How to implement an alarm function for liquid level changes
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It is quite common for level gauges in storage tanks of chemical enterprises to have alarm functions for upper and lower level limits, as well as upper and lower extreme limits. I would like to ask whether it is possible to implement an alarm function for the change in liquid level What does that mean? Suppose the liquid level in the storage tank normally drops by 10% per hour, which is equivalent to a drop of 1% every 6 minutes. If, due to reasons such as the pump not being able to deliver sufficient flow, the pump stopping suddenly, blockages in the pump pipes, or the control valve being set too tightly, the drop in level over 6 minutes is less than 1%, this will affect the proper addition of material. In such a situation, is it possible to implement an audio-visual alarm function using a DCS? How to achieve it? Please give me some advice. Thank you!
This function can be achieved by setting up a level change alarm logic in the DCS system. First, set a timer to measure the liquid level every 6 minutes, then compare the newly measured level with the previous one to calculate the percentage decrease in the liquid level. If the percentage decrease is less than the threshold you set (e.g., 1%), an audio-visual alarm is triggered. You can achieve this by setting the relevant alarm parameters in a Programmable Logic Controller (PLC) or within a DCS. .
It’s achievable! The EOEG unit is equipped with an interlock that activates when the oxygen concentration changes too rapidly; as for the specific implementation details, it is necessary to consult the DCS manufacturer.
A low flow alarm for the pump can be set
Look for the DCS module; there should be a module for controlling the rate of change
I’m not sure what DCS system is used in the original poster’s home. The ECS700 control system has a dedicated alarm function for rate changes; you can ask the system technicians to see if it’s possible to implement this
Create a loop interrupt: subtract the constant value from the previous cycle’s constant value, and then use memory variables to indicate whether the result is greater than or less than a certain threshold in order to trigger audible and visual alarms. Use the value resulting from the subtraction for alarm purposes, and the historical trend can be displayed. This program is quite simple
The 300 system of the central control unit has a rate-of-change alarm, while the 1.06a model from Youwen has a degradation alarm. I don’t know what system you use. In my opinion, modern DCS configuration software should all have similar settings (either in the database or in the I/O configuration).
There is a quick alarm function block within the DCS function blocks, which can be used. If no suitable solution can be found within the system, logical blocks can be used to construct it.
The constant value from the previous loop? DCS is always a variable; it’s not as simple as you think