MSS SP-120-2017 Flexible Graphite Packing Sealing for Rising Stem Valves.pdf

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1、MSS SP-120-2017 Flexible Graphite Packing Sealing for Rising Stem Valves 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) 281-6671 E-mail: st

2、andardsmsshq.org www.msshq.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 experienced volunteers to p

3、rovide 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 MSS Standard Practice

4、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 applicable. MSS has no p

5、ower, 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 statement. “Unless i

6、ndicated 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 shall remain silent on th

7、e 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 connection therewith. MS

8、S 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, and references are c

9、onstrued 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 include mandatory requ

10、irements. The U.S. customary units and SI (metric) units in this Standard Practice are regarded separately as the standard; each should be used independently of the other. Combining or converting values between the two systems may result in non-conformance with this Standard Practice. This Standard

11、Practice has been substantially revised from the previous 2011 edition. It is suggested that if the user is interested in knowing what changes have been made, that direct page by page comparison should be made of this document and that of the previous edition. Non-toleranced dimensions in the Standa

12、rd Practice are nominal unless otherwise specified. Excerpts of this Standard Practice may be quoted with permission. Credit lines should read Extracted from MSS SP-120-2017 with permission of the publisher, Manufacturers Standardization Society of the Valve and Fittings Industry. Reproduction and/o

13、r electronic transmission or dissemination is prohibited under copyright convention unless written permission is granted by the Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. All rights reserved. Originally Published: March 1997 Current Edition Approved: April 2017 Cu

14、rrent Edition Published: May 2017 MSS is a registered trademark of the Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. Copyright , 2017 by Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. Printed in U.S.A. MSS STANDARD PRACTICE SP-120ii FO

15、REWORD 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 manufacture and procurement of packing systems with design features for rising-stem valves that utilize flexibl

16、e 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 a broad spectrum of industry applications. This Standard Practice shall not be construed to be effective for all pr

17、essures 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 design measures that are outside the scope of this Standard Practice. This 2017 edition includes a complete rewrite f

18、or valve stem packing from the previous general packing requirements updating to the current low emissions packing requirements. The definitions, packing types, materials and ring configuration types are now inclusive within this Standard Practice. In addition, valve stems, stuffing boxes, packing g

19、lands, lubrication of gland bolting, and paint free areas are detailed. Leakage performance is added to meet the current industry-driven requirements by U.S. Environmental Protection Agency actions and other international standards. The packing set height was updated. A new table for allowable clear

20、ance between the stem and stuffing box has also been added, with figures showing packing, stuffing box, and gland specific requirements. Additional revisions include various editorial and formatting corrections, and updating of the organizations and external references in Annex A. MSS STANDARD PRACT

21、ICE SP-120iii TABLE OF CONTENTS SECTION PAGE 1 SCOPE . 1 2 DEFINITIONS . 1 3 PACKING TYPES . 1 4 PACKING SET MATERIALS 2 5 PACKING RINGS AND JOINT TYPES 2 6 VALVES 2 7 LEAKAGE PERFORMANCE 5 TABLE 1 Allowable Radial Clearance for Standard Cross Sections of Braided Packing 3 FIGURE 1 Skive Cut Joint 2

22、 2 Stuffing Box Maximum Perpendicularity 4 3 Packing Gland Maximum Chamfers 4 4 Packing Gland Minimum Insertion into Stuffing Box 5 ANNEX A Referenced Standards and Applicable Dates 6 MSS STANDARD PRACTICE SP-120iv This Page Intentionally Left Blank Manufacturers Standardization Society of the Valve

23、 and Fittings Industry MSS STANDARD PRACTICE SP-1201 FLEXIBLE GRAPHITE PACKING SEALING FOR RISING STEM VALVES 1. SCOPE(1)1.1 This Standard Practice is applicable to valves that use flexible graphite packing stem sealing to achieve reduced or low emissions. 1.2 This Standard Practice encompasses dime

24、nsions and tolerances applicable to ASME B16.34 gate and globe valves designed with rising non-rotating and rising rotating stems. 1.3 This Standard Practice applies to valves in which a flexible graphite packing assembly is used as the primary stem-sealing system. 1.4 Valves that include a lantern

25、ring as part of its packing system, and bonnetless valves with split glands, are outside the scope of this Standard Practice. 2. DEFINITIONS 2.1 Flexible Graphite Specially processed mineral graphite used as a sealing material. Can be supplied in various shapes and densities. 2.2 Low Emissions Reduc

26、ed emissions limits of VOC emissions that are required to meet industry performance standards. 2.3 Skive Cut A type of diagonal cut (skive), usually at a 45 angle, that is designed to improve packing life, minimize stem packing leakage, and allow for field replacement. 2.4 VOCs Volatile Organic Comp

27、ounds 2.5 Wiper Rings/Anti-Extrusion Rings Die-formed and/or braided packing rings placed at the top and bottom of a packing set, specifically to help prevent extrusion and keep debris from contaminating the sealing ring. 2.6 See MSS SP-96 for additional definitions of terms used in this Standard Pr

28、actice. 3. PACKING TYPES 3.1 General The packing types described in Section 3.2 through 3.4 below are for use in valves which are designed with a means of adjustment to the packing at any given time. They are intended for service in applications where low emissions performance is required (see Secti

29、on 7) and stuffing box temperatures are up to 398 C (750 F). 3.2 Type A (Carbon or Graphite Wiper/Anti-Extrusion Rings) These rings have a carbon assay of 98% minimum and include a corrosion inhibitor applied at the time of manufacture. Typically used as a top and bottom ring in conjunction with a T

30、ype B (see Section 3.3) or C (see Section 3.4) material. Note that this can include high density die-formed graphite rings. 3.3 Type B (Expanded Graphite Die-Formed Rings) These rings have a carbon content of 98% or better. Typically used as a sealing ring with a Type A ring (see Section 3.2) at the

31、 top and bottom of the installed set. Typical minimum density of Type B rings is 1442 kg/m2(90 lbs/ft3). 3.4 Type C (Braided Graphite Yarn Packing) This material may be constructed with a reinforcement material, such as a wire filament or other fiber/yarn, to improve extrusion resistance. NOTE: (1)T

32、his Standard 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). MSS STANDARD PRACTICE SP-1202 4. PACKING SET MATERIALS 4.1 The base graphite material shall have a maximum of 750 ppm total sulfur. 4.2 Chloride

33、content of the finished packing shall be a maximum of 750 ppm total/100 ppm leachable. 4.3 Corrosion inhibitor shall be applied to graphite packing materials. 4.4 Packing Set Height The recommended height of the packing set is equal to or not less than five (5) times the distance between the shaft d

34、iameter and the stuffing box Inside Diameter (I.D.). 5. PACKING RINGS AND JOINT TYPES 5.1 Die-formed graphite tape rings can be supplied as solid or skive cut. 5.2 Braided packing rings shall be skive cut (see Figure 1 below). 5.3 The skive joint is oriented so that a load applied by the gland nose

35、would clamp the overlapping ends of the ring to minimize any leakage paths. 5.4 Each skive cut ring shall be oriented so that the joint is rotated between 90 and 120 from the ring below it (in a uniform, clockwise, rotational direction). FIGURE 1 Skive Cut Joint 6. VALVES 6.1 General This section id

36、entifies minimum critical requirements for low emissions valves to meet the leakage performance requirement. 6.2 Stem 6.2.1 The surface finish in the packing sealing area shall be within the range of 0.4 0.8 m (16 32 in), as per API 622 requirements. 6.2.2 Stem-to-bore acceptable radial clearance fo

37、r each standard packing cross section shall be a as provided in Table 1. MSS STANDARD PRACTICE SP-1203 6.2.3 Stuffing Box 6.2.3.1 Radial clearance relative to the finished stem dimension shall be a minimum as provided in Table 1. 6.2.3.2 The bottom of the stuffing box shall be perpendicular to the s

38、tuffing box wall within a maximum of 5 degrees (see Figure 2). 6.2.3.3 The surface finish shall be within the range of 2.57 4.4 m (100 175 in), as per API 622 requirements. 6.3 Packing Gland 6.3.1 The maximum chamfer or radius permitted on the gland at the I.D. or O.D. (see Figure 3) shall be 0.127

39、mm (0.005 in.). 6.3.2 Packing glands shall be torqued to the packing manufacturers final value prior to API 598 testing. 6.3.3 Packing gland insertion into the stuffing box, before compression, must be a minimum of 1 packing ring in height (see Figure 4). After installation and compression, the rema

40、ining gland nose penetration shall meet the valve manufacturers requirements. 6.3.4 Petroleum based lubrication should not be applied to any components that may contaminate (or are a component of) the packing area of the stuffing box. This prevents false positives from VOC monitoring caused by off-g

41、assing of the lubrication. 6.3.4.1 Gland bolts, gland nuts, gland nose, and the follower should be free of any paint that emits VOCs, as paint used on the valve may present a false positive from VOCs caused by off-gassing during emissions testing or in-service monitoring. 6.4 For reconditioned valve

42、s, low emissions requirements are specified in API RP 621, Annex B. TABLE 1 Allowable Radial Clearance for Standard Cross Sections of Braided Packing Packing Cross Section mm (fractional in.) Maximum Total Combined Allowable Radial Clearance Between Stem ANSI/ASME B16.34-2013* Valves Flanged, Thread

43、ed and Welding End * The 2017 edition supersedes the current version as a reference herein. ISO 15848-1:2015 Industrial Valves Measurement, test and qualification procedures for fugitive emissions Part 1: Classification system and qualification procedures for type testing of valves; including Amendm

44、ent 1 (2017) MSS; ANSI/MSS SP-96-2017 Terminology for Valves, Fittings, and Their Related Components SP-99-2016a Instrument Valves SP-105-2016a Instrument Valves for Code Applications The following organizations appear in the above list: ANSI American National Standards Institute 25 West 43rd Street

45、, Fourth Floor New York, NY 10036-7406 API American Petroleum Institute Two Park Avenue New York, NY 10016-5990 ASME American Society of Mechanical Engineers (ASME International) Two Park Avenue New York, NY 10016-5990 ISO International Organization for Standardization 1, ch. de la Voie-Creuse, Case

46、 Postale 56 CH-1211 Geneva 20, Switzerland MSS Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. 127 Park Street, NE Vienna, VA 22180-4602 MSS STANDARD PRACTICE SP-1207 This Page Intentionally Left Blank Manufacturers Standardization Society of the Valve and Fittings Ind

47、ustry MSS STANDARD PRACTICE SP-1208 This Page Intentionally Left Blank Manufacturers Standardization Society of the Valve and Fittings Industry Purchase or View a Full Listing of MSS Standards at: http:/msshq.org/Store/PriceList.cfm MSS Standard Practices (SPs) related to or referenced in this publi

48、cation: ANSI/MSS SP-96 Terminology for Valves, Fittings, and Their Related Components American National Standards Published by MSS, an ANSI-accredited Standards Developer:ANSI/MSS SP-25 Standard Marking System for Valves, Fittings, Flanges, and UnionsANSI/MSS SP-44 Steel Pipeline FlangesANSI/MSS SP-

49、55 Quality Standard for Steel Castings for Valves, Flanges, Fittings, and Other Piping Components Visual Method for Evaluation of Surface IrregularitiesANSI/MSS SP-58 Pipe Hangers and Supports - Materials, Design, Manufacture, Selection, Application, and InstallationANSI/MSS SP-96 Terminology for Valves, Fittings, and Their Related ComponentsANSI/MSS SP-114 Corrosion Resistant Pipe Fittings Threaded and Socket Welding Class 150 and 1000ANSI/MSS SP-134 Valves for Cryogenic Service, including Requirements for Body/Bonnet ExtensionsANSI/MSS