REGULATING VALVES

These valves are special devices designed for regulating Pressure and Flow Rate of water. The valves used for this purpose are commonly known as ‘PRV’.

What is a PRV?
Design Criteria
Applications
Types of Valves used as PRV

PRV is a control valve, where ‘R’ stands for Reducing/Regulating/Relief, simultaneously performing these functions based upon application.

» Pressure Reducing Valve - for energy dissipation at the outlet.
» Pressure Regulating Valve – for flow regulation based upon requirement.
» Pressure Relief Valve – for safety relief by limiting Pressure rise in the system.

When a PRV is needed, its design must fulfill the following criteria:

» Noise level must not be hazardous for the people working in the power station.
» Valve must dissipate a large amount of energy in the water, not to cause problem at downstream.
» When the valve opens water flow must not be dangerous for both personal and structures.

» In bypass PRV is used in end of line solution for energy dissipation and flow regulation.
» In turbine transient regulation PRV is used as a safety device with simultaneous functioning of flow regulation and energy dissipation.

» Conical Jet Valve (CJV)
» Plunger Valve (PLV)
» Slide Valve (SLV)
» Needle type Valve

Conical Jet Valve

CJV are used as free discharge devices in pressure piping systems.

Advantages on Conical Jet valve:

More cost effective
Lower maintenance
Adaptable to manual, hydraulic and electric actuators.
Dissipates enormous energy by breaking up discharge water into large hollow jet.

Fixed Cone Valve
Ring Jet Valve

Controls and dissipates enormous amount of energy by breaking up the discharge water into a large hollow expending jet. Suitable for submerged application.

Similar to fixed cone type it has an external hood that concentrates the discharge spray into a jet. Not suitable for high heads and submerged applications.

Plunger Valve

Plunger Valve is a type of control valve with annular flow cross-section for continuous regulations at high pressure differences and flow rates.
PLV plunger valves are used as shut-off and regulating devices in pressure pipe systems.

Advantages on Plunger Valve:

Suitable for high pressures.
Adaptable to manual, hydraulic and electric actuators.
Valve with counterweight acts as a safety device and ensures fail safe opening.
Longer service life as bearings are not in contact with medium.
One-piece compact body design.

Types of Plunger Valve

Cut-off edge
Slotted cylinder
Perforated cylinder

It has a sudden enlargement of cross-section area at the seat and is suitable for regulating flow where enough back pressure is present.

Suitable to regulate/control water with suspended solid particles and prevention of cavitation in case of high-pressure difference.

Suitable to regulate/control flow and prevention of cavitation in case of high-pressure difference

Slide/Sleeve Valve

Slide Valves are designed with a self-closing tendency. The opening is controlled hydraulically or by suitably designing it for its own medium.
SLV slide valves are used as shut-off devices in pressurized piping system.

Advantages on Slide Valve:

Suitable for high pressures.
Compact design.
Low head loss.
Lower maintenance and very long service life.
Low vibrations and sound levels.
Higher wear and corrosion resistance as complete valve is made of stainless steel.

Needle type Valve – synchronized application with turbine

It is a safety cum regulating device suitable for projects having Francis & Kaplan units in order to limit pressure rise and speed rise in permissible range.

Advantages on Needle type Valve:

Fail safe safety device, as mechanical / hydraulic linkages are used for synchronous operation with turbine.
Lesser noise and vibrations as water is discharged through large orifice cylinder.
Highly effective in energy dissipation/pressure reduction.
Highly effective in flow regulation as per the control requirement of turbine transient.