Pressure dependent, manual balancing technology has been used in heating and cooling systems for decades, here are the key differences in this category of valves.
The simplest type of balancing valve is a globe valve, a cross section of which is shown in Figure 3-1.
Flow enters the lower valve chamber, flows upward through the orifice between the seat and the disc, then exits from the upper chamber. The gap between the disc and the seat determines the hydraulic resistance created by the valve. Turning the valve's stem changes the gap between the seat and the disc, which changes the valve's hydraulic resistance. The closer the disc is to the seat, the greater the valve’s hydraulic resistance. The greater the valve’s hydraulic resistance, the greater the pressure drop across the valve at any given flow rate. Although globe valves were traditionally used for balancing they lack several features that modern balancing valves provide.