Emerson Exchange 365

How do you ramp when in RCAS?

We have comes across an issue where we cannot ramp setpoints when in RCAS. We have multiple sequences in which we lock the relevant modules (like controllers) and then use RCAS to change the setpoint. The PID module has the ability to ramp up/down the setpoint, but when we move to RCAs the setpoint does not ramp when changed, it goes instantaneously to the new setpointd. The reason for locking the modules is to prevent the operator from "playing" with equipment being used by the sequence.

We are playing with adding some ramping logic which we turn on or off based on the whether we are in RCAS or not, but we are wondering if there is another way to do the ramping or have we missed something within the PID module which would allows us to ramp the CAS-In value or the PID setpoint.

Thanks

Col

• ramping
• RCAS
• DeltaV

Colin Welsh

• 19 Jan 2018 7:05 PM
• Cancel

1 Reply

• Andre Dicaire

  

  • 19 Jan 2018 8:05 PM

  Colin, The DeltaV Books On Line shows that in CAS mode, the setpoint bypasses the ramping block. What is not shown is how the SP signal propagates when in RCAS. All indication in BOL is that the signal chain will be the same for RCAS as for CAS, and you've confirmed the Ramping is indeed not functioning when in RCAS.
  
  In general, the RCAS set point should be ramped at the source. I would be looking to have the controlling sequence or module ramp the SP in RCAS. That leaves the Ramp settings in the PID for use in Auto or CAS. You can read the PID ramp settings to match the ramp to the PID rates if you want the ramp rates to always match.

  Andre Dicaire

  • Cancel