Switching valve design with dual solenoids

Having power applied to either valve ensures that it can still open in the event of a failure of the solenoid valve; requiring power to be applied to both valves at the same time is a measure to ensure safety when a valve is in a faulty state

It mainly depends on whether you need it turned on or off; it has to be considered from a technical perspective

This should be part of the safety interlock system, mainly for safety reasons

From a safety perspective~~considering probabilistic issues, to decide whether to use series or parallel solenoid valves~~

One improvement is security, and the other is improved availability

For switch valves that are also controlled by dual solenoids, some are designed so that the valve will open only when both solenoids are powered; if either one loses power, the valve closes. Others are designed so that the valve can open as long as at least one of the solenoids is powered, and the valve remains functional even if one of them loses power. Why is it designed this way? What factors are taken into consideration? For switch valves that are also controlled by dual solenoids, some are designed such that the valve will open only when both solenoids are energized; it will close if either solenoid loses power. From a process perspective, this allows for the controlled step-by-step opening or closing of the valve. For example, piston-type electro-hydraulic valves – an introduction to piston-type electro-hydraulic valves: The FBDF series of CNC electro-hydraulic valves are valves that are controlled by solenoid pilot valves, with the pressure of the medium itself driving the main valve piston to move to any desired position. Controlled through specialized computer software, these valves enable automatic control over the flow rate, velocity, and pressure of the conveyed medium, offering functions such as constant flow, constant pressure, and elimination of water hammer effects. It is a new type of numerically controlled electro-hydraulic automatic control valve developed on the basis of diaphragm-type electro-hydraulic valves. The valve body can be made of cast aluminum, cast steel, full stainless steel, etc., offering a wide range of applications. The reliability and controllability of this product are superior to those of diaphragm-type electro-hydraulic valves. Working principle of the piston-type electro-hydraulic valve: The FBDF series of piston-type digital control electro-hydraulic valves consists of six valves in total, including one normally open solenoid valve, one normally closed solenoid valve, three 3/8” manual ball valves (needle valves), and the main valve (piston cut-off valve) (as shown in the figure). The normally open solenoid valve is installed on the upstream pipeline of the control circuit, while the normally closed solenoid valve is installed on the downstream pipeline of the control circuit. During the pipeline transportation of media, when it is necessary to open a valve, a signal to open the valve is sent by the computer; the normally open solenoid valve is energized (closed), while the normally closed solenoid valve is energized (opened). At this point, the passage from the upstream side to the upper chamber of the main valve piston is blocked, while the passage from the upper chamber of the main valve piston to the downstream side becomes open. At this point, the pressure of the medium at the lower part of the piston is higher than that at the upper part; the medium in the upper chamber of the main valve piston is discharged into the downstream pipeline through the channel of the normally closed solenoid valve, causing the main valve to open. When it is necessary to close the valve, the computer sends a signal to close the valve; the normally open solenoid valve loses power and thus closes, while the normally closed solenoid valve also loses power and thus closes as well. At this point, the passage from the upstream side to the upper chamber of the main valve piston becomes open, while the passage from the upper chamber of the main valve piston to the downstream side is closed. The high-pressure medium from upstream enters the upper chamber of the main valve piston through a normally open solenoid valve. At this point, the pressures on the upper and lower sides of the piston are equal, and the spring force causes the main valve to close. During the opening and closing of the main valve, the normally open solenoid valve is energized (closed), while the normally closed solenoid valve is de-energized (closed). At this point, both the upstream and downstream passages are in a closed state; the medium pressure is trapped in the upper chamber of the main valve piston, locking the main valve in a fixed open position and thus maintaining a constant flow rate of the medium at the main valve outlet. When the upstream flow rate changes, the microcomputer sends signals to the corresponding solenoid valves based on the feedback from the flow meter, thereby allowing automatic adjustment back to the preset flow rate value. The control circuit of the FBDF series of digital control electro-hydraulic valves is also equipped with two manual ball valves that serve as response valves for the main valve. The one located in the upstream control circuit is used to close the control valve, while the one in the downstream control circuit is used to open it. By adjusting the opening degree of these two small valves according to the viscosity of the medium and the actual pipeline pressure, it is possible to fine-tune the opening and closing of the main valve (closure level: not more than 3/4) ； To more effectively eliminate water hammer in pipelines. The FBDF series DN100 piston-type electro-hydraulic valves are equipped with a ball valve in the downstream control circuit as a manual control valve; when power is lost or the solenoid valve fails to function, operating this valve manually can be used to open or close the main valve. It can also be used to check whether the piston of the main valve is working properly or is damaged. Some are designed to open the valve whenever there is a power supply, while the valve remains functional even in the absence of power; they are mainly used to control whether the valve is open or closed. This applies to pneumatic ball valves and butterfly valves. Why is it designed this way, and what factors are taken into consideration? : This mainly needs to be considered from a technological perspective

This is all for safety reasons related to the process or equipment; the valve can open only when both solenoids are powered, which indicates the importance of that valve to the process or equipment. The minimum number of safety protection elements required is two； Either of the two solenoids can open the valve when powered, which is also a measure for safety – by using one of the two options, it is ensured that if one solenoid fails and is unable to open the valve, the other solenoid can be used to do so. I wonder if the original poster has noticed this: as can be seen from the diagram, when both solenoids are powered at the same time, there are certain priorities regarding which one takes effect.

It’s either two-out-of-two or two-out-of-one; once you understand sequential logic, you’ll understand this as well

The solenoid valve is normally powered; the valve will operate only when both solenoids lose power at the same time, which indicates that these two solenoids are connected in parallel, as shown in Figure 1； If either solenoid loses power and the valve operates, it indicates that the two solenoids are connected in series, as shown in Figure 2 ； When the solenoid valves are normal, they are not charged with electricity. If both solenoid valves are powered at the same time and the valve operates, it indicates that these two solenoid valves are connected in series; on the other hand, if either solenoid valve is powered and the valve operates, it means that the two solenoid valves are connected in parallel