How to detect and monitor corrosion in explosively clad pipelines and surfacing-welded fittings
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Dear experts, there are many explosion-clad pipelines and surfaced pipe fittings in the production area where I work. The data obtained using thickness gauges is not very accurate, which often leads to problems. Do you have any testing methods? I would appreciate it if you could share your insights
A measurement taken with tightly layered layers isn’t accurate, right?
(1) Composite pipes are generally seamless or welded steel pipes to which a corrosion-resistant alloy layer is bonded to the base steel through coating or lining. (2) The internal cladding method refers to the metallurgical cladding approach using metallurgical composite sheets or surfacing welding techniques. (3) The lining method refers to a mechanical composite process in which a corrosion-resistant alloy layer is adhered to the surface of carbon steel by either expanding the diameter of the alloy-lined pipe or reducing the diameter of the base carbon steel pipe. (4) Fittings are generally compounded by internal lining, rather than through lining. (5) The wall thickness of in-service pipes is generally measured using an ultrasonic thickness gauge; for composite pipes with an inner lining, the total thickness can be measured directly ； For composite pipes with a lining, only the thickness of the base steel can be measured. (6) When there are fluctuations in the measured values of the composite pipe wall thickness obtained by the internal coating method, if the measurement point happens to be at the area where the coating has separated from the base layer, the displayed value will represent the thickness of the base layer. By taking this point as a center and selecting additional points around it for testing, it is possible to determine the extent of the separation. (7) It should be noted that test blocks with an internal coating method should be prepared, and during the testing process, the ultrasonic thickness gauge must be calibrated.