B–11

Introduction

The Bailey Valve model B-11 sleeve valve has been designed to incorporate features that provide superior valve performance for atmospheric or submerged discharge in flow control and pressure reduction applications. Typical applications for the model B-11 are turbine bypass, reservoirs discharge and ground water recharge. The Bailey model B-11 valve dissipates energy and controls flow by diverting the water through multiple orifices located within the sleeve and discharging to atmosphere or body of water. The valve modulates flow by sliding one pipe called the gate over another pipe called the sleeve. The sleeve is designed with multiple sized and space tapered nozzles for each specific project. This design controls cavitation by directing damaging implosions away from any metallic surfaces, thus reducing vibrations and noise normally associated with modulating valves. The nozzles are placed within the sleeve in a helical pattern that allows for specifically desired incremental volume change with movement of the gate. Each sleeve nozzle configuration is designed for the application needs to produce superior flow pressure control over the entire requested flow range. Flow passes from the inside of the valve out through tapered nozzles in the sleeve and energy is dissipated outside of the valve body. The advance and retract movement of the gate is accomplished through drive screw(s) or hydraulic cylinder(s) located on the top of the valve. The Bailey Valve model B-11 is capable of flowing 500 GPM to over 443,939 GPM.

Sizes

8” (200mm) through 72” (1830mm)

Pressure Class

ANSI B16.5
Class 150 => 250
PSI Class 300 => 640
PSI Class 600 => 1000 PSI

B11 Overview

Size Range

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 (σ), 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:

σ = Po - Pv / Pi - Po

Where:
Pi = Inlet Pressure (psig)
Po = Outlet Pressure (psig)
Pv = Vapor Pressure (-14.6 psig for 60°F water at sea level)

Step 3 - Velocity Flow

The maximum flow rate (Qmax) is compared to the figure in the following sample 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.

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 of Cv of the application. The Cv equation is as follows:

Cv = Q / (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 potentional 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 value size for the application. The chosen valve size must have a higher capacity than the C20 calculated form the operationg conditions. The valve size chosen from the Cv table is then compared to the value size chosen from the previous table (Velocity Flow) and the larger of the two valves is the correct size for the application coditions.

B11 Valve Sizing
B11 Valve Sizing B11 Valve Sizing