Abstract: Disclosed herein are a system, method, and apparatus for arresting flames in an air return line. The apparatus includes a flame barrier containing one or more metal mesh layers and configured to permit airflow there through while preventing flame break-through. The flame barrier can also have or be connected to one or more temperature or pressure sensors configured to detect blockage of airflow through the flame barrier and to detect damage to the flame barrier. The apparatus can also include additional temperature or pressure sensors for detecting the propagation of deflagration in the air return line.

Abstract: Disclosed herein are a system, method, and apparatus for arresting flames in an air return line. The apparatus includes a flame barrier containing one or more metal mesh layers and configured to permit airflow there through while preventing flame break-through. The flame barrier can also have or be connected to one or more temperature or pressure sensors configured to detect blockage of airflow through the flame barrier and to detect damage to the flame barrier. The apparatus can also include additional temperature or pressure sensors for detecting the propagation of deflagration in the air return line.

Abstract: Apparatus and method for optically measuring temperature by spectroscopically determining the temperature-induced changes in the wavelength spectrum of light interacting with a semiconductor temperature sensor. The method includes providing illumination from a radiant energy source with a broad wavelength spectrum, guiding the radiant energy to a remote semiconductor sensor, returning the radiant energy after interaction with the semiconductor sensor, and analyzing the returned wavelength spectrum to determine the temperature-induced spectral changes due to the absorption edge of the semiconductor sensor. One embodiment of the invention comprises a quartz-halogen lamp, an optical multiplexer, optical fiber lightguides, a gallium arsenide semiconductor sensor, a fast scan spectrometer, an analog to digital converter and a microprocessor for processing the information of the returned wavelength spectrum for determining and displaying the sensor temperature.

Abstract: A non-metallic fiber-optic device is provided for measuring the level of fluid in a tank, reservoir, or other vessel. Light from a broadband light source is transmitted through a fiber optic waveguide and an optical coupler to an optical pipe sensor which is immersed in the fluid to be measured. The optical pipe sensor includes a monotonically varied diffraction grating in the surface and along the length of the sensor which serves to retroreflect wavelengths of light as a function of the local spacing of the diffraction grating. For light entering the sensor from the waveguide, wavelengths of light corresponding to the local spacing of the diffraction grating above the fluid level are retroreflected, whereas wavelengths of light corresponding to the diffraction grating spacing below the fluid level either escape into the fluid, are absorbed, or are coupled to a return fiber to be detected.