Differences in the methods for implementing interlock switching and fault switching for pumps or fans

The last edit to this post was made by HEJIYUER on 2016-1-16 at 21:52. My understanding of what you mean by “switching the exhaust fans” is as follows: there are two exhaust fans, A and B, which serve as backups for each other; under normal conditions, the pressure is maintained by one of the exhaust fans, and when the pressure drops, the backup fan is activated； A failure in the fan itself also requires the startup of the backup exhaust fan. 1. It is necessary to consider the process’s ability to withstand low-pressure conditions and the duration for which it can do so. In cases where high standards are required, low-pressure PSL switching should be employed to increase the pressure in advance, thereby preventing potential hazards for the process later on. This PSL start signal is sent from the instrument to the electrical system. 2. If PSL only affects operations and does not involve hazardous conditions, for example, if Fan A stops, it is acceptable to start the backup fan within 2 minutes; it can be set up so that when Fan A stops, Fan B takes over automatically. Well, the electrical engineering field can carry out this switching on its own. The basis of this switching design is that the pressure will definitely drop when the fan stops. However, if low pressure is not caused solely by the fan stopping (there may be other pipeline or operational reasons), then this solution is not appropriate, as the pressure can also drop even when the fan is running. 3. From an electrical perspective, the issuance of a \"fault signal\" means that the motor has stopped (this is how it’s designed in most cases; you can verify this by consulting electrical engineering experts). The fault signal is used for alarm purposes as well as to help identify the cause of the problem. It is more reasonable to use PSL for switching, because whatever fault occurs, it is ultimately reflected in PSL, and it can be “known in advance”. In practice, it can be done this way: the DCS/PLC controller is used to switch the fans, utilizing the PSL signal ； All operation and fault signals of the fan are fed into the DCS for monitoring and comparison. It can be said that the fault signal is for observation only; it does not participate in triggering interlocks. For applications with high interlock requirements, method 1 is used with PSL; we refer to this as \"process parameter interlock, process auto-start\"” ； For those with low requirements, the switching can be handled electrically using method 2; we call this \"double-pump mutual switching\". I wonder if I made myself clear? @jiaguoyun

'Faults are generally only used for monitoring purposes; in other words, when there is a fault with the pump or fan itself, the flow rate or pressure that is important for the process will inevitably deviate from the required values, which will certainly trigger my switching interlock. In such cases, performing a fault switch is actually unnecessary. Can it be explained this way?

This post was last edited by HEJIYUER on 2016-1-16 21:51. The motor stopped working suddenly, and it’s necessary to analyze the reasons: is it related to the manufacturing process? The motor itself? Is it at the MCC control equipment? Is the instrument giving false signals? Start by checking with the electrical department first. And an “electrical fault” is generally defined as: a failure in the electrical control components of this motor ； Either the motor is stuck, resulting in an extremely high current that causes the circuit protection devices to trip; both of these red indicators can be signs of an electrical fault. Therefore, it’s necessary to have an understanding of electrical engineering: what do the \"fault signals\" you are detecting represent? Since this fault signal was generated, did the motor also stop at the same time? For low-voltage motors, it’s basically this: the fault signal is sent = the motor has tripped. So “electrical fault” is used just for checking, as a means of analysis. . . . Using PSL interlocking is more straightforward ； If a fault means shutdown, then I will use the motor’s operating signal as the interlock condition (shutdown = NOT RUNNING). If the fault does not result in shutdown, then the so-called \"fault signal\" is generated; what is the pressure level in the process at that time? So you still need to check the PSL signal. . .