The plug valve is a valve that uses a plug body with a through hole as an opening and closing part, and realizes the opening and closing action through the rotation of the plug body and the valve stem. The plug valve has simple structure, rapid opening and closing, and low fluid resistance. In this paper, some improvements and strength calculations have been made to the problems of plug valves used in drilling.
The opening and closing part of the plug valve is a cylindrical body with a hole, which rotates around an axis perpendicular to the passage, so as to achieve the purpose of opening and closing the passage. The plug valve is mainly used to open and close pipelines and equipment media. The main advantages of the plug valve are: suitable for frequent operation, quick opening and closing, and light. The fluid resistance is small. Simple structure, relatively small size, light weight and easy maintenance. Good sealing performance is not restricted by the installation direction, and the flow direction of the medium can be arbitrary. No vibration and low noise. However, the plug valve used in drilling often has the problem that it is not easy to open after being closed. This article has conducted a series of discussions and improvements on this problem.
1 Under the action of three given loads, the stress under tensile load is the highest and the safety factor is the smallest. Therefore, the strength conditions under tensile load are the main contradiction.
2 The stretching is calculated with the commonly used plug valve material 40CrMnMo, and the safety factor is 1.71>1.5, which can meet the strength requirements.
3 The stress concentration at the knob orifice under tensile load is relatively large, and the yield limit of the material is reached at the stress concentration point. According to the new strength criterion, the maximum stress concentration point is 935.75MPa<2MPa, which satisfies the stability condition.
4 The reference stress and stress generated by the inner groove during stretching are also relatively large, but it can meet the strength requirements. In the design, attention should be paid to reduce the stress concentration here.
5 Under the action of given torsion and internal pressure load, the safety factor of each dangerous section is very large, and its strength can be ignored.