Discharge Regulator & Fixed Cone Dispenser Valve

The Fouress-Boving discharge regulator is a fixed cone valve with a movable sleeve. Such valves are typically installed on the terminal installed on the terminal end of a pressure conduit and convert the potential energy of water under pressure to the kinetic energy of water in free discharge. The movable sleeve functions as a variable area nozzle, therefore, the valve is useful not only for the dissipation of hydraulic energy, but for flow control as well.

Figure 1 is a schematic cross-section through the valve. The body is cylindrical and flanged at the upstream end for connection to the conduit. The body cylinder is connected to a downstream dispersing cone by a streamlined radial ribs forming an equally sized series of discharge ports. Flow control is effected by a reinforced stainless steel lined cylindrical gate which slides over copper alloy glide strips to close the discharge ports. Sealing is by metal-to-metal contact with a seat ring attached to the dispersing cone.

The dispersing cone thus transforms the discharging jet of water into a hollow divergent cone in which the kinetic energy is dissipated by air friction if discharged to atmosphere, or by turbulence if operating submerged.

By virtue of its axial hydraulic balance, the valve gate is subject to negligible end loads and consequently requires relatively small operating forces to overcome piston seal sliding friction and operate smoothly over the full valve stroke.

Additional advantages of the Fouress-Boving fixed cone discharge regulator over other types of free discharge valves include:

• Low initial cost of valve and civil works                      
• Low maintenance
• No downstream channel erosion                      
• Absence of vibration
• High discharge co-efficient                                    

Features

Flow Characteristic

The hydraulic characteristics of Fouress-Boving discharge regulators have been established through a series of model tests performed with the jet discharging both to air and also under conditions of submergence.

Flow through the valve is calculated as:

Q = CdA (2gH)0.5 Where

Q = flow in cubic meters per second

Cd = co-efficient of discharge, determined experimentally in model tests

A = valve cross sectional area m²

g = acceleration due to gravity – 9.81 m / sec²

H = net head on the valve measured at valve inlet, in meters

Figure shows the minimum discharge co-efficient plotted against the percentage of gate opening. Two curves are shown, one based on laboratory model tests showing a full gate Cd value of 0.83, and another showing results of field tests conducted on full size valves. As indicated, discharge co-efficient for full size valves are upto 5% greater than those obtained from model tests. Discharge co-efficient are useful to designers considering upstream conduit sizes leading to the flow control valve. When design conditions involve high flow rates, high heads, and large detailed engineering investigation is recommended to confirm design assumptions.

Seal Arrangements

The downstream end of the valve sleeve ia accurately machined and suitably bevelled to provide line contact sealing on the stainless steel seat ring bolted and spigotted to the valve body. By careful selection of seal materials and correct positioning of the seat ring angle, this arrangements has proved to be drop-tight and free from cavitation and erosion. The design can be simply modified to accept a moulded rubber sealing ring which is firmly secured against the dispersing cone and compressed by the valve sleeve on valve closure. Leakage between the sleeve and body on the upstream side is prevented by a specially designed rubber ring, housed in rectangular section groove in the body cylinder. The seal combines resilience with resistance to friction wear and is self-adjusting.

Operating Gear

To avoid jamming of the valve sleeve and ensure uniform seal loading at the closed position, the operating force is applied at diametrically opposite points on the sleeve. These points are invariably on the sleeve. These points are invariably on the horizontal centerline of the valve, permitting convenient positioning of the operator above the valve. The most commonly used types of operator on discharge regulators are electric or manula via bell crank lever, twin screw mechanism and oil hydraulic. The earliest and simplest form of operation is the bell crank lever (Figure 3) in which the rotary drive from a rising spindle headstock is transmitted through a forked lever and links to the valve sleeve. The connecting rod from the manual and/or electrical operator can be extended vertically or horizontally to suit operating positions above or behind the discharge regulator. Shafts and bearing bushes are proportioned for either self-lubricating materials or gunmetal bushes, grease lubricated from a convenient maintenance position.
In the twin screw mechanism (Figure 4) the manual or electric operator above the valve is connected by extended drive shafting, through a mitre gearbox mounted on the valve body, to worm gearboxes located on the side of the valve body. The twin operator screws of the worm gears control the valve sleeve through bronze nuts mounted on the sleeve flange. This method of operation is appreciably more compact than the bell crank arrangement and is commonly used in the large diameter high head applications where its favourable mechanical advantage permits a smaller operator. Gearboxes are oil or grease filled and adequately sealed against the ingress of water. Operating screws are supplied in stainless steel or high tensile bronze and are protected by fabric bellows and telescopic tubes against water, dirt and damage.

Oil Hydraulic

Hydraulic operation of the discharge regulator (Figure 5) is continually providing economical and reliable on many installations especially where close proximity of the electrical operator is not possible. Movement of the valve sleeve is accomplished by two diametrically opposite oil hydraulic operating cylinders mounted between the upstream side of the valve body and the downstream stiffening ring of the sleeve. A simple oil hydraulic power pack including oil pump valves, provides the force to smoothly operate and maintain the valve in any desired position. In the event of failure of motor power supply, the valve can be conveniently operated by a hand pump connected in the oil circuit.

Deflections & Hoods

In cases where the angle of the free discharge jet must be reduced or limited to a cylindrical form, a suitable deflector arrangement should be required with the valve design. The Fouress-Boving deflector plate, fitted to the end of the valve sleeve will ensure that the jet angle at initial openings is reduced from 60 to 40. Many installations confine the diverging jet with a steel hood embedded in concrete downstream of the discharge regulator. Fouress-Boving valves can be supplied with hoods proportioned to confine the jet to cylindrical form and considerably reduce backsplash. The energy of the discharge jet can be reduced within the valve hood by an integrally fitted dissipator capable of absorbing upto 80% of the jet kinetic energy.