Emerson Exchange 365

PCSD Valve module

Can anyone explain what the difference is between an 'Interlock' and a 'Force' within a PCSD Valve module?

Stuart Jolley

• 17 Oct 2018 7:11 PM
• Cancel

6 Replies

• Stuart Jolley

  

  • 17 Oct 2018 7:21 PM

  The PCSD valve module has Interlocks, Permissives and Force Setpoint Composites

  • Cancel
• IntuitiveNeil

  

  • 17 Oct 2018 7:38 PM

  In reply to Stuart Jolley:

  Pre PCSD v13 the valve module did have these composites (replaced by EDC at V13)
  
  Intelocks in pre v13 PCSD valve modules always trip and hold the valve to/in the passive state (state 0)
  
  Permissives prevent the valve moving away from the passive, but wouldn’t trip to passive if already in an active state.
  
  Force SP allow a particular state (passive/active 1 or active 2) to be driven under certain conditions, force SP would be used for simple control functions rather than protection functions (as for Interlocks and permissives). E.g in a drain sump opening an outlet valve on high level and closing a valve om low level.

  • Cancel
• Stuart Jolley

  

  • 17 Oct 2018 7:47 PM

  In reply to IntuitiveNeil:

  Thank Neil, I'm using v11.3.1. From what I've been reading, the FORCE_SP works only in CAS MODE, which isn't much use as the valve normally operates in AUTO to allow our operations staff to OPEN/CLOSE a number of times during the day.
  
  We already have logic that Interlocks the valve in its PASSIVE state but we now have a requirement to create a function that interlocks it in its ACTIVE1 state.

  • Cancel
• Matt Stoner

  

  • 17 Oct 2018 8:22 PM

  In reply to Stuart Jolley:

  Interlocks are conditions that always work regardless of mode, can be configured to latched requiring a manual reset, automatically are permissives and in your version can only go to the Passive State (v13 these conditions can go to any state because of the new DCC and EDC blocks)
  
  Permissives are conditions which prevent changes to an Active State but won't force to Passive if already in an Active State and the Passive Setpoint (SP) is allowed at anytime. This means it will Prevent going to another Active state if already in another Active state for when there are more than 1 Active SP.
  
  Force Setpoints (FSP) are one shot conditions that will change the SP to the defined SP (Passive or Active). These by default work in CAS in your version but can be configured to also work in AUTO mode by setting the FS_IN_AUTO parameter True on the DC_CTRL composite. In Version 13 you select what mode the FSP will work on the DEVICE_OPTS on the EDC block. For cases where you don't like the Force Setpoint working as one-shot you can include Current SP <> Desired FSP SP in the condition so it will become True again if the SP changes or include mode if you only want a condition to work in CAS while others in AUTO. (example uses are Agitator Control based on Level or Sump Pump control)

  • Cancel
• Stuart Jolley

  

  • 17 Oct 2018 8:43 PM

  In reply to Matt Stoner:

  thanks for your comments Matt. gives me something to think about.

  • Cancel
• Michael Krispin

  

  • 18 Oct 2018 4:00 AM

  In reply to Stuart Jolley:

  Hi Stuart,
  As the other guys stated here the function for interlock and force sp
  You might have a possibility to go into an active interlock if you configure the IL condition in an external module which set mode lock, owner id maybe as "Interlocked" and let force sp do the action in Cas mode. If the mode can't changed back to Auto, then the operator can't change the SP.
  I have done similar very often.
  For an own library I had developed an own DC as composite years ago, which gave the functionalities as they are now similar available from DV 13.x

  • Cancel