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how to test the quality of the finned tubes ?
Nov 23, 2018

The finned tube is a heat exchange tube. The main function is to improve the heat exchange efficiency. Usually, the fin surface is added to the surface of the heat exchange tube to increase the external surface area (or internal surface area) of the heat exchange tube to acchieve the purpose of heat exchange efficiency.  So how could the quality of the finned tube be tested?

Method for pre-buried detection of finned tubes:

(1) Double-finned tubes shall be buried in the pile diameter of 0.6-0.8m; three finned tubes shall be buried in the pile diameter of 0.8-2.0m; four finned tubes shall be buried in the pile diameter of 2.0m or more, depending on the specific conditions of the Chifeng Bridge, the pile foundation Three finned tubes can be buried.

(2) The sound wave detection fin tube should be made of steel pipe, plastic pipe or steel bellows, and its inner diameter should be 50-60mm. The joint of the finned tube should be smoothly transitioned, the fin mouth should be higher than the top of the pile by more than 100mm, and the height of the tube of each detecting fin tube should be the same. The lower end of the tube should be closed, the upper end should be covered, and the fin tube should not be covered. Foreign body, the fin body must not be damaged.

(3) The finned tube can be welded or bundled on the inner side of the reinforcing bar, and the finned tubes should be parallel to each other.

On-site inspection method for purchasing finned tubes:

(1) Determine the delay time t of the sound wave monitor transmitted to the receiving system before the on-site inspection. And calculate the sound time correction value.

(2) When transmitting and receiving, the probe should be raised and lowered at the same elevation or by maintaining a fixed height difference.

(3) The measuring point distance is 40cm, and then encrypted to 20cm when an abnormality is found.

(4) Select the appropriate transmit voltage and amplifier gain, and remain unchanged during the test.

(5) Display and record the time history curve of the received signal in real time.

(6) The multiple finned tubes are combined in a single inspection section, and the profiles are completed.

(7) After each group of test tubes is tested, the test points should be randomly repeated 10%, and the relative standard deviation of the sound should not exceed 5%; the relative standard deviation of the amplitude should not exceed 10%.