Compare SILcet with exSILentia

To perform the SIL verification in process industry, according to IEC 61508 and IEC 61511, there are several software tools such as “exSILentia” by Exida, our SILcet software and others.

In the process industry “exSILentia” is, without a doubt, the reference software with great international recognition. It is a great suite of applications, including “SILver” (SIL verification), which is the tool we want to compare with SILcet (SIL Calculation Excel Tool).

Each tool has its advantages and disadvantages. The user must analyze in each case which one best suits their needs. The decision should not be based on the results of the calculations but on other criteria, because, as we will see in the examples at the end, the calculated values of PFDavg, RRF and MTTFS are very similar with either of the two tools.

Let us briefly see what, in our opinion, are the main differences between SILcet 6 and the standard exSILentia package.

Advantages of exSILentia online version (SILver)

• It works on both Windows and Mac, the calculation engine is in the cloud (Exida server) which has advantages and disadvantages (SILcet needs Windows and Excel, to use it on a Mac you have to do it in a Virtual Machine).
• Integrates other applications (SRS, LOPA, SILect).
• Integrated database of more than 200 manufacturers with the data used in the calculations (failure rates, etc.). SILcet allows the user to create their own database with the SIF elements used in the project.
• Generates reports in Word format (SILcet generates reports in Excel format exportable to PDF).
• The user interface is better (SILcet is an Excel file so the interface development possibilities are more limited).

Advantages of SILcet 6

• It is an Excel based application with macros whose advantage is the flexibility it provides.
• The license price for 12 months is much lower (the price of the full version of SILcet is 375 EUR, almost 20 times less than exSILentia Standard suite).
• No internet connection required (Excel files and data are on the user’s PC). We have noticed that exSILentia slows down when many SIFs are used because the calculations are performed on the Exida server. There is also the “stand-alone” version of exSILentia whose price is not published on its website.
• SILcet incorporates several options to compare different designs of the same SIF.
• The report generation is more flexible with SILcet. There are 4 sheets for reports with different contents. In addition, with the new “SRS_Tool” the user can customize his/her own reports.
• SILcet allows to select a different Route (1H/2H/IEC61511) for each element of the SIF.
• When the license expires you can open SILcet and view the content (in exSILentia this is not possible).

In the following two tables we show calculation results of several examples performed with both tools. We observe that they are very similar.

In both cases it is necessary that the user has knowledge of Functional Safety in order to enter the data correctly. Both tools are very mature and have been well tested.

For the calculations we have considered elements of prestigious manufacturers.

–SENSOR subsystem: transmitter, interface, process connection (“clean service”).
–LOGIC SOLVER: generic Safety PLC.
–ACTUATOR subsystem: ball valve, spring actuator, solenoid, relay.

To know more you can download this technical paper.