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Technology Factsheet

Non-Intrusive Liquid Level Detection System

Category: Characterization > Monitors > Multipurpose Detectors
Reference # : OST No 2403, DOE/EM-0507 Model No : NLLDT

Infrared-based Non-Intrusive Liquid Level Detection Technology (NLLDT) was utilized to detect if liquids were present in tanks, vessels and piping assemblies and the levels of liquid. The NLLDT system uses the process of converting heat emitted from the object into a visible dynamic TV-like picture. All objects ­V animate or inanimate, liquid, solid, or gas- constantly exchanges thermal energy in the form of electromagnetic radiation with its surrounds. If there is a temperature difference between the object in question and its environment, there will be a net energy transfer in the form of heat; a colder object will be warmed at the expense of its surroundings, a warmer object cooled. The differences in the physical properties of various materials (i.e. stainless tanks or pipes and liquids that may be contained there in) will result in temperature variations that can be detected using infrared imaging cameras as tons of gray or color contours in the picture. These color or gray image contours map the temperature variations of the object being viewed with great precision. The NLLDT system consists of the following components: ,h Infrared Imaging Camera and tri-pod and Digital Visual Camera. The cameras consist of at least five basic parts: optical components, filter, detector, electronics, and temperature display. ,h Heating unit to be used as required The principle component of the NLLDT system is the Infrared Imaging Camera. By creating a detailed two-dimensional temperature pattern (thermogram) of the surveyed surface, information on temperature is obtained from several thousand points in the field of view of the scanner, or detector array, in about one thirtieth of the second. The voltage variations that are obtained of the surveyed surface are amplified and shown on a CTR display. The differences in heat radiation appear as tones of gray or color variations in the picture. The continuous gray tone makes the interpretation of detailed thermal patterns of the surfaces possible with temperature differentials as low as 0.2oC. Weight of Infrared Imaging Camera and tri-pod, 8 pounds Weight of Digital Visual Camera, 4 pounds


The use of the NLLDT System to detect liquids in vessels and pipes eliminates the need to physically open and inspect these vessels. Risks to workers associated with gaining access to these type objects and the possible exposure to radioactive or contaminated materials can nearly be eliminated.


Piping assemblies represent a special problem in direct liquid level detection. Usually successful detection of liquids will require a post-test analysis of a carefully planned sequence of infrared images. The technology is useful for site characterization in support of D&D engineering design and during and subsequent to D&D activities.




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