Piping Systems, Valves and Pumps
1.1 The Rules in this Section apply to piping systems, including the selection of materials and the design of pipes, pipe connections, fittings and pumps, depending on the media conveyed.
1.2 Reference to other GL Rules
GL Rules II - Materials and Welding, Part 1 Metallic Materials, Part 2 Non-metallic Mate-rials and Part 3 Welding
Section 9 - Fire Protection and Fire Extinguish-ing Equipment
Section 17 - Oil Firing Equipment
Section 16 - Pressure Vessels
Section 15 - Auxiliary Steam Boilers
GL Rules VI Additional Rules and Guidelines, Part 3 Machinery Installations, Chapter 5 - Guidelines for the Design, Equipment and Test-ing of Gas Welding Installations on Seagoing Ships
2. Documents for approval
The following drawings / documents are to be submit-ted for approval in triplicate:
2.1 Engine room arrangement plan
2.2 Diagrammatic plans of the following piping systems including all the details necessary for ap-proval, e.g. lists of valves, fittings and pipes:
boiler feed water systems
fuel systems (bunkering, transfer and supply systems)
seawater cooling systems
fresh water cooling systems
lubricating oil systems
starting air, control air and working air systems
exhaust gas systems
air, overflow and sounding pipes including de-tails of filling pipe cross sections
closed overflow systems
sanitary water systems (fresh water, seawater) sewage discharge systems
drinking water systems
equipment for the treatment and storage of bilge water and fuel oil residues
chilled water systems
fuel storage, transfer and replenishment systems
aviation fuel systems
2.3 For remotely controlled valves:
diagrammatic piping plans and diagrammatic plans of the arrangement of piping and control stands in the ship
diagrammatic plans and electrical circuit dia-grams of the control stations and power units, as well as drawings of the remotely controlled valves, control stands and the corresponding pressure accumulators
2.4 For pipes, pipe connections and accessories, as far as not defined otherwise in this Section, recog-nized national or international standards have to be applied.
3. Pipe classes
For the purpose of testing of pipes, selection of joint-ing, welding and heat treatment, pipes are subdivided into three classes as indicated in Table 8.1.
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Table 8.1 Classification of pipes into pipe classes
Medium/type of pipeline Design pressure PR [bar] Design temperature t [C] Pipe class I II III
Inflammable liquids heated above flash point Inflammable liquids with a flash point of 60 C or less Flammable gases
Steam PR > 16 or t > 300
PR 16 and t 300
PR 7 and t 170
Air, gases (inflammable) Inflammable, hydraulic fluids Boiler feedwater, condensate Seawater and fresh water for cooling Brine in refrigerating plant
PR > 40 or
t > 300
PR 40 and
PR 16 and
Liquid fuels, lubricating oil, flammable hydraulic fluids 2
PR > 16 or t > 150
PR 16 and t 150
PR 7 and t 60
Cargo pipelines for supply tankers all
Open-ended pipelines (without shutoff), e.g. drains, vent pipes, overflow lines and boiler blowdown lines all
1 classification in Pipe Class II is possible if special safety arrangements are available and structural safety precautions are arranged
2 for liquid fuels > 60 C the design pressure is to be at least 14 bar
B. Materials, Testing
1.1 Materials must be suitable for the proposed application and comply with GL Rules II - Materials and Welding, Part 1 Metallic Materials.
In case of especially corrosive media, GL may impose special requirements on the materials used.
1.2 Where non-magnetic construction is required, non-magnetizable materials are to be selected.
1.3 Potential differences between contiguous elements are to be kept as small as possible.
1.4 Potential differences caused by inevitable combinations of different materials are to be compen-sated by suitable measures, such as isolation and/or protection of the material of lower potential. The ele-ment made of higher potential material shall be ar-ranged, where possible, downstream.
2.1 Pipes, valves and fittings of steel
Pipes belonging to Classes I and II must be either seamless drawn or fabricated by a welding procedure
approved by GL. In general, carbon and carbon-manganese steel pipes, valves and fittings are not to be used for temperatures above 400 C. However, they may be used for higher temperatures provided that their metallurgical behaviour and their strength prop-erty according to C.2.3 after 100 000 h of operation are in accordance with national or international regula-tions or standards and if such values are guaranteed by the steel manufacturer. Otherwise, alloy steels in ac-cordance with the GL Rules for Materials are to be used.
2.2 Pipes, valves and fittings of copper and copper alloys
2.2.1 Pipes of copper and copper alloys must be of seamless drawn material or fabricated by a method approved by GL. Copper pipes for Classes I and II must be seamless.
In general, copper and copper alloy pipe lines shall not be used for media having temperatures above the following limits:
copper and aluminium brass 200 C
copper nickel alloys 300 C
high-temperature bronze 260 C
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2.2.2 At locations with restricted cross section as occurring at orifices, valves, etc., pipes made of cop-per alloys are to be protected by a GL-approved coat-ing, for a length as follows:
5 d upstream of the section restriction
10 d downstream of the restriction
d = inner diameter of pipe
2.3 Pipes, valves and fittings of nodular ferritic cast iron
Pipes, valves and fittings of nodular ferritic cast iron according to the Rules for Materials may be accepted for bilge and ballast pipes within double-bottom tanks and for other purposes approved by GL. In special cases (applications corresponding in principle to classes II and III) and subject to GL's special approval, valves and fittings made of ferritic nodular cast iron may be accepted for temperatures up to 350 C. Nodu-lar ferritic cast iron for pipes, valves and fittings fitted on the ship's side must comply with the GL Rules for Materials.
2.4 Pipes, valves and fittings of lamellar-graphite cast iron (grey cast iron)
Pipes, valves and fittings of grey cast iron may be accepted on supply tankers for cargo pipes within cargo tanks and on the weather deck up to a working pressure of 16 bar.
Ductile materials must be used for cargo hose connec-tions and manifolds.
This applies also to the hose connections of fuel and lubricating oil filling lines.
The use of grey cast iron is not allowed:
for pipes, valves and fittings for media having temperatures above 220 C and for pipelines subject to water hammer, severe stresses or vi-brations
for sea valves and pipes fitted on the ship sides and for valves fitted on the collision bulkhead
for valves on fuel and oil tanks subject to static head
The use of grey cast iron in cases other than those stated is subject to GL approval.
2.5 Plastic pipes
2.5.1 Plastic pipes may be used upon special ap-proval by GL. 1
1 See IMO Resolution A.753 (18), "Guidelines for the Applica-
tion of Plastic Pipes on Ships"
The use of plastic pipes made of polyvinyl chloride (PVC) is not permissible.
2.5.2 Pipes, valves and fittings made of plastic materials are to be subjected to a continuous GL-approved quality control by the manufacturer.
2.5.3 Pipe penetrations through watertight bulk-heads and decks as well as through fire divisions are to be approved by GL.
2.5.4 Plastic pipes are to be continuously and per-manently marked with the following particulars:
standard specification number
outside diameter and wall thickness of pipe
year of manufacture
2.5.5 Valves and connecting pieces made of plastic must, as a minimum requirement, be marked with the manufacturer's marking and the outside diameter of the pipe.
2.6 Aluminium and aluminium alloys
Aluminium and aluminium alloys must comply with GL Rules II Materials and Welding and may in individual cases, with the agreement of GL, be used for temperatures up to 200 C. They are not acceptable for use in fire extinguishing lines.
2.7 Application of materials
For the pipe classes mentioned in A.3. materials must be applied according to Table 8.2.
3. Testing of materials
3.1 For piping systems belonging to class I and II, tests in accordance with the GL Rules II Materi-als and Welding and under GL's supervision are to be carried out in accordance with Table 8.3 for:
pipes, bends and fittings
valve bodies and flanges
3.2 Welded joints in pipelines of classes I and II are to be tested in accordance with the GL Rules II - Materials and Welding, Part 3 Welding.
4. Hydraulic tests on pipes
4.1.1 Maximum allowable working pressure, PB [bar], Formula symbol: pe,zul
This is the maximum allowable internal or external working pressure for a component or piping system
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Table 8.2 Approved materials
Pipe class Material or application
I II III
Steel pipes for high-temperatures above 300 C, pipes made of steel with high-/low temperature toughness at temperatures below 10 C, stainless steel pipes for chemicals
Pipes for general applications
Steel not subject to any special quality specification, weldability in accordance with GL Rules for Welding
Forgings, plates, flanges
Steel suitable for the corresponding service and processing conditions, high-temperature steel for temperatures above 300 C, steel with high-/low temperature toughness for temperatures below 10 C, steel with high-/low temperature toughness
Bolts for general machinery con-structions, high-temperature steel for temperatures above 300 C, steel with high-/low temperature toughness for temperatures below 10 C
Bolts for general machinery construction
High-temperature cast steel for temperatures above 300 C, cast steel with high-/low tempera-ture toughness at temperatures below 10 C, stainless castings for aggressive media
Cast steel for general applications
Nodular cast iron Only ferritic grades, elongation A5 at least 15 %
Cast iron with la-mellar graphite
At least GG-20 up to 200 C, grey cast iron is not permitted in valves and fittings on ship's side, on the collision bulkhead and on fuel and oil tanks
Copper, copper alloys
low-temperature copper-nickel-alloys by special agreement
For seawater and alkaline water only corrosion resistant copper and copper alloys
Aluminium, alu-minium alloys
Only with the agreement of GL up to 200 C, not permitted in fire extinguishing systems
On special approval (see 2.5)
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Section 8 Piping Systems, Valves and Pumps III - Part 1GL 2004
Table 8.3 Approved materials and types of certificates
Type of certificate EN 10204 (DIN 50 049)
Type of component
Design temperature Subject to testing
GL Rules II Materials
and Welding Part 1 Metallic
3.1C (GL) 3.1 B 2.2
DN 3 > 32 Pipes, pipe elbows, fittings
Steel, copper, copper alloy
Chapter 2, Section 2 Chapter 3, Section 2
DN > 32 Steel, cast steel
> 300 C DN 32
Chapter 2, Section 3, Chapter 2, Section 4
PB 4 DN > 2500 or
DN > 250 Steel,
cast steel, nodular cast iron
300 C PB DN 2500
Chapter 2, Section 3 Section 4, Section 5
DN > 32 > 225 C
PB DN > 1500
I + II Valves, flanges, metal expansion, joints and hoses, other components
Copper, copper alloy
225 C PB DN 1500
Chapter 3, Section 2
III Valves, 2 flanges, other components
Steel, cast steel, grey cast iron 1, nodular cast iron, copper, copper alloy
Chapter 2, Section 3 Section 4
Chapter 3, Section 2
1 no material test in the case of grey cast iron
2 casings of valves and pipe branches fitted on the ship sides are to be included in Pipe Class II
3 nominal diameter
4 maximum allowable working pressure [bar]
with regard to the materials used, piping design re-quirements, the working temperature and undisturbed operation.
4.1.2 Nominal pressure, PN [bar]
This is the term applied to a selected pressure-temperature relation used for the standardization of structural components. In general, the numerical value of the nominal pressure for a standardized component made of the material specified in the standard will correspond to the maximum allowable working pres-sure PB at 20 C.
4.1.3 Test pressure, PP [bar] Formula symbol: pp
This is the pressure to which components or piping systems are subjected for testing purposes.
4.1.4 Design pressure, PR [bar] Formula symbol: pc
This is the maximum allowable working pressure PB for which a component or piping system is designed with regard to its mechanical characteristics. In gen-eral, the design pressure is the maximum allowable working pressure at which the safety equipment will
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interfere, e.g. activation of safety valves, opening of return lines of pumps, operating of overpressure safety arrangements, opening of relief valves, or at which the pumps will operate against closed valves.
The design pressure for fuel pipes shall be chosen according to Table 8.3a.
Table 8.3a Design pressure for fuel pipes
Max. working temperature
Max. working pressure
T 60 C T > 60 C
PB 7 bar
3 bar or max. working pressure, whichever is greater
3 bar or max. working pres-sure, whichever is greater
PB > 7 bar max. working pressure
14 bar or max. working pres-sure, whichever is greater
4.2 Pressure test prior to installation on board
4.2.1 All Class I and II pipes as well as steam lines, feedwater pressure pipes, compressed air and fuel lines having a design pressure PR greater than 3,5 bar together with their integral fittings, connecting pieces, branches and bends, after completion of manufacture but before insulation and coating, if this is provided, shall be subjected to a hydraulic pressure test in the presence of the Surveyor at the following value of pressure:
[ ]p cp 1,5 p bar=
where pc is the design pressure. For steel pipes and their integral fittings intended to be used in systems with working temperature above 300 C the test pres-sure PP is to be as follows:
( ) ( )p zul zul cp 1,5 100 / t p= zul (100) = permissible stress...