Tightness detection method for 90 degree fillet weld at CM node of LNG ship

Abstract

The invention relates to a tightness detection method for a 90 degree fillet weld at a CM node of a LNG ship, which carries out a tightness detection through the special detection device. A vacuum device structure comprises a panel, sealing plates, surrounding plates, rubber sponges and joints. The method comprises the steps of: during the tightness inspection, spraying soap liquid to a 45 degreefillet weld at the CM node after the vacuum device is prepared, covering the fillet weld with the vacuum device, finely adjusting through position of the vacuum device, and compressing the rubber sponges to form sealing space; adjusting a ventilation valve, and when the pressure gauge reaches a specified pressure value, detecting whether bubbles bubble up on the fillet weld through, and achievingtightness detection of the fillet weld; closing the ventilation valve after detection is completed; if a defect on the fillet weld is detected, repeating the three steps after repairing; if the filletweld is intact, the detection is complete. The method and the vacuum device of the invention can overcome a difficulty that conventional vacuum cover cannot detect, and improves construction efficiency of the LNG ship cargo tank.

Description

technical field [0001] The invention relates to ship construction, in particular to a method for tightness detection of 90° fillet welds at CM nodes in LNG ship construction and a special vacuum detection device. Background technique [0002] During the construction of LNG ships, there are many CM nodes with the same angle in the liquid cargo tank. After the segmental construction is completed, the fillet welds at the nodes need to be tested for tightness. Due to the special structure of the CM nodes, the platform plate and longitudinal The fillet weld formed by the wall plate is 90°, and the end of the platform plate forming the fillet weld is only 30mm. Since the installation and maintenance system of the liquid cargo tank takes a long time, the weld tightness test is required to be carried out in sections and overall The first stage is completed, and the only method suitable for testing the tightness of the weld at this stage is the vacuum test. [0003] According to the...

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Problems solved by technology

[0003] According to the vacuum test device commonly used in the current technology, it can generally only meet the detection of welds where the ends of the two structural surfaces of the formed fillet welds are far away from the welds. For LNG ships, the CM At the node, because the weld seam is too close to the end of the platform, ordinary vacuum hoods cannot detect the tightness of the 90° weld seam there

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