Adjustment of balancing valve

Balancing valve adjustment is performed to throttle pressure or limit a specified flow rate.

In the case of throttling excess pressure in the system, pressure gauges should be installed before the valve, and adjustment is carried out by turning the adjustment wheel until the desired pressure drop is achieved.

Limiting flow with a balancing valve is also done by turning the adjustment wheel, but in this case, flow is monitored based on heat meter readings, flow meters, or by using a device that determines the flow rate through the valve based on pressure losses on it and the adjustment position.

In most cases, there is no heat meter or flow meter in front of the balancing valve, and the flow rate should be limited at least approximately. In this case, one of the indirect methods of determining the water flow rate passing through the balancing valve can be used.

1 Each adjustment position of the balancing valve corresponds to a specific Kv flow coefficient, which is specified in the technical characteristics of the balancing valves. The Kv value is numerically equal to the water flow rate at a temperature of 20°C in m³/h at which the pressure loss on the valve is 1 bar. Knowing the actual pressure loss on the balancing valve (for this, pressure gauges should be installed before and after the valve), and the fact that a change in flow by 'n' times leads to a change in pressure losses by 'n²' times, it is not difficult to determine the actual flow rate through the valve.

2 If we are talking about a heating system with a known thermal power and known coolant temperatures at the inlet and outlet, the flow rate can be determined by the formula:

G = (3.6 * Q)/(4.19 * (t1 - t2)), kg/h

where

Q - thermal power of the system, W
t1 - coolant temperature at the inlet of the system, °C
t2 - coolant temperature at the outlet of the system, °C
3.6 - conversion coefficient from W to J
4.19 - specific heat capacity of water kJ/(kg K)

The website section 'Calculations' provides a program for calculating the balancing valve, which will give you the percentage of opening of the valve from the full stroke of the stem. Knowing the number of turns from full closure to full opening, it is easy to determine how many turns the handle needs to be turned to open the valve to the calculated stroke. You can also determine the required flow coefficient to throttle a specified flow rate with certain pressure losses on the valve.

In complex systems with a large number of circulation loops, the balancing valve adjustment should be carried out using special methods, which you can learn more about from specialized publications of Danfoss and Tour Andersson companies.