The issue of valve opening and closing time
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During work, it was found that there are time requirements for opening and closing certain valves; for example, they need to be opened within 3 seconds and closed within 5 seconds. I know some colleagues are here, so please tell me how these time limits are achieved – how is the time calculated?
This is because of the technical requirements you have; valve manufacturers will increase the speed at which valves open and close in accordance with the client’s demands. Our company adds one or two pneumatic amplifiers to the valves
Many cut-off valves that require precise control also have specifications regarding the speed at which they can be opened and closed. Under high pressures, even a few seconds of delay can result in a large amount of material passing through. The time taken for this process can be measured simply by observing it on-site; from the moment a command signal is sent from the control room until the valve actually moves and closes, this time interval can be recorded using a stopwatch, or specialized measuring tools can be used. In practice, the valve manufacturer will determine the pressure of the spring inside the valve based on your process requirements, as well as the pressure difference between the two ends of the valve when it is closed or opened, along with other parameters such as the volume of air supplied and discharged.
This time period is usually provided by the customer and the valve manufacturer; the manufacturer can reduce this time by increasing the power output. However, there are quite strict requirements regarding the material used – too high a speed can cause significant damage to the valve. Therefore, if you want a faster processing time, there are still specific material requirements, and the associated solenoid valves also have corresponding requirements.
Valves with time requirements generally need to complete opening or closing within a specified time once they receive a command to do so! For pneumatic valves, it is necessary for air intake and exhaust to occur quickly; this is achieved by increasing the flow rate of air intake and exhaust, for example by enlarging the diameter of the air inlet on the actuator or increasing the air pressure, as well as by installing quick-release valves at the exhaust outlet
This is implemented by the valve manufacturer in accordance with the user’s requirements; for example, if rapid opening is required, a quick-release valve must be added to the valve’s exhaust port to achieve this.
Recently, our project has also encountered this issue regarding the requirement that action time be less than 5 seconds. This is how we resolved it; it’s for reference only. If anyone has any suggestions, feel free to share them. We use ASCO solenoid valves; they address this issue by using solenoid valves with larger orifices, thereby accelerating the valve’s operation through rapid exhaust, which has the same effect as adding a quick-opening valve at the valve’s exhaust port. For example, for ordinary pneumatic shut-off valves, a 1/4 NPT size is used; if the required actuation time is less than 5 seconds (and it’s possible to achieve less than 3 seconds), then a 1/2 NPT diameter valve should be chosen.
Generally, manufacturers calculate the time based on the torque of the valve, the speed of the actuator, and the number of rotations required to fully close or open it
Simply put, the opening and closing times of the valve are calculated based on process data. Valve manufacturers can supply products according to your requirements.
The process puts forward requirements – the valve supplier helps to meet them!
Put forward the conditions to the manufacturer at the time of ordering, and the manufacturer will handle it
The valve opening and closing speed is related to the structure of the actuator and the pressure of the control gas; the specific definition of this speed depends on the requirements of process control. Generally, to increase the opening and closing speed of a valve, a quick exhaust valve can be used, or a speed control valve can be employed to adjust the valve’s opening and closing speed.
Regarding the timing of valve opening and closing, we generally consider that for valves of different sizes, the time required to complete one full cycle is determined by the length of that cycle and the speed at which it occurs. In the case of pneumatic valves equipped with positioners, it is the positioner that controls the amount of air used to open and close the valve, while in electric valves, it is the electrical circuit that handles this control. (This is for reference only; discussions are welcome.)
It depends on the shape of the valve core. 1. When the cross-section of the valve core is a triangle with a smooth apex, the flow characteristics are proportional to the degree of valve opening, that is, linear. 2. When the cross-section is a trapezoid with sharp edges but smooth corners, the flow characteristics follow a parabolic pattern as the opening increases. 3. When the cross-section is approximately rectangular, the flow characteristics involve rapid opening
The flow rate is proportional to the valve opening, that is, it is linear
Generally, quick exhaust systems are equipped with solenoid valves, and the exhaust time can be determined by the length and size of the exhaust pipeline!
Each process valve is accompanied by a very detailed order data sheet, the details of which are filled out jointly by the process engineering and instrumentation teams: including the CV value, nominal diameter, flow rates (maximum, minimum, normal), material of the valve core and seat, type of actuator, pipe material, as well as requirements for all installation accessories
We need to use a slow opening; if it’s opened quickly, the steam will cause excessive vibration in the pipes!
I’ve encountered the same issue as the original poster; I’m still working on solving it. These turn-off and turn-on times are determined by the manufacturing process; the instrument cannot determine them. (Perhaps some instruments are so powerful that they could be mentioned as well.) Because there are many factors to consider at this time, I only remember one of them being water hammer. Additionally, there are process-related reasons that require a certain amount of time. I didn’t pay attention to anything else either. Keep an eye on this post.
It is also necessary to analyze the medium inside the pipeline and the pipeline pressure. .
Hello! I was wondering if this will work? Is it better to use a gas control valve or a quick-release valve?