Rise of LNG as a Fuel

With clean burning properties and lower operating

costs for emission compliance, the marine

transportation industry is turning to LNG as a fuel.

The safe control and operation of small scale LNG

transfers and fuelling (also known as bunkering) pose

special challenges requiring innovative technical

solutions. LNG’s deep cryogenic properties mean it

requires careful handling in large and small quanti-

ties. Linked ship- shore Emergency Shut Down (ESD)

systems for large scale LNG have underpinned an

exemplary safety record for over 50 years.

Trelleborg Marine and Infrastructure is the acknowl-

edged world leader providing this technology to the large

scale LNG industry where its systems overcome

inter-compatibility issues and support data and control

requirements while assuring Safety Integrity to IEC

61508 SIL2.

The Trelleborg USL-8810 uses ISO 20519 compliant

links for bunkering of LNG fuelled vessels and provides

main and backup systems as per large scale LNG

practice within ISO 28460:2010.

For LNG transfer and fuelling the link should:

Enable a single operator to monitor and control

both sides of the transfer process to ensure that

measurements remain within safe criteria

Shut down the process automatically and safely

without risk of damaging surge pressures should

these criteria be exceeded

Operate safely and reliably in a gas-

hazardous zone

Overcome problems of inter-compatibity between

LNG fuelled vessels and onshore LNG terminals

Enhanced Fiber Optic Link:

The fiber optic system uses standard digital SONET data

transmission. Standard military-specification harsh-

environment expanded beam connectors couple the USL

system to its shore or ship counterpart; the connectors

can transmit light signals without interruption despite

contamination.

With the fiber optic system activated, the umbilical cable

is connected to a counterpart system. The fiber optic

system performs a data handshake and the counterpart

LNG tank configurations are set for the operator to

observe. The ESD trip signals are set to ‘healthy’

enabling the LNG transfer to begin. The principal

operator can observe temperatures and pressures of

both systems throughout the transfer process. Pre-set

alarm limits enable the transfer to be monitored in order

to manage and, where possible, avoid an ESD trip event.

Following an ESD trip, a ‘first-up’ indication shows where

the ESD was initiated. This facilitates quick identification

of the cause of the ESD event, helping to minimize

downtime in primary and back-up modes.

Fiber Optic System Supports:

High integrity ESD signals

The fibre optic link meets the requirements of

SGMF ‘Type 3’ BSL

Interconnection of custody transfer system

Mooring line data

CCTV signals

Telephony

Network interface (for up to 100BaseT)

Fixed fiber optic, electric and

pneumatic connection box

Fixed control unit

Portable fiber optic, electric and

pneumatic umbilical reels

Typical safety screen mimics

Electric SIGTTO Link:

The electric system uses intrinsically safe circuitry and

the industry standard 5 pin connector as defined in the

SIGTTO guidelines and ISO 20519. The electric link is

considered a backup for ESD signalling only. The Electric

SIGTTO Link meets the requirements of SGMF ‘Type 2’

BSLs.

Pneumatic Link:

The pneumatic link offers further redundancy and

compatibility with large and small scale applications. It is

regarded as a backup for low volume, low flow rate

applications (<150m³/hr), as specified in ISO 20519.

The pneumatic link meets the requirements of SGMF

‘Type 1’ BSLs.

Typical Systems Comprise:

Main Control Unit with colour data display monitor

Transfer area/shipboard connection box

with primary fiber optic socket and back-up

electric and pneumatic socket for ESD only

operation

Hand portable cable reel including 25 metre

umbilical cable with MIL-DTL-83526 military

specification expanded beam plugs for primary

(fiber optic) syste

5 pin SIGTTO Connector

Hand portable reels including 25 metre umbilical

cable with SIGTTO link plugs and 25 metre

pneumatic hose for back-up systems

Hotline communication telephone

Benefits:

A primary system with high integrity digital trans-

mission and robust signal path enables secure

high band width data transfer

A common system architecture and interface

reducing work-load and training costs

An intrinsically safe ESD back-up system

Assured inter-compatibility of safety link systems

throughout the small scale and fuelling supply

chain

Future-proof for new process data

Assists safety and monitoring of simultaneous fuel

oil bunkering if required

In-built system test & diagnostics

Option for breakaway coupling