How many levels can be set for the DCS level alarm?
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I would like to ask everyone, how many levels can be set for the DCS level alarm? For example, there are LALLL, LALLLL, LALLLLL... How should this be represented? Expressed as LA3L, LA4L, LA5L……? Additionally, how many levels of alarms or interlocks can be set in a DCS?
Generally, when we make settings, there are 4 levels: high-high alarm LSHH, high alarm LSH, low alarm LSL, and low-low alarm LSLL. However, the setting of alarm values should be determined based on process requirements; generally, not all of them will be needed. The primary purpose is to serve the manufacturing process, facilitating its operation and enabling the timely detection of any abnormalities in it. There is no fixed value for this; it depends on the manufacturing process
Process requirements and production conditions determine the actual status!
Depending on the process operations (or responses) after an alarm is triggered, different alarm values correspond to different responses. Generally, a DCS is configured with two levels of alarms; having more would actually lead to a “cry wolf” effect, rendering them ineffective. Indeed, some processes (such as reactors) are designed with 3 or 4 levels of alarms, and this is certainly related to the characteristics of the process.
An effective alarm requires both an alarm signal and corresponding action by the operator. So it doesn’t help much to have too many. Generally, HH H L LL is sufficient
Thank you for the reply! What I want to ask is: can the DCS achieve this no matter how many levels of alarm are set? Or can DCS only have four levels: H, HH, L, LL? Can it not have more than that? Usually it is indeed at four levels, but in some water systems, higher requirements are imposed; or due to various operating conditions, when only one liquid level is used for control, multiple alarm or interlock levels for that liquid level arise. I want to know that, in such a case, is it possible to implement DCS, or can only four-level alarm interlocks be used? Thank you!
High, high, low, lowlow is enough. In special cases, you can add high high high, low low low.
The computing capability of DCS is limited; generally, setting it to LL-L-H-HH is sufficient. If there is a system for auxiliary calculations, variable data can be extracted to enable various types of secondary monitoring; for example, machine learning can be used to determine a relatively reliable range based on historical data, thereby adding an additional layer of alarm functionality.
If the simulated level signal can be converted through high-precision A/D conversion, it is theoretically possible to set an infinite number of alarm levels, but what’s the point of having that many? It’s not possible to set an alarm for every single millimeter change in liquid level.
The DCS system for such applications allows for the setting of numerous alarms according to the user’s needs. However, the alarm settings must be reasonable; otherwise, alarms that have no practical value are merely redundant and serve no purpose! The data collected via interlocks can be displayed in the DCS; however, it constitutes a relatively independent system. This setting value is determined during the design phase and cannot be changed at will based on process requirements!