1、AN AMERICAN NATIONAL STANDARD ASME PTC 19.3 TW-2016(Revision of ASME PTC 19.3 TW-2010)ThermowellsPerformance Test CodesASME PTC 19.3 TW-2016(Revision of ASME PTC 19.3 TW-2010)ThermowellsPerformance Test CodesAN AMERICAN NATIONAL STANDARDTwo Park Avenue New York, NY 10016 USADate of Issuance: Februar
2、y 26, 2016This Code will be revised when the Society approves the issuance of a new edition.ASME issues written replies to inquiries concerning interpretations of technical aspects of this Code.Interpretations are published on the Committee Web page and under go.asme.org/InterpsDatabase.Periodically
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10、nt of this code or standard.ASME accepts responsibility for only those interpretations of this document issued in accordance with the establishedASME procedures and policies, which precludes the issuance of interpretations by individuals.No part of this document may be reproduced in any form,in an e
11、lectronic retrieval system or otherwise,without the prior written permission of the publisher.The American Society of Mechanical EngineersTwo Park Avenue, New York, NY 10016-5990Copyright 2016 byTHE AMERICAN SOCIETY OF MECHANICAL ENGINEERSAll rights reservedPrinted in U.S.A.CONTENTSForeword vCommitt
12、ee Roster . viCorrespondence With the PTC Committee viiSection 1 Object and Scope 11-1 Object 11-2 Scope 1Section 2 Nomenclature 2Section 3 Jurisdiction of Codes . 43-1 Reference Standards and Governing Codes 43-2 Specification of Thermowells 4Section 4 Dimensions 54-1 Configurations 54-2 Dimensiona
13、l Limits . 5Section 5 Materials 105-1 General Considerations . 10Section 6 Stress Equations . 116-1 General Considerations . 116-2 Corrosion and Erosion 116-3 Flow-Induced Thermowell Stresses 126-4 Strouhal Number, Drag Coefficients, and Lift Coefficient . 146-5 Natural Frequency of Thermowells 156-
14、6 Mounting Compliance Factor . 176-7 Unsupported Length, Diameter, and Fillet Radius . 196-8 Frequency Limit 206-9 Magnification Factor 236-10 Bending Stresses 246-11 Pressure and Shear Stresses . 286-12 Steady-State Static and Dynamic Stress Limits . 296-13 Pressure Limit 31Section 7 Overview of Ca
15、lculations . 327-1 Quantitative Criteria 327-2 Fluid Properties 327-3 Fluid Velocity . 327-4 Material Properties and Dimensions . 327-5 Reynolds and Strouhal Numbers 337-6 Natural Frequency at Operation Temperature 337-7 Natural Frequency at Expected Mode of Operation 337-8 Steady-State and Dynamic
16、Stresses 337-9 Allowable Fatigue Limits . 337-10 Pressure Rating . 33Section 8 Examples 348-1 Tapered, Welded Thermowell for a Steam-Header Application(U.S. Customary Units) . 348-2 Step-Shank, Threaded Thermowell for a Hot Water Application(SI Units) . 39iiiSection 9 Statement of Compliance . 469-1
17、 Specification of a Thermowell . 469-2 Velocity and Pressure Ratings . 46Section 10 References. 4710-1 Referenced Documents 4710-2 Referenced ASME Documents . 47Figures4-1-1 Schematic Diagram of a Thermowell 64-1-2 Examples of Straight-Shank Thermowells 74-1-3 Examples of Step-Shank Thermowells . 84
18、-1-4 Examples of Tapered Thermowells 96-3.1-1 Fluid-Induced Forces and Assignment of Axes for Calculation ofThermowell Stresses 126-6-1 Unsupported Length of Thermowells 186-8.1-1 Schematic Indicating Excitation of Resonances When ExcitationFrequency Coincides With the Thermowell Natural Frequency .
19、 206-8.1-2 Schematic Showing the Amplitude Response of a Thermowell Subjected toFluid-Induced Forces as Solid Lines, for In-Line and TransverseExcitation Modes . 216-10.1-1 Bending Moment, Stress at the Support Plane, and Locations ofMaximum Steady-State or Oscillating In-Line Stress . 256-10.7-1 Mo
20、unting of a Thermowell in an Elbow, With the Tip FacingDownstream . 276-10.7-2 Geometry to Be Used in Calculation of Thermowell Ratings . 276-10.7-3 Mounting of a Thermowell in an Elbow, With the Tip Facing Upstream 28Tables4-1-1 Dimensional Limits for Straight and Tapered Thermowells Within theScop
21、e of This Standard . 74-2-1 Dimensional Limits for Step-Shank Thermowells Within the Scope ofThis Standard 86-5.3-1 Parameters for Natural Frequency Calculation for Step-ShankThermowells . 166-12.3-1 Allowable Fatigue-Stress Amplitude Limits for Material Class A andClass B . 30Nonmandatory AppendixA
22、 Conversion Factors . 49ivFOREWORDIn 1957, the ASME Performance Test Codes Committee 19.3 determined that the 1930 editionof the Supplement on Temperature Measurement dealing with thermowells was unsatisfactory. Sincethe design of thermowells requires both thermal and stress considerations, the ASME
23、 Boiler andPressure Vessel Committee was approached for assistance. However, the special needs for thedesign of intrusive pipe fittings were deemed beyond the scope of what could be properlyincluded in the vessel codes.The PTC 19.3 Committee is charged with temperature measurement and thermowell des
24、ign.The purpose of the thermowell is to facilitate temperature measurement while resisting fluidforces of the process. This committee undertook the task of providing guidance in this area, onthe basis of a paper authored by J. W. Murdock1, ultimately leading to the publication ofPTC 19.3-1974, Suppl
25、ement on Instruments and Apparatus, Part 3, Temperature Measurement. Priorto the acceptance of PTC 19.3-1974, the incidence of thermowell failures during the start-uptesting of high-pressure steam turbines was unacceptable; its subsequent use in steam serviceshas been highly successful at preventing
26、 catastrophic thermowell failure.Since its publication, PTC 19.3 has received widespread acceptance and use in both steam andnonsteam applications outside the scope of the performance test codes. In 1971 an ASME ad hoccommittee, PB51, under the jurisdiction of the PTC Board, was formed to assess the
27、 thermowellstandard. This committee, designated PTC 19.3.1, produced a draft thermowell standard. In 1999,PTC 19.3 undertook the task of completing this draft. In the course of this effort, it was discoveredthat a number of thermowells designed to PTC 19.3-1974 but placed in nonsteam services suffer
28、edcatastrophic failure. Review of the literature revealed that the PTC 19.3.1 draft did not incorporaterecent, significant advances in our knowledge of thermowell behavior, and in 1998 the committeedecided to thoroughly rewrite the standard. The goals of the new Standard were to provide athermowell
29、rating method that could be used in a myriad array of services, including processesinvolving corrosive fluids; offer advice where fatigue endurance is critical; and establish criteriafor insuring sensor reliability. These factors resulted in a more reliable basis for thermowell designthan the PTC 19
30、.3-1974 Supplement. By 2004, it was decided that users would be better servedif the new thermowell strength calculation Standard was separated from the rest of PTC 19.3.The publication of the 2010 edition was well received by industry and adoption of the Codegenerated significant feedback. In additi
31、on to several Technical Inquiries, a Code Case wasapproved by the PTC Standards Committee in 2012 to add additional guidance for passingthrough the in-line resonance condition and adjust the manufacturing tolerances in the tables.Citing the continued industry feedback, the PTC Committee decided to r
32、evise the documentagain to incorporate the Code Case and add clarifications to elbow and angled installations. Itis intended that this Edition of the Standard not be retroactive.This Edition of PTC 19.3 TW was approved as an American National Standard by the ANSIBoard of Standards Review on January
33、5, 2016.vASME PTC COMMITTEEPerformance Test Codes(The following is the roster of the Committee at the time of approval of this Code.)STANDARDS COMMITTEE OFFICERSP. G. Albert, ChairJ. W. Milton, Vice ChairF. Constantino, SecretarySTANDARDS COMMITTEE PERSONNELP. G. Albert, ConsultantR. P. Allen, Consu
34、ltantJ. M. Burns, Burns EngineeringA. E. Butler, ST Global however, they shouldnot contain proprietary names or information.Requests that are not in this format may be rewritten in the appropriate format by the Committeeprior to being answered, which may inadvertently change the intent of the origin
35、al request.ASME procedures provide for reconsideration of any interpretation when or if additionalinformation that might affect an interpretation is available. Further, persons aggrieved by aninterpretation may appeal to the cognizant ASME Committee or Subcommittee. ASME does not“approve,” “certify,
36、” “rate,” or “endorse” any item, construction, proprietary device, or activity.Attending Committee Meetings. The PTC Standards Committee and PTC Committees regularlyhold meetings and/or telephone conferences that are open to the public. Persons wishing to attendany meeting and/or telephone conferenc
37、e should contact the Secretary of the PTC StandardsCommittee. Future Committee meeting dates and locations can be found on the Committee Pageat go.asme.org/PTCcommittee.viiINTENTIONALLY LEFT BLANKviiiASME PTC 19.3 TW-2016THERMOWELLSSection 1Object and Scope1-1 OBJECTThe object of this Standard is to
38、 establish a mechanical design standard for reliable service of tapered, straight,and stepped-shank thermowells in a broad range of applications. This includes an evaluation of the forces causedby external pressure, and the combination of static and dynamic forces resulting from fluid impingement.1-
39、2 SCOPEThis Standard applies to thermowells machined from bar stock and includes those welded to or threaded into aflange as well as those welded into a process vessel or pipe with or without a weld adaptor. Thermowells manufac-tured from pipe are outside the scope of this Standard.Thermowells with
40、specially designed surface structures (e.g., a knurled surface or a surface with spiral ridges)are beyond the scope of this Standard, due to the difficulty of providing design rules with broad applicability forthese types of thermowells.Thermowell attachment methods, standard dimensions, parasitic v
41、ibration of a sensor mounted inside the ther-mowell, and thermal equilibrium of the sensor relative to the process stream are beyond the scope of this Standard.In addition, thermowells fabricated by welding, including flame spray or weld overlays, at any place along thelength of the shank or at the
42、tip are outside the scope of this Standard.The application of the overlay to a bar-stock thermowell may affect any number of critical attributes such asnatural frequency, damping, material properties, or surface finish. These changes are difficult to account for in thecalculations, therefore, there
43、is risk that an inappropriately designed thermowell could be installed.1ASME PTC 19.3 TW-2016Section 2NomenclatureFor U.S. Customary units, lb denotes pound as a unit of mass, lbf denotes pounds-force, kip denotes 103pounds-force, and ksi denotes 103pounds-force per square inch or kips per square in
44、ch. When parameters are specified inmixed units within the U.S. Customary unit system (e.g., diameter B in inches, velocity V in feet per second),conversion factors between feet and inches will be needed in the calculations. See para. 6-4.1 and subsection 8-1for examples.A p outside diameter of ther
45、mowell at support plane or root, based on which point is closest to the thermowelltip, m (in.)App projected area of thermowell perpendicular to direction of flow and exposed to the flow stream, m2(in.2)a p polynomial function used in eq. (6-8-4), dimensionlessB p outside diameter at tip of thermowel
46、l, m (in.)b p fillet radius at the root of the thermowell shank, m (in.)bSp fillet radius at the base of the reduced-diameter length of a step-shank thermowell, m (in.)CDp coefficient for steady-state drag pressure, dimensionlessCdp coefficient for oscillating-drag (in-line with flow) pressure, dime
47、nsionlessClp coefficient for oscillating-lift (transverse to flow) pressure, dimensionlessc p corrosion allowance, m (in.)cip coefficients used in eq. (6-5-3), dimensionlessD p outside diameter at any cross section, m (in.)Dap average diameter of the thermowell, as defined in para. 6-5.3, Step 1, m
48、(in.)d p bore diameter of thermowell, m (in.)E p modulus of elasticity at service temperature, Pa psi or lb/(in.sec2) (Refer to Nonmandatory Appendix Aand para. 6-5.3 for a discussion of units of E.)Erefp reference value of modulus of elasticity, Pa (psi)FDp in-line static drag force on thermowell,
49、due to fluid impingement, N (lbf)Fdp in-line dynamic drag force on thermowell, due to fluid impingement, N (lbf)Flp transverse dynamic drag force on thermowell, due to fluid impingement, N (lbf)FMp magnification factor for thermowell oscillations transverse to fluid flow, dimensionlessFMp magnification factor for thermowell oscillations in-line with fluid flow, dimensionlessf p frequency, Hzfap approximate resonance frequency of thermowell, Hzfncp resonance frequency of thermowell with compliant support, Hzfnp natural frequency with ideal clamping, HzfSp vortex shedding frequency o
