Structural improvement and strength calculation of plug valve

The plug valve uses a plug body with a through hole as an opening and closing element, and a valve that opens and closes through the rotation of the plug body and the valve stem. The plug valve has a simple structure, rapid opening and closing, and low fluid resistance. We made some improvements and strength calculations for the problems that occurred with the plug valves used in drilling.

The opening and closing member of the plug valve is a perforated cylindrical body that rotates about an axis perpendicular to the passage to achieve the purpose of opening and closing the passage. Plug valves are primarily used to open and close pipes and equipment media. The main advantages of the plug valve are: it is suitable for frequent operation, quick and easy opening and closing. Fluid resistance is small. Simple structure, relatively small size, light weight, and easy maintenance. The sealing performance is not limited by the mounting direction, and the flow of the medium can be arbitrary. No vibration, low noise. However, the plug valve used in drilling is often not easy to open after closing. This article has carried out a series of discussions and improvements on this issue.

1 Under the action of three kinds of given loads, the stress under the action of tensile load is high and the safety factor is small. Therefore, the strength condition under tensile load is the main contradiction.

2 Stretching is calculated by 40CrMnMo, which is a common plug valve material. The safety factor is 1.71>1.5, which can meet the strength requirements.

3 The stress concentration at the opening of the knob is greater under tensile load, and the material yield limit is reached at the stress concentration point. According to the new strength criterion, the large value of the stress concentration point is 935.75 MPa<2 MPa, which satisfies the stability conditions.

(4) The reference stress and stress of the inner groove during drawing are also large, but it can meet the strength requirements. Attention should be paid to reducing the stress concentration at the time of design.

5 Under the given torsional and internal pressure loads, the safety factor of each dangerous section is very large and its strength can be ignored.