Pneumatic timer valves are devices that control the timing of pneumatic signals in various systems and applications. They use air pressure to activate or deactivate a valve after a preset time interval, without the need for electrical components. Pneumatic timer valves can be used for switch-on delay or switch-off delay functions, depending on the type of valve and the desired outcome.
Types of Pneumatic Timer Valves
There are two main types of pneumatic timer valves: rotor-based and vacuum-based.
- Rotor-based pneumatic timer valves use a centrifugal force driven rotor system with a reduction gear to set the time delay. The rotor rotates at a constant speed and triggers a 5/2-way spool valve when it reaches a certain position. The spool valve then switches the pneumatic signal on or off, depending on the configuration. Rotor-based pneumatic timer valves can be set in six different time intervals, ranging from 0.3 seconds to 100 hours.
- Vacuum-based pneumatic timer valves use a vacuum principle to set the time delay. The vacuum is created by a spring-loaded piston that moves inside a cylinder. The piston is connected to a 3/2-way poppet valve that controls the pneumatic signal. The piston can be adjusted to change the time delay, which is proportional to the vacuum level. Vacuum-based pneumatic timer valves can be set in three different time intervals, ranging from 0.5 seconds to 180 seconds.
The following table summarizes the main features and differences between the two types of pneumatic timer valves:
| Feature | Rotor-based | Vacuum-based |
|---|---|---|
| Valve type | 5/2-way spool valve | 3/2-way poppet valve |
| Operation type | Centrifugal force driven rotor system | Vacuum principle |
| Pressure range | 1.2 to 10 bar | 1.5 to 8 bar |
| Time range of setting | 0.3 s to 100 h | 0.5 s to 180 s |
| Relative timing error | From ±1 to ±2% of end scale value | From ±1 to ±2% of end scale value |
| Function | Switch-on delay or switch-off delay | Normally closed or normally open |
Applications of Pneumatic Timer Valves
Pneumatic timer valves can be used in various applications where precise timing control of pneumatic signals is required or where electrical power supply is not available or permitted. Some examples of such applications are:
- Fire protection systems: Pneumatic timer valves can be used to activate or deactivate sprinklers, alarms, or valves in fire protection systems, especially in ATEX environments where electrical sparks can cause explosions.
- Industrial automation: Pneumatic timer valves can be used to control the sequence, duration, or frequency of pneumatic actuators, cylinders, or motors in industrial automation processes.
- Pneumatic logic circuits: Pneumatic timer valves can be used to create pneumatic logic circuits that perform basic functions such as AND, OR, NOT, NAND, NOR, etc. using pneumatic signals.