Technical information

Technical information

Principle of Pressure regulating valve

Kofloc Pressure regulating valve

The pressure regulating valve (reducing valve) is used to control the pressure applied to the flow so that it will be constant during flow control.

Various types of valves are used according to application, as explained below.



Pressure regulating valves are classified into general regulating valves and backpressure valves, and are represented by the symbols shown in the


The regulating valve controls the outlet side pressure so that it will be constant when the supply-side pressure changes. It is frequently used in the initial stage of a system.

Meanwhile, the back-pressure valve is a kind of continuous flow relief valve that removes gas to keep the primary-side pressure constant.



The regulating valve controls the outlet-side pressure, and a pressure gauge is provided on the outlet side.

The KOFLOC 6600 is equipped with a pressure gauge port, and a pressure gauge is connected to the port in such a case.

The pressure at that port is practically equivalent to the outlet pressure; therefore, the pressure gauge can be connected to the outlet side.

Flow characteristics of regulating valve

The flow characteristics graph of a regulating valve shown in the cata-log is based on the flow sheet shown in the figure.

Flow sheet of regulating valve fl ow characteristics test


In the example graph, the primary pressure (supply pressure) is 686 kPa.

In the succeeding stage of the regulating valve, the secondary pressure is set as a load resistance by a regulating valve when the valve remains closed (0 flow).

This value is the flow 0 in the graph, namely, the value at the left end.

Then the needle valve is opened to let gas flow, and

the change of the pressure (secondary pressure) that is set according to the flow is plotted.

The state in which the set pressure does not change is ideal, but because of the characteristics of a regulating

valve, there is some influence up to a certain flow, and the pressure will change when the flow reaches the limit.

This area where the change is minimum is the area where reducing valves should be used.

In the case of a backpressure valve, the primary pressure is the set pressure. The way to understand the flow characteristics graph is the same as that for the reducing valve.

Kofloc Pressure characteristics

In the case of a regulating valve, the pressure change on the secondary side, when the primary-side pressure on the aforementioned flow sheet is changed, is shown.

The control characteristics differ slightly depending on whether the primary pressure increases or decreases,and the changing condition is shown by the arrows.