Calculation min. operating time butterflyvalve ?!?
Calculation min. operating time butterflyvalve ?!?
(OP)
Who can help me?
Look at the following formulas
v = (354 * Q)/ DN^2 then Q = (v * DN^2) / 354
t = (5157 * Q ) / (DN^2 * dP)
Added those formulas together i get;
t = (14.56 * v)/ dP
For liquids v is aprrox. 5m/s
So the valve size is not a factor in closing time, only pressure?!? So the operating time to prevent waterhammer is equal for every size? Were do i go wrong?
Many thanks in forward!
Look at the following formulas
v = (354 * Q)/ DN^2 then Q = (v * DN^2) / 354
t = (5157 * Q ) / (DN^2 * dP)
Added those formulas together i get;
t = (14.56 * v)/ dP
For liquids v is aprrox. 5m/s
So the valve size is not a factor in closing time, only pressure?!? So the operating time to prevent waterhammer is equal for every size? Were do i go wrong?
Many thanks in forward!





RE: Calculation min. operating time butterflyvalve ?!?
t = 2 L / a
where:
t = critical period, sec
L = length of the pipe, m
a = speed of the pressure wave, m/s
If the condition above is realized, that is the valve is closed/opened within the time t, this will be considered as instantaneous and the water hammer H will be evaluated using the following formula
H = a v / g
where:
H = water hammer, m water column
a = speed of pressure wave, m/s
v = change in flow velocity, m/s
g = gravity (9.8 m/s^2)
The speed of the pressure wave (a) depends on the fluid.
You stated that "For liquids v is aprrox. 5m/s", but to get this value for any given flow rate you have only one pipe size.
RE: Calculation min. operating time butterflyvalve ?!?
To be more precise the speed of pressure wave (a) in ft/s can be written as
a = 4600/SQRT[1+k*(OD/s-2)/E]
where
k = Fluid bulk modulus, psi
E = Pipe modulus of elasticity, psi
OD = pipe outer diameter, inch
s = pipe thickness, inch