KEYWORDS: Sensors, Combustion, Structural health monitoring, Temperature metrology, Safety, Optical fibers, Fiber optics sensors, Finite element methods, Interferometry, Head
This work presents application of SHM system based on optical fiber sensors for a power boiler monitoring. The test
object was a modern fluid boiler made by RAFAKO SA. Because of the need to replace the pre-heaters it was necessary
to make sure that such refurbishment would not menace the safety of the whole construction. Possible dangers could
arise from the fact that additional openings in the main combustion chamber walls were made. For this purpose an SHM
system based on SOFO® sensors was applied. The main task of the system was to locally measure a deformation of the
construction, to give information about emerging threats as well as to start programmed alarms. The data obtained were
continually published on the secured website. The arrangement of the sensors was supported by FEM analysis of the
whole construction made by boiler producer. The sensors were installed on 12 strings of the combustion chamber.
Additional 12 sensors were located directly on the chamber walls. Applied sensors were used to measure the deformation values in selected points. Then determined strain/stresses were compared with the design as well as with calculated values. It enabled evaluation of the inhomogeneous loads distribution and increased safety of the construction during its repair.
In this paper application of integrated Optical Fiber Sensors for strain state monitoring of composite high pressure
vessels is presented. The composite tanks find broad application in areas such as: automotive industry, aeronautics,
rescue services, etc. In automotive application they are mainly used for gaseous fuels storage (like CNG or compressed
Hydrogen). In comparison with standard steel vessels, composite ones have many advantages (i.e. high mechanical
strength, significant weight reduction, etc). In the present work a novel technique of vessel manufacturing, according to
this construction, was applied. It is called braiding technique, and can be used as an alternative to the winding method.
During braiding process, between GFRC layers, two types of optical fiber sensors were installed: point sensors in the
form of FBGs as well as interferometric sensors with long measuring arms (SOFO®). Integrated optical fiber sensors
create the nervous system of the pressure vessel and are used for its structural health monitoring. OFS register
deformation areas and detect construction damages in their early stage (ensure a high safety level for users). Applied
sensor system also ensured a possibility of strain state monitoring even during the vessel manufacturing process.
However the main application of OFS based monitoring system is to detect defects in the composite structure. An idea of
such a SMART vessel with integrated sensor system as well as an algorithm of defect detection was presented.
In the present work we present the results of our latest research into an implementation of optical fiber sensors for flaw
tolerance test application on high pressure composite hydrogen vessels. For monitoring influence of flaws on composite
parameters, as point measurement heads permanently installed on tank's surface, fiber Bragg gratings (FBG) were used.
The aim of our experiments was to examine structural behavior of the composite hydrogen vessels and test appropriate
topologies of sensors to detect the damages.
In the present work we demonstrate measurements obtained using optical fiber head sensors for high pressure composite vessel, composite strengthened concrete beam and the high-voltage composite insulator.
The key to efficient systems based on fiber bragg gratings is a flexible and accurate inscription of these components with demanded parameters. This paper presents basic information about fiber Bragg gratings and offers a flexible method of writing long gratings at any wavelength with the same phase mask.
In this paper there are described setup for modification of exposure time in fiber Bragg gratings fabrication with using scanning phase mask method. Using this laboratory stage we are able to write uniform, apodized and chirped gratings. Depending on exposure time and grating length it is possible to write gratings with various attenuation for Bragg wavelength. Also, it is possible to change Bragg wavelength, and obtain chirped gratings by linear and gradient post-processing respectively.
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