ricketycricket
Member
Hey,
I am a newbie when it comes to process control and PLCs as I am just out of college and at my first job. I am trying to get a system set up that will pump air through two separate, independent systems using only one blower. Each leg of the system will require a different flow rate profile than the other (e.g. 20 min at one flow rate, ramp to another flow rate for 30 min). The profiles will need to be changed often and so I think each leg will need its own programmable controller that will have an input from an LFE and control the process via a butterfly valve. What I am unsure of is how to control the blower with these two independent control loops. My plan is to have both controllers output the valve signal to something that is capable of comparing the two signals and transmitting the larger of the two signals to a VFD to control the blower. So the leg of the blower system that requires the most flow will be the signal getting to the VFD. My question is can a PLC compare the two signals and output the higher of the two? Is there a simpler method? How ignorant am I when it comes to process control? Any advice is appreciated.
I am a newbie when it comes to process control and PLCs as I am just out of college and at my first job. I am trying to get a system set up that will pump air through two separate, independent systems using only one blower. Each leg of the system will require a different flow rate profile than the other (e.g. 20 min at one flow rate, ramp to another flow rate for 30 min). The profiles will need to be changed often and so I think each leg will need its own programmable controller that will have an input from an LFE and control the process via a butterfly valve. What I am unsure of is how to control the blower with these two independent control loops. My plan is to have both controllers output the valve signal to something that is capable of comparing the two signals and transmitting the larger of the two signals to a VFD to control the blower. So the leg of the blower system that requires the most flow will be the signal getting to the VFD. My question is can a PLC compare the two signals and output the higher of the two? Is there a simpler method? How ignorant am I when it comes to process control? Any advice is appreciated.