Limiting a pump speed

I have a chemical mixing system which is controlled by a Controllogix system and using Factory Talk SE for display and HMI. I have 3 pumps which the operator can bring up a pop-up keypad for entering the speed of the pumps. I want to be able to limit the input to a maximum of 40 hertz. Is this best done from the FTSE side or the processor side? If FTSE is best way, how do I do this? I have a little experience with making changes on the screens, although I don't particularly like Factory Talk. If from the Controllogix side, what is the best way to program this? Thank for all assistance.

You obviously have a VFD, I would do it there because if some bozo walks up to the drive and changes it to keypad control, the speed limit is still in place. Theoretically on a "qualified worker" would take the next step in reprogramming the drive, and most drive provide for some sort of password protection for that.

If you do that, set the drive up to give the PLC a "Reached Speed" signal that you display in FTSE as "Max Speed Reached" so that operators know why it's not responding to their insistence on going faster.

Thank you for the suggestion. I hadn't even thought about limiting the drive itself. Makes sense. The VFD is a Yaskawa V1000, and I haven't found any way to lockout the keypad. I won't worry about that too much. The VFD runs a chemical transfer pump to move material from one tank to another. I doubt if any of the operators will notice a difference anyway. They usually just start it up and walk away.

jraef definitely has the right idea. For my money's worth, I always set the drive limits to the actual physical limits of the machine, and limit it from a process control point of view in the PLC. I match the entry limits on the SCADA to the limits programmed in the PLC, purely so that the operator can see their range of adjustment from the SCADA.

ASF said:

jraef definitely has the right idea. For my money's worth, I always set the drive limits to the actual physical limits of the machine, and limit it from a process control point of view in the PLC. I match the entry limits on the SCADA to the limits programmed in the PLC, purely so that the operator can see their range of adjustment from the SCADA.

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I pretty much do this....I almost always scale all drives the same (0 to 100% = 0 to 60Hz or 90Hz depending on the application). I'd rather in the future if a limit change is needed a technician do it in the PLC/HMI vs rescaling or limiting a drive.

Jim G. said:

I want to be able to limit the input to a maximum of 40 hertz. Is this best done from the FTSE side or the processor side? If FTSE is best way, how do I do this? I have a little experience with making changes on the screens, although I don't particularly like Factory Talk. If from the Controllogix side, what is the best way to program this? Thank for all assistance.

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Depends on what "best" means.
Option 1) Desire to restrict the operator, but want to allow techs/engineers to exceed limits put it in the HMI.
Option 2) Desired limits are when the drive is in 'remote', Operators and techs/engineers are restricted, limit it in the PLC.
Option 3) Desired limits include when the drive is in 'remote' or 'local' mode, then limit it in the drive.

I would put it in the HMI (option 1) even if I wanted one of the other options to apply. This way the operator gets feedback when he tries to enter a speed that is out of range. If this isn't done, depending on how the limits are made, either the speed change is rejected, or its limited to something different from what the operator entered, and he may not recognize that he didn't get what he wanted.