Exploratory research on infrared imaging for inspection of electrofusion joints in polyethylene gas pipe. Final report, July 1990-July 1992
The main thrust of the study was on the use of infrared imaging as an nondestructive examination (NDE) method for electrofusion fittings. However, a cursory study of ultrasonics, X-ray, acoustic emissions and wire resistivity as NDE methods was also considered. The concept of infrared (IR) imaging as an NDE technique involved observing the surface of the fitting during the fusion process to detect distortions in the heat pattern caused by subsurface defects. If defects could be detected in this manner, the distorted pattern would be recorded on infrared sensitive film. The thermal conductivity of the PE was too low and only large defects could be detected in this manner. Ultrasonic waves are reflected by the EF heating wires and these signals mask reflections from defects. X-ray of fittings on pipe must be made double wall (source on one side of the pipe and film on the other) and the dense wires likewise will mask defects in the less dense PE. Also, X-ray is incapable of detecting delaminations at the fusion line. A measure of the change in resistivity of the heating wires during fusion is a good NDE method used by at least one manufacturer but the technique is insensitive and only large defects are detected. Acoustic emissions as an NDE method shows promise. The limited experiments performed indicate that no sound is emitted from melting and fusion of PE but that sounds are emitted when defects are formed.
- Research Organization:
- Southwest Research Inst., San Antonio, TX (United States)
- OSTI ID:
- 6936265
- Report Number(s):
- PB-93-157261/XAB; CNN: GRI-5090-260-2001
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
PIPE JOINTS
INSPECTION
POLYETHYLENES
JOINING
ALGORITHMS
ALLOCATIONS
BENCH-SCALE EXPERIMENTS
DEFECTS
DETECTION
DISTRIBUTION
HEAT
HEATING
MELTING
PATTERN RECOGNITION
PIPE FITTINGS
PIPES
SIGNALS
SYSTEMS ANALYSIS
THERMAL CONDUCTIVITY
ULTRASONIC WAVES
WIRES
X-RAY DIFFRACTION
COHERENT SCATTERING
DIFFRACTION
ENERGY
FABRICATION
JOINTS
MATHEMATICAL LOGIC
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
POLYMERS
POLYOLEFINS
SCATTERING
SOUND WAVES
THERMODYNAMIC PROPERTIES
032000* - Natural Gas- Transport
Handling
& Storage
360601 - Other Materials- Preparation & Manufacture