Section
5 Carbon and low alloy steels
5.1 General
5.1.3 The minimum
thickness t
b, of a straight steel pipe to
be used for a pipe bend is to be determined by the following formula,
except where it can be demonstrated that the use of a thickness less
than t
b would not reduce the thickness below t at any point after bending:
where symbols are as defined in Pt 15, Ch 1, 4.1 Design symbols 4.1.1.
c and σ
are obtained as in Pt 15, Ch 1, 5.1 General 5.1.2
In general, R is to be not less than 3D.
Table 1.5.1 Minimum thickness for steel
pipes
| External diameter D
|
Minimum pipe thickness
|
| mm
|
mm
|
| 10,2 -
12
|
1,6
|
| 13,5 -
19
|
1,8
|
| 20 -
44,5
|
2,0
|
| 48,3 -
63,5
|
2,3
|
| 70 -
82,5
|
2,6
|
| 88,9 -
108
|
2,9
|
| 114,3 -
127
|
3,2
|
| 133 -
139,7
|
3,6
|
| 152,4 -
168,3
|
4,0
|
| 177,8 and
over
|
4,5
|
Note
1. The thickness of air, overflow and
sounding pipes for structural tanks is to be not less than 4,5 mm.
Note
2. The thickness of bilge, ballast and
general sea water pipes is to be not less than 4,0 mm.
Note
3. The thickness of bilge, air, overflow
and sounding pipes through ballast and fuel oil tanks, ballast lines
through fuel oil tanks and fuel oil lines through ballast tanks is to
be not less than 6,3 mm.
Note
4. For air, bilge, ballast, fuel oil,
overflow, sounding, and venting pipes as mentioned in Notes 1 to 3,
where the pipes are efficiently protected against corrosion the
thickness may be reduced by not more than 1 mm.
Note
5. For air and sounding pipes the minimum
thickness applies to the part of the pipe outside the tank but not
exposed to weather. The section of pipe exposed to weather may be
required to be suitably increased in thickness in accordance with
statutory and loadline requirements as applicable.
|
5.1.4 For pipes
passing through tanks, where the thickness has been calculated in
accordance with Pt 15, Ch 1, 5.1 General 5.1.2 or Pt 15, Ch 1, 5.1 General 5.1.3, an additional corrosion allowance
is to be added to take account of external corrosion; the addition
will depend on the external medium and the value is to be in accordance
with Table 1.5.2 Values of corrosion allowance
(c) for steel pipes .
Table 1.5.2 Values of corrosion allowance
(c) for steel pipes
| Piping
service
|
c, in mm
|
| Saturated
steam systems
|
0,8
|
| Compressed
air systems
|
1,0
|
| Hydraulic
oil systems
|
0,3
|
| Lubricating
oil systems
|
0,3
|
| Fuel oil
systems
|
1,0
|
| Refrigerating plants
|
0,3
|
| Fresh water
systems
|
0,8
|
| Sea-water
systems in general
|
3,0
|
5.1.5 Where
the pipes are efficiently protected against corrosion, the corrosion
allowance, c, may be reduced by not more than 50 per
cent.
5.1.6 The maximum
permissible design stress, σ, is to be taken as the lowest of
the following values:
where
|
E
t
|
= |
specified minimum lower yield or 0,2 per cent proof stress at
the design temperature |
|
R
20
|
= |
specified minimum tensile strength at ambient temperature |
|
S
R
|
= |
average stress to produce rupture in 100 000 hours at the design
temperature |
Values of E
t, R
20 and S
R may be obtained from Ch 6 Steel Pipes and Tubesof the Rules for Materials. Intermediate values may be obtained
by interpolation.
5.1.7 Steel
stub pipes between the shell plating and the sea valve are to be of
short rigid construction, adequately supported and of substantial
thickness.
Table 1.5.3 Carbon and carbon-manganese steel
pipes
| Specified minimum tensile strength, N/mm2
|
Maximum permissible design stress, N/mm2
|
| Maximum design temperature, oC
|
| 50
|
100
|
150
|
200
|
250
|
300
|
350
|
400
|
410
|
420
|
430
|
440
|
450
|
| 320
|
107
|
105
|
99
|
92
|
78
|
62
|
57
|
55
|
55
|
54
|
54
|
54
|
49
|
| 360
|
120
|
117
|
110
|
103
|
91
|
76
|
69
|
68
|
68
|
68
|
64
|
56
|
49
|
| 410
|
136
|
131
|
124
|
117
|
106
|
93
|
86
|
84
|
79
|
71
|
64
|
56
|
49
|
| 460
|
151
|
146
|
139
|
132
|
122
|
111
|
101
|
99
|
98
|
85
|
73
|
62
|
53
|
| 490
|
160
|
156
|
148
|
141
|
131
|
121
|
111
|
109
|
98
|
85
|
73
|
62
|
53
|
5.2 Steel pipe joints
5.2.1 Joints in steel pipelines may be made by:
- Welded-on bolted flanges, see
Pt 15, Ch 1, 5.3 Welded-on flanges, butt welded joints and fabricated branch pieces.
- Butt welds between pipes and between pipes and valve chests, see
Pt 15, Ch 1, 5.3 Welded-on flanges, butt welded joints and fabricated branch pieces.
- Threaded connections, see
Pt 15, Ch 1, 5.4 Fittings having threaded end connections.
- Threaded sleeve joints and threaded couplings, see
Pt 15, Ch 1, 5.5 Threaded sleeve joints and threaded couplings.
- Socket weld joints, see
Pt 15, Ch 1, 5.6 Socket weld joints.
- Welded sleeve joints, see
Pt 15, Ch 1, 5.7 Welded sleeve joints.
- Mechanical couplings, see
Pt 15, Ch 1, 5.8 Other mechanical couplings.
- Special types of joints that have been shown to be suitable for the
design conditions. Details are to be submitted for consideration.
5.2.3 Where pipes are joined by welding a suitable number of flanged joints are
to be provided at suitable positions to facilitate installation and removal for
maintenance.
5.2.4 Where welded pipes are protected against corrosion then the corrosion
protection is to be applied after welding or the corrosion protection is to be made good
in way of the weld damaged area.
5.2.5 Where it is not possible to make good the corrosion protection of the weld
damaged area, then the pipe is to be considered to have no corrosion protection.
5.2.6 Where backing rings are used for welding pipes, then the effect of the flow
obstruction of the backing ring and erosion/crevice corrosion of the backing ring is to
be taken into account.
5.2.7 Piping with joints is to be adequately adjusted, aligned and supported. Supports or
hangers are not to be used to force alignment of piping at the point of connection.
5.3 Welded-on flanges, butt welded joints and fabricated branch pieces
5.3.1 The dimensions
and material of flanges and bolting, and the pressure-temperature
rating of bolted flanges in pressure pipelines, in accordance with
National or other established standards will be accepted.
5.3.2 The types
of welded-on flanges are to be suitable for the pressure, temperature
and service for which the pipes are intended.
5.3.4 Welded-on
flanges are not to be a tight fit on the pipes. The maximum clearance
between the bore of the flange and the outside diameter of the pipe
is to be 3 mm at any point, and the sum of the clearances diametrically
opposite is not to exceed 5 mm.
5.3.5 Where
butt welds are employed in the attachment of flange type (a), in pipe-to-pipe
joints or in the construction of branch pieces, the adjacent pieces
are to be matched at the bores. This may be effected by drifting,
roller expanding or machining, provided that the pipe wall is not
reduced below the designed thickness. If the parts to be joined differ
in wall thickness, the thicker wall is to be gradually tapered to
the thickness of the thinner at the butt joint. The welding necks
of valve chests are to be sufficiently long to ensure that the valves
are not distorted as the result of welding and subsequent heat treatment
of the joints.
Figure 1.5.1 Typical examples of welded flange connections
5.3.6 Where
backing rings are used with flange type (a) they are to fit closely
to the bore of the pipe and should be removed after welding. The rings
are to be made of the same material as the pipes or of mild steel
having a sulphur content not greater than 0,05 per cent.
5.3.7 Branches
may be attached to pressure pipes by means of welding provided that
the pipe is reinforced at the branch by a compensating plate or collar
or other approved means, or alternatively that the thickness of pipe
and branch are increased to maintain the strength of the pipe. These
requirements also apply to fabricated branch pieces.
Table 1.5.4 Limiting design conditions for
flange types
| Flange
type
|
Maximum pressure
|
Maximum
temperature
|
Maximum
pipe o.d.
|
Minimum pipe bore
|
|
|
|
oC
|
mm
|
mm
|
| (a)
|
Pressure-temperature ratings to be in accordance with a
recognised standard
|
No
restriction
|
No
restriction
|
No
restriction
|
| (b)
|
Pressure-temperature ratings to be in accordance with a
recognised standard
|
No
restriction
|
168,3 for
alloy steels*
|
No
restriction
|
| (c)
|
Pressure-temperature ratings to be in accordance with a
recognised standard
|
No
restriction
|
168,3 for
alloy steels*
|
75
|
| (d)
|
Pressure-temperature ratings to be in accordance with a
recognised standard
|
425
|
No
restriction
|
No
restriction
|
| (e)
|
Pressure-temperature ratings to be in accordance with a
recognised standard
|
425
|
No
restriction
|
75
|
| (f)
|
Pressure-temperature ratings to be in accordance with a
recognised standard
|
425
|
No
restriction
|
No
restriction
|
| * No restriction for carbon steels
|
5.4 Fittings having threaded end
connections
5.4.2 In piping systems conveying flammable or toxic liquids, consideration will be given to
instrumentation fittings having threaded connections with suitable sealing arrangements
up to a size of DN15.
5.5 Threaded sleeve joints and threaded
couplings
5.5.1 Threaded sleeve joints and threaded couplings in accordance with National or other
established standards may be used with carbon steel pipes within the limits given in
Table 1.5.5 Limiting design conditions for threaded sleeve joints and threaded
couplings. Such joints are not to be used
in piping systems where fatigue, severe erosion or crevice corrosion is expected to
occur or where flammable or toxic liquids are conveyed.
Table 1.5.5 Limiting design conditions for threaded sleeve joints and threaded
couplings
| Thread type
|
Outside pipe
diameter, in mm
|
| Class I
|
Class II
|
Class III
|
| Tapered thread
|
<33,7
|
<60,3
|
<60,3
|
| Parallel thread
|
-
|
-
|
<60,3
|
| KEY
|
| - Application is not
allowed
|
5.6 Socket weld joints
5.6.1 Socket weld joints may be used in Class III systems with carbon steel pipes
of any outside diameter. Socket weld fittings are to be of forged steel and the material
is to be compatible with the associated piping. In particular cases, socket weld joints
may be permitted for piping systems of Class I and II having outside diameter not
exceeding 88,9 mm. Such joints are not to be used where fatigue, severe erosion or
crevice corrosion is expected to occur or where toxic liquids are conveyed See
also
Pt 15, Ch 4, 7.3 Welded-on flanges, butt welded joints and fabricated branch pieces 7.3.9.
5.6.2 The thickness of the socket weld fittings is to meet the requirements of
Pt 15, Ch 1, 5.1 General 5.1.3 but is to be not less than 1,42 times the nominal
thickness of the pipe or tube tube in order to satisfy the throat thickness requirement
in Pt 15, Ch 1, 5.6 Socket weld joints 5.6.3. The diametrical clearance between the outside diameter of
the pipe and the bore of the fitting is not to exceed 0,8 mm, and a gap of approximately
1,5 mm is to be provided between the end of the pipe and the bottom of the socket.
See also
Ch 13, 5.2 Manufacture and workmanship 5.2.9 of the Rules for the Manufacture, Testing and Certification of Materials, July 2022.
5.6.3 The leg lengths of the fillet weld connecting the pipe to the socket weld
fitting are to be such that the throat dimension of the weld is not less than the
nominal thickness of the pipe or tube.
5.7 Welded sleeve joints
5.7.2 The thickness of the sleeve is to satisfy the requirements of Pt 15, Ch 1, 5.1 General 5.1.2 and Table 1.5.1 Minimum thickness for steel
pipes but is to be not less than
1,42 times the nominal thickness of the pipe in order to satisfy the throat thickness
requirement in Pt 15, Ch 1, 5.7 Welded sleeve joints 5.7.3. The radial clearance between the outside
diameter of the pipe and the internal diameter of the sleeve is not to exceed 1 mm for
pipes up to a nominal diameter of 50 mm, 2 mm for pipes up to a nominal diameter of 200
mm and 3 mm for pipes of larger nominal diameter. The pipe ends are to be separated by a
clearance of approximately 2 mm at the centre of the sleeve.
5.7.3 The sleeve material is to be compatible with the associated piping and the leg lengths
of the fillet weld connecting the pipe to the sleeve are to be such that the throat
dimension of the weld is not less than the nominal thickness of the pipe or tube.
5.7.4 The minimum length of the sleeve is to conform to the following formula:
5.7.6 Welded sleeve joints may be used in piping systems for the storage, distribution and
utilisation of oil fuel, lubricating or other flammable oil systems in machinery spaces
provided they are located in readily visible and accessible positions.
5.7.7 Welded sleeve joints are not to be used in bilge pipes in way of deep tanks.
5.7.8 Welded sleeve joints are not to be used below the bulkhead deck in scupper
pipes as detailed in Pt 3, Ch 4, 9.4 Scupper arrangements 9.4.5 unless the scupper pipes are provided with an
automatic non-return valve at the shell. Where this is not practical, welded sleeve
joints may be accepted provided that they are kept to a minimum and located as close as
possible to the underside of the bulkhead deck.
5.8 Other mechanical couplings
5.8.2 Where
the application of mechanical joints results in a reduction in pipe
wall thickness due to the use of bite type rings or other structural
elements, this is to be taken into account in determining the minimum
wall thickness of the pipe to withstand the design pressure.
5.8.3 Materials
of mechanical joints are to be compatible with the piping material
and internal and external media.
5.8.4 Mechanical
joints for pressure pipes are to be tested to a burst pressure of
4 times the design pressure. For design pressures above 200 bar the
required burst pressure will be specially considered.
5.8.5 Mechanical joints, which in the event of damage could cause fire or
flooding, are not to be used in piping sections directly connected to the ship’s side
below the bulkhead deck of passenger ships and freeboard deck of cargo ships or tanks
containing flammable fluids.
5.8.6 Mechanical
joints are to be designed to withstand internal and external pressure
as applicable and where used in suction lines are to be capable of
operating under vacuum.
5.8.7 The number of mechanical joints in flammable fluid systems is to be kept to a minimum.
In general, flanged joints are to conform to a recognised standard.
5.8.8 Generally,
slip-on joints are not to be used in pipelines in cargo holds, tanks,
and other spaces which are not easily accessible. Application of these
joints inside tanks may only be accepted where the medium conveyed
is the same as that in the tanks.
5.8.9 Usage of slip type slip-on joints as the main means of pipe connection is
not permitted except for cases where compensation of axial pipe deformation is
necessary.
5.8.10 Restrained slip-on joints are permitted in steam pipes with a design pressure of 10 bar
or less on the weather decks of oil and chemical tankers to accommodate axial pipe
movement, see
Pt 15, Ch 2, 2.2 Provision for expansion.
5.8.11 Mechanical
joints are to be tested in accordance with the test requirements of
LR’s Type Approval Test Specification Number 2, as relevant
to the service conditions and the intended application. The programme
of testing is to be agreed with LR.
Figure 1.5.2 Examples of mechanical joints
(Part 1)
Figure 1.5.3 Examples of mechanical joints
(Part 2)
Table 1.5.6 Application of mechanical
joints
| Systems
|
Kind of connections
|
|
|
| Pipe unions
|
Compression
couplings
|
Slip-on
joints
|
Classification of
pipe system
|
Fire
endurance test condition, see Note 7
|
| Flammable fluids (flash point > 60°C)
|
| Fuel oil lines,
see Notes 2 & 3
|
+
|
+
|
+
|
wet
|
30 min
wet (*)
|
| Lubricating oil
lines, see Notes 2 & 3
|
+
|
+
|
+
|
wet
|
| Hydraulic oil,
see Notes 2 & 3
|
+
|
+
|
+
|
wet
|
| Thermal oil,
see Notes 2 & 3
|
+
|
+
|
+
|
wet
|
| Sea water
|
| Bilge lines,
see Note 4
|
+
|
+
|
+
|
dry/wet
|
8 min dry + 22 min
wet (*)
|
| Permanent water
filled fire‑extinguishing systems, e.g. fire main, sprinkler systems,
see Note 3
|
+
|
+
|
+
|
wet
|
30 min wet
(*)
|
| Non-permanent water
filled fire‑extinguishing systems, e.g. foam, drencher systems and fire
main, see Note 3
|
+
|
+
|
+
|
dry/wet
|
8 min dry + 22 min wet (*)
For foam systems FSS Code to be observed
|
| Ballast system,
see Note 4
|
+
|
+
|
+
|
wet
|
30 min wet
(*)
|
| Cooling water
system, see Note 4
|
+
|
+
|
+
|
wet
|
30 min wet
(*)
|
| Tank cleaning
services
|
+
|
+
|
+
|
dry
|
Fire endurance test
not required
|
| Non-essential
systems
|
+
|
+
|
+
|
dry, dry/wet,
wet
|
Fire endurance test
not required
|
| Fresh water
|
| Cooling water
system, see Note 4
|
+
|
+
|
+
|
dry
|
Fire
endurance test not required
|
| Condensate return,
see Note 4
|
+
|
+
|
+
|
dry
|
| Non-essential
system
|
+
|
+
|
+
|
dry
|
| Sanitary/drains/scuppers
|
| Deck drains
(internal), see Note 5
|
+
|
+
|
+
|
dry
|
Fire
endurance test not required
|
| Sanitary
drains
|
+
|
+
|
+
|
dry
|
| Scuppers and
discharge (overboard)
|
+
|
+
|
+
|
dry
|
| Sounding/vent
|
| Water tanks/dry
spaces
|
+
|
+
|
+
|
dry, wet
|
Fire
endurance test not required
|
| Oil tanks (f.p. >
60°C), see Notes 2 & 3
|
+
|
+
|
+
|
dry
|
| Miscellaneous
|
| Starting/control
air, see Note 4
|
+
|
+
|
+
|
dry
|
30 min dry
(*)
|
| Service air
(non-essential)
|
+
|
+
|
+
|
dry
|
Fire
endurance test not required
|
| Brine
|
+
|
+
|
+
|
wet
|
| CO2
system (outside protected space)
|
+
|
+
|
+
|
dry
|
30 min dry
(*)
|
| CO2
system (inside protected space)
|
+
|
+
|
+
|
dry
|
Mechanical joints shall be constructed of materials with a
melting point above 925°C. Ref. to FSS Code Chapter 5.
|
| Steam
|
+
|
+
|
+ see Note
8
|
wet
|
Fire endurance test
not required
|
| Abbreviations:
+ Application is allowed.
- Application is
not allowed.
* Fire endurance test as specified in LR’s Test
Specification No. 2, Ch 5, Appendix 4 – Mechanical pipe joints – Fixed
connections, 4.2.7.
|
|
If mechanical joints include any components which readily deteriorate in
case of fire, the following footnotes are to be observed:
Note
1. A fire endurance test shall be applied when mechanical joints
are installed in pump-rooms and open decks.
Note
2. Slip-on joints are not accepted inside machinery spaces of
category A or accommodation spaces. They may be accepted in other
machinery spaces provided the joints are located in easily visible and
accessible positions (refer to MSC/Circ.734).
Note
3. Mechanical joints are to be of approved fire-resistant types
except in cases where such mechanical joints are installed on open decks,
as defined in SOLAS Chapter II-2, Regulation 9.2.3.3.2.2(10), and not
used for fuel oil lines.
Note
4. A fire endurance test shall be applied when mechanical joints
are installed inside machinery spaces of category A.
Note
5. Only above bulkhead deck of passenger ships and freeboard deck
of cargo ships.
Note
7. If a connection has passed the ‘30 min dry’ test, it is
considered suitable also for applications for which the ‘8 min dry + 22
min wet’ and/or ‘30 min wet’ tests are required. If a connection has
passed the ‘8 min dry + 22 min wet’ test, it is considered suitable also
for applications for which the ‘30 min wet’ test is required.
|
Table 1.5.7 Application of mechanical joints
depending on class of piping
| Types of joints
|
Classes of piping systems
|
| Class
I
|
Class
II
|
Class
III
|
|
Pipe unions
|
|
|
|
| Welded and brazed type
|
+(OD ≤
60,3 mm)
|
+(OD ≤
60,3 mm)
|
+
|
|
Compression couplings
|
|
|
|
| Swage type
|
+
|
+
|
+
|
| Bite type
|
+(OD ≤
60,3 mm)
|
+(OD ≤
60,3 mm)
|
+
|
| Typical compression type
|
+(OD≤
60,3mm)
|
+(OD≤
60,3mm)
|
+
|
| Flared type
|
+(OD ≤
60,3 mm)
|
+(OD ≤
60,3 mm)
|
+
|
| Press type
|
–
|
–
|
+
|
|
Slip-on joints
|
|
|
|
| Machine grooved type
|
+
|
+
|
+
|
| Grip type
|
–
|
+
|
+
|
| Slip type
|
–
|
+
|
+
|
| KEY
|
|
|
|
| + Application is allowed
|
|
|
|
| – Application is not allowed
|
|
|
|
|