I was wondering if anyone know whether a globe valve or a butterfly valve would be preferred in the situation of a Cv of 177, and the fluid flowing is water. the valve also needs to be made of cast iron or stainless steel. from my research, I haven't been able to find any global valve that could reach a Cv that high. so is a butterfly valve the only solution? Also, do butterfly valves usually have automated control?

 

What's the size of the pipe?

Either of the valves can be automated depending on the availability of actuator energy (air, hydraulics, or electric).

 

> What's the size of the pipe?

Thanks for replying,

There is no fixed size, but it probably can't be too big, I'd say around maybe 5" to 6"

 

Hi wanj2219,

You are basically asking what is the length of a piece of string ... any length you want.

You have listed some criteria; water, 5" to 6", stainless or iron, flow capacity CV around 177.

To select your valve you also need; inlet & outlet pressure, temperature, flow rate, water composition (conductivity, chlorides, other contaminants), shutoff class required, fail state, actuation air/electric/hydraulic, flow characteristic (linear, equal%, don't care), control method (4-20mA - on/off - regulator?), and there will be more questions as you dig deeper.

Butterfly valves can be pretty crappy (you should be able to get CV=177 in a 3"), globe valves are a bit fancier (you will probably need a 4" or larger globe for CV=177). For reasonable quality water service I would probably pick an eccentric plug valve with equal percent characteristic - but this may not suit your site or budget.

For a basic valve with an actuator and positioner you will be spending around USD $5k to $15k depending on requirements.
If you don't get your application right you end up with an expensive paperweight - I suggest finding an instrument engineer or a knowledgeable vendor you trust to help your selection.

Cheers,
PB

 

I worked in mining for many years, it was common to use large butterfly valves to add water to the mills. They can cavitate quite badly without sustaining damage since it occurs in the pipe downstream. An eccentric disk is a better valve.

Both can be modified with a simple slip in plate to reduce the noise.