Control valves
operating torque , a 25 square inch actuator would be able to operate a 4 ” valve .
A 2 ” HRV exhibits CONSTANT FLOW RATES with various outlet pressures
Test results
A 2 ” prototype was built and submitted to the Water Research Lab at the University of Utah for evaluation , using water as test medium . Here are the results : Rated Cv = 60 , Fl at 100 % travel = 0.72 , Fl at 20 % travel = 0.63 , Xfz = 0.35 at 100 % travel and 0.49 at 20 % travel . Instability at 100 psig inlet and o psig outlet = none . Torque : nil , not measurable . Choked flow occurred between 19 % to 22 % of inlet pressure ( equivalent choking gas at 9.5 to 11 % of P1 ). Resultant flow downstream stayed constant within +/ -2 % as indicated in Figure 3 .
Sound level measurements
A microphone was placed downstream of the test specimen during most of the test runs . Figure 4 shows the results of a typical test run . The sound levels were exceptionally low . Part of the reason was that about one third of the pressure range happened to be in the laminar flow regime . Fluid mechanics tells us that , in a laminar flow regime , there can be no turbulence , hence , no sound . In order to dramatize the about 14 dB sound reduction , the author plotted the sound emitted from a conventional butterfly valve having the same data input . See Figure 4 . Once the choked flow induced constant flow and velocity is achieved , the only constant sound level comes from turbulence inside the downstream pipe , which typically only measures 70-80dB .
Noise ( dBA )
Higher levels can only be expected from the final pressure drop at the end user .
Adherence to acoustic laws
Assuming Xfz = 0.35 , Xy = 0.675 : The first stage : Lp1 = 30 log ( 1 / 0.5Xfz ) = 22.7 dB The second stage : Lp2 = 10 log ( Xfz / 0.5 Xfz ) = 3 dB Third stage : Lp3 = 60 log ( Xy / Xfz ) = 17.1 dB Fourth stage : Lp4 = -60 log ( X / Xy ) = -10.2 dB With the basic sound level ( A + B ) from the ‘ Baumann ABC ’ method = 57 dB , then we can find a maximum noise level to occur at Xy , which then is 57 + lp1 + lp2 + lp3 = 57 + 22.7 + 3 + 17.1 = 99.8 dB ( Figure 4 shows 99 dB ).
Sound Level comparison between 2 ” High-Recovery Valve ( HRV ) and 2 ” Z-Disk Butterfly 140
120
100
80
60
40
20
0.5Xfz Xfz
GPM
450
400 350
300 250 200 150 100 50
Xy
HRV ( dBA ) Z-Disk ( dBA )
Conditions : 100 psi water inlet pressure , Cv = 60 , FL = 0.6 , Fd = 0.35 , XFz = 0.35 * HRV Test Data Source : Utah Water Research Laboratory Report 5 / 14 / 2022
0
100 % open
50 % open
20 % open 20 40 60 Outlet pressure with 100 psig inlet pressure
Fig . 3 : Flow rates from a 2 ” prototype high-pressure recovery control valve .
80 psia
Note , that the line between 0.5Xfz and Xfz in Figure 4 is linear , which proves that there is laminar flow ; hence the 10 log in Lp2 . The data indicates that there is a 3dB increase in external sound in the second stage , even though laminar flow cannot produce sound . The real reason is , that in this region , the pipe transmission loss decreases by 3dB due to orifice velocity changes between 0.5 Xfz and Xfz . Note : While the above data is based on measurements with water , using fluid mechanic laws , there should be no appreciable differences if such a valve is used for gaseous fluids as long as FL 2 is substituted for Xfz .
Applications
The range of applications for this device include :
• Pressure reduction for gases and liquids ( with reduced cavitation effects )
• Fuel flow control for oil and gas to burner nozzles
• Pump cavitation avoidance
• A steady flowing quantity regardless of tank level makes it ideal for the filling of tanks
• Pump discharge pressure regulator
• Constant flow through fire hoses regardless of altitude .
Conclusion
The above data demonstrates that high-recovery valves can be a viable alternative to conventional control valves since they do not depend on high turbulence for fluidic energy conversion . The author hopes that this article may inspire others to revisit the high-pressure recovery valve and develop it for the benefit of other applications .
X = 0.175 X = 0.35
0 0 20 40 60 80 100 120
Differential pressure ( psi )
Fig . 4 : Sound comparison between a 2 ” high-recovery valve ( HRV ) and a 2 ” Z-Disk butterfly valve
References “ A simple aerodynamic noise estimating method-why not ”, by Hans D . Baumann , VALVE WORLD , issue 10 , November 2016 ( copies available from the publisher ).
42 Valve World August 2023 www . valve-world . net