1

Revision Control ................................................................................................................................ 3

2

Safety Instrumented System ............................................................................................................. 4

2.1

Introduction .................................................................................................................................. 4

2.2

Functional Description ................................................................................................................. 4

2.3

Reference Documentation........................................................................................................... 5

3

Risk Analysis & Allocation of Safety Functions ................................................................................. 6

3.1

Risk Assessment ......................................................................................................................... 6

3.2

Security Risk Assessment ........................................................................................................... 6

3.3

Allocation of Safety Functions ..................................................................................................... 7

4

SIL Design & Verification Considerations ......................................................................................... 8

4.1

Random Hardware Failure Rate.................................................................................................. 8

4.1.1

IEC 61508 SIL Certificated Devices ................................................................................... 8

4.1.2

Mean Time Between Failures (MTBF)................................................................................ 8

4.1.3

In Service Failure Data ....................................................................................................... 8

4.2

SIS Subsystem Requirements..................................................................................................... 9

4.2.1

Sensor(s)................................................................................................................................. 9

4.2.2

Logic Solver........................................................................................................................... 10

4.2.3

Final Element(s) .................................................................................................................... 11

4.3

SIS General Requirements........................................................................................................ 12

4.3.1

General ............................................................................................................................. 12

4.3.2

Process Safety Time......................................................................................................... 13

4.3.3

Safety Manuals, Maintenance, Operation & Proof Testing............................................... 14

5

Certified PFD – In service adjustment............................................................................................. 15

5.1 Process and Environmental Impact .............................................................................................. 15

5.2 PFD adjustment ............................................................................................................................ 16

6

Competence .................................................................................................................................... 17

7

System Model.................................................................................................................................. 18