Emerson Exchange 365

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MOV Logic via DC function block

hi to everyone,

i have a problem with logic of MOV by DC function block. i have 2 DIs as Close Limit Switch and Open Limit Switch and 2 DOs as Close Command (Remote) and Open Command (Remote).

everything is OK when i received Limit Switches on Local and Remote. but when in local mode and i didn't receive Limit Switches and change the position from Local to Remote, suddenly the DOs are energized via valve setpoint on DC block and i don't want this. i want to stay at the last position (NOT open or NOT close)!

how can do this?

• MOV
• DC Block

semova2

• 6 Jan 2017 2:41 PM
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4 Replies

• Matt Forbis

  

  • 9 Jan 2017 12:33 PM

  In my experience, on an MOV, we typically convert the DC block to be a 3 state device. STOP, OPEN and CLOSE. This means you can then use the Passive on Active Confirm when it reaches either state. This should help keep from driving the outputs if the device has reached it's limit.

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• Matt Stoner

  

  • 9 Jan 2017 2:31 PM

  In addition to what Matt F described, in v13 and using the EDC block you can make the STOP discrete inputs on the STATE_MASK be don't care (greyed out) and the PV_D will still indicate OPEN/CLOSE/UNDEFINED status and not cause a failure for STOP command. The same configuration on the DC block will work but the PV_D will be STOP which is probably not useful to see what the valve position currently is.

  Here is a view of the MOV STATE_MASK configuration I described above:

  

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• semova2

  

  • 11 Jan 2017 4:39 AM

  In reply to Matt Forbis:

  thank you Matt. i did it via 3 states: Stop, Start, Undefined. when in local mode, i can't receive any status of open/close, the status of output (F_OUT_D3) switch to true and others go to zero.

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• semova2

  

  • 11 Jan 2017 4:40 AM

  In reply to Matt Stoner:

  thank you Matt :)

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