Pneumatic control valves : characteristics

Control valves are a group of pneumatic elements, whose task is to control the direction of flow of the working medium in the pneumatic drive and control systems by connecting or switching flow paths. The flow direction change takes place depending on the valve design using a dividing plate (for mechanical valves) or with disk.

In pneumatic systems, control valves are used to move actuators. (pneumatic actuators with linear or pendulum and rotary motion), stopping the actuator in a certain position and performing control functions, regulation.

Characteristics

Distribution control valves characterized:

• the number of paths of the working environment;
• the number of adjustable positions of the flow control element;
• valve size;
• method and control options.

Number of Workflow Flow Paths

Distribution valves are divided into:

• 2 running;
• 3-running;
• 4-running;
• 5-running.

Number of adjustable positions

Number of controlled positions of the flow control element:

• 2 positions;
• 3 positions;
• multiposition valve.

In the case of 3-position valves, various options for the central position of the valve are possible.

Valve size

The size of the valve is usually determined by the flow rate through the dividing valve. In pneumatics, the most common inch pipe thread from G1 / 8 “to G2”, metric threads from M3 to M6 are also found in the case of small size valves. Atypical elements, controlling the direction of the flow of the working fluid, are threaded, other than specified. Some directories have a DN value (nominal diameter), what does hole diameter mean, through which compressed air passes.

Control method

The control method determines the offset method of the separator element (usually spool), which changes the position of the flow paths inside the spool valve. There are following ways to control spool valves:

• electromagnetic (electric) management;
• pneumatic control (by increasing or decreasing pressure);
• mechanical control;
• mixed control.

By type of control valves are divided into:

• directly controlled
• indirectly controlled.

In valves with direct control (with electromagnetic control) the working movement of the spool is provided by the electromagnet pin, which is connected to the golden. Direct actuation is typically applied to low flow spool valves and low pressure solenoid operated shutoff valves.. This is due to the need to use electromagnets with high power coils., necessary to create the necessary force to overcome the resistance to movement of the separating element and the pressure of the working environment.

The advantage of direct control is the quick response of the valves, lack of contact of the working medium with the internal elements of electromagnets and simplicity of design.

Indirect control of diverter valves by means of an additional auxiliary valve, often referred to as "pilot" (with direct control), which, after an electrical signal, applies the pressure of the working fluid to the active surface of the primary valve spool, causing it to shift. Usually an additional mechanical control in the form of a button is also used., auxiliary valve, which allows you to control the valve without an electrical signal.