Bailey Valve, Inc. - Model B-5 (Horizontall 3 - 12")

Model B-5 (Horizontall 3 - 12") - Sizing

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 60 o F 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
3	200	661	1.47	0.95	0.04
4	250	1174	2.62	1.69	0.07
6	300	2642	5.89	3.81	0.17
8	350	4698	10.47	6.76	0.30
10	400	7340	16.35	10.57	0.46
12	450	10570	23.55	15.22	0.67

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
3	200	115	0.26	0.16	75	0.17	0.11	0.01
4	250	206	0.46	0.30	136	0.30	0.20	0.02
6	300	467	1.04	0.67	307	0.68	0.44	0.04
8	350	831	1.85	1.20	547	1.22	0.79	0.06
10	400	1299	2.89	1.87	855	1.91	1.23	0.10
12	450	1871	4.17	2.69	1232	2.74	1.77	0.14
*Cv values are ± 5%

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Step 1 - Data

Step 2 - Sigma

Step 4 – Flow Capacities (Cv)