Questions regarding the DI module of the CS3000 system
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After the CS3000 system has been operating normally in the field for a year, the valve position signals started to malfunction yesterday; as a result, the valve positions of several valves within the same module were not displayed. Upon inspection, the following issues were found. Please advise: 1. Only one valve is having problems – why does this affect the display of the valve positions of the other valves as well? (The DI card model is ADV151-P00.) 2. The reason for the problem is that for the valve in question, both the open and closed positions were detected simultaneously; this is what caused several valves within the same module to fail to display their positions (experiments were conducted). 3. When the incoming cable at the site was removed and the DCS system terminals were directly shorted together, there was no issue with the open position, but problems arose when trying to short the closed position. 4. When the faulty valve was connected to the DI channel of another working valve, several valves still failed to display their positions ； 5. Measure the voltage after removing the incoming cable at the site: when the connection is in good condition, the voltage is only a little over 10 volts, with a maximum of 11.51 volts; when it’s faulty, one of the connections has voltage while the other does not. 4. There’s something special about this issue – the condition alternates between good and bad. The periods of good performance last as short as a little over 10 seconds, or as long as half a day or a whole day. :Dizzy: I would appreciate it if the seniors could help explain each of these questions one by one. Thank you in advance. :(
The system is grounded; please check it carefully as there are some loose connections.
Is there insurance? Has the fuse burned out?
1. There is only one valve that has a problem – why does this affect the valve position displays of the other valves as well? (The DI card model is ADV151-P00.) This indicates that there is a problem with the module; the cause of this issue is either a short circuit in that channel or a problem with the bus. 2. The reason for the problem is that for the valve in question, both the open and closed positions are detected simultaneously, which results in several valves within the same module not showing their respective positions (experiments were conducted). There is an issue with the signals being received, leading to logical errors ； If the connection works fine, then one of the channels is shorted. 3. Remove the incoming wire at the site and directly short-circuit the terminals of the DCS system; short-circuiting the valve position works fine, but when the valve is closed, there are problems. A short circuit inside the valve causes all channels on that entire module to become shorted. 4. Move the valve with the problem to the DI channel of another functioning valve, but still several valves fail to display any signal ； It has nothing to do with the other good valve channels; it’s the problematic channel that causes the short circuit. I’m not sure about the last two points – I’ve never used the CS3000, but I’ve encountered the same problem several times with other devices, and in those cases I simply left that channel unused. As for the short circuit mentioned upstairs, I’m not very clear about it; I’m also a newcomer. The insurance issue shouldn’t be a problem; if the insurance expires, it’s over, and there should be no fluctuations.
The wiring on the DI card is not independent; it is usually connected to a 24V power supply, with the negative terminal connected to the common point and the positive terminal connected to the on-site valve position switch. Could your problem be caused by the power supply?
Indeed, whether the DI cards are isolated in groups or individually for each channel – it seems that the owner should opt for group isolation, so that if one channel fails, only that group will be affected. It’s also possible that the voltage at the DI terminals is too high, or there are other issues; in such cases, the DI cards aren’t properly isolated. Could the original poster please let us know if the problem has been resolved?
Has the valve indicator at the site been replaced? Is it of the type that changes from normally open to normally closed, or is it sensor-based? If it’s sensor-based, the main power supply is connected to the position where it’s open, while the auxiliary power supply is connected to the DCS circuit; in this case, it cannot be short-circuited directly, as this would cause serious short-circuit problems. Also, check the grounding situation – if necessary, provide separate power supply for this valve