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1、MSS SP-121-2006 Qualification Testing Methods for Stem Packing for Rising Stem Steel Valves MSS Standard Practice Developed and Approved by the Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. 127 Park Street, NE Vienna, Virginia 22180 Phone: (703) 281-6613 Fax: (703) 2
2、81-6671 E-mail: infomss-hq.org www.mss-hq.org Copyright MSS Provided by IHS under license with MSS Not for ResaleNo reproduction or networking permitted without license from IHS MSSSTANDARD PRACTICESP-121 i This MSS Standard Practice was developed under the consensus of the MSS Technical Committee 3
3、08 and the MSS Coordinating 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
4、 for common practice by the manufacturer, 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, speci
5、fication, sales contract, or public law, as applicable. 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 the date of issue of this MSS SP. (See Annex A.) U.S. customary units in
6、 the Standard Practice are the standard; the metric units are for reference only. In this Standard Practice all notes, annexes, tables, and figures are construed to be essential to the understanding of the message of the standard, and are considered part of the text unless noted as “supplemental“. A
7、ll appendices appearing in this document are construed as “supplemental“. Supplemental“ information does not include mandatory requirements. Any part of this standard may be quoted. Credit lines should read Extracted from MSS SP-121, 2006 with permission of the publisher, the Manufacturers Standardi
8、zation Society. Reproduction prohibited under copyright convention unless written permission 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 Fitt
9、ings Industry, Inc. Printed in U.S.A. Copyright MSS Provided by IHS under license with MSS Not for ResaleNo reproduction or networking permitted without license from IHS MSSSTANDARD PRACTICESP-121 ii FOREWORD This Standard Practice was developed by a cooperative effort of representatives of valve an
10、d packing manufacturers. This Standard Practice is intended primarily to be an aid for verification of the performance of valve stem packing materials and material combinations at selected pressure and temperature conditions. It is based on packing systems to be used in rising stem steel valves that
11、 generally use flexible graphite packing systems in accordance with MSS SP-120. While MSS SP-120 addresses only flexible graphite packing systems, it does not preclude use of specified system design features for other types of packing systems. This Standard Practice references MSS SP-120 design feat
12、ures and packing systems qualified in accordance with this Standard Practice and may be considered by manufacturers and users for application in rising stem steel valves that otherwise comply with MSS SP-120. This Standard Practice shall not be construed to be effective in qualifying packings for al
13、l types of services expected of ASME B16.34 or equivalent valves. Special service applications such as low fugitive emissions control or toxic fluid may require additional or different qualification testing or leakage measurement methods that are outside the scope of this Standard Practice. Copyrigh
14、t MSS Provided by IHS under license with MSS Not for ResaleNo reproduction or networking permitted without license from IHS MSSSTANDARD PRACTICESP-121 iii TABLE OF CONTENTS SECTIONPAGE 1 SCOPE. 1 2 DEFINITIONS. 1 3 TEST FIXTURES 2 4 TEST PROCEDURES. 4 5 QUALIFICATION REPORT 7 FIGURE 1 Corrosion Test
15、 Fixture. 9 2Test Outline for Basic Qualification Tests. 10 3 Qualification Report Abstract 11 ANNEX AReferenced Standards and Applicable Dates 12 Copyright MSS Provided by IHS under license with MSS Not for ResaleNo reproduction or networking permitted without license from IHS MSSSTANDARD PRACTICES
16、P-121 1 QUALIFICATION TESTING METHODS FOR STEM PACKING FOR RISING STEM STEEL VALVES General Note: More chemically aggressive line fluids may damage packings and degrade sealing performance. Packings qualified in accordance with this Standard Practice may not be satisfactory for applications with suc
17、h fluids. 1.4 Environmental pollution regulations (e.g. fugitive emissions) or limitations on leakage of hazardous or toxic fluids may require additional or different qualification tests that are outside the scope of this Standard Practice. 1.5 This Standard Practice is not intended to apply to pack
18、ings for valves developed for and predominantly used in instrument piping systems. 2. DEFINITIONS 2.1 See MSS SP-96 for definitions of common terms used in this Standard Practice. 2.2 Detectable Leakage For the purposes of this Standard Practice, detectable leakage of a packing assembly is defined a
19、s follows: 2.2.1 Standard criteria (1) Visible leakage of liquid water which results in breaking away of droplets to form a dripping action or a steady stream (2) Leakage of saturated or superheated steam that is visible as condensed vapor or detectable as condensation in a cold trap, on a mirror, o
20、r with a similar device (3) Leakage of air or nitrogen sufficient to produce continuous bubbling in a liquid leak detector solution applied in the packing gland area 2.2.2 Alternate criteria At the discretion of the test sponsor, more conservative (lower) allowable leakage rate criteria may be selec
21、ted. If this is done, leakage shall be measured quantitatively (e.g., in ml/hr as liquid or condensed vapor or as an air or nitrogen volume at standard atmospheric conditions). The alternate “detectable leakage” definition and the method of measurement shall be described in the Qualification Report.
22、 1. SCOPE 1.1 This Standard Practice provides procedures and guidelines for testing and evaluation of valve stem packing materials and material combinations. This testing provides qualification by verifying the adequacy of specific packing material combinations for service within defined limits of s
23、ize, pressure, temperature, and cyclic duty. Such specific combinations generally represent products of individual manufacturers, although generic qualification of raw materials may be demonstrable in certain cases. 1.2 It is intended that this Standard Practice apply to qualification of stem packin
24、gs for Class 150 through 4500 ASME B16.34 or equivalent steel or special alloy valves (including intermediate classes and Standard, Special, and Limited Class ratings) with rotating/rising and non-rotating/rising stems, as traditionally used in globe and gate valves. Other valve stem types (e.g. qua
25、rter-turn) may involve additional considerations not within the scope of this Standard Practice. 1.2.1 The requirements herein apply to qualification of traditional compression packings. Rod seal elements such as “O“ rings, “V“ rings, and similar proprietary seals are not within the scope. 1.2.2 Ste
26、m packings may be prequalified by experience or by test programs conducted prior to publication of this Standard Practice if a qualification report is prepared based on documented evidence. 1.3 This Standard Practice is intended to provide experimental qualification of packing materials and material
27、s combinations for service with water, steam, and other common liquids, vapors, and gases. Some of the procedures identified in detail use water and steam as test fluids, but air or nitrogen may also be used with appropriate modifications in testing and data acquisition methods. Copyright MSS Provid
28、ed by IHS under license with MSS Not for ResaleNo reproduction or networking permitted without license from IHS MSSSTANDARD PRACTICESP-121 2 2.2.3 Static vs. dynamic leakage When observed, detectable leakage shall be further identified as static if the stem is stationary and dynamic if the stem is m
29、oving. 2.3 Maximum Qualified Packing Pressure The maximum pressure rating for a packing material or material combination at room temperature 50 to 1000F (10 to 380C) conditions based on tests in accordance with this Standard Practice. See Section 4.1.3. 2.4 Maximum Qualified Packing Temperature The
30、maximum continuous temperature (expressed as a mean temperature of the packing chamber) for a packing material or material combination based on tests in accordance with this Standard Practice. See Section 4.1.4. 2.5 Qualification Report A concise report documenting results of tests conducted in acco
31、rdance with this Standard Practice. See Section 5. 3. TEST FIXTURES 3.1 Performance Test Fixtures(1) may be valves or mockups of valves including stems and packing assemblies as described in MSS SP-120. Stem and pressure boundary materials shall be representative of those used in construction of val
32、ves used for pressures and temperatures corresponding to specified test conditions. 3.1.1 Test Fixtures shall be representative of a specific valve pressure class number and designation in accordance with ASME B16.34 (e.g., Standard Class 1500). Successful testing of a packing material or material c
33、ombination at conditions corresponding to a given pressure class shall qualify that material or combination for that and all lower class numbers. Supplementary Information: (1) While not required by this Standard Practice, it is recommended that test fixtures be designed to permit non-destructive re
34、moval of packing assemblies after test to allow examination of individual packing rings. Example: Successful performance at Standard Class 1500 conditions qualifies a packing material or material combination for Standard Class 150 through 1500 service and any other applications with the same or lowe
35、r pressure ratings. 3.1.2 Test fixtures shall provide a valve stem travel length representative of the maximum expected travel in valves having the same stem diameter used in the test fixture. Successful testing of a packing material or material combination in a fixture with a given stem diameter sh
36、all qualify that material or material combination for use with stem diameters from half through twice the diameter tested; this qualification applies to any stem travel not exceeding that tested (expressed as a multiple of stem diameter). Note: Tests with a stem travel length of at least four times
37、the stem diameter qualify a packing material or material combination for use with any longer travel. Examples: a) Testing of a 1.0 inch (25.4 mm) diameter stem with a 1.0 inch (25.4 mm) travel qualifies a packing material or material combination for use with a 0.5 inch (12.7 mm) diameter stem with u
38、p to 0.5 inch (12.7 mm) travel or a 2.0 inch (50.8 mm) diameter stem with up to 2.0 inch (50.8 mm) travel. b) Testing of a 3.0 inch (76.2 mm) diameter stem with a 12.0 (4.0 x 3.0) inch (305 mm) travel qualifies a packing material or material combination for use with a 1.5 inch (38.1 mm) diameter ste
39、m or a 6.0 inch (152 mm) diameter stem with any stem travel. Note: Upward or downward extrapolation in size is valid for specific packing combinations only when the same material and construction is used over the full qualified size range. For example; the qualification is not valid where different
40、braiding methods (e.g., square braid instead of lattice braid) or core materials are used in packings smaller or larger than the size tested. Copyright MSS Provided by IHS under license with MSS Not for ResaleNo reproduction or networking permitted without license from IHS MSSSTANDARD PRACTICESP-121
41、 3 3.1.6 As a minimum, test fixture instrumentation shall provide for continuous or periodic measurement of: a) Fluid pressure b) Fluid temperature c) Mean temperature of packing chamber (based on at least one metal temperature reading) d) Stem temperature at a location just outboard of the gland (w
42、hen stem is in innermost position) e) Stem actuating force or torque due to packing friction f) Fluid leakage rate, if alternate criteria are used to define “Detectable Leakage” (see Section 2.2.2). 3.2 Corrosion Test Fixtures shall be designed to contain packing material in the same way it is conta
43、ined in a valve for evaluation of the tendency of the material to cause damage to valve stems under wet lay-up (stocking) conditions. 3.2.1 Figure 1 illustrates a fixture design based on dimensions given for a 1 inch (25.4 mm) diameter stem in MSS SP-120. Use of these dimensions and the procedures i
44、n this Standard Practice should give standardized results that will be comparable when performed by different laboratories. Dimensions not given in MSS SP- 120 may be determined for convenience in manufacture. 3.2.2 Stem specimens shall be of corrosion resistant materials corresponding to actual all
45、oys used for valve construction. At least one test fixture shall include a stem of martensitic stainless steel (e.g. type 410). Tests with any specific stem material qualify a packing material or material combination for use with other more cathodic stem materials (in Galvanic Series). Specific mate
46、rial specifications for valve stem materials used shall be identified in the Qualification Report. Example: Successful tests with type 410 stem specimens qualify a packing for use with type 316 or Monel stems providing that stem surface finishes are equal. 3.1.3 Test fixtures shall provide stem moti
47、on representing either rotating/rising or non- rotating/rising (linear) valve stem motion. Successful tests of a packing material or material combination with a rotating/rising stem shall qualify that material or material combination for application with either the same or non- rotating/rising stem
48、motion. Qualification based on tests of fixtures with linear stem travel shall apply only to applications with non- rotating/rising stems. 3.1.4 Test fixtures shall incorporate stem and packing chamber dimensions consistent with Table 1 of MSS SP-120. Diametrical clearances (stem to packing gland, p
49、acking gland to bonnet, and stem to bonnet) shall be controlled closely to ensure conservatism in demonstrating resistance of packing materials to extrusion. Actual dimensions shall be documented in the Qualification Report and shall limit the qualification of the packing material or material combination tested (e.g. closer clearances in the tests shall require closer clear