Electric valves and pneumatic valves
Thread Content
Valves should be installed at the inlet and outlet of a filter to enable automatic backwashing based on the DO signal from the DCS. The original design used electric butterfly valves, but the owner requested pneumatic valves – how should a choice be made? The medium is water, with a diameter of DN300
Compared to electric butterfly valves, which one requires a higher investment in terms of cost?
Pneumatic cut-off valves can also use butterfly valves; the difference between electric and pneumatic versions lies only in the actuator. Pneumatic switches have faster switching times; for the same switching time, pneumatic actuators are cheaper
Of course, pneumatic valves are more economical.
It is preferable to use pneumatic ball valves; pneumatic disc valves are more cost-effective. Of course, the main issue with disc valves is leakage, which needs to be properly addressed: handshake
This issue needs to be considered carefully! A comprehensive evaluation can be carried out by looking at the following points: 1. Is there a clean air supply required for the pneumatic valves on site? If so, how far is it? This directly determines the amount of investment needed. 2. What are the requirements regarding the functions of the valves? What is the allowable level of leakage? Are there any safety requirements? For example, if high leakage limits apply, butterfly valves cannot be used. Are there any requirements in terms of power supply continuity? 3. Are interlocks required for the process? Are there any requirements regarding response time? 4. Are there any requirements regarding control? Is it convenient to use DCS or PLC interfaces? If the valves are located far away from the control room, can the control requirements still be met?
If it is in an explosion-proof area, it is best to use a pneumatic valve； Electric valves are unsafe.
I’m a beginner; hehe, I studied the analysis on floor 7 and found it quite reasonable.
If there is a dry gas source available on site, it is more economical to choose to operate the pneumatic butterfly valve. Judging from the design, it can be rinsed with water and is used for filtering; presumably the requirement regarding leakage volume isn’t very high.
I also think using pneumatic butterfly valves is more cost-effective!
When selecting a pneumatic valve with a large diameter of DN300, the instrument air pressure must be taken into consideration; it is generally required to be ≥500 kPa. Therefore, the total air pressure should be in the range of 700–800 kPa, which meets the requirements of the design specifications relatively well. When using it at the waterline, the material of the valve core also needs to be taken into consideration.
Butterfly valves are prone to leakage; it’s better to choose pneumatic ball valves