By-pass valve - CV vs Size
By-pass valve - CV vs Size
(OP)
Hello,
I am a junior process engineer working for an EPC company and we are in the detailed engineering phase. The basic studies have been performed by another company.
My problem is that i have the following list of CV and sizes for by-pass valves and i want to know wich manufacturer and which type of valve have been selected:
3/4" --> Cv=10
1/2" --> Cv=6.6
1" --> Cv=12
3/2" --> Cv=36
Furthemore i have heard of a scaling rule for geometrically similar valve that states: Cv=K*d^2 (K a constant and d the by-pass valve size). I have also heard that for gate: K=48, for globe: K=14.
Based on that and on the data provided during the basic studies, i have performed calculation that give me the following info:
3/4" --> K=18
1/2" --> K=26.4
1" --> K=12
3/2" --> K=16
My conclusion is that the 3/4", 1" and 3/2" by-pass valve give a K fairly close to K=14 and that they could be globe valve. Is it correct? Also what about the 1/2" by-pass vale?
Also could you please tell me if my approach is sensible?
P.S: sorry for my poor english as i am french
I am a junior process engineer working for an EPC company and we are in the detailed engineering phase. The basic studies have been performed by another company.
My problem is that i have the following list of CV and sizes for by-pass valves and i want to know wich manufacturer and which type of valve have been selected:
3/4" --> Cv=10
1/2" --> Cv=6.6
1" --> Cv=12
3/2" --> Cv=36
Furthemore i have heard of a scaling rule for geometrically similar valve that states: Cv=K*d^2 (K a constant and d the by-pass valve size). I have also heard that for gate: K=48, for globe: K=14.
Based on that and on the data provided during the basic studies, i have performed calculation that give me the following info:
3/4" --> K=18
1/2" --> K=26.4
1" --> K=12
3/2" --> K=16
My conclusion is that the 3/4", 1" and 3/2" by-pass valve give a K fairly close to K=14 and that they could be globe valve. Is it correct? Also what about the 1/2" by-pass vale?
Also could you please tell me if my approach is sensible?
P.S: sorry for my poor english as i am french
"We don't believe things because they are true, things are true because we believe them."
"Small people talk about others, average people talk about things, smart people talk about ideas and legends never talk."





RE: By-pass valve - CV vs Size
Your scaling rule seems to come from the same basis as Equation 3-16 from Crane TP410, but the Crane formula is more complete. In Crane the "K" used is the same "K" as is used in flow resistance calculations for pipe fittings (we have had that discussion!!) and it is
Cv = ( 29.9*d2 ) / ( K0.5 )
where d is in inches
In your equation your "K" is equal to Crane's 29.9 / ( K0.5 )
Katmar Software
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RE: By-pass valve - CV vs Size
"We don't believe things because they are true, things are true because we believe them."
"Small people talk about others, average people talk about things, smart people talk about ideas and legends never talk."