torque calculation to move (to control) a butterfly valve

Generally, you can put a torque wrench on the shaft and measure. I'm sure this Honeywell can handle whatever you have:

Honeywell makes excellent actuators that can be programmed, when the signal fails, to open, close, or stay put:

https://estore.industrialcontrolsonline.com/Default.aspx?page=category%20search%20results&CatList=322&Parent=186&tree=173*Damper+Actuators*0@@186*Honeywell+Herculine+Actuators*322@@

Contact a dealer for the unit for your application.

You should also have a fail-safe emergency shut off valve. If the power is lost, it will close:

http://www.maxoncorp.com/Pages/product-Valves-Shut-Off-Hazard

Again, contact manufacturer for model and size.

Depends on the valve... pretty hard to help when you don't even give the valve size or the line pressure...

So based on the input you have given I would say 52. Hope that helps.

Steve the problem is not the size of the valve or the line pressure, the problem is what will happen to the disc if the mechanism between disc and actuator breaks, the day after the break on the disc will be same if disc is DN300 or DN800 and if pressure is 1bar or 4bars, will open, will close, remains is same position?, this is the problem and second some formulas to calculate the torque needed to control the disc, and in the formula we need to know the size and the pressure.

Thank you

apostolos

Ok, sorry but now I am very confused.

Are you looking for a calculation of the torque needed to close the valve?

Or are you concerned about what the valve disc position ultimately will be if the control arm breaks?

In either case, the valve design will dictate (including the lengths of the control linkages, and the size of the disc). Most control valves have a fail open design since if you need it closed you typically have a manual block valve near by that can be closed. There may either be spring acuation or flow forces that cause the valve to go open, and there may be stops in the design that prevent it from going full open (the stop maybe set at 80% for instance). But you would have to look at the valve data and design sheet for that.

Still need to know more about the valve to help. I would suggest that you ask the valve vendor, as he should have all this info easily available.

Valve manufactures can provide this information for their valves provided the valves are properly installed.

As a general rule a fully closed butterfly valve will remain closed when under pressure and an open valve will remain open with the possibility of opening about half way. Valves that are very loose may respond differently.

But this is a mute point because there is something very wrong with you valve or actuator if the linkage breaks, most likely the valve packing was over tightened or there is something in your pipe that shouldn't be there.

The disk will flutter. (butterfly) The disk will partly close to 30% then open to 70%. Depending on the speed of the fluid, the swing could last a 10th of a second to 5-10 seconds. You would end up with pulses in your pipe/duct.

Butterfly valves are not control valves, they should be used for isolation only. Go to a globe valve for controlling flow. If you ever have closed a butterfly fly valve with flow , you will notice that it is easy at first then becomes harder as you get near the end. If you try is slowly its all most impossible, sort of need a positive action to get it shut or open.

Let us examine 2 limit cases:

1. Linkages snapped when Butterfly was in SHUT position: Will now remain in SHUT position.No flow at any pressure.
2. Linkages snapped when Butterfly was in fully OPEN position: Will now remain in fully OPEN position.( Assuming butterfly mass symmetrical around axis)

Kind of extension to Newton's Law#1

Butterfly valves have locking tabs on them for this reason. They do NOT remain in their position without this lock. They will float (flutter), just because you quoted Sir Mr. I. Newton's #1, it's #2 and #3 that come into play here, a dash of Bernoulli's and a pinch of Pascals. Don't forget to pre heat, nobody seems to do that any more, it's all micee now.

"Butterfly valves are not control valves"

Excuse me? Butterfly valves are indeed used as control valves and are used for suction throttling control of centrifugal compressors all the time. Part of the reason why I keep asking for more details on the application.

If you need additional info on control valves go here...

http://people.clarkson.edu/~wilcox/Design/valvselc.pdf

This discussion provides even more evidence that we need more info on your valve..

Sorry all to hay!!! Thought I read in the question something about liquid and kind of thought it was to control such. Air type valves have a hole through them so they don't flutter.

That is the problem, I'll have to go back and re read but I don't think he ever even told us what the fluid is, or if it is liquid or gas...

Hi all,

The torque needed to move a butterfly valve is a function of:

• The flow rate across the valve (fluid speed → Dynamic torque)
• The position of the disc (usually, for symmetric disc and centered shaft, the maximum dynamic torque is required when the valve is open about 30º)
• The friction of shaft / bearings
• The friction of disc on seat to withstand the differential pressure when closed
• Valve dimensions, position of shaft (horizontal/vertical), etc.

If the valve is closed when the actuator/valve link fails, possibly the valve should get closed, if the valve is full open, possibly remain open. But if is in an intermediate position, it depends, possibly as already said the valve will "flutter" moved by the hydrodynamic torque.

Even it has disappeared from the last editions, previous versions of ANSI/AWWA C 504 give some guidance on how to calculate the torque needed to move a butterfly valve.

Cheers

valve size : 1000 mm nominal bore

flow rate : 19850 Nm3/hr

pressure : 25 Kpa

medium : LD Gas

temperature : 53 deg cel

desnsity of gas : 1.38 kg/m3

the above given is the data maximum available with us

kindly send the details of torque calculations.

regards

design dept

If the disc is "lens" shaped and the shaft is concentric, the valve will close abruptly if the acuator is disconnected from the shaft - and if the fluid is a liquid there's danger of water hammer. The reason is that the flow through the disk will create a low-pressure region behind the disk which tends to unevenly distributed across the disk back and is more significant behind the side of the attack edge, resulting in a hydrodynamic effect that creates a torque in the direction that closes the valve.

The closing is extremely fast because the torque is a function of the fluid velocity, which increases when the valve gets closer to the closed position, accelerating the angular movement of the disk (same effect as a door being slammed by the wind).

Butterfly Valve: Size 150 mm

Valve Body: CI

Valve Disc: SGI

Valve seat: EPDM

PN10 and temp is Ambient,

My flow is 140 cu m/hr and its water. I want to use Rotex actuator ECF-110 @4bar with a pneumatic Positioner RX1200. Rotex guy said its possible to all this.

My questions:

1. Can I control the flow of water using a butterfly valve.I mean like 30 % , 40 % flow should be possible.if so how?

2. I would like to know the torque require to open/close this valve. I want to know if there is a calculator available to determine torque online.

3. I want to know if my valve is in continious use, should I be using a superseal in the actuator. Especially if my water is surface water.

I guess this questions would cover most of the doubts everyone has. Would be glad if someone answered my queries.

Thank you,

The consideration <...the valve disc if the control mechanism failed while the fluid is still moving on the pipe i.e. the disc will close? Will open? Or stay in his position...> is a fundamental design issue and needs to be considered at the HazOp Study for the plant in question. It is a process requirement rather than a consequence!