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Pneumatic control valves use compressed gas to prevent dangerous situations in various devices. They are commonly found in industrial machinery and are monitored by sensors or external systems. Older systems used a test module to monitor for problems. Most use compressed atmospheric air, as other gases pose risks of asphyxiation or explosion.
A pneumatic control valve is a valve that works by compressed gas to limit a device, preventing overload, explosion, or any number of other harmful effects. Newer control valves work through sensors that monitor the internal conditions of a device. The most common gas present in a pneumatic control valve is compressed atmospheric air. In addition to compressed air, most pneumatic control valve gases contain a small amount of oil vapor that keeps the internal parts of the valve lubricated during operation.
A pneumatic control valve can be found on a huge number of different devices and machines. These types of valves are very common in industrial and factory machinery, such as manufacturing and processing machines. Additionally, they are found on heavy hand tools such as riveters and within residential and commercial machinery such as heating and cooling systems.
In nearly all cases of a pneumatic control valve, the valve requires a burst of compressed air to force a plug into a set position that prevents a dangerous situation from occurring. This explosion typically creates a mechanical reaction that forces the cork into an opening that prevents a gas or liquid from passing through. Sometimes this process also reveals a secondary opening that allows the system to purge stuck material.
These systems typically respond to abnormally high heat, pressure, or flow rate. Any of these situations could lead to damage to the device or even an explosion. In most modern equipment, these factors are monitored by an external system that also directly controls the pneumatic control valve. When a dangerous situation begins, the system is alerted to the problem and activates the valve.
Older systems typically had a less high-tech method of monitoring for problems. These systems had a wide variation based on overall design, but typically worked via a test module within the machine. In many cases, as temperature or pressure increases, a system within the device would force air or water into a connected chamber. When the substance in the chamber reaches a certain level, the device trips the valve, which calms the system and empties the chamber. This process would then start all over again.
Most pneumatic systems used compressed atmospheric air. Almost all other gases, with the exception of oxygen, pose a significant risk of asphyxiation if any gas escapes from the system. Oxygen, in almost any concentration above atmospheric, is so flammable that it could ignite an explosion if used.
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