[foxboro] Fw: Fw: peer 2 peer loop strategy conclusion
- From: Ajit.S.Kumar@xxxxxxxxxxxxx
- To: Terry Doucet <doucet427@xxxxxxxxxxx>
- Date: Mon, 2 Apr 2012 03:05:05 +0300
Thanks Terry,
Very well said....
This complex loop is for Boiler master control and we had plant upset due
to the measurement failure as you hinted.
we have the AOUT (FBM04) which is not redundant and is in e.g CP1 , and
AIN as redundant (FBM05) and this is in CP2. The AIN is part of the
Combustion control schema which nose dived the Combustion control valves (
fuel/air) to close , causing a Boiler to trip from the ESD due to loss of
Combustion. This happened unfortunately due to the CP1 ( FBM04
-AOUT)totally dead and SUBSEQUENTLY lost the measurement in CP2 (FBM05)
causing the Combustion control valves to close.
All alternatives were considered and finally the only solution seen was to
consider converting the FBM04 to FBM05 as redundant,as P2P is not a better
solution we will stick with the redundancy.
Any other approach will be welcome if possible.
Thanks again and regards
A.kumar
----- Forwarded by Ajit S Kumar/Technical/SAMREF/SA on 04/02/2012 02:44 AM
-----
From: Terry Doucet <doucet427@xxxxxxxxxxx>
To: <foxboro@xxxxxxxxxxxxx>
Date: 04/02/2012 01:53 AM
Subject: Re: [foxboro] Fw: peer 2 peer loop strategy conclusion
Sent by: foxboro-bounce@xxxxxxxxxxxxx
The classic Foxboro software peer to peer connection is when you are
working in CP1 and you make reference to an external (in CP2)
Compound:Block.Parameter. What you are describing is a hard wired station
to station connection that is between peers but amongst Foxboro this
people has a totally different set of issues.
The software peer to peer is not recommended for critical control loops.
All communications into and out of a CP are at the same priority so this
peer communication has the same priority as an alarm message to a printer
or logging system. So during an alarm storm, you may not get your
measurement updates on a regular basis. If you have CP270 then loading is
probably not an issue but with some of the older CP's loading could be an
issue that would have a negative impact on your control loop. There are a
lot of lists and tables that are created with peer communications and each
has upper limits that could affect the communication in a negative manner.
Even the hard wired method where you have an AOUT sending a signal to an
FBM (eg. 4-20mA out) and that FBM is hard wired to another FBM (eg 4-20 mA
in) there are some risks that would not be present if only one CP was
running the entire control loop. With hard wire, there is no quality of
the signal transmitted to the second CP. So if the measurement goes BAD
(Foxboro term), then the second CP has no signal to tell it that the
measurement is BAD. Your control loop might "wind up" and get into a
dangerous state.
Terry
> To: foxboro@xxxxxxxxxxxxx
> CC: Timothy.Lowell@xxxxxxxxxxx
> Subject: [foxboro] Fw: peer 2 peer loop strategy conclusion
> From: Ajit.S.Kumar@xxxxxxxxxxxxx
> Date: Mon, 2 Apr 2012 01:29:23 +0300
>
> Thanks Timothy,
> True....we have it in different CP. However we have the AOUT of one
block
> (channel) connected through hardwired to AIN of the another block in
> different CP controlling the process. The reason is both are located in
a
> different instrument house. The design concept was to avoid P2P due to
> complexity of the loop originally. Now to reconsider the loop strategy
can
> this be connected as P2P if yes then was are the consequences in case of
> P2P failure.
> ESD System's do not permit Soft linkages or P2P as in the case PLC to
DCS
> it is hardwired.
>
> Thanks and best regards
>
> A.kumar
>
>
>
> ----- Forwarded by Ajit S Kumar/Technical/SAMREF/SA on 04/02/2012 01:19
AM
> -----
>
> From: "Lowell, Timothy" <Timothy.Lowell@xxxxxxxxxxx>
> To: "foxboro@xxxxxxxxxxxxx" <foxboro@xxxxxxxxxxxxx>
> Date: 04/02/2012 01:17 AM
> Subject: Re: [foxboro] peer 2 peer loop strategy conclusion
> Sent by: foxboro-bounce@xxxxxxxxxxxxx
>
>
>
> Perr-to-peer refers to loops that have connections across Control
> Processors, not between two FBM's that are hosted by the same Control
> Processor.
>
> The disadvantage of peer-to-peer
> ________________________________________
> From: foxboro-bounce@xxxxxxxxxxxxx [foxboro-bounce@xxxxxxxxxxxxx] On
> Behalf Of Ajit.S.Kumar@xxxxxxxxxxxxx [Ajit.S.Kumar@xxxxxxxxxxxxx]
> Sent: Sunday, April 01, 2012 3:43 PM
> To: 'foxboro@xxxxxxxxxxxxx'
> Subject: [foxboro] peer 2 peer loop strategy conclusion
>
> Dear All,
> Suggestions required, Thanks in advance.
> What are the advantages/disadvantages of P2P communication in an complex
> loop.
> We have few control loop hardwired between FBM's due to complicity but
> need to find a better way to avoid FBM failures or Open wires which
drives
> the complex loops to plant upset.
> Is P2P a better industrial way in the Refinery Applications. The present
> scenario is to convert the FBM to redundant type, but still we need a
> better answer to use P2P.
>
> Thanks and best regards
>
> A.kumar
>
>
>
>
>
> _______________________________________________________________________
> This mailing list is neither sponsored nor endorsed by Invensys Process
> Systems (formerly The Foxboro Company). Use the info you obtain here at
> your own risks. Read http://www.thecassandraproject.org/disclaimer.html
>
> foxboro mailing list: //www.freelists.org/list/foxboro
> to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
> to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave
>
>
>
> _______________________________________________________________________
> This mailing list is neither sponsored nor endorsed by Invensys Process
> Systems (formerly The Foxboro Company). Use the info you obtain here at
> your own risks. Read http://www.thecassandraproject.org/disclaimer.html
>
> foxboro mailing list: //www.freelists.org/list/foxboro
> to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
> to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave
>
>
>
>
>
> _______________________________________________________________________
> This mailing list is neither sponsored nor endorsed by Invensys Process
> Systems (formerly The Foxboro Company). Use the info you obtain here at
> your own risks. Read http://www.thecassandraproject.org/disclaimer.html
>
> foxboro mailing list: //www.freelists.org/list/foxboro
> to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
> to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave
>
_______________________________________________________________________
This mailing list is neither sponsored nor endorsed by Invensys Process
Systems (formerly The Foxboro Company). Use the info you obtain here at
your own risks. Read http://www.thecassandraproject.org/disclaimer.html
foxboro mailing list: //www.freelists.org/list/foxboro
to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave
_______________________________________________________________________
This mailing list is neither sponsored nor endorsed by Invensys Process
Systems (formerly The Foxboro Company). Use the info you obtain here at
your own risks. Read http://www.thecassandraproject.org/disclaimer.html
foxboro mailing list: //www.freelists.org/list/foxboro
to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave
Other related posts:
- » [foxboro] Fw: Fw: peer 2 peer loop strategy conclusion - Ajit . S . Kumar
