Hydrocarbon Processing - October 2021 - 70

Heat Transfer
etry used is shown in FIG. 2. It has four tube rows (the bottom
three shock rows have bare tubes and a fourth row from
the bottom has studded tubes), with circular holes for tube
placement. Below each tube row's flanges are support for the
tubes passing through the holes. The tubesheet is supported
from the ends at the support location placed above the first
tube row. The CCR fired heater-where these tubesheets
are installed-uses oil and gas in combination as fuel. The
tubesheet material used in this design-ASTM A560 Gr.
50Cr-50Ni-Cb-recommended using fuel oil for firing. The
improved design-A297 Gr. HP Mod (25Cr-35Ni-Nb)-
recommended fuel gas for firing, which was being used at the
customer's facility. The HP Mod material has better creeprupture
strength and better thermal shock resistance.
TABLE 1. Material properties for ASTM A560, Grade 50Cr50Ni-Nb
Temperature,
°C
800
725
667
614
590
550
Young's
modulus,
GPa
124
137
143.96
149.6
150
156
Poisson's
ratio
Coeffi cient of thermal
expansion, mm/mm°C * 10-6
18.3
18
0.3
17.8
17.6
17.5
17.3
Tubesheet failure. In the convection bottom cast intermediate
tubesheets within one of the fired heater installations,
cracks were repeatedly found in the tubesheet web ligaments
of the first tube row from the bottom, as well as in the first tube
row's bottom flange. Typical crack locations in the tubesheet
are shown in FIG. 2. After replacing the tubesheets with a similar
design, repetitive cracks were found in the installation,
which led to repeated shutdowns for repair and replacement
and loss of production time.
The following are the design factors and probable causes of
failure of the tubesheet:
* Dead weight of the tubes and the tubesheet
* Friction between the tube hole and the tube, and friction
between the tubesheet support and resting surfaces
* Thermal expansion of the tubesheet in the direction
of its length and the relative position of the tubes
FIG. 3. FEA model.
FIG. 2. Configuration of the tubesheets and locations of cracks.
FIG. 4. Dead weight load case.
70 OCTOBER 2021 | HydrocarbonProcessing.com

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Hydrocarbon Processing - October 2021

Table of Contents for the Digital Edition of Hydrocarbon Processing - October 2021

Contents
Hydrocarbon Processing - October 2021 - Cover1
Hydrocarbon Processing - October 2021 - Cover2
Hydrocarbon Processing - October 2021 - Contents
Hydrocarbon Processing - October 2021 - 4
Hydrocarbon Processing - October 2021 - 5
Hydrocarbon Processing - October 2021 - 6
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Hydrocarbon Processing - October 2021 - Cover3
Hydrocarbon Processing - October 2021 - Cover4
Hydrocarbon Processing - October 2021 - GP-1
Hydrocarbon Processing - October 2021 - GP-2
Hydrocarbon Processing - October 2021 - GP-3
Hydrocarbon Processing - October 2021 - GP-4
Hydrocarbon Processing - October 2021 - GP-5
Hydrocarbon Processing - October 2021 - GP-6
Hydrocarbon Processing - October 2021 - GP-7
Hydrocarbon Processing - October 2021 - GP-8
Hydrocarbon Processing - October 2021 - GP-9
Hydrocarbon Processing - October 2021 - GP-10
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Hydrocarbon Processing - October 2021 - GP-21
Hydrocarbon Processing - October 2021 - GP-22
Hydrocarbon Processing - October 2021 - GP-23
Hydrocarbon Processing - October 2021 - GP-24
Hydrocarbon Processing - October 2021 - GP-25
Hydrocarbon Processing - October 2021 - GP-26
Hydrocarbon Processing - October 2021 - GP-27
Hydrocarbon Processing - October 2021 - GP-28
Hydrocarbon Processing - October 2021 - GP-29
Hydrocarbon Processing - October 2021 - GP-30
Hydrocarbon Processing - October 2021 - GP-31
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Hydrocarbon Processing - October 2021 - GP-35
Hydrocarbon Processing - October 2021 - GP-36
Hydrocarbon Processing - October 2021 - GP-37
Hydrocarbon Processing - October 2021 - GP-38
Hydrocarbon Processing - October 2021 - GP-39
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Hydrocarbon Processing - October 2021 - GP-43
Hydrocarbon Processing - October 2021 - GP-44
https://www.nxtbook.com/gulfenergyinfo/gulfpub/HPI-Market-Data-2023-v3
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