Double wall pipe for LNG, methanol and ammonia fuel transfer, carried on a CFRP flex support instead of a steel spring or a welded plate. Built by Haegang Hi-Tech, a Hanla IMS subsidiary in Busan, and approved by MAN Energy Solutions.
On this page
- Where it goes on board›
- What the support has to do›
- The CFRP flex support›
- High pressure and low pressure piping›
- Insulated pipe for liquefied fuel›
- Sizes›
- Materials and manufacture›
- Approvals and record›
Where it goes on board
Fuel runs from the bunkering station to the fuel tank, through the fuel gas preparation room, and on to the main engine, the generators and the boilers. Wherever it passes through an enclosed space it is carried in double wall pipe, so that a leak from the inner pipe is contained by the outer one and vented to a safe place.
| Fluid | LNG at −163 °C as a liquid; fuel gas from −90 to +60 °C. Also methanol and ammonia |
|---|---|
| High pressure | 330 bar and above — MAN ME-GI dual fuel engines |
| Low pressure | About 10 to 20 bar — ME-GA and X-DF dual fuel engines, generators and boilers |
| Rule | The amendment to the IGF Code adopted as resolution MSC.458(101) on 14 June 2019 requires liquefied fuel pipes to be protected by a secondary enclosure able to contain leakage. It applies to ships built on or after 1 January 2024 |
What the support has to do
The support inside the annulus does two jobs. It holds the inner pipe on the centreline of the outer pipe, and it takes up the movement — thermal contraction as cold fuel enters the line, and engine room vibration. To do the second it has to behave as a spring rather than a rigid bracket.
MAN Energy Solutions sets the requirement in its design guidelines for double wall piping on dual fuel engines:
| Flexibility | Stiffness 60 N/mm or more, elasticity 6 mm or more, to absorb thermal expansion and engine room vibration |
|---|---|
| No metal to metal contact | The annulus is hazardous zone 1, so metal touching metal is a potential ignition source |
| Maintenance | To be low |
The CFRP flex support
Carbon fibre reinforced plastic: ten times the strength of steel at a fifth of the weight. Haegang designed the support and MAN ES approved it, and one design covers both high and low pressure piping. Where the steel spring support has two springs and only meets its figures at 45° and 225°, the CFRP support has six legs and performs the same in every direction, so it does not have to be clocked to a particular angle on installation.
| Spring flex support | CFRP flex support | MAN ES guideline | |
|---|---|---|---|
| Form | Two springs | Six legs | |
| Material | Stainless steel brace with an engineering plastic bearing; tensile strength 1,350 MPa | Carbon fibre reinforced plastic; tensile strength 2,175 MPa | |
| Stiffness | 60 N/mm at 45°/225° only | 100 N/mm and above in all directions; 130 N/mm or more measured | More than 60 N/mm |
| Allowable deformation | Max. 6 mm at 45°/225° | Max. 8 mm at all points | 6 mm |
| Installation | Must be set at 0°/90° or 45°/225° | No angular restriction | Correct angular position required |
| Metal to metal contact | None, through the bearing | None | None |
| Fatigue | — | Tested to 150,000 cycles | |
| Life | — | 50 years (100,000 cycles) | |
| Temperature | −90 to +60 °C | −100 to +80 °C | −90 to +60 °C |
High pressure and low pressure piping
The same CFRP support covers both duties. What it replaces differs.
| High pressure, 330 bar and above | The alternative is MAN’s spring flex support. It meets the stiffness and deformation figures at 45° and 225° only, so it has to be installed at the right angle |
|---|---|
| Low pressure, 10 to 20 bar | The alternative is a welded plate support in the same material as the pipe. It needs a 1 mm gap to keep metal off metal and a fixed welded support to hold that gap, it restricts the ventilation area, and the welding can carry defects — a crack in a support welded straight to the inner pipe caused a gas leak in an LNG carrier in 2011 |
| CFRP support | No welding in fabrication or installation, so no welding defects and no fixed support needed. Fits the same small annular space, and can be assembled by hand |
Insulated pipe for liquefied fuel
Where the line carries liquid rather than gas, the inner pipe is insulated inside the annulus so the outer pipe stays out of the cold. The insulation is applied in the shop, with half pipes made up for the joints closed in the field.
| Fluid | LNG at −163 °C |
|---|---|
| Insulation | Aerogel, ORYZA SIL 650 or equivalent, 25 to 45 mm thick |
| At the support | A 1 to 2 mm heat insulator between the CFRP support and the inner pipe |
| Cold test | Compressive test at −170 °C: stiffness 170.7 kN/m |
| Thermal conductivity | CFRP support under 3.0 W/m/K, against 20 to 26 for stainless steel |
| Why aerogel | Lowest thermal conductivity, so the outer pipe can be a size smaller. Water repellent, which keeps water out and corrosion with it. Flexible to fit, low dust, fire resistance grade A. Tested to ASTM C1728 |
Sizes
Standard double wall pipe with CFRP flex support. The annular space is 23 mm; the support fits a small annulus. Other sizes are made to order.
| Inner pipe | Outer pipe | Inner pipe | Outer pipe | |
|---|---|---|---|---|
| 15A | 65A | 80A | 125A | |
| 25A | 65A | 80A | 150A | |
| 25A | 100A | 100A | 150A | |
| 40A | 100A | 100A | 200A | |
| 50A | 100A | 125A | 200A | |
| 65A | 125A | 125A | 250A | |
| 65A | 150A | 200A | 300A | |
| 250A | 350A |
Insulated double wall pipe. Insulation thickness is set for an ambient of 32 °C, 85% relative humidity and 5 m/s wind.
| Inner pipe | Insulation | Outer pipe | Inner pipe | Insulation | Outer pipe | |
|---|---|---|---|---|---|---|
| 25A | 25 mm | 100A | 200A | 40 mm | 300A | |
| 40A | 25 mm | 100A | 250A | 45 mm | 400A | |
| 50A | 30 mm | 125A | 300A | 45 mm | 450A | |
| 65A | 30 mm | 150A | 350A | 45 mm | 450A | |
| 80A | 30 mm | 150A | 400A | 50 mm | 500A | |
| 100A | 35 mm | 200A | 450A | 50 mm | 550A | |
| 150A | 40 mm | 250A |
Materials and manufacture
| Inner pipe | SUS304L, SUS316L or duplex |
|---|---|
| Outer pipe | SUS304L or SUS316L |
| Process | Material receiving and inspection, pipe cutting, welding, non-destructive examination, hydrostatic test, passivation, packing, delivery and installation |
| Quality control | Inspection and test plan, qualified welding procedures and welders, fabrication control, hydraulic and leak test, certificate issued on completion |
Approvals and record
- MAN Energy Solutions approved supplier of double wall piping flex support, listed in the MAN ES design guidelines
- DNV factory approval and welding workshop approval; welding procedure approvals from DNV, ABS, BV, LR, NK and KR
- ISO 9001, ISO 14001 and ISO 45001
- Approved double pipe manufacturer at Hanwha Ocean, Samsung Heavy Industries, HD Hyundai, Daesun Shipbuilding & Engineering and DH Shipbuilding
- CFRP flex support patented in Korea, Japan and China
- Supplied for LNG and LPG carriers, container ships, tankers, FPSOs and special purpose vessels
Send the piping arrangement with the fuel, the design pressure and the inner and outer pipe sizes, and we will come back with a quotation and lead times.