Valve Sizing

http://www.controlpix.com/steamvalve.html

http://www.spiraxsarco.com/Resources/Pages/Steam-Engineering-Tutorials/control-hardware-el-pn-actuation/control-valve-sizing-for-steam-systems.aspx

https://www.engineeringtoolbox.com/flow-coefficients-d_277.html

..click on chart for full size...

http://spartan-pd.com/sizing-steam-valves/

http://cgproducts.johnsoncontrols.com/met_pdf/347vb.pdf

https://www.controlpix.com/steamvalve.html

http://www.spiraxsarco.com/resources/pages/calculators.aspx

Guess 2 of the links must be good, as we both posted them. I was going to ask if mine were not good enough but I see I posted them only a minute before yours.

Appears to me, you gentlemen got this one covered in record time.

It would appear great minds think alike!

Your two minds sure did!

Some good sources have already been mentioned. Also worthwhile is literature from ASCO, a mfr of solenoid and other valves. For info on C_v (K_v) at partially open conditions, I think there are some butterfly valve makers that cover this nicely, but I don't remember which.

A telephone call to the local friendly valves distributor is always worthwhile as the organisation can make a selection based upon the requirements, particularly if there is the risk of a sale occurring as a result of that call.

Guys thanks for your links

But i need know that, the density of steam is no were related to Cv calc.

And kindly post any literature to calculate Cv for Steam...

There are publications called "Steam Tables", which give the thermodynamic properties of steam at all combinations of temperature and pressure, This information is fundamental to the correct selection and sizing of control valves for steam.

If the protocol for sizing in-house doesn't exist, then ask the Valves Distributor to size and select the valve on the basis of the steam conditions and expected flow rate; these people are doing this sort of thing every day whereas the in-house facility might only be doing it once per year for example.

"I might not know what two twos are, but I do know where to look it up." - Anonymous Poster #0

There are two different annotations Cv, one is heat capacity at constant volume, and that is known, the other is valve coefficient Cv. Quite different parameters with totally different usage and intent, and context.

That's an important point. It always pays to define abbreviations before using them.

So kindly provide the example if it exists with you.

It will be useful for my learning

However, unlike the specific heat capacity of water, the specific heat capacity for superheated steam varies considerably with pressure and temperature and cannot be taken as a constant. The value of 2.0 kJ/kg °C given above is therefore only the mean specific heat capacity over the specified temperature range for that pressure. There is no direct relationship between temperature, pressure and the specific heat capacity of superheated steam. There is, however, a general trend towards an increase in specific heat capacity with increasing pressure at low degrees of superheat, but this is not always the case. Typical value range: 2.0 kJ/kg °C at 125°C and 1.013 bar a (0 bar g) 3.5 kJ/kg °C at 400°C and 120 bar a.

Thus there is no constant value of heat capacity for steam in general, as it depends on the conditions of the steam employed.

reference: http://www.spiraxsarco.com/Resources/Pages/Steam-Engineering-Tutorials/steam-engineering-principles-and-heat-transfer/superheated-steam.aspx

CV of steam flow: http://www.spiraxsarco.com/global/us/Products/Documents/Steam_Sizing_Chart-Technical_Information.pdf

There are all the examples you need.

• "Kempe's Engineer's Yearbook", any edition.
• Perry: "The Chemical Engineer's Handbook", any edition.
• Mayhew & Rogers: "Thermodynamic Properties of fluids", any edition.
• Simply use Google on the topic "Steam Tables".

Spirax/Sarco use their numbers for steam valve sizing, although you will then be guilty of plagiarism if for work or school. For your own use, OK.

Steam valve sizing - you have been warned

The link shows you how to calculate whatever you need to know.