As you may already know, control is one of the most important part in plant. To ensure that every operating condition is controllable, we install many control valves that connected to a kind of process parameters, such as pressure, temperature, level, or phase interface. Control of parameter can be done by pneumatic control or electric control.
The availability of pneumatic control has declined, except in one area: gas pipeline industry. The main reason is pressurized gas is available to run the controller. It is essentially free and it does not introduce any additional hazard.
Electric controls are not used in gas pipeline due to several reasons:
- They are vulnerable to interruptions in the power supply, especially for gas pipeline which is installed in remote area
- Pneumatic control is not affected by lightning
- Pneumatic controls do not introduce an ignition source
Table below shows comparison between pneumatic controllers and electric controllers.
- GPSA Engineering Data Book, Vol I, Gas Processors Suppliers, Association
- Digital vs Pneumatic Control