I'm going to do some SIL verification for an reactor in a paper mill.

The safety function consist of two pressure transmitters (1oo2) from the mid of 80's, a Safety PLC and a frequency converter. If the pressure in the reactor goes over a high limit the frequency converter will stop to prevent explosion of the reactor. The target is SIL2.

It has not been any problem finding PFD-values for the PLC nor the frequency converter. The pressure transmitters are so old that they don't have any values which I can use.

Can I use any generic values in the calculations or do I have to change to new transmitters?

 

You have the best source of PFD data on the existing transmitters in your plant records - any values for new equipment will be estimates and will not necessarily apply to your operating environment or maintenance practices. If you have had no problems with them in the past, that is the best evidence you could have that they are suitable for the application. The main concern is that, at 25 years old, they may be nearing the end of their life.

 

Can I use old sensors as proven in use without very good documentation about the problem? In other words a lot of work just to gather the documentation.

When I use the SIL verification software (exsilentia) I can use generic pressure transmitters and that give me a very good value. I need to achieve SIL2 and those transmitters are 1oo2 so they gave SIL2.