SNAM Rete Gas – Gas pipeline monitoring

The progress of a landslide over time can damage pipelines and put them out of service. Three symmetrically disposed vibrating wires, chosen as the most at risk according to a preliminary engineering evaluation, were installed in several sections at a distance of 50/100 m. These sensors were very helpful, but could not fully cover the length of the pipeline and could only provide local measurements.

Aim of monitoring:

The three types of sensors from Smartec that were used were SMARTape, SMARTcord, and Temperature Sensing Cable. The SMARTape sensor consists of a sensing optical fiber integrated into the 200-micrometer thick fiber-reinforced composite tape. Three parallel lines constituted of five segments of this sensor were installed over the whole length of the concerned area. The lengths of segments ranged from 71 m to 132 m and the position of the sensors, concerning the pipeline axis, were at 0°, 120°, and –120° approximately. The strain resolution of the SMARTape is 20 micro-strains, with a spatial resolution of 1.5 m and an acquisition range of 0.25m, which provides monitoring of average strains, average curvatures, and the deformed shape of the pipeline. The SMARTcord sensor consists of a sensing optical fiber integrated into the fiber of a reinforced plastic cord with a diameter of 6 millimeters. Below the pipeline, a single 500-meter-long sensor was installed in the soil to monitor the strain changes. The resolution of the SMARTcord is the same as for SMARTape. These measurements have been correlated with the SMARTape measurements to evaluate the strain transfer from the soil to the pipeline. The Temperature Sensing Cable was installed onto the upper line (0°) of the pipeline to compensate for the strain measurements for temperature. The temperature resolution of the sensor is 1°C with the same resolution and acquisition of the SMARTape. All the sensors are connected to a Central Measurement Point using extension optical cables and connection boxes. They are read from this point by using a single DiTeSt® reading unit. Since the landslide process is slow, the
measurement sessions are performed once a month. In case of an earthquake, a series of measurements are performed immediately after the event. All the measurements obtained with the DiTeSt® system will be correlated with the measurements obtained with vibrating wires.

Main results:

At the present stage, all the sensors are successfully installed and the first measurement session was performed. A gas leakage simulation was performed with success using the temperature-sensing cable.

Related Papers:

1. Fibre Optic Methods for Structural Health Monitoring, Branko Glisic and Daniele Inaudi, John Wiley & Sons, Ltd – 2007
2. Overview of fiber optic sensing to structural health monitoring applications, D. Inaudi, ISISS’2005, International Symposium on Innovation & Sustainability of Structures in Civil Engineering, Nanjing, China, November 20-22 – 2005
3. Field Applications of Fiber Optic Strain and Temperature Monitoring Systems, D. Inaudi, B. Glisic, Opto-electronic Sensor-based Monitoring in Geo-engineering, Nanjing, P.R.China, November 23-24 – 2005
4. Application of distributed Fiber Optic Sensory for SHM, D. Inaudi, B. Glisic, 2nd International Conference on Structural Health Monitoring of Intelligent Infrastructure (SHMII-2’2005), Shenzhen, China, November 16-18 – 2005
5. Reliability and field testing of distributed strain and temperature sensors, D. Inaudi, B. Glisic, SPIE Smart Structures and Materials Conference in San Diego. 2006 February 27, March 2 – 2006
6. Distributed Fiber optic Strain and Temperature Sensing for Structural Health Monitoring, D. Inaudi, B. Glisic, IABMAS’06 The Third Int’l Conference on Bridge Maintenance, Safety, and Management, 16 – 19 July 2006, Porto, Portugal – 2006
7. Long-Range Pipeline Monitoring By Distributed Fiber Optic Sensing, D. Inaudi, B. Glisic, 6th International Pipeline Conference September 25 – 29, 2006, Calgary, Alberta, Canada – 2006
8. Health monitoring with optical fiber sensors: from the human body to civil structures, Éric Pinet, Caroline Hamel, Branko Glišic, Daniele Inaudi, Nicolae Miron, 14th SPIE Annual Symposium on Smart Structures and Materials & Nondestructive Evaluation and Health Monitoring, San Diego (CA), USA – (6532-19) – 2007
9. Distributed Fibre Optic Sensing for Long-Range Pipeline Monitoring, Daniele Inaudi, Branko Glisic, The 3rd International Conference on Structural Health Monitoring of Intelligent Infrastructure – SHMII-3, November 13-16 – (on conference CD) – 2007
10. Pipeline Leakage Detection and Localization Using Distributed Fiber Optic Sensing, D. Inaudi, B. Glisic, A. Figini, R. Walder, Rio Pipeline Conference 2007, Rio de Janeiro, Brazil, October 2-4 – 2007
11. Distributed Fiber Optic Sensors: Novel Tools for the Monitoring of Large Structures, Daniele Inaudi, Branko Glisic, Geotechnical News – (Volume 25, Number 3, Pages 8-12) – 2007