Selection of the water supply flow control valve for the boiler?
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The water supply control valves for boilers that I’ve seen are all electric, but some people think pneumatic ones are better.
The boiler feed water pressure is high, so electric control valves are generally used, which offers cost advantages.
Power station boilers generally use electric control valves, so no special instrument air is required.
We use pneumatic control valves, and whether they are easy to control depends mainly on the pressure difference before and after the valve. In some projects, the design is too conservative; excessive pressure losses due to pipes, elbows, and process valves are taken into account, when in reality these losses are not as great as assumed. As a result, the outlet pressure of the boiler feed pump is set too high, which means that the pressure reduction has to be accomplished by the control valve. In such situations, control valves with a large pressure difference must be used, resulting in a shorter service life and significant energy losses.
We also use pneumatic control valves for filling water into our low-pressure saturated steam boilers； Initially, electric valves were designed for use in boiler plants; those valves were domestically produced at the time, but their performance was poor. Due to factors such as the small size of the steam drum and low water supply temperatures, the control valves had to be operated frequently, which caused them to break down quickly and resulted in high maintenance costs. Things improved after switching to pneumatic valves.