How do I find information

[PaperWeight]

I am trying to determine how many scfm are required to stroke an actuator that came with an ITT Hammel Dahl 8" valve. The old vendor manual I have doesn't give this information. It does say that it is a 200 in^2 diaphram with a 3.5 in stroke. But I really nead to know the scfm required to actuate this valve. I realize this will depend on the spring and possibly some other parameters, but I was wondering if anyone out there knew of a resource for this type of information.

 

[snubengr]

Adequate pneumatic pressure will actuate the valve, depending on spring rate, packing friction, other friction factors, valve and process characteristics, etc. Flowrate (ie scfm) in combination with the particular actuator characteristics, (ie. volumes, diaphragm area, etc.) as well as the other factors mentioned above), will help you to determine the stroking speeds.

Not much help, I realize, but I think you need a lot more info to find what you're looking for. The actuator vendor or a good instrumentation vendor might be able to walk you through it.

Cheers,

Dennis

 

[rbcoulter]

Interesting. Assuming that this is a standard actuator, it would probably require instrument air (standard compressed air but cleaned, moisture removed, etc.). One doesn't usually speak of CFM required to open a valve. It would be assumed that the plant instrument air system would supply the necessary volume. The key is do you have enough pressure to open the valve.
Why not hook the actuator up to the plant instrument air system? Use an air regulator to determine the minimum pressure needed to open the valve fully.
If you are that concerned about the actuator consuming too much instrument air , you can install a needle valve on the inlet to the actuator to slow the air consumption to a very low rate (as low as needed). The key is to
have enough pressure. Note: The needle valve doesn't change the actual volume of air needed to open the valve, just the flow rate of air.

 

[PaperWeight]

Thanks for your responses.

I guess I should have described the scenario better. I work at a Nuke plant. The actuator we are speaking about is a safety-related device. There is a volume tank and a check valve associated with this valve. The check valve isolates the volume tank and actuator from the rest of the plant air system, such that if plant instrument air is lost, the volume tank can still provide the required cfm at an adequate pressure to actuate the valve if needed.

I need to replace the actuator. Therefore, I need to no how much air must be provided by the volume tank in order to ensure delivery of enough air at adequate pressure.

 

[rbcoulter]

If you are replacing the actuator then the actuator vendor should be able to tell you what your supply air requirements should be. If the vendor doesn't have the specs, buy an actuator from a vendor that does.
Or do I have this wrong? Are you trying to size the new actuator to the existing volume supply tank?
How many times is the valve expected to cycle (open/close) if the plant air goes down? This effects the cfm consumption. The volume of your cylinder is about 0.4 cu.ft. Five cycles, for example, will require at least 2 cubic ft of air at the fully compressed (against the springs) position. Multiply this number by the absolute pressure needed to open the valve (psia) and divide by 14.7 to get the amount of air needed at standard conditions. For example, let's assume that it takes 50 psi to stroke the valve. That's about 65 psia. The amount of air in the cylinder at that point is about (65/15)*0.4 = 1.73 standard cu.ft. A standard air cylinder provided by a local gas supplier (like BOC) would have no problem supplying a cylinder to provide that amount of air .