Regarding the operating time of pneumatic on-off valves
Thread Content
On the specification sheet for pneumatic switch butterfly valves, there is an item titled “full-stroke time of the actuator”. If there are no specific requirements specified in the process, how should this value be chosen or determined? Are there any standard requirements regarding this time? I checked online myself; it says that “the time should be no less than the valve body size (in inches), but for any valve, this time must not exceed 30 seconds.” DN200 – 8 seconds; DN250 – 10 seconds; DN300 – 12 seconds; DN400 – 16 seconds; DN500 – 20 seconds; DN600 – 24 seconds
That time is not a strict requirement; it mainly depends on the process and safety considerations for making a decision. DN600 can also require 3 seconds; it is not mandatory to have <24 seconds.
If the process does not specify it, what is the requirement according to common practice? ?
If there are no requirements regarding processes or safety, time is generally not a requirement.
When there are no specific requirements defined in the process, several factors need to be considered when selecting or specifying the operating time of pneumatic on-off valves: 1. Process requirements: If the process has special demands regarding the speed at which the valve must operate, such as the need for rapid switching or slow opening and closing, then the appropriate setting can be chosen based on those specific requirements. 2. Pipeline flow rate and pressure: Higher pipeline flow rates may require more time to complete the opening and closing process, while higher pressures may demand greater force to operate the valve; these factors all influence the selection of the actuation time. 3. Safety considerations: Too fast or too slow movement times may affect the safety of the process. If the action speed is too fast, it may cause issues such as pressure surges or medium leakage ； Too slow movement times, on the other hand, may affect the stability of the process. Regarding whether there are any regulatory requirements for this issue, there are currently no clear international or domestic standards that specify exact values for the time required to perform the action. However, it is generally believed that the full stroke time of the actuator should be no less than the valve size (in inches), and at the same time should not exceed 30 seconds. So the data obtained through online searches that you mentioned are common reference values, but they are not absolute rules. The final decision should be based on specific process requirements, pipeline characteristics, and safety considerations to select an appropriate actuation time. .
For ordinary customers who have no specific requirements regarding manufacturing processes, the timing is determined in accordance with the standards set by the valve manufacturers. Once the diameter of the actuator reaches a certain level, the manufacturer will make adjustments to the accompanying components in order to improve air intake and exhaust. Such customers, having no time-related requirements, generally have the timing determined based on the operating time of the valves produced by those manufacturers
How to roughly calculate the response time of a shut-off valve? A: According to 10.3.5.5 in SHT3005, the total travel time of the valve starting from the control signal should not exceed 3 times the size of the valve body in inches (in seconds), and it should not be less than the size of the valve body in inches (in seconds)； The maximum travel time of the emergency shut-off valve (the time from the valve’s normal operating position to the safe position required by the interlock) should not exceed 10 seconds. The full-stroke closing and opening times of the on-off valve shall meet the requirements for safety under load and process operation. Section 5.4.2.8 of SHT3184 should specify appropriately the rated full-stroke time for pneumatic on-off valves. This specification must take into account the requirements of storage and transportation processes; at the same time, the stroke time should not be too short, as this could lead to \"water hammer\" or vibrations in the pipes, resulting in damage to the valves and pipes or a reduced lifespan. The rated full-stroke time should not be less than 10s × valve diameter in mm/100. Communications with the manufacturer also confirmed the above points; therefore, based on experience, it can generally be assumed that for each additional size increment (in inches) in the diameter, the single stroke time increases by 1 second, regardless of whether there is a load or not. For example, DN50 requires 3 seconds, DN80 requires 4 seconds, and DN100 requires 5 seconds. Generally, there are no requirements regarding response time for control valves. However, for anti-surge control valves, the following guidelines may be referred to: According to Section 10.1.2.5 b) in SHT3005, when the output signal of the anti-surge control valve drops to 4 mA or when the solenoid valve loses power, the time it takes for the valve to move from fully closed to fully open should not exceed 2 seconds ； When the output signal reaches 20 mA or the solenoid is energized, the time it takes for the valve to go from fully open to fully closed should not exceed 5 seconds. To meet this requirement, the control valve manufacturer should equip it with accessories such as boosters and rapid release valves