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Technical Briefs

Assuring Tube-to-Tubesheet Joint Tightness and Strength

[+] Author and Article Information
Stanley Yokell

MGT Inc.
F201 The Academy,
970 Aurora Avenue,
Boulder, CO 80302-7299
e-mail: syokell@mgt-inc.com

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received June 27, 2011; final manuscript received October 25, 2011; published online October 18, 2012. Assoc. Editor: William J. Koves.

J. Pressure Vessel Technol 134(6), 064502 (Oct 18, 2012) (7 pages) doi:10.1115/1.4006123 History: Received June 27, 2011; Revised October 25, 2011

This paper describes preparing mockup tubesheet specimens for visual examination using a digital microscope to determine that tube-to-tubesheet joint welds are of the specified size and that expanded joints are satisfactory for the intended purpose. It discusses nondestructive examinations (NDE) of the tubesheets and tube joints intended to assure achieving sufficient tightness and strength to satisfy the uses to which the exchangers will be put. This paper refers to the ASME Boiler and Pressure Vessel Code (Code) paragraphs that apply to tube joint welds and expanded joints including shear load testing when the Code requires it [1]. The discussion also addresses the need for manufacturers to have qualified tube joining procedures and personnel qualified to use the qualified procedures. The work concludes with a summary of ways to assure tube joint tightness and strength.

Copyright © 2012 by ASME
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References

Figures

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Fig. 1

Ultrasonic testing feedwater heater tubesheet after weldwire cladding and machining

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Fig. 2

Liquid penetrant examining a feedwater heater tubesheet cladding after machining

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Fig. 3

Gas leak bubble testing feedwater heater tube-to-tubesheet joints

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Fig. 4

Typical layout of mockup tubesheet specimen for feedwater heater with two tube thicknesses

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Fig. 5

Photograph of specimen A 0.035 wall tubes

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Fig. 6

Photograph of specimen B 0.035 wall tubes

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Fig. 7

Photograph of specimen A 0.049 wall tubes

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Fig. 8

Photograph of specimen B 0.049 wall tubes

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Fig. 9

VHX digital microscope used to examine the specimens shown in Figs. 10–16

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Fig. 10

Tube-to-tubesheet welds at 6L and 7R Leak paths 0.0364 in. and 0.0364 in. Unexpanded gaps behind weld roots 0.387 in. and 0.375 in.

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Fig. 11

7R and 6l Groove 1. Discontinuities are insignificant. Grooves are trapezoidal.

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Fig. 12

7R and 6L Land between grooves. No discontinuities.

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Fig. 13

6R and 7L Groove 2. Insignificant discontinuities. Grooves are trapezoidal.

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Fig. 14

Tube 6L and 7R at 2 in. No discontinuities.

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Fig. 15

Tube 6L and 7R at 5 in. No discontinuities over the expanded length.

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Fig. 16

Tube 7R and 8L at 2 in. Tube 8L is not in intimate contact with the tubesheet and the expansion is unacceptable.

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