1、 MSS SP-120-2011 Flexible Graphite Packing System for Rising Stem Valves Design Requirements Standard Practice Developed and Approved by the Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. 127 Park Street, NE Vienna, Virginia 22180-4602 Phone: (703) 281-6613 Fax: (703)
2、 281-6671 E-mail: infomss-hq.org MSS www.mss-hq.org MSS STANDARD PRACTICE SP-120i This MSS Standard Practice was developed under the consensus of the MSS Technical Committee 308 and the MSS Coordinating Committee. The content of this Standard Practice is the resulting efforts of competent and experi
3、enced volunteers to provide an effective, clear, and non-exclusive standard that will benefit the industry as a whole. This MSS Standard Practice describes minimal requirements and is intended as a basis for common practice by the manufacturer, the user, and the general public. The existence of an M
4、SS Standard Practice does not in itself preclude the manufacture, sale, or use of products not conforming to the Standard Practice. Mandatory conformance to this Standard Practice is established only by reference in other documents such as a code, specification, sales contract, or public law, as app
5、licable. MSS has no power, nor does it undertake, to enforce or certify compliance with this document. Any certification or other statement of compliance with the requirements of this Standard Practice shall not be attributable to MSS and is solely the responsibility of the certifier or maker of the
6、 statement. “Unless indicated otherwise within this MSS Standard Practice, other standards documents referenced to herein are identified by the date of issue that was applicable to this Standard Practice at the date of approval of this MSS Standard Practice (see Annex A). This Standard Practice shal
7、l remain silent on the validity of those other standards of prior or subsequent dates of issue even though applicable provisions may not have changed.” By publication of this Standard Practice, no position is taken with respect to the validity of any potential claim(s) or of any patent rights in con
8、nection therewith. MSS shall not be held responsible for identifying any patent rights. Users are expressly advised that determination of patent rights and the risk of infringement of such rights are entirely their responsibility. In this Standard Practice, all text, notes, annexes, tables, figures,
9、 and references are construed to be essential to the understanding of the message of the standard, and are considered normative unless indicated as “supplemental”. All appendices, if included, that appear in this document are construed as “supplemental”. Note that supplemental information does not i
10、nclude mandatory requirements. U.S. customary units in this Standard Practice are the standard; (SI) metric units are for reference only. Substantive changes in this 2011 edition are “flagged” by parallel bars as shown on the margins of this paragraph. The specific detail of the change may be determ
11、ined by comparing the material flagged with that in the previous edition. Non-toleranced dimensions in this Standard Practice are nominal, and, unless otherwise specified, shall be considered “for reference only”. Excerpts of this Standard Practice may be quoted with permission. Credit lines should
12、read Extracted from MSS SP-120-2011 with permission of the publisher, Manufacturers Standardization Society of the Valve and Fittings Industry. Reproduction and/or electronic transmission or dissemination is prohibited under copyright convention unless written permission is granted by the Manufactur
13、ers Standardization Society of the Valve and Fittings Industry Inc. All rights reserved. Originally Published: March 1997 Current Edition Approved: October 2010 Current Edition Published: October 2011 MSS is a registered trademark of Manufacturers Standardization Society of the Valve and Fittings In
14、dustry, Inc. Copyright 2011 by Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. Printed in U.S.A. MSS STANDARD PRACTICE SP-120ii FOREWORD This Standard Practice was developed by a cooperative effort of representatives of valve and packing manufacturers. This Standard Pr
15、actice is intended primarily to be an aid for the manufacture and procurement of packing systems with design features for rising-stem 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
16、 Practice represents the consensus input from 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
17、 fluid, may require additional or different design measures that are outside the scope of this Standard Practice. MSS STANDARD PRACTICE SP-120iii TABLE OF CONTENTS SECTION PAGE 1 SCOPE 1 2 DEFINITIONS 1 3 PACKING ASSEMBLY 1 4 STEM 2 5 PACKING GLAND 2 6 PACKING CHAMBER 2 7 PACKING WASHER OR VALVE BON
18、NET . 2 TABLE 1 Packing System Details (U.S. Customary Units) 3 2 Packing System Details (SI/Metric Units) 4 FIGURE 1 Packing System Details (U.S. Customary Units) . 3 2 Packing System Details (SI/Metric Units) 4 3 Stem Bonnet Details (U.S. Customary Units) 5 4 Stem Bonnet Details (SI/Metric Units)
19、6 5 Geometric Symbols Definitions 7 ANNEX A Referenced Standards and Applicable Dates . 8 MSS STANDARD PRACTICE SP-1201 1. SCOPE (1)1.1 This Standard Practice establishes material and dimensional requirements for valve packing, packing chamber, packing gland, packing washer, bonnet, and the stem, as
20、 they relate to the total packing assembly. 1.2 This Standard Practice applies to standard, special, and limited Class 150 through Class 4500 (including intermediate classes) ASME B16.34 type gate, globe, and angle valves designed with rotating/rising and non-rotating/rising stems. 1.3 This Standard
21、 Practice applies to valves in 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 S
22、P-96 for definitions of terms used 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 assemb
23、ly that is constructed with a braided carbon or braided graphite or metal-mesh that reinforces the flexible graphite may not require end rings. NOTE: (1) This Standard Practice is not intended to apply to valves developed for and predominantly used in instrument piping systems (see MSS SP-99 and MSS
24、 SP-105). The end rings shall serve 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 two (2) splits per ring to facilitate valve packing installation. Braided end ri
25、ngs shall contain a maximum of one (1) split per ring and molded end rings shall contain a maximum of two (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
26、graphite without end rings may be used; however, 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 co
27、ntain a dispersed passive corrosion-inhibitor, a 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
28、specified by the purchaser. 3.3 The pre-installed 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 pr
29、essure equal to the valves 100 F pressure rating at 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. FLEXIBLE GRAPHITE PACKING SYSTEM FOR RISING
30、 STEM VALVES DESIGN REQUIREMENTS MSS STANDARD PRACTICE SP-1202 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 widths (“W“) and/or smaller depths (“L“) may be used when qualified to
31、 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 (microinch) (0.80 micrometers) or smoother. These stem characteristics shall a
32、pply 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 tolerance shall be such that the maximum diametrical clearance between the p
33、acking 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, taper, and straightness requirements encompassed in a cylindricity
34、tolerance of 0.003“ (0.08mm) for 3 inch and smaller stems and 0.004“ (0.10mm) for stems larger than 3 inches (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, pits, or voids deeper than 0.002“ (0.05mm). 5. PACKING GLAN
35、D 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“), as illustrated in Table 1 and Table 2, are not exceeded. 6. PACKING CHAMBER
36、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. The packing depth 4W or 5W illustrated in Table 1 and Table 2 refers to the equivalent
37、 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 Figure 1 and Figure 2. A chamfer or radius may be used at the entrance of the packing chamb
38、er. 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 Figures 3 and 4). 6.3 The packing chamber bore shall meet circularity, taper, and straig
39、htness 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“ ( 0.13mm) as presented in Figures 3 and 4. 6.5 The packing chamber bore shall be free o
40、f 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 diametrical clearance between the stem and the bonnet or packing washer (“C“), as ill
41、ustrated in Table 1 and Table 2, is not exceeded. MSS STANDARD PRACTICE SP-1203 (For Illustrative Use Only)TABLE 1 Packing System Details (U.S. Customary Units) Stem Size () Stem Diameter Tol. #1 (Maximum) Packing Chamber I.D. Tol. #2 (Maximum) Width ANSI/ASME B16.34-2009 Valves Flanged, Threaded an
42、d Welding End; including Supplement (2010) Y14.5-2009 Dimensioning and Tolerancing MSS SP-96-2011 Guidelines on Terminology for Valves and Fittings SP-99-2010 Instrument Valves SP-105-2010 Instrument Valves for Code Applications SP-121-2006 Qualification Testing Methods for Stem Packing for Rising S
43、tem Steel Valves The following organizations appear in the above list: ANSI American National Standards Institute, Inc. 25 West 43rdStreet, Fourth Floor New York, NY 10036-7406 ASME American Society of Mechanical Engineers (ASME International) Three Park Avenue New York, NY 10016-5990 MSS Manufactur
44、ers Standardization Society of the Valve and Fittings Industry, Inc. 127 Park Street, NE Vienna, VA 22180-4602 Listing of MSS Standard Practices TITLE SP-6-2007 Standard Finishes for Contact Faces of Pipe Flanges and Connecting-End Flanges of Valves and Fittings SP-9-2008 Spot Facing for Bronze, Iro
45、n and Steel Flanges SP-25-2008 Standard Marking System for Valves, Fittings, Flanges, and Unions SP-42-2009 Corrosion Resistant Gate, Globe, Angle and Check Valves with Flanged and Butt Weld Ends (Classes 150, 300 however, the contents of these “historical” SPs are now part of newly revised SP-58-20
46、09. MSS is an ANSI-accredited American National Standards developer. A number of former MSS Standard Practices have been adopted and published by other developers as American National Standards. In order to maintain a single source of authoritative information, MSS has withdrawn its Standard Practices in such cases. Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. 127 Park Street, NE, Vienna, VA 22180-4620 (703) 281-6613 Fax # (703) 281-6671 MSS SP-120-2011
