I need to provide 2003 level voting on a vessel for SIL 1 shutdown. I only have two tappings (upper and lower) on the vessel.

Option 1: Provide a cross pipe with flanged tappings for remote dp seal transmitters on the upper and lower tappings.

Option 2: Provide a stand pipe. Weld 3 flanged tappings for the upper tapping and also for the lower tapping.

Please advise which option is best for the 2003 voting requirement.

 

It is not clear as how 2003 voting requirement comes up in SIL#1 application. Guess, you have considered a pessimistic failure rate of sensing device (applicable FMEDA report/Prior Use guideline) and also a very high proof test interval.

Even the architectural constraint do not demand second order hardware redundancy in SIL#1 application as long as device SFF is better that 60%.

Safety engineering require elimination of common mode failure (beta). Hence the tapping should be separate for each transmitter may be through 3"/2" stand pipe (depending on nature of service), though your SIL#1 compliance requirement may not demand so.

Regards.
Abhijit Goswami

 

Firstly 2003 seems excessive for a Sil 1 system and most modern Level instruments would be compliant as a single installation. however for a 2003 installation is generally used for Sil 3.

You basically need to install 3 means of level measurement. they could be the same make and model and utilise any 2 signals from the 3 inputs to activate the shutdown. they do need to be on different tappings as you are simply increasing the measurement at that point.

If you measure at different points you are not truly using 2003 technology as you then have 1001 at each measurement point.