 1 and Figure 2. A chamfer or radius may be used at the entrance of the packing chamber. 6.2 The packing chamber bore shall meet squareness to the bonnet gasket surface or other appropriate datum surface encompassed in a perpendicularity tolerance of 0.006“ (0.15mm) regardless of bore size, (see Fi
28、gures 3 and 4). 6.3 The packing chamber bore shall meet circularity, taper, and straightness requirements encompassed in a cylindricity tolerance of 0.006“ (0.15mm), (see Figures 3 and 4). 6.4 The packing chamber bore and bonnet stem hole shall be concentric within a positional tolerance of 0.005“ (
29、0.13mm) as presented in Figures 3 and 4. 6.5 The packing chamber bore shall be free of scratches, pits, or voids deeper than 0.006“ (0.015mm). 7. PACKING WASHER OR VALVE BONNET 7.1 The tolerance on the valve bonnet or the packing washer, when a packing washer is used, shall be such that the maximum
30、diametrical clearance between the stem and the bonnet or packing washer (“C“), illustrated in Table 1 and Table 2, is not exceeded. 3.4 The dimensional requirements of the packing assembly shall be per Table 1 and Table 2. The minimum width “W“ and minimum depth “L“ are listed. 3.5 Smaller packing w
31、idths (“W“) and/or smaller depths (“L“) may be used when qualified to the requirements of MSS SP-121. All other provisions of the Standard Practice shall apply. 4. STEM 4.1 The dimensional tolerances (bilateral or unilateral) shall be per Table 1 and Table 2. The stem finish shall be 32 Ra (microinc
32、h) (0.80 micrometers) or smoother. These stem characteristics shall apply in the area that contacts the packing during the full stroking of the valve. The stem diameter tolerance as shown in Table 1 and Table 2 applies to the stem diameter that contacts the packing I.D. 4.2 The stem diameter toleran
33、ce shall be such that the maximum diametrical clearance between the packing gland or follower I.D. (“B“) and bonnet or packing washer (“C“) as required in Table 1 and Table 2 is not exceeded. 4.3 The stem diameter that contacts the packing during the full stroking of the valve shall meet circularity
34、, taper, and straightness requirements encompassed in a cylindricity tolerance of 0.003“ (0.08mm) for 3“ and smaller stems and 0.004“ (0.10mm) for stems larger than 3“ (see Figures 3 and 4). 4.4 The stem surface that contacts the packing during full stroking of the valve shall be free of scratches,
35、pits, or voids deeper than 0.002“ (0.05mm). 5. PACKING GLAND 5.1 The dimensional tolerances of the gland or follower I.D. and O.D. shall be such that the maximum diametrical clearance between the stem and gland or follower (“B“) and packing chamber bore and gland or follower (“A“) illustrated in Tab
36、le 1 and Table 2 are not exceeded. Copyright MSS Provided by IHS under license with MSS Not for ResaleNo reproduction or networking permitted without license from IHS MSSSTANDARD PRACTICESP-120 3 FIGURE 1 Packing System Details (U.S. Units) (Illustrative Only) TABLE 1 Packing System Details (U.S. Un
37、its) NOTE, DIMENSIONS ARE IN INCHES WIDTH & DEPTH OF PACKING DIAMETRICAL CLEARANCE - MAXIMUM STEM SIZE STEM DIAMETER TOL. #1 - MAXIMUM PACKING CHAMBER I.D. TOL. #2 - MAXIMUM W MINIMUM L MINIMUM A (1) B (1) C (1) 1/4” thru 1/2” 0.008 0.010 1/84W.020.040.040 1/2” thru 11/16 0.008 0.010 3/164W.020.040.
38、040 11/16” thru 1 1/4” 0.008 0.010 1/44W.025.050.050 1 1/4” thru 2” 0.009 0.010 5/165W.025.050.050 2” thru 3” 0.011 0.010 3/85W.025.050.050 3” thru 3 1/2” 0.011 0.015 7/165W.030.065.065 3 1/2” thru 4 1/4” 0.011 0.015 1/25W.030.065.065 4 1/4” thru 5” 0.011 0.015 9/165W.030.065.065 5” thru 7” 0.011 0.
39、015 5/85W.030.065.065 General Note: Dimensions are in inches Note (1) The manufacturer may need to revise diametrical clearances for severe services and/or high pressure applications. Copyright MSS Provided by IHS under license with MSS Not for ResaleNo reproduction or networking permitted without l
40、icense from IHS MSSSTANDARD PRACTICESP-120 4 MSSSTANDARD PRACTICESP-120 FIGURE 2 Packing System Details (Metric Units) (Illustrative Only) FIGURE 2 Packing System Details (Metric Units) (Illustrative Only) TABLE 2 Packing System Details (Metric Units)TABLE 2 Packing System Details (Metric Units) NOT
41、E : DIMENSIONS ARE IN MILLIMETERS NOTE : DIMENSIONS ARE IN MILLIMETERS WIDTH & DEPTH OF PACKING WIDTH & DEPTH OF PACKING DIAMETRICAL CLEARANCE - MAXIMUM DIAMETRICAL CLEARANCE - MAXIMUM STEM SIZE STEM SIZE STEM DIAMETER TOL. #1 - MAXIMUM STEM DIAMETER TOL. #1 - MAXIMUM PACKING CHAMBER I.D. TOL. #2 -
42、MAXIMUM PACKING CHAMBER I.D. TOL. #2 - MAXIMUM W MINIMUM W MINIMUM L MINIMUM L MINIMUM A (1) B (1) C (1) 6.4 thru 12.7 6.4 thru 12.7 0.20 0.20 0.25 0.25 3.2 3.2 4W 4W 0.51 0.51 1.02 1.02 1.02 1.02 12.7 thru 17.5 12.7 thru 17.5 0.20 0.20 0.25 0.25 4.8 4.8 4W 4W 0.51 0.51 1.02 1.02 1.02 1.02 17.5 thru
43、 31.8 17.5 thru 31.8 0.20 0.20 0.25 0.25 6.4 6.4 4W 4W 0.64 0.64 1.27 1.27 1.27 1.27 31.8 thru 50.8 31.8 thru 50.8 0.23 0.23 0.25 0.25 7.9 7.9 5W 5W 0.64 0.64 1.27 1.27 1.27 1.27 50.8 thru 76.2 50.8 thru 76.2 0.23 0.23 0.25 0.25 9.5 9.5 5W 5W 0.64 0.64 1.27 1.27 1.27 1.27 76.2 thru 88.9 76.2 thru 88
44、.9 0.28 0.28 0.38 0.38 11.1 11.1 5W 5W 0.76 0.76 1.65 1.65 1.65 1.65 88.9 thru 108.0 88.9 thru 108.0 0.28 0.28 0.38 0.38 12.7 12.7 5W 5W 0.76 0.76 1.65 1.65 1.65 1.65 108.0 thru 127.0 108.0 thru 127.0 0.28 0.28 0.38 0.38 14.3 14.3 5W 5W 0.76 0.76 1.65 1.65 1.65 1.65 127.0 thru 178.0 127.0 thru 178.0
45、 0.28 0.28 0.38 0.38 15.9 15.9 5W 5W 0.76 0.76 1.65 1.65 1.65 1.65 General Note: Dimensions are in millimeters General Note: Dimensions are in millimeters Note (1) The manufacturer may need to revise diametrical clearances for severe services and/or high pressure applications. Note (1) The manufactu
46、rer may need to revise diametrical clearances for severe services and/or high pressure applications. 4 A (1) B (1) C (1) Copyright MSS Provided by IHS under license with MSS Not for ResaleNo reproduction or networking permitted without license from IHS MSSSTANDARD PRACTICESP-120 5 FIGURE 3 Stem/Bonn
47、et Details (U.S. Units) (Illustrative Only) TYPICAL BONNET TYPICAL STEM Copyright MSS Provided by IHS under license with MSS Not for ResaleNo reproduction or networking permitted without license from IHS MSSSTANDARD PRACTICESP-120 6 FIGURE 4 Stem/Bonnet Details (Metric Units) (Illustrative Only) TYP
48、ICAL BONNET TYPICAL STEM Copyright MSS Provided by IHS under license with MSS Not for ResaleNo reproduction or networking permitted without license from IHS MSSSTANDARD PRACTICESP-120 7 DATUM FEATURE DEF. A Datum Feature is used to designate a Datum Surface or Feature CYLINDRICITY DEF. Cylindricity is a condition of a surface of revolution in which all points of the surface are equidistant from a common axis. POSITION DEF. A Position Tolerance defines a zone within which the axis or center plane of a feature is permitte