Which brand offers switch valves with partial stroke detection (PST) that are of better quality?
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Partial Stroke Testing (PST) is primarily used for most safety emergency valves that remain in a fixed, stationary position for extended periods of time. The most common failure mode of such valves is being stuck and unable to operate; most failures can be detected through certain stroke tests, and through these tests a single valve may meet the SIL2 requirements. Which domestic company offers such valves? What form is it in? What is the actual performance in real-world use?
There are increasingly more doubts surrounding the PST concept; it’s possible that a device was working fine originally, but performing PST tests ends up causing problems, so it’s not as widely promoted as it used to be in previous years；
Haven’t heard of it! It seems my knowledge is still limited!
Isn’t PST claimed to be capable of achieving SIL certification?
There are usually three ways to implement PST functions: one is using solenoid valves along with pneumatic accessories and detection modules； One method uses a position switch combined with a solenoid valve, while another approach makes use of a valve positioner with PST functionality. The first type of solenoid valve, along with its detection module and pneumatic accessories, is operated via on-site manual buttons or remote signals, which cause the solenoid valve to lose power for a short period of time, resulting in the valve closing due to the loss of air pressure. Once the valve reaches the set position (usually within 15°), a signal is sent back through the detection module, which then re-energizes the solenoid valve, allowing the valve to open fully. This process does not cause any significant change in the process flow, thereby completing the reliability test of the valve. The second mode is the position switch combined with a solenoid valve; its principle is similar to that of the first mode. It also involves manual operation on-site or control via remote signals, which causes the solenoid valve to lose power for a short period of time, allowing the valve to start closing. Once the set point is reached, the sensor module re-energizes the solenoid valve. The third method is to use a locator with PST functionality; this intelligent locator also enables local and remote operation, with certain travel points being set via programming. However, although this approach sounds advanced, the locator still needs to incorporate solenoid valves; as a result, its positioning adjustment function becomes redundant. The setting of the travel distance is done via software, which is not as straightforward as in the first two methods, and it also increases costs.
Are there any Haiyous that have not been used in practice?
I’ve seen this on the turbine emergency shut-off valves in MAN; it’s a bit complicated
It’s not clear in China; however, MAXON valves imported from abroad come with PST control boxes that enable PST testing functionality
(1) Emerson Process Management Fisher valves, DVC6000 SIS model: HART communication, SIL3, intrinsically safe/isolated； (2) METSO-neles VG800 series and RCI: HART communication, SIL3, intrinsically safe/isolated ； (3? SAMSON’s 3730-3ESD model: HART communication, SIL4 (solenoid valve function), intrinsically safe ； (4) DRESSER-Masoneilan SVI II ESD: HART communication, SIL3, intrinsically safe/isolated ； (5) INVENSYS-Foxboro-Eckardt’s SRD991/960: HART or bus, SIL3 ； (6) SIEMENS SIPART PS2: HART or bus, SIL2, intrinsically safe/isolated.
Is this a self-question and self-answer? And it asks about domestic manufacturers, yet all listed are foreign products
Could not find it domestically; found the information online.