Let’s take a look at the working principle of this control valve with three solenoid valves, and how to use it
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This post was last edited by Extend Yan’an on 2020-3-2 21:59. As the title suggests, this valve is a liquid level discharge valve for storage tanks, and it is equipped with three solenoid valves. I would like to ask everyone about its working principle and how it operates. Thank you all for your enthusiastic answers. I got some information, but I still don’t quite understand it. Please everyone answer. Thank you
I’ve never seen a configuration with three solenoid valves like this. Are there any photos of the actual device?:o
This post was last edited by Northwest Corner of the Wall on 2020-2-25 at 19:58; there may be an issue
HX50202A and B are clearly connected in parallel; physically they are both in series and in parallel, while logically they are in parallel. The failure of either solenoid valve does not affect the proper functioning of the air circuit； HX50202C acts in the opposite direction of the pneumatic diaphragm actuator. It is also necessary to know the logical relationship among the three solenoid valves; otherwise, it is difficult to make a judgment.
It is recommended to check the design specifications; the symbols used are not quite standardized. In accordance with hg20505-2014
During normal operation, the control signal reaches the diaphragm of the control valve via the positioner >50202C>50202A; 50202C is used to determine whether the valve should operate in normal regulation mode or be opened fully immediately; 50202A and 50202B serve as redundant components for each other. In the event of a fault, the air supply to the solenoid valve is cut off, and the gas inside the diaphragm is released through 50202A>50202B. Since there are no specific design specifications, this is the most reasonable assumption
When properly adjusted, the A.B solenoid valves serve as a dual safety mechanism; if both A.B solenoid valves fail, the valves will remain fully open. When the liquid level is high and it is required by design, losing power to the A.B solenoid valves will cause the valves to stay fully open. When the C solenoid valve loses power, the valve closes completely.
I spent half an hour looking at this diagram but still didn’t really understand it. It’s best to understand what the intent of the process is. If it is merely a discharge valve for a storage tank (which should be a control valve), there is no need at all for such a complicated air circuit control, and it is also unsafe. When S-05020 is triggered, if the HX-50202B solenoid valve is damaged and cannot switch, the consequence will definitely be that the interlock function will no longer work. Moreover, the drawing is inaccurate; the FC valve is located at the upper part of the diaphragm for air control, which looks uncomfortable to look at. Hehe, it’s just my personal opinion; I hope it can serve as a starting point for further discussion.