Abstract
In this work, we report the in-field demonstration of a liquefied petroleum gas monitoring system based on optical fiber technology. Long-period grating coated with a thin layer of atactic polystyrene (aPS) was employed as a gas sensor, and an array comprising two different fiber Bragg gratings was set for the monitoring of environmental conditions such as temperature and humidity. A custom package was developed for the sensors, ensuring their suitable installation and operation in harsh conditions. The developed system was installed in a real railway location scenario (i.e., a southern Italian operative railway tunnel), and tests were performed to validate the system performances in operational mode. Daytime normal working operations of the railway line and controlled gas expositions, at very low concentrations, were the searched realistic conditions for an out-of-lab validation of the developed system. Encouraging results were obtained with a precise indication of the gas concentration and external conditioning of the sensor.
Highlights
Hydrocarbons are a very dangerous species, even when considered at low concentrations, due to high flammable and volatile behavior
liquefied petroleum gas (LP gas) is one of the dangerous species being transported with higher frequency by railways lines
Concerning the red curves, where the environmental uncertainty in the resonant wavelength detection induces an error in concentration of ±0.14 vol %, condition changes have been compensated, we found that the resonance wavelength moves in a range i.e., ±8% of the butane lower explosive limit (LEL)
Summary
Hydrocarbons are a very dangerous species, even when considered at low concentrations, due to high flammable and volatile behavior. Methane detection was achieved in [27] by using a LPG coated with polycarbonate/cryptophane-A HRI overlay, and in [28] through a coated LPG in photonic crystal fiber Such devices were used for hydrocarbon detection in fuel, water and atmospheric environment [29,30]. The monitoring system is based on the aPS coated LPG butane (the main component of LP gas) sensor, which is combined with two fiber Bragg grating sensors for the measurement and compensation of environmental temperature and humidity changes.
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