42
LNG
INDUSTRY
SEPTEMBER
2014
opinions and feedback, which was positive for the damping
systems and simple cable actuation.
As the prototype design process was progressed,
Design Failure Modes and Effects Analysis (DFMEA) was
carried out during the development phase to identify any
areas of weakness in the design.
Following these activities, a 4 in. (DN 100) prototype
coupling was manufactured to test the various concepts of
the design. This design and concept testing phase lasted for
12 months and concluded with successful tests using liquid
nitrogen to simulate, as close as possible, the coupling
functionality in an actual ship-to-ship transfer and
separation.
Industry requirements,
testing and approvals
After the successful prototype test phase, further DFMEAs
were carried out and the coupling was upscaled to an 8 in.
(DN200) nominal bore for Class approval.
To enable APC to develop an ERC for LNG transfer, the
product must meet the following five technical
requirements:
Approval from a Class Society such as DNV GL,
Lloyd’s Register or ClassNK.
BS1447-1 (2008) Installation and equipment for liquefied
natural gas - design and testing of marine transfer
systems. Part 1: Design and testing of transfer arms.
BS1447-2 (2008) Installation and equipment for
liquefied natural gas - design and testing of marine
transfer systems. Part 2: Design and testing of transfer
arms.
BS1447-3 (2008) Installation and equipment for
liquefied natural gas - design and testing of marine
transfer systems. Part 3: Design and testing of transfer
hoses.
Compliance with the guidelines of The Society of
International Gas Tanker and Terminal Operators
(SIGTTO).
In addition to the industry requirements, the coupling
must have a minimum pressure drop at high flow rates in
excess of 1200 m
3
/hour.
Over a 12-month period, exhaustive testing comprising
hydrostatic, flow, controlled closures under high flow
conditions and cryogenic elements were undertaken as
part of the process to not only meet the rigorous industry
standard requirements, but also achieve peak
performance.
An example of these procedures was the Test 8 - 8 in.
LNG Coupling Type Approval Testing – Horizontal
Cryogenic Test, including separation with a load applied to
the coupling to simulate the loading effects of an LNG hose
filled with product. The test is designed to cause separation
of the coupling in a horizontal position with load applied,
and to analyse the performance of the coupling under such
conditions. Liquid nitrogen was used to bring the coupling
to cryogenic temperature.
A predetermined load was applied at various angles to
the coupling centre axis by means of a pneumatic cylinder;
and a 25 mm layer of ice was then built up around the
coupling and the collar mechanism. The coupling was
pressurised to the requirements of the above standards and
inspected for leakage over a period of time.
The first release cable was pulled, activating the two
internal valves and sealing each coupling half. The second
release cable was then pulled, activating the collar
release mechanism and allowing coupling separation. In
the coupling’s separated state, the seal faces were
monitored for leakage and inspected for evidence of
deformation.
This test was among a programme of intensive product
testing that was undertaken at APC’s facilities located in the
North East of England.
As there was limited flow testing facilities available to
carry out the demanding test schedule that was planned,
APC invested in excess of £1 million to create a specialist,
in-house test rig.
Through the procurement of a pump, tanks and diesel
engine, along with in-house engineering, the rig was
created to not only provide new product testing, but also
manage the overhaul, retesting and re-commissioning of
units that had already been in operation around the
globe.
The test facility utilises a pressurised water system,
which is calibrated to supply water at a comparable rate to
LNG during ship-to-ship transfer. It establishes the flow rates
through the coupling and pressures when the coupling is
closed down, simulating a damped closure of the internal
valves. It also incorporates instrumentation and data loggers
to record pressure and flow to enable detailed analysis.
Following this extensive process, the couplings range
was submitted for class approval. This was received from
within the Class Society and enabled APC to take the
products to market. Initial reaction to the couplers has been
positive from within the LNG sector, emphasising the
requirements from industry for an alternative solution to the
challenges of safe and effective LNG transfer.
Conclusion
With the projected increase in the use of LNG as an
effective fuel for ships and ferries, the industry must
ensure that LNG transfer is completed safely and securely
to protect vessels, operatives and the environment.
This need was recently highlighted by an LNG leak that
occurred during truck-to-ship bunkering operations involving
a cruise ferry at Risavika, Norway. According to the
Norwegian Directorate for Civil Protection, 100 kg of LNG
leaked from the hose connection in the bunkering room
on-board a Fjord Line 1500-passenger ship. According to the
Directorate, the hose disconnect appeared to have occurred
because the ship’s stabilising systems were not engaged.
This incident, and others like it, serves as a wake-up call
for the LNG-fuelling sector and reinforces the requirement
for the application of technology, such as APC’s Breakaway
ERCs, that prevent product spills or releases into the
atmosphere.
