The annular space of an LNG tank cannot be physically inspected once construction is complete, because it is permanently sealed and filled with perlite insulation. The only way to obtain reliable data from within the annular space is through sensors installed before sealing during the original construction phase. These include fiber optic Tank Movement Monitoring Systems (TMMS), Distributed Temperature Sensors (DTS) for leak detection, and structural strain gauges embedded in the surrounding concrete.
Traditional temperature monitoring relies on multiple Resistance Temperature Detectors (RTDs) to produce a basic temperature profile. Roctest’s Fiber Optic Distributed Temperature Sensor (DTS) uses a single fiber optic cable installed at different levels along the tank perimeter to generate a comprehensive, high-resolution temperature map of both the tank interior and the annular space. This makes leak detection dramatically faster and more precise, identifying thermal anomalies that signal potential breaches well before they become critical failures.
Fiber optic sensors are the preferred technology for LNG tank monitoring as they are intrinsically safe, meaning they are immune to electrical interference and spark risks. This makes them suitable for use in explosive atmospheres. They can withstand cryogenic temperatures down to -169°C on a permanent basis, unlike conventional electronic sensors. A single fiber optic cable can provide distributed measurements across the full perimeter of a tank, delivering far more data points than a network of discrete point sensors at a fraction of the installation complexity.
A Distributed Temperature Sensor, or DTS, uses a single fiber optic cable to generate a continuous temperature profile along its entire length. In LNG tank applications, a DTS cable installed at multiple levels along the tank perimeter provides comprehensive temperature mapping of both the tank interior and the annular space. This dramatically improves leak detection capability — thermal anomalies that indicate cryogenic breaches can be identified early and precisely, before they escalate to critical failures. DTS is significantly more effective than traditional Resistance Temperature Detector (RTD) arrays, which provide only limited point measurements.
LNG leaks in storage tanks are most effectively detected through comprehensive temperature monitoring of the annular space. A cryogenic breach causes a distinct thermal anomaly — a localized cold spot — that a Distributed Temperature Sensor (DTS) system can identify rapidly and precisely. Traditional leak detection relying on discrete RTD sensors provides far fewer data points and may miss early-stage breaches or fail to pinpoint their location accurately. Fiber optic DTS systems installed during construction provide the most reliable and cost-effective leak detection available for LNG storage tanks.
LNG storage tank leaks are most commonly caused by structural failure of the inner wall resulting from undetected differential movement, cumulative thermal cycling fatigue, or unexpected settlement. Because the inner wall undergoes significant contraction at cryogenic temperatures during every operational cycle, structural stress accumulates over time. Without continuous monitoring of wall movement and temperature in the annular space, early indicators of breach risk go undetected until a leak or catastrophic failure occurs.
Yes — with the right instrumentation. Fiber optic Distributed Temperature Sensing systems continuously monitor temperature throughout the annular space and can identify thermal anomalies indicative of a developing breach well before a full leak occurs. Similarly, Tank Movement Monitoring Systems detect structural deformation patterns that may precede leakage. Early detection through integrated monitoring allows operators to take preventive action rather than responding to emergencies.
LNG facilities in seismically active regions require integrated structural monitoring systems capable of providing immediate post-event safety assessments. Real-time data from TMMS, tiltmeters, inclinometers, DTS, and strain sensors — all timestamped to the seismic event — allows operators to quickly determine whether tank walls have shifted, the foundation has settled unevenly, or temperature anomalies suggesting a breach have emerged.
Here are the rewritten FAQ answers, grounded in the DTS and temperature monitoring content:
The cost of DTS-based temperature monitoring is best understood relative to what it replaces and what it protects. A single DiTemp fiber optic cable installed during construction covers the entire tank perimeter and annular space delivering continuous, spatially resolved leak detection that would otherwise require hundreds of individual RTD sensors and wiring runs. Instrumentation installed at this stage represents a small fraction of overall project cost, while providing the only means of detecting a cryogenic breach before it escalates. The cost of not monitoring — in the form of undetected leakage, unplanned shutdowns, or catastrophic failure — consistently exceeds the cost of comprehensive DTS coverage.
Yes. Roctest’s DTS ecosystem is designed for full LNG terminal surveillance. The DiTemp system can monitor distributed temperature over distances of up to 30 km, making it suitable for covering multiple tanks, pipeline runs, and foundation slabs across an entire terminal from a single readout unit. Coverage extends to leak detection in permanently sealed annular spaces, thermal mapping of concrete slab bases for frost heave prevention, and real-time anomaly identification following seismic or operational incidents. All data feeds into DiView and from there into the control room PLC alongside daily operational information.
Yes. The DiTemp system communicates over standard industrial protocols including Modbus, Ethernet, and RS-485, and is designed to feed measurement data directly to any existing PLC platform. The DiView software provides an HMI-style graphical interface that displays temperature as a continuous color-mapped profile, making anomalies immediately visible to control room operators without specialist interpretation. The goal is a single unified data environment — not another isolated monitoring silo.
The DiTemp Harsh+ is built specifically for permanent deployment in the most demanding LNG environments — including cryogenic temperatures, potentially explosive atmospheres (ATEX-certified), and the long operational cycles of LNG storage facilities. Fiber optic cables installed in the annular space and concrete slab conduits during construction are not accessible after commissioning, so the system is designed to operate without recalibration or physical intervention for the full facility life. The integrated ATTS self-test function runs simulated leak events every hour to continuously verify system availability, ensuring the monitoring capability remains reliable across decades of operation.
