Yes. "... and show it in my PID?" Not clear what you're asking here.princessme said:I have 3 streams entering my vessel and 2 of the streams are dependent on the 3rd stream's flow rate in a certain ratio. Is there a way to control the flow rate of the 2 dependent streams using the flow rate of the 3rd stream and show it in my P&ID?
What I meant was how should the configuration of the control loop be in my P&ID? I'm aware of how to show the control loop for 2 streams, but I'm having issues for 3 related streams to be controlled. Any references that I could refer to for this?Bystander said:Yes. "... and show it in my PID?" Not clear what you're asking here.
For instance, both the first and third stream are dependent on the flow rate of the first, both in different ratios. Does it mean that I need to have 2 control loops - one for streams 1 and 2, and another for streams 2 and 3?Bystander said:You've a couple possibilities: the third stream flow rate can be described as a function of the flow rate of either of the other two; pick one.
Yup. Third stream as fnn of first, or of second; of second is easier since it's a fixed ratio.princessme said:2 control loops
Noted. Thanks for the help.Bystander said:Yup. Third stream as fnn of first, or of second; of second is easier since it's a fixed ratio.
My plan was to put a control valve on stream 1 and 3, which are connected to a ratio station each. Each ratio station is connected to the FT on stream 2. Does that make sense?Bystander said:... and, when the third stream "runs away," how do you sense that upset condition?
Makes sense if you can be certain that which ever stream you leave as an "open loop" doesn't get plugged up, run dry, or otherwise fail.princessme said:Does that make sense?
So I should consider doing 2 closed control loops instead?Bystander said:Makes sense if you can be certain that which ever stream you leave as an "open loop" doesn't get plugged up, run dry, or otherwise fail.
Alright, thanks for the suggestion.Bystander said:FT on primary stream (set point) to "ratio" for two dependent streams, and FC plus FT sensing output for each dependent stream is the way I'd do it.
One does the trick --- two can have a nasty tendency to start calling each other liars.princessme said:1 be sufficient?
Ratio control for multiple streams is a process control technique used in industries such as chemical, oil and gas, and food and beverage to maintain a fixed ratio between two or more process streams. It involves continuously adjusting the flow rate of one stream based on the flow rate of another stream to maintain a specific ratio.
Ratio control for multiple streams offers several benefits, including improved product quality, increased process efficiency, and reduced waste. By maintaining a consistent ratio between process streams, it ensures that the desired product specifications are met, and resources are utilized effectively.
Ratio control for multiple streams typically involves the use of flow meters, control valves, and a controller. The flow rate of one stream is measured by a flow meter and compared to the desired ratio set by the controller. The controller then adjusts the flow rate of the other stream by opening or closing the control valve to maintain the desired ratio.
One common challenge with ratio control for multiple streams is maintaining a consistent ratio when there are changes in the process conditions, such as variations in flow rates or pressure. This can be addressed by using advanced control strategies, such as cascade control, and regularly calibrating the flow meters and control valves.
Yes, there are alternative methods to ratio control for multiple streams, such as cascade control, feedforward control, and model predictive control. These methods use more advanced control strategies and can offer better performance in terms of maintaining a consistent ratio between process streams.