Research Papers: Design and Analysis

Support Flexibility and Natural Frequencies of Pipe Mounted Thermowells

[+] Author and Article Information
David S. Bartran

Exothermics, Inc.,
14 Columbia Drive,
Amherst, NH 03031
e-mail: dbartran@yahoo.com

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received February 5, 2014; final manuscript received October 17, 2014; published online February 20, 2015. Assoc. Editor: Chong-Shien Tsai.

J. Pressure Vessel Technol 137(4), 041201 (Aug 01, 2015) (6 pages) Paper No: PVT-14-1016; doi: 10.1115/1.4028863 History: Received February 05, 2014; Revised October 17, 2014; Online February 20, 2015

A simplified model of a pipe mounted thermowell provides a measure of insight into the design and application of intrusive pipe fittings. A combination of Fourier and Green’s function methods together with a distributed load model of the thermowell/pipe wall interface are used to calculate the support compliance and subsequently the natural frequencies of the thermowell. These are compared with limited though independent calculations. This comparison confirms a profound reduction in natural frequencies for commonly encountered thermowell installations, reductions that should not be ignored where the risk of flow-induced resonance is high.

Copyright © 2015 by ASME
Your Session has timed out. Please sign back in to continue.


ASME, 2010, “Thermowells—Performance Test Codes,” ASME Paper No. PTC 19. [CrossRef]
Porter, M. A., and Martens, D. H., 2002,“Thermowell Vibration Investigation and Analysis,” ASME Pressure Vessels and Piping Conference, Vancouver, BC, Canada, Aug. 5–9, pp. 171–176.
Swindell, R., 2007, “Extension and Update of the Guidelines for the Avoidance of Vibration Induced Fatigue of Process Pipework, Intrusive Element Assessment,” Energy Institute Report No. AVIFF-2005-13, pp. 1–25.
Yuan, S. W., 1946, “Thin Cylindrical Shells Subjected to Concentrated Loads,” Q. J. Appl. Math., 4(1), pp. 13–26.
Yuan, S. W., and Ting, L., 1957, “On Radial Deflections of a Cylinder Subjected to Equal and Opposite Concentrated Radial Loads-Infinitely Long Cylinder and Simply Supported Cylinder With Simply Supported Ends,” ASME J. Appl. Mech., 24(2), pp. 278–282.
Morley, L. S. D., 1960, “Computing Green’s Functions of Biharmonic Equation for Multiply Connected Regions,” Q. J. Mech. Appl. Math., 13(1), pp. 24–37. [CrossRef]
Brock, J. E., 1974, “Stress Analysis of Thermowells,” Report No. NPS-59B074112A, Naval Postgraduate School Report No. AD/A-001 617, Naval Postgraduate School, Monterey, CA.
Ogura, K., and Fujii, T., 1999, “Flow-Induced Vibration Test of Thermowell in Secondary Cooling System of the Prototype FBR,” 7th International Conference on Nuclear Engineering, Tokyo, Japan, ICONE-7380.
Leissa, A. W.,1973, “Vibration of Shells,” NASA Report No. SP-288.
Karczub, D. G., 2006, “Expressions for the Direct Evaluation of Wave Number in Cylindrical Shell Vibration Studies Using the Flügge Equations of Motion,” J. Acoust. Soc. Am., 119(6), pp. 3553–3557. [CrossRef]
O’Donnell, W. J., 1960, “The Additional Deflection of a Cantilever Due to the Elasticity of the Support,” ASME J. Appl. Mech., 27(3), pp.461–464. [CrossRef]
Brown, J. M., and Hall, A. S., 1962, “Bending Deflection of a Circular Shaft Terminating in a Semi-Infinite Body,” ASME J. Appl. Mech., 39(1), pp. 86–90. [CrossRef]
MacBain, J. C., and Genin, J., 1973, “Natural Frequencies of a Beam Considering Support Characteristics,” J. Sound Vib., 27(2), pp. 197–206. [CrossRef]
MacBain, J. C., and Genin, J., 1973, “Effect of Support Flexibility on the Fundamental Frequency of Vibrating Beams,” J. Franklin Inst., 296(4), pp. 259–273. [CrossRef]
Weaver, W., Timoshenko, S. P., and Young, D. H., 1990, Vibration Problems in Engineering, 5th ed., John Wiley & Sons, New York.
Xue, L., Widera, G. E. O., and Seng, Z., 2006, “Flexibility Factors for Branch Connections Subject to In-Plane and Out-of-Plane Moments,” ASME J. Pressure Vessel Technol., 128(1), pp. 89–94. [CrossRef]


Grahic Jump Location
Fig. 1

Shell mounted cantilevers of length L and diameter d for isolated and opposed load distributions. The midsurface diameter of the shell is 2a with thickness h. Out-of-plane bending is shown in the figures, while in-plane bending refers to loads directed along the shell axis.

Grahic Jump Location
Fig. 2

Relationship between the differential load at B, a distance yB from the neutral axis, and the deformation at point N, a distance yN from the neutral axis of the beam, after [12]

Grahic Jump Location
Fig. 3

Natural frequency of a pipe-mounted thermowell versus wall thickness for NPS10 pipe, with thermowell dimensions listed in Table 1

Grahic Jump Location
Fig. 4

Natural frequency of pipe-mounted thermowell versus wall thickness for NPS18 pipe with thermowell dimensions listed in Table 1

Grahic Jump Location
Fig. 5

Natural frequency of a pipe-mounted thermowell versus wall thickness for NPS24 pipe with thermowell dimensions listed in Table 1

Grahic Jump Location
Fig. 6

Support compliance for the pipe-mounted thermowell in Fig. 4 versus wall thickness for NPS10 pipe. Note that the finite element data, in this case, do not exhibit a limiting condition as pipe wall thickness is increased. This appears to be an artifact of the meshing protocols used.

Grahic Jump Location
Fig. 7

Support compliance for the pipe-mounted thermowell in Fig. 5 versus wall thickness for NPS18 pipe

Grahic Jump Location
Fig. 8

Support compliance for the pipe-mounted thermowell in Fig. 6 versus wall thickness for NPS24 pipe



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In