Valve Sizing Method

• Write down your flow: For example your application is 800 GPM ( 182 m3/h )
• Calculate pressure difference (ΔP) between valve inlet and outlet: For example your application’s pressure difference is 4 psi ( 0.28 kg/cm2 )
• Calculate Cv(Kv): This example should be            
• Decide Valve size:  Chose those valve which Cv (Kv) Value are greater than the Cv (Kv) you calculated at Step 3. In general, the valve’s Cv (Kv) value should be 1.4 times than the Cv (Kv) value you calculated. In this case, you should choose DN150 (6″), which Cv value is 590, Meet your requirement.
• Check flow velocity: Having decide valve, you may check flow velocity. This case’s velocity should be 9.4 fps (2.86m/s) this value may read from above photo.
• Make your decision: Depending on your application, velocity flow through valve may different. In general, application such as pressure relief, velocity should be greater than normal. So valve size should be smaller than you have calculated at Step 4. In this case, you should choose DN125 (5″). If you need those modulating valve, such as pressure reducing valve, suggested velocity should beyond the shadow area of the above photo. In this case, DN150 (6″) should be chosen, and if you have chosen an optional V-port plug, you should use DN200 (8″). If your valve are similar with Solenoid Control valve, which act as an ON/OFF valve, velocity should below 6.5 fps (2m/s). In this case DN200 (8″) should be chose.

Pressure Loss Curve – Standard

Pressure Loss Curve – V-port Plug

Cavitation Area

• How to use1. Write down upstream pressure, for example, 147 psi (10.3 kg/cm2)
  2. Draw a horizontal line till it intersect with the bound of the shadow.
  3. Read the outlet pressure valve of this intersect point. In this case should be 37 psi (2.6 kg/cm2)
  4. The outlet pressure should greater than this valve to avoid cavitation. for example, 65 psi (4.6 kg/cm2)

• About Cavitation

  While acting as Pressure Reducing Valve or Pressure Relief Valve, cavitation may occur if pressure difference between valve’s inlet and outlet is greater enough. When water flow across valve seat and disk at high speed, water pressure will drop down. If pressure drops below the vapor pressure, vapor bubbles maybe formed. These bubbles will generate terrible damage to valve’s parts. And cavitation may cause vibration and noise.

• Preventing Cavitation

  A.Increase downstream pressure if possible. B.Select a larger valve in order to decrease flow velocity. C.Use more valves in parallel to reduce inlet pressure. D.For pressure reducing application, use more valves in serial to decrease the ΔP through a single valve.

Option:V-port Plug

	V-port Plug A component installed at the bottom of the bonnet that interfere the flow between the bonnet and the valve body. Suitable occasions: low flow rate, high differential pressure. Changing the proportion of water volume that the spool opens to achieve the same volume of water, which has a longer opening stroke than a flat retainer. when the amount of water changes, the opening height of the valve can be adjusted automatically to stabilize the water flow and reduce noise and vibration.