# Selecting a Valve for Natural Gas Flow

• cjm181
In summary, the conversation discusses the process of sizing a valve for regulating the flow of natural gas. The chosen valve type is the V250 rotary ball valve and the data sheet provides values for Cv, Kv, Fd, Fl, and Xt. The required valve size in inches is determined from the range of sizes given in the data sheet, and the estimated percentage of the chosen valve being open to carry the required flow is also calculated. The equations used include Kv=qm/31.6YSQRT(xp1P1) and Y=1-(x/(3FyXt)), where Y is the expansion factor and Fy is the specific heat ratio. The conversation also mentions the use of xT factors from a table
cjm181

## Homework Statement

A valve is required to regulate the flow of natural gas. Details of the gas are given in table below. It can be assumed that the pipe size and the valve size are the same [i.e. piping geometry does not have to be allowed for].

The chosen valve type is the V250 rotary ball valve by Fisher Controls International I have this data sheet, it the chart it gives values for Cv, Kv, Fd, Fl, Xt

1) Determine the required valve size in inches from the range of sizes given in the data sheet [the data sheet gives a range of nominal pipe sizes (NPS) in inches].

2) Estimate the percentage the chosen valve would have to be open to carry the required flow.

required volumetric flow rate = 2.8x10^6 litre per min
Density (@STP) = 0.724 kg/m^3
Specific heat ratio (y) = 1.31
inlet pressure = 20barg
outlet pressure 6barg
inlet temp 20degC

## Homework Equations

Kv=qm/31.6YSQRT(xp1P1) ...1
where kv is valve coefficient
qm is mass flow in kg/h
Y is expansion factor
p1 density
P1 inlet pressure

Y=1-(x/(3FyXt)) ...2

Fy = y/1.4

## The Attempt at a Solution

So, I think here I have to find the value of Kv, then use that to size the valve on the sheet. So to satisfy equation 1, I must find Y

the issue is I am not given Xt. Xt features on the valve chart, so how can I specify this? Or am I off in the wrong direction?

Did you get given the equation for x?
x = dp / P1
x limit = xT * Fk

If dp / P1 > xT * Fk then your flow is choked and x = xT * Fk
If dp / P1 < xT * Fk then your flow is not choked and x = dp / P1

This determines what x you use in the sizing equation. (NOTE make sure you use bara in all your equations) 21.01325 bara.

For preliminary sizing you could;
1. Use a range of xT factors from table (maybe at 80 / 90% open and estimate required Kv)
2. Select appropriate valve from datasheet
3. Calculate flow of selected valve at range of opening % using provided kv / xT and plot curve
5. Typically good control range is between 20 - 80% open. If your valve is > 80% open maybe do the same procedure for the next valve size up and check % open.

Hope this helps.

## What factors should be considered when selecting a valve for natural gas flow?

When selecting a valve for natural gas flow, there are several factors that should be considered. These include the pressure and temperature of the gas, the flow rate, the type of gas being transported, the type of valve (ball, gate, globe, etc.), and the material of the valve.

## What are the different types of valves that can be used for natural gas flow?

The most commonly used valves for natural gas flow include ball valves, gate valves, globe valves, and butterfly valves. Each type has its own advantages and disadvantages, so it is important to consider the specific needs of the gas flow before selecting a valve.

## How do I determine the appropriate size of valve for my natural gas flow?

The size of the valve needed for natural gas flow is determined by the flow rate of the gas. This can be calculated using the gas flow rate, pressure, and temperature. It is important to choose a valve with a size that can handle the maximum expected flow rate to avoid any potential issues or failures.

## What is the recommended material for valves used in natural gas flow?

The recommended material for valves used in natural gas flow is usually carbon steel or stainless steel. These materials are able to withstand the high pressure and corrosive nature of natural gas. It is important to also consider the compatibility of the material with the gas being transported.

## How do I ensure the safety and reliability of the valve for natural gas flow?

To ensure the safety and reliability of the valve for natural gas flow, it is important to follow proper installation and maintenance procedures. Additionally, regular inspections and testing should be conducted to identify any potential issues and address them before they become major problems.

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