Preventive Maintenance Frequency for SIL Based Instruments

What do the OEM manuals suggest as a PM frequency for the instruments?

I would suggest you RTFM!

If all else fails call the OEM they will have the answers.

Yeah, what to say.

Define it, assign it, control it, study it more, do the mathematics, help yourself.

Now by having said that you can start with helping yourself by looking up SIL and PM.

Is the meaning clear?

Instrument PM frequency and type are based on the OEM requirements and the ambient conditions the instrumentation is being used in.

You need to first determine all of the ambient operating conditions that affect the instrumentation (caustic, acidic, low, medium, or high pressure? Abrasive? Wet? Dry? Mean Temperature? UV exposure? Vibration?) then contact the OEM technical group for consulting and guidance services.

The OP may have just as well just written this:

I have a GM vehicle and was wondering how often I should perform repairs and maintenance on it.

What frequency should I do the maintenance at????

Too little information and I don't feel like playing 20 questions!

Would that be the infamous Chevy Cavalier? My mom had one of those, and wow what a grossly anemic machine that was (back in the late '70's to early '80's. At least it would start and run, but she got the interior carpet wet once in a flooded section of road, and the sour towel smell could never be overcome....black mold in cars?

Before you start doing something as sophisticated as a Safety Integrity Level study you should learn how to search the web where you'll find a standard called IEC 61508 that might help you, not an anonymous bunch of strangers who have no culpability for any mistakes that you will make.

I resemble that remark. At least someone here knew the standard and what SIL is all about. I did not. Sounds like something I would have ignored anyway.