Hi All,
I am David from Emerson Process Management Malaysia, as Project Engineer since March last year.
My Client required SIS System Communication Failure with Adjustable Time Delay.
Loss of communication between/among logic solvers will not trip immediately, but with an adjustable time delay.
Please share with me if you have done it before.
Hi David,
The data transfer between SIS Logic Solvers is through Secured Parameters . You can create a Secured Parameter in one SLS and create a reference in another.
Place a timer in between them . Now let's say that if the timer runs out and you don't have the required bit , you may cause a trip/shutdown as per requirement.
I wonder if we can use something from diagnostics too.
Regards
ASIM
In reply to M_ASIM_B:
The above comment is misleading.
You cannot place a timer between the SP and SP_REF.
You must place the timer AFTER the SP_REF and before it is used.
Having said that - this NAIVE approach will also delay any trip that utilizes the SP_REF. Are you sure you want that ?
I would consider looking at the STATUS of the SP_REF , and masking it out for normal trip, but using a delayed version of the STATUS for a trip on loss of comms.
You are going to need a CALC block and a timer or other means of generating the delay.
In reply to Gary Law:
Hi Gary,
Thanks a lot Gary for the correction of my comment.I have considered the following while performing a simulation as i haven't encountered such a requirement before.
1:The SLS holds only the C&E and concerned IO.
2:SP_REF will cause a PCS Trip (The trip can't be caused through a SLS)
3:The delay thing works like a heartbeat . You must send and receive the pulse in a small duty cycle, probably milliseconds . If there is a mismatch, you will cause a trip.(sorry for my mistake)
I have used the heart beat as way of testing communication between different PLCs and HMI and it works. I have tested it between HIMA and Control Logix.
M_ASIM_B