Issues regarding the calculation of the opening and closing times of pneumatic actuators
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The pipe is 8'' 600#, the cylinder volume of the pneumatic actuator is 24L, and the air supply port is 3/4'' NPT. The air control valve has inlet and outlet ports of 1'' NPT; the exhaust port is 1.25'' NPT. The flow coefficient is 10, and the effective cross-sectional area is 280 mm2. Instrument air pressure is 6 bar. Based on the above conditions, can the times when the valve opens and closes be calculated, or are there any formulas that can be used as a reference? Please ask the experts to take a look, thank you
This can be asked to the manufacturer; personally, I think it’s impossible to calculate an exact value – it can only be regarded as a test value. Firstly, the switching time is influenced by many factors such as the design of the gas circuit, the pressure difference under operating conditions, the fit of the valve seat, and the frictional force of the valve stem. Once all these factors are taken into account, it becomes impossible to determine a precise value
Thank you, moderator. In fact, the manufacturer has provided the time values; they are results obtained by entering the model and relevant parameters into software. I just want to know more details about it.
This is related to many factors such as the pressure difference across the medium, the type of valve, the specific performance of the valve (such as packing seals), the actuator (single- or double-acting), the positioner, related pipe and valve components, the exhaust port, and whether the valve is open or closed... In general, I have not seen the switching speed having an impact on the requirements. If rapid opening and closing is truly necessary, one can specifically request the purchase of a quick-acting valve
24L cylinder, about 6 seconds
It’s the startup time; the shutdown time is generally a few tenths of a second slower.
If the cylinder operates in a single-acting mode with shutdown upon failure, that is, when air and power are supplied the valve opens; in this case, the theoretical opening time of the valve is 2.4 seconds. For the case where the valve closes due to spring return, it is advisable to consult the cylinder manufacturer, as they usually have specific values for this timing. If it is double-acting, the switching time is shorter.