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Buterfly Valves

02/09/2017 12:04 AM

I wolud like to know that how to find the pressure drop valve for the butterfly valve and what are the procedure to be followed..???

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#1

Re: Buterfly valves

02/09/2017 12:17 AM
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#2

Re: Buterfly valves

02/09/2017 12:24 AM

Consult manufacturers' literature, and consider any piping that might reduce size before/after the valve.

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#3

Re: Buterfly valves

02/09/2017 3:06 AM

There are two sample ways to do. One is by calculation the pressure at the inlet pipe and the pressure at the outlet pipe with some formula including the opening percentage of the butterfly valve. The other method is to install two pressure gunge, one at the inlet pipe and the other is at the outlet pipe. You will be able to see the difference of the pressure between the inlet pipe and the outlet pipe. Basically it will be very small pressure drop.

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#4

Re: Buterfly Valves

02/09/2017 8:23 AM

Manufacture of the butterfly valve would have this, as well as the pressure drop against percentages open of the valve itself.

Its empirical information, that is based on the type of product in the flow, (its based on water) anything other than water, or properties of water is difficult. Such as viscosity of the liquid affects the ΔP (Delta P).

This is an excellent resource, Flow of Fluids through Valves, Fittings and Pipes, Technical paper 410 by Cramer.

Its been invaluable to me for the past 25 years

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#5
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Re: Buterfly Valves

02/10/2017 2:32 PM

Now that is a very very useful link. It even includes the bees knees, and a basket of berries.

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#7
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Re: Buterfly Valves

02/10/2017 2:38 PM

I've been using that for a very long time, and is very useful

there are actually some outdated PDFs on the web, but that's copyright.

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#6

Re: Buterfly Valves

02/10/2017 2:34 PM

We who are exactly savvy in Texas called them "wafer valve", since the moving part of the valve is, in fact, a wafer with a seal on its edge, or not, and also has a seal in the barrel of the valve that the wafer rests on and seals against during closure. These are not now, and never were intended as metering valves, although on automated ones, there are adjustment Allen head screws on the actuator plate that will prevent full open, or full close, depending on use.

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#8

Re: Buterfly Valves

02/10/2017 5:27 PM

In addition to Crane Technical Paper 410, which I hardly go anywhere without, Cameron Hydraulic Data is a good reference with lots of data and examples easy to follow, to calculate the pressure drop.

The valve manufacturer is the preferred source for accurate flow data, they will list it as Cv, which is the flow through the valve in US gallons per minute that results in a 1 psi pressure drop, in US units, all that I have memorized.

You probably will find in doing the calculation that the valve itself is the least influential of the flow components, regarding pressure drop, unless it is partially closed. In that case, you will want to get the Cv curve at various openings from the manufacturer. Cameron & Crane have the formulae to convert Cv to pressure drop at various flows

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#9
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Re: Buterfly Valves

02/10/2017 8:21 PM

To determine the Cv, one needs to know the ΔP across the valve. Based from empirical data that the manufacture would have.

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#11
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Re: Buterfly Valves

02/12/2017 10:30 AM

i does'nt know my inlet pressure and out let pressure of mu BV so how would i could my cv..

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#12
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Re: Buterfly Valves

02/12/2017 10:47 AM

Your English is a little broken.

I take it as a question, how do you do it?...

one actual has to test it..., not a good alternative. Thats why the best way is contact the manufacture.

In one project, I used a butterfly valve with a positioner as a throttling valve for a cooling line.

I contacted the manufacturer of the valve and they gave me the data I needed as per the valve opening position. Data such as for ΔP (Delta P) and flow rate relation as per the percentage open.

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#13
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Re: Buterfly Valves

02/12/2017 11:36 AM

Apologies for my poor English...

I am a fresher working in a butterfly valve manufacturing company. as design engineer.I have developing a 300NB metal seated butterfly valve so i need to do my design calculation. i need to find my 1.torque, 2.discharge(but i didnt know my pressure inlet and outlet) so how can i find it..???

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#14
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Re: Buterfly Valves

02/12/2017 12:52 PM

Don't worry about your English, most here if you don't come across clearly enough, they'll ask for more details.

Now, to find the CV, that is very difficult without a prototype. Do you have or have access to any CFD software?

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#15
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Re: Buterfly Valves

02/12/2017 1:02 PM

yes i have solidworks simulator & auto desk simulator how i could find with help of this

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#16
In reply to #15

Re: Buterfly Valves

02/12/2017 1:38 PM

Purchase the solidworks add-on and take a few classes. Or you can also google 'solidworks cfd simulation videos'. I'm sure there out there.

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#17
In reply to #15

Re: Buterfly Valves

02/12/2017 3:19 PM

You need to model the hydraulic resistance of your valve in a pipe line, and come up with the Cv or Kv (flow factor) as a result. You are developing the data that the purchaser of your valve will use to apply it. See http://www.valvias.com/flow-coefficient.php.

Eventually your valve could be set up in a test stand with the values as described for the parameter, Kv is cubic meters per hour of water at 16C that gives you a pressure drop of 1 bar

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#18
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Re: Buterfly Valves

02/12/2017 5:22 PM

I think he's trying to develop a base line ahead of actual testing. But yes, empirical data is best.

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#19
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Re: Buterfly Valves

02/13/2017 11:04 AM

You could baseline the design based on existing wafer (butterfly) valves with same or very similar wafer profile, and cross-sectional area. Water (or oil) does not much care about what material the wafer actually is.

Once you have baseline experience (Cv available of other valves), you should be able to model this as a finite element in a hydraulic circuit. OR go actually make the first prototype of this valve and test it in a physical test stand.

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#20
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Re: Buterfly Valves

02/16/2017 3:53 AM

By experiment.

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#21
In reply to #13

Re: Buterfly Valves

02/16/2017 8:29 AM

For your torque, it looks like you will have to know the friction loss data, an interesting calculation set for operator torque sizing is here,

http://www.f-e-t.com/images/uploads/Torque%20Calculation.pdf

and also here

http://www.thraco.com/Weco/Actuator%20Sizing%20Torque.htm

There is some disagreement on the valve position associated with maximum hydrodynamic operator torque, 45degrees vs 80 degrees, which may be explained by the geometry of the valve and shaft placement(?)

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#22
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Re: Buterfly Valves

02/18/2017 2:36 AM

http://www.f-e-t.com/images/uploads/Torque%20Calculation.pdfin the above link i need to know how to find the velocity and friction loos... for my butterfly valve,,,

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#23
In reply to #22

Re: Buterfly Valves

02/19/2017 9:58 AM

It looks like most are done by testing the actual product, as mentioned several times above. However, as also mentioned, some CFD software adapted for your design might get you a theoretical change in energy with velocity. They do close the possible options by specifying water at a given temperature. You pick the flow.

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#24
In reply to #21

Re: Buterfly Valves

05/26/2017 11:40 AM

In the above attachment, I have a doubt, thus the torque of a butterfly valve depends on the weight of the material are not and how to find the torque with reference to the offsets (eccentricity)

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#25
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Re: Buterfly Valves

05/26/2017 12:17 PM

You might try measuring the offset of various valves, and see how the distance affects the force.

You would expect the distance of the offset (trim center to shaft center) to linearly affect the force, 10% longer distance gives you 10% larger force, simple mechanics, and just lump the hydrodynamic forces on similar valve trim and sizes, keep the same trim angle in the valve body so the fluid forces are equivalent.

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#10

Re: Buterfly Valves

02/11/2017 7:40 AM

It depends what you're trying to do. If it's a line size isolating valve, fully open, you can use flow and Cv in formula others have posted.

If it's a control valve you need to consider the complete system, with flow range, other losses etc. Depending on whether it's gravity or pumped, the valve ΔP needs to be about 20 - 25% of total system ΔP to give good control. Control valves are usually a size or 2 below line size, and to allow for this, Cvs are usually taken as 0.8 x the listed figure (swaging factor).

If it's an existing setup, maybe you just need to measure up- and downstream pressures.

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#26

Re: Buterfly Valves

05/28/2017 11:17 AM

i would like to know weather torque as a relation with the material of the valve

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#27
In reply to #26

Re: Buterfly Valves

05/31/2017 6:43 PM

The material of the valve will affect the torque, especially noticeable with resilient seat material, such as compressing a rubber ring. There is some small friction with different and similar metals, this you should also be able to research, static or sliding friction.

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