1、 MSS SP-117-2011 Bellows Seals for Globe and Gate 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: infomss-hq.org MSS
2、 www.mss-hq.org MSS STANDARD PRACTICE SP-117i This MSS Standard Practice was developed under the consensus of the MSS Technical Committee 114 and the MSS Coordinating Committee. The content of this Standard Practice is the resulting efforts of competent and experienced volunteers to provide an effec
3、tive, 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 does not in its
4、elf 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 power, nor does
5、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 otherwise specif
6、ically noted in this MSS Standard Practice, other standards documents referred to herein are identified by the date of issue that was applicable to this Standard Practice at the date of issue of this Standard Practice (see Annex B). This Standard Practice shall remain silent on the applicability of
7、those other standards of prior or subsequent dates of issue even though applicable provisions may not have changed. References contained herein which are bibliographic in nature are noted as supplemental in the text.” By publication of this Standard Practice, no position is taken with respect to the
8、 validity of any potential claim(s) or of any patent rights in connection 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
9、this Standard Practice, all text, notes, annexes, tables, figures, 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 construe
10、d as “supplemental”. Note that supplemental information does not include 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
11、of this paragraph. The specific detail of the change may be determined 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 Sta
12、ndard Practice may be quoted with permission. Credit lines should read Extracted from MSS SP-117-2011 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
13、 convention unless written permission is granted by the Manufacturers Standardization Society of the Valve and Fittings Industry Inc. All rights reserved. Originally Published: April 1996 Current Edition Approved: October 2010 Current Edition Published: October 2011 MSS is a registered trademark of
14、Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. Copyright 2011 by Manufacturers Standardization Society of the Valve and Fittings Industry, Inc. Printed in U.S.A. MSS STANDARD PRACTICE SP-117ii TABLE OF CONTENTS SECTION PAGE 1 SCOPE . 1 2 MARKING 1 3 DESIGN . 1 4 INSPE
15、CTION AND TEST 3 5 SHIPPING INFORMATION . 4 6 ORDERING INFORMATION 4 FIGURE 1 Typical Bellows Stem Seal Arrangement 5 ANNEX A Definitions . 6 B Referenced Standards and Applicable Dates . 7 MSS STANDARD PRACTICE SP-1171 1. SCOPE (1)1.1 This Standard Practice covers requirements for design, materials
16、, fabrication, installation, qualification, examination, testing, and shipment of metal bellows and/or bellows assemblies to be installed in manual and automated on-off globe and gate valves. 1.2 This Standard Practice is applicable to metal bellows used in conjunction with steel globe and gate valv
17、es which otherwise satisfy the requirements of standards such as API 600, API 602, ASME B16.34, and API 603. Such standards are referred to herein as the “parent” valve specifications. 1.3 This Standard Practice does not apply to non-metallic bellows or bellows made of low melting point materials su
18、ch as brass, phosphor-bronze, or similar materials. 1.4 Except where specifically noted in the text of this Standard Practice, the requirements here are not intended to supersede or replace those requirements of the parent valve standard. This Standard Practice specifies additional requirements for
19、those valves utilizing bellows seals. 1.5 It is the responsibility of the bellows valve manufacturer to ensure compliance with this Standard Practice. 2. MARKING 2.1 Valves utilizing bellows seals shall have a corrosion-resistant metal identification plate securely attached, giving the following inf
20、ormation: a) Bellows seal as per MSS SP-117 b) Bellows Material: (insert actual bellows material) Note: (1)This Standard Practice is not intended for valves developed for and predominantly used in instrument piping systems. Note: If the parent valve elevated pressure-temperature rating is to be de-r
21、ated or service temperature limited due to bellows design limitations, any bellows rated limitations to the parent valve pressure-temperature rating shall be marked as required by the parent valve specification. 3. DESIGN 3.1 General 3.1.1 The purpose of the bellows seal is to provide a metal barrie
22、r between the stem at its point of entry through the pressure boundary and the process fluid within the valve to eliminate stem leakage. The bellows seal is not intended to be a structural member of the valve nor is it considered to be the ultimate pressure containing mechanism of the valve. Thus, t
23、he bellows seal is to be designed in conjunction with and not as a substitute for the conventional pressure boundary components normally required. See Figure 1 for an example of a typical valve assembly with a bellows seal. 3.1.2 Because a conventional pressure boundary mechanism is available to act
24、 as the ultimate pressure containing mechanism, latitude is permitted in the design of bellows seals so long as they satisfy the performance and all other requirements of this Standard Practice. 3.1.3 Except as specifically noted herein, the rules governing the design of all other valve components f
25、ound in the parent valve specifications apply. 3.2 Pressure-Temperature Ratings 3.2.1 The Pressure-Temperature ratings of ASME B16.34, or other parent specification, for the pressure class and body material of the valve, apply as well to the bellows seal. The bellows shall withstand the parent valve
26、 class full 100 F rating. The valve manufacturer may choose to de-rate the bellows seal to some lower pressure rating at elevated BELLOWS SEALS FOR GLOBE AND GATE VALVES MSS STANDARD PRACTICE SP-1172 temperatures than the pressure-temperature rating of the parent valve. The manufacturer may also app
27、ly an elevated temperature limitation due to the bellows limitations. The valve manufacturer shall provide a published rating to the end user when a de-rated pressure-temperature rating applies. 3.3 Materials 3.3.1 Bellows seal material shall be selected so that the maximum temperature is below the
28、creep range. 3.3.2 Acceptable bellows materials are: a) Stainless Steel Types 321 and 316L: ASTM A240/A312 b) Stainless Steel Types 304 and 304L: ASTM A240/A312 c) Stainless Steel Type 347: ASTM A240/A312 d) Alloy 600: ASTM B168/B167 e) Alloy 625: ASTM B443 f) Alloy 718: ASTM B670 g) Alloy 400: ASTM
29、 B127/B165 h) Alloy C22: ASTM B575/B622 i) Alloy C276: ASTM B575/B622 Note: Other materials may be used with the concurrence of the purchaser. 3.3.3 Acceptable materials for the bellows end fittings, including rings, caps, or flanges, if utilized, are: a) Stainless Steel Types 321 and 316L: ASTM A27
30、6/A479 b) Stainless Steel Types 304 and 304L: ASTM A276/A479 c) Stainless Steel Type 347: ASTM A276/A479 d) Alloy 600: ASTM B564 e) Alloy 625: ASTM B446 f) Alloy 718: ASTM B637 g) Alloy 400: ASTM B164/B564 h) Alloy C22: ASTM B574 i) Alloy C276: ASTM B574 Note: Other materials may be used with the co
31、ncurrence of the purchaser. 3.3.4 The bellows, bellows end fittings, and final attachment point, such as the stem, shall be weld compatible and have no negative effect on the bellows corrosion resistance. 3.3.5 The bellows material shall be free of weld repair. 3.4 Bellows Fabrication 3.4.1 The bell
32、ows may be constructed by forming individual convolutions from butt welded tube or drawn tube or by welding a series of formed disks together at both the outside diameter and the inside diameter of the individual disks. Forming may be accomplished either mechanically of hydraulically or any other su
33、itable manufacturing method. The bellows type shall be in accordance with the parent valve specification. 3.4.2 Precautions must be taken in the fabrication of multi-ply bellows to prevent moisture or other contamination between the plies. 3.4.3 Bellows may be welded together in series to accommodat
34、e the stroke requirements of the valve. Mechanical connections between bellows are not permitted. 3.4.4 Appropriate design features must be included to prevent squirm (buckling) of the bellows and to prevent localized contact between the bellows convolutions, valve body, and stem; which could lead t
35、o accelerated wear and premature failure. 3.4.5 Material certification of conformance for the bellows and end fittings is required to be furnished by the bellows manufacturer for each shipment, if requested by the customer. Material certification should also be required for the end fittings of the b
36、ellows, when furnished by the manufacturer. MSS STANDARD PRACTICE SP-1173 3.5 Stem/Disk or Moving Connection 3.5.1 The bellows, or a ring welded to the end of the bellows at the moving end, shall be attached to the disk/stem of the moving component by welding. A mechanical connection between the ste
37、m/disk or moving component and the bellows is not permitted. 3.5.2 The bellows shall not be subjected to torsional loads associated with operating the valve. 3.6 Fixed Connection 3.6.1 The bellows fixed end shall be welded to the body, the bonnet, or to a flange clamped or welded between the body an
38、d the bonnet. A mechanical connection to the bellows is not permitted. If welded to the valve body, this weld must be cut in order to perform maintenance of the valve seat. 3.7 Bellows Compression-Extension 3.7.1 Appropriate means shall be included in the valve design by the valve manufacturer to pr
39、event compression or extension of the bellows beyond that qualified by the cycle life test. 3.8 Bellows Cycle Life 3.8.1 A cycle is defined as fully open to fully closed to fully open. The bellows design shall be qualification tested in accordance with the following table, unless otherwise agreed to
40、 by the valve manufacturer and end user: Valve Size (NPS) Minimum Cycle Life Gate Globe Up to and including Class 800 valves: 4 1,000 2,000 Above Class 800 valves: 4 1,000 1,000 3.8.2 The suitability of the bellows assembly design shall be demonstrated by means of prototype tests upon representative
41、 samples as per Section 4.1. 3.9 Bellows Welding 3.9.1 All welding of the bellows and bellows attachment welds must be performed by qualified operators using qualified procedures. All welding qualifications shall be per ASME Boiler and Pressure Vessel Code, Section IX. 3.9.2 Bellows welds and bellow
42、s attachment welds, if not attached directly to the valve body or bonnet, are excluded from heat treat requirements of the parent specifications. 4. INSPECTION AND TEST 4.1 Bellows Design and Qualification Testing 4.1.1 The bellows assembly shall be cycle life tested either by cycling in an assemble
43、d valve without packing, or in a test rig which replicates the actual installation; including the clearance, stroke, loading, pressure, and wear couples of the parent valve. When required by the parent valve specification, an optional high temperature test shall be performed as designated in API 602
44、. 4.1.2 Any variation that constitutes a change in basic design parameters that affect cycle life of the bellows will require requalification by cycle testing (e.g. change in bellow supplier, material specification, number of plies, wall thickness, or diameter). A change in overall length or number
45、of convolutions may not require requalification, provided that the percentage of the bellows movement in both compression and extension are the same or less than that of the originally qualified bellows, where: Mc= (L1 Lc) x 100 / L1Me= (Le L1) x 100 / L1MSS STANDARD PRACTICE SP-1174 Where: Mc= perc
46、ent of movement in compression L1= live length Lc= compressed length Me= percent of movement in extension Le= extended length 4.1.3 After welding bellows to fittings and prior to qualification testing, each bellows assembly shall be Helium leak tested and exhibit no detectable leakage, using an inst
47、rument with sensitivity of 10-6cc/sec He. 4.1.4 Prior to cycle testing, each bellows assembly shall be hydrostatic pressure tested at 1.5 times the 100 F valve design pressure. Each bellows assembly shall be fixed at the length where the valve is in the open position, as required by the normal valve
48、 shell test. The pressure shall be applied on the same side as the valve is designed to operate in service. Water used for testing of stainless steel bellows assemblies shall contain less than 100 ppm chlorides. 4.1.5 The frequency of cycling shall take into consideration excessive heat which may be
49、 generated by abnormally fast cycling. In no case shall the frequency of cycling exceed one cycle per second. 4.1.6 Cycling shall be carried out at ambient temperature and at the 100F rated pressure of the bellows. The pressure shall be applied in a manner to simulate normal valve shell tests. 4.1.7 A minimum of three bellows of each basic design and material selected at random from those produced using the standard production manufacturing processes shall by cycled to achieve the appropriate minimum cycle life requirement of Section 3.8. 4.1.8 After cycling the bellows p
