APPENDIX D — EN 13849 COMPLIANCE
Curtis Model 1351 – December 2018
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pg. 136
APPENDIX D — EN 13849 COMPLIANCE
Conformance to the European Machinery Directive requires that the Safety Related Parts of the Control
System (SRPCS) be designed and veried upon the general principles outlined in EN13849. is standard
determines the safety Performance Level (PL) as a function of Designated Architecture, Mean Time To
Dangerous Failure (MTTFd), Common Cause Faults (CCF), and Diagnostic Coverage (DC). ese gures
are used by the OEM to calculate the overall PL for each of the safety functions of their vehicle or machine.
e OEM must determine the hazards that are applicable to their vehicle design, operation, and
environment. Standards such as EN13849-1 provide guidelines that must be followed in order to
achieve compliance. Some industries have developed further standards (called type-C standards)
that refer to EN13849 and specically outline the path to regulatory compliance. As an example,
EN1175-1 is a type-C standard for battery-powered industrial trucks. Following a type-C standard
provides a presumption of conformity to the Machinery Directive.
e 1351, being a system controller, is designed to have extensive and custom VCL programming
running major functions of the application. Many applications will involve motions or other
hazardous situations. ese hazards must be mitigated by VCL programming and are not inherent
functions of the 1351. What the 1351 does provide is a secure and safe platform to develop these
applications. e 1351 includes the Operational Integrity Safety Function that ensures that the basic
inputs and outputs are operating within design limits, that the internal logic functions are operating
correctly, and that all memory locations are secure and contain valid data.
Curtis has analyzed each circuit of the safety function and calculated its Mean Time To Dangerous Failure
(MTTFd) and Diagnostic Coverage (DC), and designed them against Common Cause Faults (CCF).
e safety-related performance of the 1351 controller, wired per the example diagram, is summarized below:
Safety Function PL
Designated
Architecture
MTTFd
Diagnostic
Coverage
Operational Integrity
Per the example wiring diagram (Figure 4)
C 2 31 yrs 91%
Annex K from EN13849 is used to determine the resultant PL
e following table lists the Included I/O and circuits blocks used in the above analysis
Components Qty
Analog Input 1
RTD Input 3
Switch Input** 5
Pot Wiper Input 1
CAN Bus 1
Accelerometer 1
Encoder 1
Voltage Clamp of Inputs 1
Logic 1
Digital Driver 1
Half Bridge Driver 2
PV Driver 5
**Assumes VCL is written to check the proper sequencing and plausibility for the operator controls.
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