Control valves which involve a plastic seal are normally sealed on delivery. The fact remains that particles are carried by the water, they will damage the seal when the valve closes. It is therefore necessary to take precautions, place a filter upstream, periodically monitor the tightness of closed valves. Using the globe valve is important now.
Can a regulating valve act effectively over its entire stroke?
The qualities of loop regulation: stability and precision are easily found in the operating ranges close to the maximum opening.
Minimum adjustment kv
An “equal percentage” characteristic presents a concavity which compensates for the non-linear behavior of the exchangers. At positions very close to closing, the characteristic presents a minimum adjustment Kv (Kvr) and a possible leakage rate (Kv0).
With an efficiency of 0.1 too low and an authority of 0.2 too low, the thermal power “leakage” is 22 %.
These power values relate to the maximum power, valve open. The publication in the journal CFP cited above gives more details on these effects.
What are the main characteristics to consider?
We must consider the different uses of control valves to locate the importance of the parameters.
Motorized valves are placed on the networks:
Either to isolate generator circuits or to segment distributions for heating or cooling in order to adapt the energy supplies as closely as possible to the needs of the zones or sub-zones (figure 2). For this, neither the characteristic curve nor the pressure drop of the valve is critical, these valves only need to be tight.