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Model B-10 (Horizontal 8-72”) - Sizing PDF E-mail
Once the Bailey valve configuration (Inline, Y-Pattern, submerged, angle or non-modulating) has been selected, the next step in choosing the best solution for the application is sizing the valve for the operating conditions. This is first done by collecting key data, which will be used to determine the severity of cavitation as indicated by the cavitation index sigma (s), velocity flow and flow capacities (Cv).

Step 1 - Data

Maximum Flow Rate => Qmax
Inlet Pressure at Qmax => Pi @ Qmax
Outlet Pressure at Qmax => Po @ Qmax
Minimum Flow Rate => Qmin
Inlet Pressure at Qmin => Pi @ Qmin
Outlet Pressure at Qmin => Po @ Qmin

Step 2 - Sigma

The sigma value or cavitation index is calculated and used to configure the performance class of sleeve valve or to determine if alternate options such as ball valves or butterfly valves are acceptable for the application conditions.  The following equation is used to calculate the sigma value:

s = Po – Pv / Pi – Po
Where:
Pi = Inlet Pressure (psig)
Po = Outlet Pressure (psig)
Pv = Vapor pressure (-14.6 psig for 60oF water at sea level)

        
 
s - Operating Range    Valve Option       
2.50 & up    Mild
A ball valve or butterfly valve can be used in this range, however, they are not recommended for continued modulating service and special care should be taken when sizing valve to ensure correct disc or ball position during operation.        
0.15 to 2.49    Standard
Standard sleeve valve operating range.  All of the Bailey valve models will provide years of superior cavitation resistance for these application ranges.       
0.02 to 0.14    Critical
Application conditions that require a hybrid solution such as series valves.  Please contact the factory for application assistance.    

Step 3 - Velocity Flow

The maximum flow rate (Qmax) is compared to the figure in the following table to determine the corresponding valve size based on an allowable continuous velocity of 30 ft/sec through the valve port. Higher velocities can be attained for intermittent operating conditions and it is recommended that you contact the factory for sizing. Your flow rate should be rounded up to the nearest table value and record the corresponding valve size.  Various units are provided for simplicity.

 
Valve Size    Flow Rate (Based on 30 ft/sec port velocity)       
(in)    (mm)    gpm    cfs    mgd    cms       
8    200    4698    10.47    6.76    0.30       
10    250    7340    16.35    10.57    0.46       
12    300    10570    23.55    15.22    0.67       
14    350    14387    32.05    20.72    0.91       
16    400    18791    41.87    27.06    1.19       
18    450    23782    52.99    34.25    1.50       
20    500    29361    65.42    42.28    1.85       
24    600    42280    94.20    60.88    2.67       
30    450    66062    147.19    95.13    4.17       
36    900    95130    211.95    136.99    6.00       
42    1000    129482    288.49    186.46    8.17       
48    1200    169120    376.80    243.53    10.67       
54    1400    214042    476.89    308.22    13.51       
60    1500    264249    588.75    380.52    16.67       
66    1670    319742    712.39    460.43    20.17       
72    1820    380519    847.80    547.95    24.01    

 
B-10

Step 4 – Flow Capacities (Cv)

The maximum flow rate (Qmax) and associated inlet pressure (Pi) and outlet pressure (Po) are used to calculate the required Flow Capacity or Cv of the application.  The Cv equation is as follows:
Cv = Q / Ö(Pi-Po)

Once the application Cv is calculated from the above equation a safety factor of 20% is added to the value for valve Cv deviation and potential nozzle fouling from entrapped debris within the flow media.  The Cv plus 20% value (C20) is compared to the following table to determine the appropriate valve size for the application.  The chosen valve size must have a higher capacity than the C20 calculated form the operating conditions. The valve size chosen from the Cv table is then compared to the valve size chosen from the previous table (Velocity Flow) and the larger of the two valves is the correct size for the application conditions.


Valve Size Flow Coefficient (Cv)
(in)    (mm)    gpm/psi^. 5    cfs/psi^.5   mgd/psi^. 5    gpm/ft^.5    cfs/ft^.5    mgd/ft^.5    cms/m^.5
8    200    987    2.20    1.42    650    1.45    0.94    0.07  
10    250    1548    3.45    2.23    1019    2.27    1.47    0.12  
12    300    2232    4.97    3.21    1469    3.27    2.12    0.17  
14    350    3040    6.77    4.38    2001    4.46    2.88    0.23  
16    400    3973    8.85    5.72    2615    5.83    3.76    0.30  
18    450    5029    11.21    7.24    3310    7.37    4.77    0.38  
20    500    6210    13.84    8.94    4087    9.10    5.88    0.47  
24    600    8942    19.92    12.88    5885    13.11    8.47    0.67  
30    450    13972    31.13    20.12    9195    20.49    13.24    1.05  
36    900    20117    44.82    28.97    13239    29.50    19.06    1.51  
42    1000    27379    61.00    39.43    18018    40.14    25.95    2.06  
48    1200    35756    79.66    51.49    23531    52.43    33.88    2.69  
54    1400    45250    100.82    65.16    29779    66.35    42.88    3.40  
60    1500    55860    124.46    80.44    36761    81.90    52.94    4.20  
66    1670    67585    150.58    97.32    44478    99.10    64.05    5.08  
72    1820    80427    179.19    115.82    52929    117.93    76.22    6.05  
*Cv values are ±0.05      
 
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