LNG Case Study – SIL2 implementation

Making Sense Of Leak Detection
May 25, 2016
Sensornet obtains world first ATEX I (M1) certification for the mining industry
January 2, 2018

Fibre-optic DTS technology is uniquely suited to a variety of monitoring tasks within an LNG facility such as Leak detection of Loading and unloading pipelines, Leak detection of storage tanks (annulus monitoring), Liquefaction and process areas, Cool-down monitoring, spill channels and impoundment pits and basins being specifically recommended for spillage detection in section 13.4 of EN 1473:2007-06.

The fibre sensor is small diameter and the system responds rapidly to changes in temperature.

Sensornet’s LNG monitoring solutions make use of fibre optical sensing probes, which are non-corrosive and intrinsically safe. Suitable for cryogenic conditions, they accurately measure temp over large distances in under a minute.

The Unique SIL-2 (Safety Integrity Level) rating and certification that Sensornet’s DTS have achieved gives you the confidence that our solution is going to work as planned, day in and day out, in ultra-high-risk environments.

Isle of Grain LNG Importation Pipeline

leak detection labeled picture

Sensornet leak detection cable installed on LNG Importation and recirculation pipelines at Isle of Grain jetty

worker looking at pipeline

The Isle of Grain LNG importation pipeline has 4.1km of 36” LNG and 14” recirculation pipes installed with 2 fibre optics lines on each pipe to provide full redundancy of the DTS leak detection system

  • Independent cable loops
  • Independent DTS systems
  • 1/8” double wall stainless steel Sensornet DTS cable
diagram of delivery and recirculation pipes

Fibre break REDUNDANCY

If the red sensing cable is broken the DTS will still test either side of the break.

The blue sensing cable will still monitor the entire pipeline length.

If blue sensing cable breaks the DTS will still test either side of the break

If 1 DTS fails, redundant system still operates

The SIL-solution offers:-

  • Sensornet cabinet solution independently tested by Technis
  • SIL2 (Safety Integrity Level 2) achieved using PLC voting system
  • Automatic trip testing system
  • PFD (Probability of Failure on Demand) @ 2 x 10-4 = 99% availability
  • This equates to a Risk Reduction Factor (RRF) of 1×106 to 1×107. In terms of Probability of Failure per Hour (PFH), this equates to 1×10-6 to 1×10-7.
  • Fibre break Redundancy
diagram showing relay logic solver and test zones
diagram of fiber optic connections

ATTS – Automated Trip Testing System


The patented ATTS provides a pseudo-random automatic system performance check, by virtue of periodically applying an actual cold event to each end of the sensing fibre. Each time the DTS detects a leak in the zones allocated to the ATTS, the DTS will energise a specific relay. Each time the ATTS produces a simulated leak event, it also energises a 

specific relay. A voting PLC applies the following logic in these events:

– ATTS leak event + DTS leak event in ATTS zone: Simulated leak, no alarm

– No ATTS leak event + DTS leak event: Real leak, raise an alarm

– ATTS leak event + no DTS leak event in ATTS zone: DTS problem, raise an alarm

Contact the SIL-2 specialist Sensornet to discuss all your SIL-2 LNG and other DTS requirements.