flow resistance of 3 way ball valve

[Spoonful]

Hi All,

Not sure if this is the right place to ask this question.

For a 3 way L port ball valve reduced bore. what flow resistance factor should I use?

Should I simply threat it as a straight reduced bore(k1) + a 90 degree bend(k2)?

So as per Crane T410 paper, K=K1+K2, where K1=formula 5 or 6 given in A-28, and K2=60fT?

Any comment on this?

Thanks

Spoonful.

 

[TD2K]

This might be a silly question but have you checked with the vendor for any Cv information?

I'd likely do it as a combination of a reduction from the line to the ball ID, the change in direction within the ball (likely as a tee with the flow through the branch) and then the expansion back to line size (if the latter loss is applicable).

 

[BigInch]

To model it using two globe valves would probably be a whole lot better. One valve (x%)open, the other (100-x%)open

From "BigInch's Extremely simple theory of everything."

 

[Spoonful]

Hi TD2K,

I don't think my supplier would be at much help,
your way of model it which is pretty much the same as my :
a reduced bore ball valve K1 + a 90 degree mitre bend(to be conservative rather than threat it as elbow) K2,

so total K=K1+K2

so dP= density*k*velocity^2/2


BigInch,

I don't quite understand you way. dP during switch is not what I am after, I am only looking for at one fully open 90 degree position dP.

BTW, dose any one have knowledge of
I.E. Idelchic - Handbook of fluid resistance, Diagram 8-3, perforated thick plate dP, I am trying to use the method given, but it seems my manual calculation result could not match these given in the graph.

Thanks for all the comments

Regards

Reynold

 

[chicopee]

If this valve was made in one of the Asian countries, be sure to check the internals for chips,burrs and fillings. I got an horror story about that.

 

[Duwe6]

You should get a VERY close approximation by using the Equivalent Length of a threaded short-radius ell with the same I.D.

 

[stanier]

Losses also depends on the bore of the valve in question. These vary between manufacturers.

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His Holiness the Dalai Lama.

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[Spoonful]

It is a reduced bore, so should I model it as simple reduced bore ball valve + a mitre bend?
I would like to use a full bore as for less pressure drop. but I found it hard to find a full bore for 50NB.

 

[katmar]

I think a reduced bore 2-way ball valve plus a mitre bend of the same (reduced bore) diameter will be a good approximation.

A full bore 3-way ball valve is virtually impossible because there isn't enough metal left to have a sufficiently strong ball. If you want a full bore 50NB valve it probably means that you will have to install an 80NB reduced bore valve.

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