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Elast
Is there difference between a ball-shaped and puppet-shaped piston in a pressure valve? View All


6 years ago - 2 weeks left to answer. - 7 responses - Report Abuse
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Niel
Thomas, do you mean poppet[1] valve?

The simple answer is yes. A ball relief has a ball held in place with a spring. It is one of the simplest possible relief valve designs there is. The design of a poppet valve is shown in the Wikipedia reference.

There are also lots of other types of relief and safety valves.

Niel Leon
engineering.com


6 years ago

Source: [1] http://en.wikipedia.org/wiki/Poppet_valve


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Elast
ASKED BY
Indeed, I ment poppet-valve.
Has the shape than an influence on the pressure drop?
I'm redesigning a pressure valve for my thesis and I am going to test different piston shapes but I want to have some theoretical background to.
I have already looked on the web and in some books, but there isn't much info about this subject.


6 years ago

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Niel
Thomass:

If you are going to analyze and contrast the pressure drop across various different design of valves you really need to do much more than simply look at different constructions.

The pressure drop across the valve with be a function of the effective orifice configuration. If I were going to analyze the system I would look a both of them as in terms of two dimensional flow. What does the two dimension flow tell you?

Niel Leon
engineering.com


6 years ago

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Elast
ASKED BY
Niel Leon,

the main purpose of my thesis is to redesign a pressure valve so the pressure, further in the machine remains constant, even with different pressures before the valve. The current valve gives pressures above the desirable pressure.

I personally believe the current valve has not the wright dimensions. Fur that, I will test with different types of pistons, orifices and I will measure the force. By experimental way, I will find the dimensions necessary for this problem so I can apply these on a new design. For actually making a mathematic model of the whole system, I will not have enough time and knowledge.

In that thought, I was wondering what I could expect when I used a flat piston, a poppet piston or a ball piston. What's the main difference?

Is it really necessary for a mathematic model in this case you think?


6 years ago

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Niel
Thomass:

The simple answer your question is - YES. You do need to a two dimension flow analysis. This can be done by looking at the change in the dimensions of the orifice as the valve opens for your three different valves.

There may not be a need for to develop a detailed Computational Fluid Dynamics model. By looking at the cross section of the valve opening you can learn a lot.

It should be noted that with Flat valve the maximum lift only has to be 1/2R, where R is the radius. Beyond that lift the valve will not flow any more. For the poppet valve this lift is different.

Niel


6 years ago

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Elast
ASKED BY
Neil,

I think I didn't understand quite well 'two dimensions flow analysis'. It's a different term in my language. But what you said here:

"This can be done by looking at the change in the dimensions of the orifice as the valve opens for your three different valves."

is exactly the plan. I have 5 or 6 orifices with a different R. The plan is to look what the influence is from the diameter to the whole system and that for the different pistons. I know that there is a difference between a ball-type, a poppet-type and a flat piston in pressure-surface, that I have calculated. I just wondered, before I will test the different types, what I could expect. For example, will the pressure-drop be proportional with the difference in pressure surface of the different kind of pistons. Or is the effect between a ball-type and a puppet-type actually small?

Thomas


6 years ago

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Niel
Your analysis and resultant testing should demonstrate the orifice efficiency across the area changes of the pressure surface for the various valve types.
For small diameters the differences in orifice efficiency will be minimal, but as the diameter of the valve gets larger the differences will be come more obvious.

Niel


6 years ago

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