Discussion on the selection of feed water valves for steam drums
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The feed water valve on the drum is commonly used in devices that generate steam, such as boilers and heat exchangers. What type of control valve is generally more suitable for use in these applications? The operating pressure for upper water valves is generally around 5 Mpa, the temperature is around 180°C, and the pressure difference before and after the valve is approximately 0.5 Mpa. I have seen mostly cage-type control valves, but after about 2 years of use, severe internal leakage began to occur. Upon disassembling the valves, cavitation was found to be the issue at the valve seats. I would like to ask: how long do the feed water valves on the steam drums that everyone maintains typically last before severe internal leakage occurs?
Everyone should be quite familiar with the feed water valve on the steam drum; internal leakage is a very common problem
We have used HCM and HCN types; generally, after 8 years, the internal leakage becomes too severe and they stop working. The actual pressure difference is definitely more than this. It is recommended to harden the valve core and seat; 17-4 precipitation-hardening or 440B can be considered. However, domestic valve bodies are not expensive, so there’s no need to worry too much about them.
I don’t know; ours are electric valves. I really haven’t paid attention to the specific type of valve
I think it’s also a cage valve, and the internal components of the valve have been hardened as well. You’re right that the actual differential pressure is higher than what the process requires; I agree with that, especially at low flow rates – the difference is even more significant! By the way, is the on-site valve control switch for your water supply valves used frequently? Here, the valves keep moving beyond 10 positions regularly; it’s because the PID tuning isn’t good, right? Over time, the filler is particularly prone to leakage.
For many control valve actuators in power plants, electric valves are often chosen, and there is no problem with that. It’s the valve body part that’s crucial; if you have time, come to the site and we can discuss it together. How often do you experience internal leakage?
When selecting anti-cavitation valve internals, foreign brands can be considered.
Not frequently, very steady. You can manually check whether it’s stable; if it is, then adjust the PID. We changed the original series design to a single-loop design, which is more stable and reliable
We changed the original cascade design to a single-loop one; isn’t the stable and reliable level control for multiple boilers based on three impulses? The cascade you mentioned? Single-loop control? What is the fuel capacity of your boiler? We have 600,000 tons per hour
I hadn’t paid attention to this; I’ve never heard the operators or technicians mention any issues with internal leakage