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My Interlock Not Working

Hello, 

I have a fail open ON/OFF valve installed in the field. 

I need to configure valve to:

Interlock valve Close

Normal operating position of valve is Open

Valve Fail Open on loss of air.

1. How do I remove the BadNotConnected from Interlock_D and Permissive_D? 

2. Currently, when interlock is activated the Out_D stays at 0, keeping the valve open, instead of close. How do I make it close on interlock?

3. When Interlock_D is activated, does the DC Block always set output to 0? For this case I need to set the output to 1 so the valve interlock close. 

Thanks for any help. 

 

• Interlock DC Block

DCS Newbie

• 20 Nov 2014 11:08 PM
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4 Replies

• Matt Stoner

  

  • 21 Nov 2014 11:05 AM

  The DC block can only interlock to the passive state (OUT_D = 0).
  
  You will need to write custom logic to get the output you desire since you want to go to the OUT_D = 1 state.
  
  In v13 there will be a new enhanced DC and DC conditions (interlock, permissive and force setpoint) blocks that will allow you to do this functionality with the standard DeltaV blocks.
  
  Regards,
  Matt

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• Robert Rijnders

  

  • 21 Nov 2014 11:22 AM

  To answer your question 1. The value status is propagated from 1 block to the next. So if you make sure that all inputs IN_Dx on the BFI block have a 'GoodNonCascade' status, the permissive_d and interlock_d inputs on the DC will also become 'GoodNC'.

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• DCS Newbie

  

  • 21 Nov 2014 2:53 PM

  In reply to Matt Stoner:

  Matt Stoner said:

  The DC block can only interlock to the passive state (OUT_D = 0).
  
  You will need to write custom logic to get the output you desire since you want to go to the OUT_D = 1 state.
  
  In v13 there will be a new enhanced DC and DC conditions (interlock, permissive and force setpoint) blocks that will allow you to do this functionality with the standard DeltaV blocks.
  
  Regards,
  Matt

  Thank you Matt for responding.

  If I switch the Passive State Output (OUT_D = 1) in the State Mask, this should Engerize on Interlock Active, correct?

  Does the State Mask set the output or is this for confirming the position of the valve? I get the two confused at times. 

  Thank you

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• Matt Stoner

  

  • 21 Nov 2014 8:21 PM

  In reply to DCS Newbie:

  Passive is usually the non-energized state but you could modify the state mask to change this to be an energized state.
  
  You will also need to change all the named sets as well.
  
  The State Mask does both Input and Output definitions.

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