ESD Valve Partial Stroke Test through DCS will abort SIL?

[bhutajulu]

Happy Day,

When we design the Safety Shutdown System, where the requirements
project is to be certified SIL-3 in full, either from the System
down to the Field Instrument.Then there are other requirements, which requested the shutdown valve shall be installed partial stroke test online. But do not mention
whether it should be through the ESD System or DCS.

If I were designing a partial stroke test it online via the DCS,
Whether this will invalidate the certification of SIL-3 from its ESD,
where the requirement as mentioned above SIL-3 - his
either a full system of systems down to the field instrument.
1. If yes, what is the reason?
My assumption, if abort SIL-3, this is caused by the DCS that
no SIL, although we use a positioner that SIL-3.
2. If not, what is the reason?
My assumption, because it is a loop PST separately (section
separately), so even though
at a stroke through the DCS has no effect on SIL-3 certified him.

Please enlightenment

Thanks

[zulqurnain]

Salam dear
Partial stroke foe ESDV's should not... never...be done via DCS
There are multiple methods to acheive via ESD
1) OLD school - USE an extra limit switch , make a logic in SIS so that once the command is issued for PST fail close signal will be"pulsed" till it reaches the x% where the limit switch is set.
2) USE smart PST modules , like drallium or made by valve manufacturers, it can be issued via digital output dedicated for PST"not for ESDV open/close"
2) HART compatible PST modules - made by valve manufacturers - to be operated via asset management systems not by SIS directly,

[zulqurnain]

forgot to touch SIL
to achieve SIL you need to do proof testing and PST contributes certain % to proof testing - it will not nullify the SIL