How should the wall thickness of the tube bundle in a shell-and-tube heat exchanger be measured?
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The heat exchanger in our unit is of the fixed tube sheet type, with a diameter of 1500 mm. The specifications for the heat exchange tubes are: ID/OD = 12/18 mm, length = 5650 mm, and there are 313 such tubes. The plant operates at a pressure of 25 MPa and a temperature of 220°C, with ethylene as the medium ； Shell side: 0.5 MPa, 35°C, cooling water. It has been in use for ten years without any inspections of the tube bundles; I don’t know what the extent of wall thickness reduction is, and due to the high pressure, I’m quite concerned. Excuse me, does anyone know what method can be used to measure the wall thickness of so many small tubes?
Eddy current testing (ECT) can be used to determine the wall thickness of pipes, but it is important to note the following: 1. Choose experienced ECT testing agencies and personnel； 2. Use tubes made of the same material as those in your heat exchanger tubes as standard specimens; during testing, the standard specimen must be used for calibration every hour ； 3. The baffle will generate a special signal that needs to be distinguished ； 4. Before testing, the inside of the tube must be thoroughly purged ； Alternatively, the inner diameter of the pipe end can be measured directly using an internal diameter micrometer and compared with the original value, which can also serve as a reference for corrosion-induced thinning.
Abroad, the IRIS system is used, but no one in China has bought it yet – it’s too expensive! ! ! Ultrasonic IRIS system – Internal rotary ultrasonic technology. The Internal Rotary Inspection System is used for inspecting tubes in operational heat exchangers: it is not affected by the electrical or magnetic conductivity of the materials, and can detect ferromagnetic, non-ferromagnetic, and non-metallic materials ； It can accurately measure the inner diameter and wall thickness of pipes ； It can provide the exact location of pipe corrosion and cracks ； It can display the cross-sectional view (B-scan) or the expanded wall view (C-scan) in real time, as well as the longitudinal cross-sectional view of the tube (D-scan).