Recent Control & Safety Systems Discussions
Similar Posts
Mode – Bumpless Transfer
PID bypass switching between MAN to CAS
Keeping Track of Bypasses
Logic Implementation for Override/bypass.
Alarm Bypass during plant start-up
Share

Is placing PID block in "Bypass" bumpless?

I have a PID block configured to serve as a cascade "master" of sorts - I was attempting to manipulate a flow from a vendor skid. But they in turn have a flow loop configured (anyhow). The two loops are too close in dynamics, so I want to put our DeltaV PID block in "Bypass" (which I have enabled in control_opts).

The loop has been run in MAN for some weeks now . . . when I invoke "bypass" mode, will "manual" mode work as always (operator sets output independent of PV), and then when I switch to AUTO or CAS, the setpoint will be "translated" to 0-100% of the PV scale and applied to the output (right?). Will there be a "bump" in the output, and if so how might one ensure it is minimal?

Thanks,

John

John Rezabek
  • James Beall
    Hey John,
    The BYPASS feature works very well. It will transistion bumplessly in the example you describe since a manual output will create the proper setpoint which will be tracked by a master loop via BKCAL_OUT of the bypassed loop. You might take a look at SP limits to make sure they won't cause a restriction as percent of scale. Be aware that the BYPASS feature even takes into account the controller action to keep the correct action of the master loop if the slave loop is bypassed. This might mean that a SP_HI_LIMIT is the low limit on the output! You might check this out.
    Hope this helps!
    James

This is the official online community site of the Emerson Global Users Exchange, a forum for the free exchange of non-proprietary information among the global user community of all Emerson Automation Solution's products and services. Our goal is to improve the efficiency and use of automation systems and solutions employed at members’ facilities by sharing our knowledge, experiences, and application information.

User Groups | World Areas | Community Guidelines | Legal Information | Privacy Policy | Contact Community Manager

Website translation provided by Website Translator

© 2015-2022 Emerson Global Users Exchange. All rights reserved.