What is the difference between the stress results and why is it important?

• WillemBouwer
In summary: When you restrain only one end, the other end will move about a bit and this could introduce errors into your analysis.
WillemBouwer
I have to run a FEA analysis on a nozzle check valve body DN700... Its been to a professional engineer and he has completed the study so I am trying to do it myself to get to know the software better... I'm using PTC CREO 2 mechanica as the software...

Attached find a picture of the valve body.

I have constaint the valve at the hole locations on the flanges, as pin constaints. Where the angular constraint is free and the axial constraint is fixed.

The valve is rated at 40 bar, therefor should be tested at 1.5 time working pressure so 60 bar... So the load I used was a pressure load on the surfaces of the entire inside of the body for full open condition, and on the surfaces up to the point where the disc should close the flow off for the fully closed condition.

I would like to analize the valve in both fully open and fully closed conditions. With the disc of the valve pressing against the diffuser and the body when fully open, and pressing against the centre piece and the body at fully closed position...

I have set the material to be SG42 Cast iron and meshed the body...

At fully open condition I get the Maximum Von Mises stress to be 224 MPa at the bolted area
At fully closed condition I et the Maximum Von Mises stress to be 221 MPa on the fins of the body...

However a picture of the professional engineers findings have been attached. He finds the Max Von Mises stress to be 312.5 MPa which differs from my analysis.

Now the question is: Why is his stress more, what am I not thinking about? Can anyone help please, thanks... It is complex to explain what I did but ask eny questions, haha...

Attachments

• 221MPa fully closed condition.jpg
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• 224MPa fully open condition.jpg
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• Body1.jpg
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Since your value is lower, it's most likey just a case of your mesh size being too small at the areas of maximum stress. Try increasing the mesh size at the obvious areas.

It's impossible to guess what the difference is. The most likely two things to check are the lioads and the boundary conditions.

FWIW, in the left hand picture it looks likke the vanes supporting the central disk are bending axially. There is a stress gradient from one end to the other similar to a cantilever beam. In the right hand picture, they are doing something different.

Plotting the deformed shape of the model might show you if something crazy is happening.

I don't have any experience of this sort of pipework analysis, but it could make a lot of difference if you restrain only one flange rather than both flanges. Think about what each end the valve is attached to - for example a stiff pressure vessel or a relatively flexible pipe.

1. What is FEA analysis on valve body?

FEA (Finite Element Analysis) is a computerized method used to analyze the structural behavior of a component or system. In the case of a valve body, it involves breaking down the complex geometry into smaller finite elements and applying mathematical equations to simulate the behavior of the structure under different loads and conditions.

2. Why is FEA analysis important for valve body design?

FEA analysis allows engineers to accurately predict how a valve body will react to different forces and environments, helping them to identify potential weaknesses or design flaws before the valve is manufactured. This saves time and resources, and ensures a more reliable and efficient valve design.

3. What are the benefits of using FEA analysis on valve body?

FEA analysis provides engineers with a detailed understanding of the structural behavior of a valve body, allowing them to optimize its design for better performance and durability. It also helps to reduce manufacturing costs and time, as well as the risk of failure or malfunction.

4. What types of simulations can be performed with FEA analysis on valve body?

FEA analysis can be used to simulate a variety of scenarios, including static stress analysis, thermal analysis, modal analysis, and fatigue analysis. These simulations can help determine the strength, stiffness, and natural frequencies of the valve body, as well as its ability to withstand thermal expansion and fatigue over time.

5. How accurate is FEA analysis on valve body?

The accuracy of FEA analysis depends on several factors, such as the complexity of the valve body geometry, the material properties, and the assumptions made in the simulation. With proper validation and verification, FEA analysis can provide highly accurate results that closely match real-world behavior. However, it is important to note that FEA analysis is a tool and should be used in conjunction with physical testing and engineering judgment for the most reliable results.