Ball Valve Sizing2
Ball Valve Sizing2
(OP)
Hello,
can someone explain me if I'm able to find the internal dimensions of reduced ball valve, knowing that it's made in comply with API 4D and has Class 600. I've looked at that API (have for 1996), but nothing was stated about the relations between ball bore size and valve nominal diameter.
thanks in advance
can someone explain me if I'm able to find the internal dimensions of reduced ball valve, knowing that it's made in comply with API 4D and has Class 600. I've looked at that API (have for 1996), but nothing was stated about the relations between ball bore size and valve nominal diameter.
thanks in advance





RE: Ball Valve Sizing2
RE: Ball Valve Sizing2
I think you'll find the API and Class 600 references relate to the valves ability to withstand temperature and pressure. This is why they have nothing to say on the valve's internal dimensions.
You would be better off looking at some manufacturer's literature or websites, as the actual dimensions of the hole through the ball vary from valve to valve.
Regards,
Brian
RE: Ball Valve Sizing2
Have you considered using a full port valve if a reduced port valve is a problem?
RE: Ball Valve Sizing2
RE: Ball Valve Sizing2
You might take a look at API STD 608, which covers ball valves and defines the dimensions required for full, regular, and reduced port valves.
The bad news is that not all ball valve manufacturers comply with API 608, so you may be left with checking catalog data anyway.
RE: Ball Valve Sizing2
Q=cv*(dP/g)^1/2 Q=flow gpm
cv=valve coefficient
dP=diff. press. psi
g=sp. gravity of fluid
for gases use the gas sizing form.
Simply calculate the required cv and pick a ball valve that matches or is greater than.
Don't worry about wether its reduced port, full port or in between port.
Hope this helps.
saxon
RE: Ball Valve Sizing2
can you please advise the formula for gas flow as well
thanks,
joisy
RE: Ball Valve Sizing2
Q=cg*P1*(520/G*T)^1/2*sin((3417/c1)*(dP/P1)^1/2)
Where:
Q=gas flow, std. ft^3/hr.
cg=gas sizing coeff.
c1=cg/cv
cv=liquid sizing coeff.
P1=inlet press., psia
dP= pressure drop across valve, psia
G= gas specific gravity
T= gas absolute temp., deg. R
NOTE: (3417/c1)*(dP/P1)^1/2 must be equal to or less than 90. If greater than 90 the form will indicate reducing flow, which is impossible.
Now that I have thourghly confused the issue, have fun.
saxon
RE: Ball Valve Sizing2
It's Fisher's equation for valve sizing out of their catalogue and they have another formula for any gas at any pressure and temperature (eg. where the compressibility is not equal to 1.0).
However, you can make the equation valid for any gas at any pressure and temperature with one slight modification:
Q=cg*P1*(520/Z*G*T)^1/2*sin((3417/c1)*(dP/P1)^1/2)
Where Z is the compressibility factor.
RE: Ball Valve Sizing2
saxon ;)
RE: Ball Valve Sizing2
Your question maybe why I do calculate this for gas if it's not intended for? Because I need to calculate some abnormal plant operation when in place of the liquid the line handles gas. Nothing got from Emerson (Fisher) on this issue :(
RE: Ball Valve Sizing2
RE: Ball Valve Sizing2
by the way: last equation can be re-written as:
Q=1.06x((RoxP1)^1/2)xCg x SIN(3417/C1 x ((dP/P1)^1/2)), lb/hr; where Ro is gas density (pounds/cub.feet)
I've got some advise that max flow through this valve can be calculated as chocked flow (Vs-sonic volume) by formula:
Vs=(KRT)^1/2, where K is specific heat ratio (usual 1.3), R=R0/M. Q=VsxSxP/(ZxR0xT). S:=Dp^2x3.14/4, where Dp is the port size.
It doesn't seem to me to be the right way, and what you think of that?
RE: Ball Valve Sizing2
However, you can do some manipulating of the equations and show that the two equations become identical with the addition of the Z term I suggested.
Joisy, the maximum flow through your valve is at choked flow or when the sin{ } term equals 1. Then, you have:
Qmax=1.06x((RoxP1)^1/2)xCg OR
Qmax=cg*P1*(520/Z*G*T)^1/2
Watch your units. Q in the 'ideal' gas equation is scfh. In Fisher's 'any gas at any temperature and pressure equation', it's shown as Qs in their catalogue with units of lb/hr.