ASME Section VIII div 2 2010. ASME Boiler and Pressure Vessel Code. Alternative Rules
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2010 SECTION VIII, DIVISION 2
4-455
4.B.3.3 It should be noted that there is a higher likelihood of personnel being close to the vessel and the
closure when accidents during opening occur, especially those due to violations of operating procedures. An
example is attempting to pry open the closure when they believe the vessel has been depressurized and it
may not be.
4.B.3.4 The passive safety features described below can help to protect against such actions, but most can
still be subverted. Protection against subversion of safety features is covered under Inspection, Training, and
Administrative Controls.
4.B.3.5 Structural Elements in the vessel and the closure require design margins. However, it is also
important to provide the suggested features listed below, for erroneous opening.
a) Passive Actuation – A passively actuated safety feature or device does not require the operator to take
any action to provide safety. An example is a pressure relief valve in a vessel or a pressure-actuated
locking device in a quick-actuating closure.
b) Redundancy – A redundant safety feature or device is one of two or more features or devices that
perform the same safety function. Two pressure-actuated locking devices in parallel are an example
application to quick-actuating closures. Another example is two or more independent holding elements,
the failure of one of which does not reduce the capability to withstand pressure loadings below an
acceptable level.
c) Fail-Safe Behavior – If a device or element fails, it should fail in a safe mode. An example applicable to
quick-actuating closures is a normally-closed electrical interlock that stays locked if power fails.
d) Multiple Lines of Defense – This can consist of any combination of two or more items from the list above.
They should consist, at the very least, of warnings or alarms.
4.B.3.6 Pressure controls and sensors that operate well at 350kPa or 700kPa (50psi or 100psi) or at much
greater pressure do not operate well at very low pressure. For example, they may not sense a small, static
head of hot fluid. Certain accidents can occur because of the release of hot fluid under static head alone, or
under very low pressure. To protect against such accidents, separate controls and sensors may be used to
maintain operating pressure on the one hand, and others may be required to prevent inappropriate opening at
low pressures.
4.B.3.7 It may be necessary or desirable to utilize electrical or electronic devices and interlocks. If these
are used, careful detailed installation, operating, and maintenance instructions (see following) shall be
required.
4.B.3.8 The effects of repetitive loading shall be considered. There are two phenomena that are of major
concern. The first is the wear produced by repetitive actuation of the mechanism. This can generally be
mitigated by routine maintenance. The second is fatigue damage produced in the vessel or in the closure by
repetitive actuation of the mechanism or by repetitive pressurization and depressurization.
4.B.3.9 The code does not provide explicit guidance for the evaluation or mitigation of wear. As well as
proper maintenance, the selection of suitable materials for mating wear surfaces and control of contact
stresses is necessary during the design process to properly control wear.
4.B.4 Installation
4.B.4.1 The manufacturer shall provide clear instructions for the installation of the quick-actuating closure
itself and any adjustments that are necessary in the field. An example is adjustment of wedges or clamps.
4.B.4.2 Instructions, preferably including schematics and drawings, shall be provided for the installation,
adjustment, and checkout of interlocks and warning devices.
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4.B.4.3 Maintenance
4.B.4.4 Vessels with quick-actuating closures are commonly installed in industrial environments subject to
dirt, moisture, abrasive materials, etc. These environmental factors are detrimental to safe and reliable
operation of mechanical, electrical and electronic sensors and safety devices. Therefore, the user should
establish a suitable cleaning and maintenance interval, and a means to verify that the equipment has been
properly cleaned and maintained.
4.B.4.5 Accidents have occurred because gaskets have stuck, and have released suddenly when pried
open. Many soft gaskets (60-70 Shore A Scale) have a combined shelf life and operating life of as little as six
months. Aging can change the properties of the gasket material and change the gasket dimensions,
impeding its proper function.
4.B.5 Inspection
4.B.5.1 It is recommended that the user inspect the completed installation including the pressure gauges
before it is permitted to operate. Records of this inspection should be retained.
4.B.5.2 It is recommended that the user establish and document a periodic in-service inspection program,
and that this program be followed and the results documented.
4.B.6 Training
4.B.6.1 Many accidents involving quick-actuating closures have occurred because the operators have been
unfamiliar with the equipment or its safety features. The greater safety inherent in current designs has
sometimes been produced by the use of sophisticated mechanical, electrical or electronic control devices. In
order to make these features produce the maximum safety, personnel should be properly trained in their
operation and maintenance.
4.B.6.2 Note that accidents may occur because hot fluid remains present in the vessel at atmospheric
pressure of 15 kPa to 20 kPa (2 psig to 3 psig). If the vessel is forced open while under this pressure, then
injuries may occur. Such specific accident sources should be guarded against by training and by
administrative procedures. It is important that sound written operating procedures, understandable by the
operating personnel and multi-lingual if necessary, exist for the quick-actuating closure, and that the
operators be trained in the proper use of all interlocks, sensing devices, and manual closure mechanisms.
4.B.6.3 Provision of written operation and maintenance procedures and training of personnel are the
responsibility of the user.
4.B.6.4 As part of the training program, testing should be performed to ensure that the trainee understands
the material he or she is trained in. Records should be retained by the user.
4.B.7 Administrative Controls
The user should provide administrative controls covering training, cleanliness, operation, periodic inspection,
and maintenance of equipment with quick-actuating closures. Records should be retained by the user.
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2010 SECTION VIII, DIVISION 2
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ANNEX 4.C
BASIS FOR ESTABLISHING ALLOWABLE LOADS FOR TUBE-
TO-TUBESHEET JOINTS
(NORMATIVE)
4.C.1 General
4.C.1.1 This Annex provides a basis for establishing allowable tube-to-tubesheet joint loads, except for the
following.
a) Tube-to-tubesheet joints having full-strength welds as defined in accordance with paragraph 4.18.10.2.a
shall be designed in accordance with paragraph 4.18.10.3 and do not require shear load testing.
b) Tube-to-tubesheet joints having partial-strength welds as defined in accordance with paragraph
4.18.10.2.b and designed in accordance with paragraph 4.18.10.4 do not require shear load testing.
4.C.1.2 The rules of this Annex are not intended to apply to U-tube construction.
4.C.1.3 Tubes used in the construction of heat exchangers or similar apparatus may be considered to act
as stays which support or contribute to the strength of the tubesheets in which they are engaged. Tube-to-
tubesheet joints shall be capable of transferring the applied tube loads. The design of tube-to-tubesheet
joints depends on the type of joint, degree of examination, and shear load tests, if performed. Some
acceptable geometries and combinations of welded and mechanical joints are described in Table 4.C.1.
Some acceptable types of welded joints are illustrated in Figure 4.C.1.
a) Geometries, including variations in tube pitch, fastening methods, and combinations of fastening
methods, not described or shown, may be used provided qualification tests have been conducted and
applied in compliance with the procedures in paragraphs 4.C.3 and 4.C.4.
b) Materials for welded tube-to-tubesheet joints which do not meet the requirements of Part 6, but in all
other respects meet the requirements of this Division, may be used if qualification tests of the tube-to-
tubesheet joint have been conducted and applied in compliance with the procedures in paragraphs 4.C.3
and 4.C.4.
4.C.1.4 Some combinations of tube and tubesheet materials, when welded, result in welded joints having
lower ductility than required in the material specifications. Appropriate tube-to-tubesheet joint geometry,
welding method, and/or heat treatment shall be used with these materials to minimize this effect.
4.C.1.5 In the selection of joint type, consideration shall be given to the mean metal temperature of the joint
at operating temperatures and differential thermal expansion of the tube and tubesheet which may affect the
joint integrity. The following provisions apply for establishing maximum operating temperature for tube-to-
tubesheet joints.
a) Tube-to-tubesheet joints made by welding shall be limited to the maximum temperature for which there
are allowable stresses for the tube or tubesheet material in Annex 3.A.
b) Tube-to-tubesheet joints that depend on friction between the tube and the tube hole such as in Joint
Types i, j, and k as shown in Table.4.C.1, shall be limited to temperatures as determined by the
following.
1) The operating temperature of the tube-to-tubesheet joint shall be within the tube and tubesheet time
independent properties as provided in Annex 3.A.
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2) The maximum operating temperature is based on the interface pressure that exists between the
tube and tubesheet. The maximum operating temperature is limited such that the interface
pressure due to expanding the tube at joint fabrication plus the interface pressure due to differential
thermal expansion,
()
oT
PP+ , does not exceed 58% of the smaller of the tube or tubesheet yield
strength in Annex 3.D at the operating temperature. If the tube or tubesheet yield strength is not
listed in Annex 3.D, the operating temperature limit shall be determined as described in 4.C.1.5.b.4.
The interface pressure due to expanding the tube at fabrication or the interface pressure due to
differential thermal expansion may be determined analytically or experimentally.
3) Due to differential thermal expansion, the tube may expand less than the tubesheet. For this
condition, the interfacial pressure
T
P is a negative number.
4) When the maximum temperature is not determined by 4.C.1.5.b.2, or the tube expands less than or
equal to the tubesheet, joint acceptability shall be determined by shear load tests described in
4.C.3. Two sets of specimens shall be tested. The first set shall be tested at the proposed
operating temperature. The second set shall be tested at room temperature after heat soaking at
the proposed operating temperature for 24 hours. The proposed operating temperature is
acceptable if the provisions of paragraph 4.C.5 are satisfied.
4.C.1.6 The Manufacturer shall prepare written procedures for joints which are expanded (whether welded
and expanded or expanded only) for joint strength. The Manufacturer shall establish the variables that affect
joint repeatability in these procedures. The procedures shall provide detailed descriptions or sketches of
enhancements, such as grooves, serrations, threads, and coarse machining profiles. The Manufacturer shall
make these written procedures available to the Authorized Inspector.
4.C.2 Maximum Axial Loads
The maximum allowable axial load in either direction on tube-to-tubesheet joints shall be determined in
accordance with the following:
max tar
L A S f Joint Types a,b,b - 1,e= (4.C.1)
max
,,
taery
L A S f f f Joint Types f g h= (4.C.2)
max
,,
taeryT
L A S f f f f Joint Types i j k=
(4.C.3)
where
()
to
Adtt
π
=− (4.C.4)
a
SkS= (4.C.5)
oT
T
o
PP
f
P
+
=
(4.C.6)
4.C.3 Shear Load Test
4.C.3.1 Flaws in the specimen may affect results. If any test specimen develops flaws, the retest provisions
of paragraph 4.C.3.11 shall govern.
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2010 SECTION VIII, DIVISION 2
4-459
4.C.3.2 If any test specimen fails because of mechanical reasons, such as failure of testing equipment or
improper specimen preparation, it may be discarded and another specimen taken from the same heat.
4.C.3.3 The shear load test subjects a full-size specimen of the tube joint under examination to a measured
load sufficient to cause failure. In general, the testing equipment and methods are given in the Methods of
Tension Testing of Metallic Materials (ASTM E 8). Additional fixtures for shear load testing of tube-to-
tubesheet joints are shown in Figure 4.C.2.
4.C.3.4 The test block simulating the tubesheet may be circular, square or rectangular in shape, essentially
in general conformity with the tube pitch geometry. The test assembly shall consist of an array of tubes such
that the tube to be tested is in the geometric center of the array and completely surrounded by at least one
row of adjacent tubes. The test block shall extend a distance of at least one tubesheet ligament beyond the
edge of the peripheral tubes in the assembly.
4.C.3.5 All tubes in the test block array shall be from the same heat and shall be installed using identical
procedures.
a) The finished thickness of the test block may be less but not greater than the tubesheet it represents. For
expanded joints, made with or without welding, the expanded area of the tubes in the test block may be
less but not greater than that for the production joint to be qualified.
b) The length of the tube used for testing the tube joint need only be sufficient to suit the test apparatus.
The length of the tubes adjacent to the tube joint to be tested shall not be less than the thickness of the
test block to be qualified.
4.C.3.6 The procedure used to prepare the tube-to-tubesheet joints in the test specimens shall be the same
as used for production.
4.C.3.7 The tube-to-tubesheet joint specimens shall be loaded until mechanical failure of the joint or tube
occurs. The essential requirement is that the load be transmitted axially.
4.C.3.8 Any speed of testing may be used provided load readings can be determined accurately.
4.C.3.9 The reading from the testing device shall be such that the applied load required to produce
mechanical failure of the tube-to-tubesheet joint can be determined.
4.C.3.10 For determining
,rtest
f
for joint types listed in Table 4.C.1, a minimum of three specimens shall
constitute a test. The value of
,rtest
f
shall be calculated in accordance with paragraph 4.C.4.1 using the lowest
value of
test
L . In no case shall the value of
,rtest
f
using a three specimen test exceed the value of
,rtest
f
given in Table 4.C.1. If the value of
,rtest
f
so determined is less than the value for
,rtest
f
given in Table 4.C.1,
retesting shall be performed in accordance with paragraph 4.C.3.11, or a new three specimen test shall be
performed using a new joint configuration or fabrication procedure. All previous test data shall be rejected.
To use a value of
,rtest
f
greater than the value given in Table 4.C.1, a nine specimen test shall be performed
in accordance with paragraph 4.C.3.11.
4.C.3.11 For joint types not listed in Table 4.C.1, to increase the value of
,rtest
f
for joint types listed in Table
4.C.1, or to retest joint types listed in Table 4.C.1, the tests to determine
,rtest
f
shall conform to the following.
a) A minimum of nine specimens from a single tube shall be tested. Additional tests of specimens from the
same tube are permitted provided all test data are used in the determination of
,rtest
f
. If a change in the
2010 SECTION VIII, DIVISION 2
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joint design or its manufacturing procedure is necessary to meet the desired characteristics, complete
testing of the modified joint shall be performed.
b) In determining the value of
,rtest
f
, the mean value of
test
L shall be determined and the standard
deviation, sigma, about the mean shall be calculated. The value of
,rtest
f
shall be calculated using the
value of
test
L corresponding to -2 sigma, using the applicable equation in paragraph 4.C.4. In no case
shall
,rtest
f
exceed 1.0.
4.C.4 Acceptance Standards for Joint Efficiency Factor Determined By Test
4.C.4.1 The value of
,rtest
f
determined by testing shall be calculated as follows.
,
test
rtest
tT
L
f
Joint Types a,b,b - 1,e
AS
= (4.C.7)
,
,,,,,
test
rtest
tTey
L
f
Joint Types f g h i j k
AS f f
=
(4.C.8)
4.C.4.2 The value of
,rtest
f
shall be used for
r
f
in the equation for
max
L .
4.C.5 Acceptance Standards for Proposed Operating Temperatures Determined By Test
The proposed operating conditions shall be acceptable if both of the following conditions are satisfied.
1,test t e y T
LAffS≥ (4.C.9)
2,test t e y T
LAffS≥ (4.C.10)
4.C.6 Nomenclature
t
A tube cross-sectional area.
o
d nominal tube outside diameter.
e
f
factor for the length of the expanded portion of the tube.
()
min / , 1.0
eo
fld=
⎡⎤
⎣⎦
for tube
joints made with expanded tubes in tube holes without enhancement and
1.0
e
f = for tube
joints made with expanded tubes in tube holes with enhancement. An expanded joint is a
joint between the tube and tubesheet produced by applying an expanding force inside the
portion of the tube to be engaged in the tubesheet. The expanding force shall be set to
values necessary to effect sufficient residual interface pressure between the tube and hole
for joint strength.
r
f
factor to define the efficiency of joint, set equal to the value of
,rtest
f
or
,rnotest
f .
,rtest
f
is
equal to the value calculated from results of test in accordance with 4.C.4 or as tabulated in
Table 4.C.1, whichever is less, except as permitted in paragraph 4.C.3.11.
,rnotest
f is equal
to maximum allowable value without qualification test in accordance with Table 4.C.1.
,rtest
f
factor to define the efficiency of joint established in a test.
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2010 SECTION VIII, DIVISION 2
4-461
,rnotest
f factor to define the efficiency of joint established without a test.
T
f
factor to account for the increase or decrease of tube joint strength due to radial differential
thermal expansion at the tube-to-tubesheet joint.
y
f
factor for differences in the mechanical properties of tubesheet and tube materials.
()
,,
min , 1.0
yytsyt
fSS
⎡⎤
=
⎣⎦
for expanded joints. When
y
f
is less than 0.60, qualification
tests in accordance with paragraphs 4.C.3 and 4.C.4 are required.
k tube load factor.
1.0= for loads due to pressure-induced axial forces
1.0=
for loads due to thermally-induced or pressure plus thermally-induced axial forces on
welded-only joints where the thickness through the weld throat is less than the nominal tube
wall thickness t .
2.0=
for loads due to thermally-induced or pressure plus thermally-induced axial forces on
all other tube-to-tubesheet joints.
l
expanded tube length.
max
L maximum allowable axial load in either direction on the tube-to-tubesheet joint.
test
L axial load at which failure of the test specimens occur.
1,test
L lowest axial load at which failure occurs at operating temperature.
2,test
L lowest axial load at which failure of heat soaked specimen tested at room temperature
occurs.
o
P interface pressure between the tube and tubesheet that remains after expanding the tube at
fabrication. This pressure may be established analytically or experimentally, but shall
consider the effect of change in material strength at operating temperature.
T
P interface pressure between the tube and tubesheet due to differential thermal growth. This
pressure may be established analytically or experimentally.
S
allowable stress from Annex 3.A for the tube at the design temperature. For a welded tube,
S is the equivalent allowable stress for a seamless tube.
a
S modified tube allowable stress.
,yt
S tube specified minimum yield strength at the design temperature from Annex 3.D.
,yts
S tubesheet specified minimum yield strength at the design temperature from Annex 3.D.
T
S tensile strength for tube material from the material test report
y
S tensile strength for tube material at operating temperature from Annex3.D.
ua
S tensile strength for tube material at room temperature from Annex 3.D.
t nominal tube wall thickness.
2010 SECTION VIII, DIVISION 2
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4.C.7 Tables
Table 4.C.1 – Efficiencies for Welded and/or Expanded Tube-To-Tubesheet Joints
Joint Type Description (1) Notes
,rtest
f
(2)
,rnotest
f
a
Welded only,
1.4at≥
3 1.00 0.80
b
Welded only,
1.4ta t≤<
3 0.70 0.55
b-1
Welded only,
at<
4 0.70 ---
e
Welded,
1.4at≥ , and expanded
3 1.00 0.80
f
Welded,
1.4at< , and expanded
Enhanced with two or more grooves
3, 5, 6, 7 0.95 0.75
g
Welded,
1.4at< , and expanded
Enhanced with single groove
3, 5, 6, 7 0.85 0.65
h
Welded,
1.4at< , and expanded
Not enhanced
3, 5, 6 0.70 0.50
i
Expanded,
Enhanced with two or more grooves
5, 6, 7 0.90 0.70
j
Expanded
Enhanced with single groove
5, 6, 7 0.80 0.65
k
Expanded
Not enhanced
5, 6 0.60 0.50
Notes:
1) For joint types involving more than one fastening method, the sequence used in the joint
description does not necessarily indicate the order in which the operations are performed.
2) The use of the
,rtest
f
factor requires qualification in accordance with paragraphs 4.C.3 and 4.C.4.
3) The value of
,rnotest
f applies only to material combinations as provided for under Section IX. For
material combinations not provided for under Section IX,
r
f
shall be determined by test in
accordance with paragraphs 4.C.3 and 4.C.4.
4) For
,rnotest
f
, refer to paragraph 4.18.10.2.b.
5) If
()
21.05
oo
dd t−<
or
()
2 1.410
oo
dd t−>
,
r
f
shall be determined by test in accordance
with paragraphs 4.C.3 and 4.C.4.
6) If the nominal pitch (center-to-center distance of adjacent tube holes) is less than
2
o
dt
+
,
r
f
shall be determined by test in accordance with paragraphs 4.C.3 and 4.C.4.
7) The Manufacturer may use other means to enhance the strength of expanded joints, provided
however, that the joints are tested in accordance with paragraphs 4.C.3 and 4.C.4.
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2010 SECTION VIII, DIVISION 2
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4.C.8 Figures
t
a
t
a
t
a
t
a
Some acceptable weld geometries where a is greater than or equal to 1.4t
Some acceptable weld geometries where a is less than 1.4t
t
0 to t max.
a
t
a
t
a
t
a
t
a
(1) (2)
(3) (4)
Figure 4.C.1 – Some Acceptable Types of Tube-To-Tubesheet Joints
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Snap Ring
Snap Ring
Cylinder
N.P.T.
Test Block
Test Block
O-Ring
(typical)
Test Apparatus Plunger
to Apply Load
Test Block
Test Block
Support
Stiffening Ring
Sectional Grips
Alternate Arrangement
for Non-Weldable Tubes
Plunger
Hydraulic Method
Figure 4.C.2 –Typical Test Fixtures for Expanded or Welded Tube-To-Tubesheet Joints
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