How to Select a Valve

The process for valve sizing can be confusing. There are many variables in oil and gas controls, and many different options to deal with those variables.

In this blog we’ll be covering:  

  1. The uses of high and low pressure valves
  2. How to use your calculated Cv
  3. Which valve to use for liquid versus gas applications

Sizing High Pressure Valves and Low Pressure Valves

The first question you need to ask when valve sizing is “What is my pressure?”

For GAS applications, if your pressure is MORE than 300psi, you need a high pressure control valve;
if it’s LESS than 300psi, you can likely use a low pressure regulator.

For LIQUID applications, if your pressure is MORE than 500psi, you need a high pressure control valve;
if it’s LESS than 500psi, you can use a mechanical or pneumatic dump valve.

While it sounds obvious to choose high pressure valve for high pressure application, there is another key factor you have to consider: Calculated Cv.

Calculated Cv

The second question you need to ask when valve sizing is “What is my Cv?” Cv is the number of gallons of water that will pass through a given flow restriction at a 1 psi differential. Basically, you can think of it as the orifice size of a valve. To calculate your Cv, plug your flow conditions into the Kimray sizing calculator

Let’s look at two examples.

Example 1

Your pressure is less than 300psi and your required Cv is 3 or greater.

In this case, a low pressure regulator should work for a gas application, while a low pressure control valve or mechanical dump valve will work for a liquid application.

Example 2 

Your pressure is still less than 300psi, but your required Cv is less than 3.

In this example. you should use a stem-guided high pressure control valve because it can meet the small Cv requirements.

This may sound counterintuitive to use a high pressure control valve for low pressure, so let’s dig a little further…

What Calculated Cv Means for Valve Trim Sizes

Kimray low pressure valves and regulators come with 2 trim options—full port or reduced port—and might be too big for the small flow rates. Kimray 2” stem-guided high pressure control valves come with 9 trim options ranging from ¼” up to 1”. Our 1” stem-guided valve trim options range from 1/8” – ½”.

Stem-guided valves have small Cvs—from .34 to 21. They can handle low flow as well as high pressure drop applications where you have a small Cv requirement.

For larger Cvs and higher pressures, Kimray’s cage-guided high pressure control valves are full port valves with a Cv range of 28.6 to 1,091.

While our stem-guided valves are available only in 1” and 2”sizes, our cage-guided valves are available in 2″ through 10″.  

Can I Change My Valve Trim? 

We’ve now walked through selecting a new valve. But what about if you have valves on an existing well and conditions change?

A key benefit of Kimray control valves is their versatility. For example, If you resize your valve with the new conditions and the calculated Cv does not fit the trim on your existing stem-guided valves, you can swap the trim for a different size. This will keep you from having to change your piping to handle the new conditions.

Kyle Andrews is an Account Manager at Kimray. Connect with him on LinkedIn or by email at kandrews@kimray.com