adjustable port valves 3

[Renoyd]

Merry christmas,

Can anyone explain the usage of the adjustable port valves? By adjusting the port size, we can change the valve capacity, right? To restrict the flow (when fully open) to a very low level, do we need a restrict orifice, or the adjustable port valve can do it itself? Thanks.

 

[JLSeagull]

Are you addressing a specific model that is described as an adjusable port valve?

The port opening size is changing for all control valves compared to on/off isolation valves. Also, valves are available with port size selections. Many reduced port (bore) ball valves have a port one line size smaller than the piping. Reduced port sizes for control valves permit trim selection applied to specific process condition ranges. However the valve internals must be replaced to change the port size.

 

[Renoyd]

As far as I know, it is a kind of valve with port height adjusting knob and port width positioning level to adjust the dimensions of the port. Just wondering if it has a full range of continuous throughput control from zero to max capacity, or just uncontinuously like valves with 1/4" trim, 3/8" trim, 1/2" ...

 

[roydm]

Masonealan have a valve with adjustable CV. It's only in small size however.
The CV is adjusted by moving a pivot point to vary the length of a lever.
Rpy

 

[JimCasey]

Roydm, you apparently refer to the Masoneilan VariPak. They also have the Varimax rotary and the Wee Willie with tinier capacities than the VariPak. All three have adjuatable capacities by moving pivot points in the linkage. The down side of that is when you set them to the low-end of adjustable range, the trim is just not opening much. With the plug close to the seat, erosion and wire-drawing are always phenomena that might occur.

Groth has/had a tank-blanketing regulator with a rotary-positionable cylinder around the trim so the user could dial in the capacity he needs for the application. A window in the cylinder could blank off part of the waterway so that the regulator's capacity was adjustable.

Most adjustable Cv valves are as JLSeagull mentioned: pop out the trim, snd insert something of a different size orifice..

 

[roydm]

JimCasey,
Yes, we do a lot of prototype gas skids the VariPak is a good fit for that because you can re-use the same valve for different conditions without having to change trim. Another favorite is Badger Research for small globe valve. I particuarly like their stepper motor actuator as it allows you to adjust the range of travel also with very little hysteresis.
Regards & Happy New Year
Roy

 

[Renoyd]

Thanks for your input. What is usually specified for design purpose for an adjustable port valve if the capacity is to be controlled to a certain level? For example, if I wanna limit the capacity to 1 MMscfd under the operating conditions, the port opening needs to be very small, what is to be specified corresponding to the desired port opening so that operations can act? Is it Cv or anything else? Thanks.

 

[roydm]

You need to specify
Connection type - screwed or flange
Material
fail action
Control method - 4-20, pneumatic, Foundation Fieldbus
Hazardous area class if applicable
Protection Class - e.g. NEMA 4
Any certification requirements
Process Conditions
Fluid you are trying to control
Inlet pressure
Outlet Pressure
Temperature
Normal & Maximum flow rate (What is MMscfm, I'm not familiar with that unit?)

Any good vendor of control valves will calculate the Cv for you.
I'm not sure that you need an adjustable port valve. I suggest you look at Badger Research they have lots of tiny valves.
If it's a lab type situation you can automate any of the small needle valves from Swagelok or Parker with an actuator from Hanbay
Regards
Roy