Finite Element Analysis and Presetting of Marine Butterfly Valves

In recent years, many companies have also put forward the problem of preset production of large-scale marine valves (such as Φ5350mm in diameter) according to their needs. However, according to the existing Marine Valve preset manuals and corresponding standards, there is still a lack of relevant large-diameter marine valve design data, and there is also a lack of preset experience for large-scale marine valves. Because of this, it is necessary to carry out careful and accurate calculation and analysis, and it is necessary to carry out deformation and force analysis and calculation. Then the preset is executed according to its Z-post result. Therefore, it is ensured that it has a satisfactory tight seal and sufficient strength. However, due to the particularity of the marine valve structure, it is difficult to use the classical mechanical method to carry out the analysis and calculation, and only the finite element method is used for the analysis and calculation as deemed appropriate. It is considered appropriate to use the finite element method to analyze and calculate the valve body and disc of the Φ5350mm marine Butterfly Valve, so as to provide a theoretical basis for its reasonable structure and preset optimization, so as to prevent indispensable material consumption.

The essence of the finite element analysis method is to idealize an elastic contiguous body with an infinite number of degrees of freedom into an ensemble of units with only a finite number of degrees of freedom through two approximations, so that the problem is simplified to a structural problem suitable for numerical solutions. The first approximation is the division of cells. Very accurate boundaries are broken down into simple boundaries. Consecutive objects are broken up into a series of elements that are only connected by nodes. Structural break up is also called grid division. The original elastic continuous body; the second approximation is the real and complex displacement distribution, which is approximately expressed in the result form after analysis Z, and the result after analysis and calculation can be seen intuitively.

What needs to be explained here is that the development and practical application of the finite element analysis method so far have used a crucial tool: the use of computers in the actual calculation. Using the systematic software of the computer to carry out the analysis and calculation greatly increases the analysis speed and plays a very important role in practical applications.

1 Structure of marine valve

This marine valve uses a positive structure as deemed appropriate. The valve body is a double flange plus ring rib type; the butterfly plate is a special-shaped plate type, and different types of ribs are reasonably placed on it. The workload of manual calculation is large, and because of this, three-dimensional finite element analysis software is used to perform the calculation.

2 Finite element calculation and analysis of valve body

Structural dispersion is the basis of the finite element method. The so-called structural fragmentation is the aggregation of the elastic contiguous body to be analyzed into a finite number of units according to certain rules, so that adjacent units are connected at the nodes, and the load between the units is only transmitted by the nodes. Structural separation is also known as grid separation, and the unit aggregation formed by the separation will replace the original elastic contiguous body.

First, establish a finite element plate type with a simple and concise structure of the valve body.

2.1 The boundary conditions are confirmed

The deformation of the valve body is mainly affected by the weight of the valve body itself and the weight of other components of the marine valve (such as valve plate, power unit), because the weight of other components should be fully considered in the calculation. Variation calculation of valve body, load group Y-direction 3g gravitational acceleration, and load Y-direction and X-direction constraints on the bottom of the valve body. At the same time, considering the problem that the diameter of the marine valve is large, the pipe end effect will be revealed, because this needs to be done in the two-piece method. Load the marine valve Z-direction constraint on the blue.

2.2 Analysis of stress conditions

Because the marine valve has a large front diameter, it is generally considered appropriate to use a steel plate welding structure, because the main consideration is the influence of the weight of the whole body of the marine valve on the valve body, so as to prevent the valve body from having a large self-weight deformation, thus affecting the marine valve. For the normal use of the valve, the acceleration of gravity is g, but in fact, considering the problem from the perspective of safety, we calculate it by 3g. Loading Y=3g, through finite element analysis and calculation, the self-weight deformation working condition of the valve body under 3 times the acceleration of gravity can be obtained. The following is the working condition of the valve body modification. It can be seen that the maximum modification amount is 0.6mm.

3 Finite element calculation and analysis of valve plate

According to the past experience of marine valve design, first give a size of the main board and its ribs on the valve plate, because it belongs to the special-shaped plate, because this needs to accurately establish its group stiffness matrix, and do group finite element analysis, because this requires group construction. This can ensure the continuity and force dependence of the entire butterfly plate shape, and ensure that the calculated result is correct.

3.1 The boundary conditions are confirmed

When working, the motor rotates together with the valve shaft and the valve plate through the speed reduction machine. The valve shaft transfers the torque to the valve plate through the joint on the valve plate. When the valve plate is subjected to the force of the fluid medium, it also transfers the force to the valve body through the joint, because the valve plate is subjected to the force of the fluid medium. The constraints at the last link should be: the three moving coordinates of X, Y, and Z should be limited, and their three rotational coordinates should also be limited. Therefore, the node of the corresponding unit that looks better than the photo of the inner wall of the joint piece is regarded as a fixed point, and its displacement and rotation angle are both zero.

3.2 Analysis of stress situation

First, consider the effect of the fluid medium in question. In this default, the office pressure is 0.1MPa (1.0kg/cm2), but in fact, considering the problem from a safety point of view, we calculate it as Pressure=0.3MPa (3kg/cm2).

Before and after the valve plate is deformed, the deformation occurs. The larger position of the deformation is at the Z outer point on the core surface of the rotary shaft of the valve plate. In this example, the larger deformation is Zmax=0.21mm.

4 Analysis of the results after Z

The deformation analysis of the marine valve is that the main components of the marine valve will be deformed after being stressed. After the Z results, it is very convenient to carefully check and analyze the working conditions after the deformation, and analyze and compare the states before and after the deformation of the components. The deformation volume of the former official point of the component can also be obtained. After calculation and analysis, if the deformation of the component after being stressed exceeds the allowable range or the deformation is extremely small, the structure (such as thickness) is corrected, so a reasonable structure is obtained.

The stress analysis of the marine valve is that the stress will be generated after the force analysis of the marine valve, and the larger stress on the component can be found out intuitively through the analysis of the results for yourself. Reasonable analysis and optimization are carried out, and the marine valves are strengthened by means of placing reinforcement bars and other forms in the position of high stress.

It can be seen from the above analysis that after the stress analysis of the main components of the marine valve and the calculation and analysis of the deformation after the force, it is possible to find out the position with the larger stress and the larger deformation on the structure, and the two are combined to implement the structure of the marine valve. Correction, get a reasonable structure, ensure that it has sufficient strength and rigidity, prevent the structure from being bulky, lead to the consumption of materials, materials and energy materials, and reduce the cost of manufacturing.

5 The conclusion

After the simulation analysis and calculation of marine valves, the following conclusions can be drawn:

(1) The stress everywhere on the marine valve device can be calculated, and the stress value can be revealed, so the position with larger stress can be found and optimized, and the latent problem can be found in the preset stage of the product, so the number of attempts is reduced, so the loss is reduced. Try funding.

(2) The deformation of the valve plate after being stressed can be displayed, and a little deformation value can also be obtained. In this example, the position where the valve plate is greatly deformed is the Z outer point perpendicular to the core surface of the valve plate rotation axis, which can be reinforced in a targeted manner to prevent the consumption of raw materials.

(3) After calculation and analysis, the structural preset is rationalized and optimized to ensure that the preset object has sufficient strength and stiffness, saving resources and reducing costs.

(4) The reliability of products and projects is guaranteed; the time to market for products is reduced.

(5) Carry out accident analysis on the marine valves that have problems, and search for the cause of the problem.

The application of finite element analysis technology in the design of marine valves has made a qualitative leap in the design level of marine valves. After the stress calculation and analysis of the key structures of marine valves, guiding opinions on the design of marine valves are given.