
CONTENTS
2
www.drexelbrook.comDRx400-x500-PM - English – SIL2/3 06-29-21 – Issue 2
DRX400 / X500
1 Introduction 4
1.1 Scope of the document..................................................................................................... 4
1.2 Revision history ................................................................................................................ 4
1.3 Type code for devices that can operate in SIL mode ....................................................... 5
1.4 Device description ............................................................................................................ 6
1.5 Related documentation .................................................................................................... 7
1.6 Terms and definitions....................................................................................................... 7
2 Specification of the safety function 9
2.1 Preconditions.................................................................................................................... 9
2.2 Definition of the safety function ....................................................................................... 9
2.2.1 General notes.......................................................................................................................... 9
2.2.2 Current output ...................................................................................................................... 10
2.2.3 Fault response time.............................................................................................................. 11
2.3 Safety application conditions (SAC)................................................................................ 12
2.3.1 General.................................................................................................................................. 12
2.3.2 Installation ............................................................................................................................ 12
2.3.3 Electrical connection ............................................................................................................ 13
2.3.4 Functionally safe configuration ............................................................................................ 13
2.4 Operation modes ............................................................................................................ 14
2.4.1 SIL mode ............................................................................................................................... 14
2.4.2 Non-SIL mode ....................................................................................................................... 14
2.4.3 Maintenance mode................................................................................................................ 14
3 Operation 15
3.1 Operation in SIL mode.................................................................................................... 15
3.1.1 General notes........................................................................................................................ 15
3.1.2 Device configuration for operation in SIL mode................................................................... 15
3.2 How to change the configuration of a device operated in SIL mode ............................. 18
3.2.1 General notes........................................................................................................................ 18
3.2.2 How to change device operation from SIL mode to non-SIL mode ..................................... 18
3.3 Error conditions.............................................................................................................. 19
3.4 Parameter types............................................................................................................. 20
3.4.1 Safety-critical parameters.................................................................................................... 20
3.4.2 Safety-relevant parameters ................................................................................................. 20
3.4.3 Non-SIL parameters............................................................................................................. 21
3.4.4 Limits for parameters related to tank configuration ........................................................... 21
3.5 Homogeneous redundancy............................................................................................. 22
3.5.1 Description of a homogeneously redundant system............................................................ 22
3.5.2 How to estimate the effect of common cause failures ........................................................ 23
4 Service 24
4.1 Maintenance ................................................................................................................... 24
4.2 Availability of services .................................................................................................... 24