Proceedings of the ASME 2011 Pressure Vessels & Piping Division Conference PVP2011 July 17-21, 2011, Baltimore, Maryland, USA
PVP2011-57331
Cold Stretching of Cryogenic Pressure Vessels Vessels from f rom Austenitic Stainless Steels 1
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Jinyang Zheng , Abin Guo , Cunjian Miao , Ping Xu* , Jian Yang , Jianjun Ye , Li Ma , Linlin Wu , Guoyi Yang
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(1. Institute of Process Equipm ent, Zhejiang University, Hangzhou 310027, P. P. R. China; 2. Institute of Applied Mech anics, Zhejiang University, Hangzhou 310027, P. R. China; 3. China Special Equipment Inspection and Research Institute, Beijing 100013, P. R. China) （*corresponding author, Phone: +86-571-879-53-393; Fax: +86-571-879-53-393; E-mail:
[email protected] E-mail:
[email protected] ）
ABSTRACT: Austenitic stainless steel (ASS) exhibits
NOMENCLATURE R k —
considerable work-hardening upon deformation while
Design stress
INTRODUCTION
retaining the characteristics of the material. The high rate of austenite deformation hardening was utilized by cold
With wide use of liquefied nitrogen, liquefied
stretching (CS) of cryogenic pressure vessels. A few
oxygen,
liquefied
hydrogen,
liquefied
argon,
and
percent deformation will give the vessel a considerable
liquefied natural gas (LNG), more and more cryogenic
and homogeneous yield strength improvement, and the
pressure vessels (CPV) from Austenitic Stainless Steel
wall thickness may be greatly reduced. The authors have
(ASS) are being used in recent years.
conducted extensive experimental and numerical studies
According to the Chinese pressure vessels standard
on CS of cryogenic pressure vessels from ASS. A
GB150[1], the allowable stress of ASS is dominated by
summary of our work as well as a brief introduction of
proof stress (also called yield strength) because of its low
the history, standards, safety, and advantages of CS are
ratio of yield strength to tensile strength and thus results
given in this paper. What should be further investigated,
in thicker wall thickness, which would cause a waste of
such as fatigue properties of cold stretched ASS
materials and make the vessel heavier.
especially under cryogenic temperature, design of cold
ASS exhibits considerable work-hardening upon
stretched transportable cryogenic vessels based on life,
deformation while retaining the characteristics of the
are also presented.
material. A few percent deformation will give the vessel a considerable
KEYWORDS: cold stretching, austenitic stainless steel,
and
homogeneous
yield
strength
improvement, and the wall thickness can be greatly
cryogenic pressure vessels, strengthening stress
reduced. Plastic deformation of 10% is possible with steels having an elongation at fracture of at least 35% in the heat treated condition.
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Copyright © 2011 by ASME
The high rate of austenitic strain hardening can be
Cold-Stretching Directions 1991 [10]. In Australia, AS
utilized by cold stretching (CS) of cryogenic pressure
1210-Supplyment2-1999 was promulgated for vessels
vessels from ASS[2]. In practice the strengthening is
using CS in 1999. In 2002, the CS technology were added
performed by pressurizing the finished vessel to a
into EN 13458-2 Appendix C and EN 13530-2 Appendix
pressure known to produce the required stress which in
C, respectively. Later on, Code Case 2596, ASME Boiler
turn gives the required amount of plastic deformation to
and Pressure Vessel Code, Section VIII, Division1, for
withstand the pressure load.
cold stretching of static ASS pressure vessels was issued
The authors have conducted extensive experimental
in 2008. Furthermore, ISO 20421-1:2006 and ISO
and numerical studies on CS of cryogenic pressure
21009-1:2008, which are equivalent to the relative EU
vessels from ASS. A summary of our work as well as a
standards, were issued. Chinese standard for CS is being
brief introduction of the history, standards, safety, and
developed.
advantages of CS are given in this paper. What should be
The main advantages of cold stretched ASS CPV can
further investigated, such as fatigue properties of cold
be summarized up as follows.
stretched ASS especially under cryogenic temperature,
(1) Saving materials
design of cold stretched transportable cryogenic vessels
The allowable stress of ASS can be approximately improved by 83%～130% and the weight of CPV can be
based on life, are also presented.
normally reduced by 20%~50% by using CS [11]. Table 1
STANDARDS AND ADVANTAGES OF CS
shows the allowable stress of ASS in different standards.
CS technology has been involved in several
Several
standards such as AS 1210 Supplement 2 [3], EN 13458-2 Appendix C
[4]
, EN 13530-2 Appendix C
including
[5]
, ISO
transportable
20421-1:2006[6], ISO 21009-1:2008 [7], and ASME Code
thousand static
cryogenic
pressure
vacuum-insulated
vacuum-insulated
vessels
vessels
vessels
and
have
been
constructed by using CS technology in P.R.China. In
[8]
Case 2596 .
practice, weight was reduced by 30%~50% in comparison
The Avesta Sheffield company in Sweden began to
with conventional vessels. A lot of material has been
investigate CS in 1956. Three years later, the first vessel
saved, which makes the products more competitive in the
was manufactured by using CS in 1959. Later in the year
market.
of 1969, the Avesta Sheffield company obtained a patent [9] in the United States (US 3456831A ). In 1975, CS was
brought into Swedish pressure vessel standardization, i.e., Table 1 Allowable stress of ASS in different standards GB150 Materials
EN13458-2 Appendix C
ASME BPVC VIII-I Code Case 2596
Allowable stress
Allowable
Rate of increase
Allowable stress
Rate of increase
/MPa
stress1)/MPa
/%
/MPa
/%
S30408 2)
137
273
99.3
270
97.1
S30403
120
267
122.5
247
105.8
S30453
137
313
128.5
--
--
S32168
137
267
94.9
--
--
2
Copyright © 2011 by ASME
S34778
137
267
94.9
--
--
S30458
160
313
95.6
293
83.1
S31658
160
--
--
293
83.1
S31608
137
--
--
270
97.1
S31603
120
--
--
247
105.8
S31653
137
--
--
270
97.1
1）It is calculated by
R k/ n s,
=1.5;
n s
2) The material name references to GB 24511-2009
[12]
.
cryogenic temperature, ASS after CS still has favorable
(2) Energy conservation and emission reduction
Due to the reduction of wall thickness, energy
mechanical properties. It is found that, for welded test
consumption can be reduced in the welding and forming.
plate of ASS with no less than 40% elongation after
According to the statistical report of the International
fracture, the elongation at ambient temperature is still
Aluminum Association [13], about 60% fuel is used to
more than 25%, and the Charpy V-notch impact energy at
carry the weight of automobile itself. It also indicates that
-196℃ can still satisfy the requirement of 31J if plastic
fuel can be reduced by 10% to 15% if the weight of
deformation is within 9%.
automobiles cuts by 10%. For transportable ASS CPV, it
DESIGN STRESS
means that less fuel is consumed and less carbon dioxide
The design stress is the maximum allowable stress at
exhaust during operation by using CS.
CS pressure, which is used to determine allowable stress.
(3) Increasing the ratio of weight to volume
Proof stress of ASS can be increased by CS. The larger
The ratio of weight to volume is an important index
the plastic deformation takes place, the higher is the proof
of energy efficiency for transportable pressure vessels.
stress. However, excessively high proof stress may lessen
Volume of ASS CPV can be increased by 2% to 10% due
safety margins. So how to determine the design stress
to plastic deformation during CS. The ratio of weight to
(also called strengthening stress) is a key factor for the
volume is reduced approximately by 50% caused by
application of the CS.
increase in volume and decrease in weight.
There are two methods for determining the design stress.
SAFETY ANALYSIS OF COLD STRETCHED ASS
(1) The design stress is proof stress plus 200MPa,
CPV
which is used in EN13458-2, EN 13530 -2.
MECHANICAL PROPERITES
(2) Considering the increment of proof stress by CS,
Based on extensive experimental and numerical
dissipated strain energy, the strain energy function-based
studies on material specimens and prototype vessels, a
method was developed to determine the design stress [17],
large amount of data from tensile test, bending test and
which
impact test, have been obtained. Meanwhile, strain
stress-strain curve of the material.
hardening rate, deformation- induced
α’-martensite
[15, 16]
strongly
related
to
the
nonlinearity
of
[14]
,
SAFETY MARGINS
flow stress and mechanical properties of ASS with various degrees of CS are studied
is
.
In order to understand the safety margins of ASS
Owing to high ductility and excellent properties at
CPV constructed by using CS, burst tests were
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conducted[18]. Six such vessels were pressurized to burst
pressure was measured under room temperature. The
at room temperature. Then the ratio of the collapse
actual tensile strength of ASS at -196 ℃ is at least twice
pressure to the design pressure, which is shown in Table 2,
that at room temperature [19]. So the actual strength
is used as safety margins.
margins will reach to 4.18-4.98, which indicates the
It shows that the safety margins of cold stretched
safety of cold stretched ASS CPV can be guaranteed.
vessels under room temperature are between 2.09 and 2.49. But it should be remembered that the collapse Table 2 Safety margins of pressure vessels under different codes GB150 Thickness Diameter No.
Plastic collapse
material /mm
/mm
EN13530-2 Appendix C
pressure/MPa
Design pressure
Strength
Design pressure
Strength
/MPa
margins
/MPa
margins
1
6.5
500
16.2
3.52
4.60
7.01
2.31
2
6.5
500
14.8
3.52
4.20
7.01
2.11
3
12.6
500
28
6.74
4.15
13.42
2.09
12.8
500
29
6.84
4.24
13.63
2.13
5
6.1
600
11.1
2.79
3.98
4.5
2.49
6
11.3
600
19.3
5.16
3.74
8.2
2.37
4
1.4301
So far, thousands of cold stretched ASS CPV have
is verified by test results
[17]
.
PRESSURE CONTROL SYSTEM FOR CS
been manufactured according to the CS standards such as AS 1210 Supplement 2, EN 13458-2, EN 13530-2 and
It is shown that pressurizing rate and CS pressure
ASME Code Case 2596 and there have no related
have significant effects on plastic deformation during
accidents reported. It has been demonstrated that the
CS[20]. In order to accurately control pressurizing rate and
security of the CS CPV can be guaranteed as long as they
CS pressure, a unique pressure control system for CS has
are under normal use.
been developed by the authors. It consists of four
NONLINEAR SIMULATION
sub-system, i.e., multi-task control subsystem, on-line
In contrast with static CPV with small volume,
automatic parameters (including pressure, circumference,
transportable CPV, and static CPV with large volume
etc.) measuring subsystem, automatic water filling
always have some structural attachments such as
subsystem, and automatic de-loading system. The system
openings, stiffening rings, anti-wave boards, subplates,
has the following functions:
etc, which would cause local structural discontinuity, and
(1)
Cold stretch several ASS CPV in parallel.
thus stress concentration under pressure. It is crucial to
(2)
Automatically
ensure that plastic deformation in those areas be within
(3) Nonlinear finite element analysis model has been by
considering
material
the
change
in
circumference and volume.
9%.
developed
measure
Automatically
fill
water,
pressurize,
and
de-pressurize.
nonlinearity,
(4)
geometrical nonlinearity, and contact nonlinearity, which
the
4
Production procedure record contains at least
following
information:
pressurizing
sequence,
Copyright © 2011 by ASME
Design, fabrication, inspection and testing[S].
changes in circumference and volume, strain rate [7]
calculated from circumference measurements. (5)
ISO
21009-1:2008.
Cryogenic
vessels-Static
vacuum-insulated vessels-Part 1: Design, fabrication,
Data management.
inspection and tests[S].
CONCLUDING COMMENTS Although CS technology has been successfully used
[8]
ASME BPVC VIII-I Code Case 2596: 2008, [S].
[9]
Cold-Stretching Directions 1991. Swedish Pressure Vessel Standardization[S].
all over the world, the following future investigations
[10] Johan Ingvar, Johansson. Austenitic Stainless Steel Pressure Vessels [P]. US 3456831 A, 1969.
should be conducted.
[11] ZHENG Jinyang, MIAO Cunjian, SHOU Binan.
(1) There is no fatigue design curve for cold stretched
Light-weight: A Trend in the Development of
ASS. The effect of plastic deformation achieved by
Pressure Vessels [J]. Pressure Vessels Technology,
CS on fatigue properties of ASS should be studied
2009, 26(9):42-48.
both at room temperature and -196 ℃.
[12] GB 24511-2009, Stainless Steel Plate, Sheet and
(2) Stress due to dynamic load on the road may cause
Strips for Pressure Equipment[S]. (in Chinese)
fatigue of cold stretched transportable cryogenic
[13] CAI Qigang. The Application and Trends of
vessels. Method for calculating such stress, which is
Aluminium Alloy for Automobile Body [J] . Guangxi Journal of Light Industry, 2009, 25(1):28-29.
the basis for fatigue prediction, should be developed by
considering
the
effect
of
[14] Cunjian Miao, Yaxian Li, Jinyang Zheng. Effect of
structure-fluid
Strain Rate on the Deformation-Induced Martensitic
interaction.
Transformation
and
Mechanical
Behavior
of
Austenitic Stainless Steels for Cold Stretched
ACKNOWLEDGEMENTS
Pressure Vessels[C]. Washington: 2010 ASME
This research is supported by National High
Pressure Vessels and Piping Conference.
Technology Research and Development Program of
[15] ZHOU Gaobin. Strain Hardening of Cryogenic
China (863 Program) (Number: 2009AA044801).
Vessels form Austenitic Stainless Steels [D]. Hangzhou, P.R.China, Dissertation Submitted to
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Copyright © 2011 by ASME
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