The plug valve is a valve that uses a plug body with a through hole as an opening and closing member to realize an opening and closing action by rotation of the plug body and the valve stem. The plug valve has a simple structure, quick opening and closing, and low fluid resistance. In this paper, some improvements and strength calculations have been made for the problems with the plug valves used in drilling. Concerned about surprises Label: plug valve; valve; drain valve Previous: Talking about Hardware market: energy saving and environmental protection is the trend of diversified development Next: NSK imported bearing wear life and precision persistence Sliding Shower Door,Bypass Sliding Door,Bypass Roller Sliding Door,Glass Shower Enclosure Zhongshan Jianjie Sanitary Ware Co.,Ltd , https://www.janjieshowerdoor.com
The opening and closing member of the plug valve is a perforated cylinder 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: suitable for frequent operation, quick opening and closing, and light. The fluid resistance is small. The utility model has the advantages of simple structure, relatively small volume, light weight and convenient maintenance. The sealing performance is not limited by the installation direction, and the flow direction of the medium can be arbitrary. No vibration, low noise. However, the plug valves used in drilling often have problems that are not easy to open after closing. This paper has carried out a series of discussions and improvements on this issue.
Structural improvement of the plug valve:
The method of opening the channel at the lower part of the valve body makes the pressure on both sides basically balanced, which makes the valve open and close conveniently, and solves the problem of the original plug valve.
The improved plug valve strength is calculated as follows:
1 Shell reference stress calculation
A, the center of the ball valve hole section 3-3
a, tensile stress concentration analysis
A, ball valve section 3-3
a, stretching
2. According to the design of pressure vessel in Chapter 5 of the Chemical Equipment Design Manual, the maximum stress of the cylindrical shell opening is found at the point where the radial hole edge is parallel to the circumferential direction, and the stress concentration factor is 2.5. The stress concentration factor when stretched alone is taken as 2.5.
Yielding occurs near the stress concentration point. But less than 2, so it is stable.
b, reverse
According to the stress analysis near the opening in the design of the pressure vessel in Chapter 5 of the Chemical Equipment Design Manual, it can be seen that the thin-walled cylindrical shell with a small hole and the torsion is present on the cross section of the hole and the shaft. The torsional cylindrical shell of the hole has a stress concentration factor of 4.
No yield will occur.
c, internal pressure p = 105MPa
When the thick-walled cylinder with small holes in the cylinder wall is subjected to the internal pressure by the "Handbook of Stress Concentration Factor", the stress concentration factor A=3.03 is obtained.
Yielding occurs at the stress concentration point, but it is stable.
B, the cross section of the snap ring 2-2
a, stretching
Checked by the Nobel map in the book Stress Concentration A= 2. 8
Yielding occurs near the stress concentration point (the intersection of the fillet and the inner wall). But stable.
b, reverse
From the "stress concentration" book, the Nobel map is found A= 1. 8
No yield will occur.
c, internal pressure p = 105M Pa
According to the "Chemical Container", the local stress calculation method for the joint of different wall thickness cylinders, the maximum stress on the thin wall side (the meridional stress)
C, cone valve hole section 4-4
a, stretching
According to the design of pressure vessel in Chapter 5 of the Chemical Equipment Design Manual, the maximum stress of the cylindrical shell opening is found on the radial section, and the stress concentration factor A=2. 5 is the stress concentration factor when it is stretched alone. .
Yielding occurs near the stress concentration point. But stable?
b, reverse
According to the stress analysis near the opening in the design of the pressure vessel in Chapter 5 of the Chemical Equipment Design Manual, the stress concentration of the torsion-treated thin-walled cylindrical shell with small holes appears at 45° with the shaft. In the section, the torsional cylindrical shell with small holes has a stress concentration factor of 4.
No yield will occur.
Section 1- 1
a, stretching
According to the design of the pressure vessel in Chapter 5 of the Chemical Equipment Design Manual, the maximum stress of the cylindrical shell opening is found at the point where the radial hole edge is parallel to the circumferential direction, and the stress concentration factor is A=2.5, which is solely affected by The stress concentration factor at the time of stretching is taken as 2.5.
Yielding occurs near the stress concentration point. stable.
b, reverse
According to the stress analysis near the opening in the design of the pressure vessel in Chapter 5 of the Chemical Equipment Design Manual, it can be seen that the thin-walled cylindrical shell with a small hole and the torsion is present on the cross section of the hole and the shaft. The torsional cylindrical shell of the hole has a stress concentration factor of 4.
No yield will occur.
3, 1 internal pressure 105MPa effect
When the thick-walled cylinder with small holes in the cylinder wall is subjected to internal pressure by the "Handbook of Stress Concentration Factor", the stress concentration factor can be obtained A = 3. 03
4 Conclusion
No yield will occur.
From the above stress analysis, the following conclusions can be drawn:
4.1 Under the action of three given loads, the stress under the tensile load is the highest and the safety factor is the smallest. Therefore, the strength conditions under tensile load are the main contradiction.
4.2 Tensile is calculated by the commonly used plug valve material 40CrMnMo, the safety factor is 1.71>1.5, which can meet the strength requirements.
4.3 Under the tensile load, the stress concentration at the orifice of the knob is large, and the yield limit of the material is reached at the stress concentration point. According to the new strength criterion, the maximum value of the stress concentration point is 935.75 MPa<2 MPa, which satisfies the stability condition.
4.4 The reference stress and stress from the inner groove during drawing are also large, but the strength requirement can be met. Care should be taken to reduce the stress concentration here.
4.5 Under the given torsion and internal pressure loads, the safety factor of each dangerous section is very large, and the strength problem can be ignored. 