Blevins,R.D., 1983, "Applied Fluid Dynamics Handbook",Van Nostrand Rheinhold gives in Table 6-10, case 9 for a ball check valve
K=2.3 (From Crane Technical Paper #410)
K=0.5 (From Boston Soc. Civil Engrs. V42#3,pp.263- 286,1955)
Idelchik,I.E. etal,1986,"Handbook of Hydraulic Resistance",2nd Ed., pg. 429 gives the following formula for a spherical valve with a spherical seat within 0.125<h/D<0.4
Lambda=K=2.7-(0.8/(h/D))+(0.14/(h/D)^2)
D is the valve diameter and h is the valve opening distance not defined for a spherical seat in a spherical valve.
The Crane book does not have ball check valves in it. Neither does Cameron Hydraulic. As far as the formula you listed, I'll see if I can track down the valve opening distance. This system is already in service, so I don't have the valve or it's information in front of me.
Extract from Fluid Flow Design Software version 1.7.
The L/D for a ball check valve is 150
For each pipe diameter, D4, D3, D2, D1 (exit to entry)
Calculate the fluid velocity,
V = Q / A
Calculate the Reynolds number,
If mixture then, Re = ?mixVD / ?mix
If vehicle then, Re = ?vehVD / ?mix
If liquid then, Re = ?liqVD / ?mix
Calculate the Fanning friction factor, ƒ
If Calc method = Newtonian mixture, vehicle, liquid then,
If Re < 2100 then, ƒ = 16 / Re
If Re > 3000 then, ƒ = 0.0625 / (LOG(k / 3.7D + 5.74 / Re0.9))2
If Re > 2100 and Re < 3000 then, interpolate
If Calc method = other procedure then,
Calculate ƒ using the selected procedure (eg Lazarus & Neilson)
Calculate the head loss in metres of mixture,
?Hpipe = (4ƒL/D)V2 / 2g and ?Hfittings = KV2 / 2g
Calculate the pipe wall pressure drop,
If mixture then, ?Ppipe = ?mix g ?Hpipe
If vehicle then, ?Ppipe = ?veh g ?Hpipe
If liquid then, ?Ppipe = ?liq g ?Hpipe
Calculate the fittings pressure drop, ?Pfittings = ?mix g ?Hfittings
I found a correlation between K and Cv. The manufacturer listed Cv on their website, but not K.
K =~ 891*(d^4)/(Cv^2) ... with "d" in inches
Using the Edward-supplied Cv value of 51.5, and an ID of 2.067 (2" SCH 40), I came up with 6.1323. Given that similar to various lift check K values, it'll do.
Thanks for all the advice! Itdepends, your reply was very informative, though a little more involved that I need. Thankfully, I'm not designing a system. I'm just trying to determine if we need some piping or pump modifications to better balance one of our sump pump systems.
Lots of good stuff in the above posts. My older (1969) Crane TP 410 lists an in-line ball check valve as L/D = 150 and convention check valve as L/D =135 provided both are FULLY OPEN.
Iha, very insightfull. For complete turbulance (rough pipes) f = 0.019 for 2 inch sch 40, therefore, K = 2.9 for the ball check and 2.5 for conventional swing check, your number.
My newer Crane TP 410 (1978) lists K = 100 * ft for a swing check with ft = turbulent friction factor for 2 inch pipe = 0.019 so K = 1.9. For 50 gpm, L/D = K/f = 1.9/0.023 = 83 diameters. It omits the in-line ball check valve.
gibsi1, IMO, k = 6.1 seems a little high for a ball check.
It is interesting to note Crane (1969) suggests a minimum pressure drop across the ball check valve of 0.25 psid (horizontal) and 2.5 psid (vertical) to fully lift the ball.
Very good info. If a ball check is truely K=2.9, why do 2" lift-type checks range from 1.1 to 11.4? I was under the impression that ball checks were highly restrictive.
At k=70, the minor loss at EACH check valve would be:
4.3 feet (or almost 2 psi) at 2 fps;
27.2 (12 psi) at 5 fps and
108.7 ft (47 psi) at 10 fps.
You would need a booster pump at each valve!
Further, the k of a 3/4 closed gate valve is 24, so a ball check would be almost 3 times as restrictive as a 3/4 closed gate valve. I've always used gate valves for isolation; I should start using ball check valves ;-0 Just a little weekend humour.
I am fairly certain k is nowhere near 70 for a ball check.
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