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Safety Evaluation Tool

Interpretation of Safety SIL level

Thread Starter: Safety-Man   Started: 2/5/2010 1:56 PM   Replies: 2

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  2/5/2010, 1:56 PM
Safety-Man
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Hi,

I was calculating the SIL according IEC 62061 standard for a system, composed by:

2 x failsafe Position Switches 3SE5
1x PLC S7-315F2DP
1x Fail-safe Module 4/8 F-DI - ET200S
1x Sinamics G120 with CU240 DP-F

Using the safety Evaluation Tool I got  a PFHD total of 7.59 E-08, however the Safety Evaluation tool give me a SIL 2, when according IEC 62061 SIL 3 is (>/=1.00E-08 to <1.00E-07).  

Someone told me that happens because of Sinamics G120 only has an approval for SIL2. Shouldn't the global value (which is inside SIL 3) prevail? Why don't happens?

Which measure I should take to increase the SIL level for SIL3 - We need SIL 3! 

Attachment: iec62061pdf.pdf  (56 Downloads)
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  2/5/2010, 3:14 PM
Safety1
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Hi Safety-Man,

You have run into something that cannot be changed. Within the 62061 is something called the SILCL "SIL Claim". All the devices within a SF "Safety Function" must have a SILCL the same as or better than the SILreq "SIL Requested". The G120 has a SILCL of 2 therefore the entire SF is SIL2.

Once a device has a SILCL it cannot be changed and therefore to reach SIL3 you will need two contactors. Siemens may ask the TUV to certify specific applications to increase the SILCL under specific conditions/parts. Ask the Siemens G120 hotline as they may some info on this.
I hope this helps

Best Regards
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  3/2/2010, 11:13 AM
SET-Team
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Hello,

a solution to reach PLe/SIL3 with S120/G120 is in progress. 
As soon as it is available, we'll publish it in the SET Forum.

Best regards

SET Team 
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