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Pressure Reducing Valves
What are Pressure reducing valves?
Hydraulically operated, control valve reduces higher upstream pressure to lower constant downstream pressure, regardless of fluctuating demand or varying upstream pressure.
There are different methods for applying pressure reduction: mechanical, electronics and hydraulics.
BERMAD is offering fully automatic hydraulic pressure reduction.
In municipal networks pressure reducing valves are required at the inlet of pressure zones or DMAs (District Metering Areas). On the one hand, for protecting the equipment at the downstream and the household’s plumbing from overpressure. On the other hand, guarantees sufficient & reliable pressure for the consumers.
In Irrigation PRVs (pressure reducing valves) are required in water headers in an entry of lower elevation field, pivot-machines, low pressure systems like dripping pipes and more.
In high rise buildings, PRVs are located on every single or several floors, for protecting the department’s plumbing and low rated fittings & connections.
How do Pressure reducing valves work?
The Hydraulic pressure reducing valve is equipped with a pressure reducing pilot designed to hydraulically sense the downstream pressure.
The pressure reducing pilot commands the valve to throttle/close when the downstream pressure increase ABOVE the pilot pressure set point and to open the valve when the downstream pressure decrease BELOW the pilot pressure set point.
When downstream pressure is higher than the required set-point, then pilot allows water to flow from the upstream to the control chamber and the valve closes.
When downstream pressure equal to the required set-point, the pilot traps the water in the control chamber and the valve stops in the required opening rate.
Once downstream pressure changes, the pilot fill or drain the control chamber and bring the valve to the required opening rate.
When downstream pressure is lower than the required set-point, then pilot drain water from the control chamber to the atmosphere and the valve opens.
*This example refers to 3-way control method.
In Waterworks and Buildings 2-Way is common as well, which has different principles of operation.
What are the common types of Pressure Reducing Valves?
System pressure can vary due to many different reasons. Starting from pumps operations, changes in topography, pipe characteristics, the resistance of equipment along the system, leaks & water theft and of course the demand flow pattern which has a direct effect on the Pressure loss across the pipeline.
In Waterworks & Buildings some systems supply water 24/7, and flow constantly varies throughout the day.
While in Irrigation & Fire Protection, flow is constant and occurs in shifts/pulses, depending on the crops or firefight emergency events.
Based on this understanding there are many different Pressure Reducing Valves and configurations for optimally suit these requirements.
Some relied on a 3-way control loop and others on 2-way. Some are full bore for minimal head loss during insufficient inlet pressure and others are reduced bore for achieving efficient pressure regulation.
Refer to pages: WW-720 or IR-120-X
Some have throttling devices to cope with low flows, and others have different mechanisms to eliminate/reduce cavitation.