Airtightness detection method of CM node area of liquid cargo tank of LNG ship

Abstract

The invention discloses an airtightness detection method of a CM node area of a liquid cargo tank of an LNG ship. The method comprises: a structural characteristic of a target CM node of a liquid cargo tank of an LNG ship is analyzed; on the basis of the structural characteristic of the target CM node, a CM node type is determined and a matched vacuum cover is selected based on the CM node type; and detection liquid is sprayed on a detected weld joint, the selected vacuum cover is in close contact with a corresponding ballast tank wall, and then vacuumization detection is started. According tothe invention, while related ship structures of the ballast tank do not form a complete tank, airtightness detection is carried out on the CM node area quickly and conveniently, so that time is earned for follow-up construction of the LNG ship containment system and the construction period of the LNG ship is shortened. Moreover, the CM node can be detected at the forming process of any construction stage like the segmentation stage and the main stage and restrictions on the construction state, the segmentation placing state, and the welding mode are eliminated.

Description

technical field [0001] The invention relates to the technical field of shipbuilding, in particular to a method for detecting the tightness of a CM node area of ​​a liquid cargo tank of an LNG ship. Background technique [0002] A liquefied natural gas carrier (LNG carrier) is a world-recognized "three-high" ship with high technology, high added value, and high reliability requirements. Its service life is as long as more than 40 years. During this period, it is necessary to ensure the ability to transport LNG at -163°C. Therefore, quite high requirements are put forward for the fatigue strength of the hull structure. [0003] The CM joints summarized in the LNG ship construction process are the connection points of the "octahedron" structure of the liquid cargo tank. The welds in the CM joint area include four types. The fillet weld, the fillet weld between the vertical downward sloping bulkhead of the ballast tank and the horizontal girder; the second type is composed of t...

AI Technical Summary

Problems solved by technology

There are two problems with this method: first, the structure of the ballast tanks in the CM node area is formed late, and the waiting period for the cabin inflation test conditions in the dock stage is long, which is not conducive to the development of the follow-up containment system work

Second, after the insulation box inside the cargo tank is installed, it will cover the welds in the CM node area, so that the welds in this area cannot be observed when the cabin inflation test is carried out later.

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