The primary attributes of this new B11.26 standard are the detailed schematic diagrams, the “Circuit Analysis Tables,” and the detailed annexes for understanding performance levels and category block diagrams as outlined in ISO 13849-1. The intent is to clarify and provide direction for functional safety applications in current and future equipment installations. These detailed generic (non vendor-specific) schematic diagrams are based on actual applications that have been successfully implemented in commerce.

Table of Contents

Foreword  (Not a normative part of ANSI B11.26-2018)
Introduction & Overview of the ANSI B11 Series of Machinery Safety Standards
1 Scope
2 References
2.1 Normative References
2.2 Informative References
3 Definitions
4 How to use ANSI B11.26
4.1 Circuit Examples and Analysis Tables
5 Preparations for Functional Safety Design
5.1 Conduct a Risk Assessment (per ANSI B11.0)
5.2 Identify Risk Reduction Measures that Involve the SRP/CS
5.3 Define the Safety Function
5.4 Determine the Reliability Design Specification for Each Circuit
5.4.1 Performance Level (PL) Methodology (ISO 13849-1)
5.4.1.1 Architecture
5.4.1.2 Select Components
5.4.1.3 Fault considerations
5.4.1.4 Diagnostic Coverage (DC)
5.4.1.5 Common Cause Failure (CCF)
5.4.1.6 Calculating a PL
5.4.2 Category methodology (ISO 13849-1 and EN 954)
5.4.2.1 Architecture
5.4.2.2 Summary of ISO 13849-1 Categories
5.4.3 Control reliable methodology (ANSI B11)
5.5 Define Basic Input, Logic and Output Elements Required
5.5.1 Inputs
5.5.2 Logic
5.5.3 Outputs
6 General Design Requirements
6.1 Integration of SRP/CS in the Overall Machine Controls
6.1.1 Typical Non-Safety Control Components Augmented by SRP/CS Components to Achieve Safety-Related Functions
6.2 Specific Functions
6.2.1 Protective Stop
6.2.2 Start Function
6.3 Electrical Design Requirements
6.3.1 Opening of Circuits for Time Dependent Functions
6.3.2 Positive/Negative Logic
6.3.3 Interfacing SRP/CS with Non-Safety PES/PLC
6.3.4 Electro-Mechanical Contact Requirements
6.4 Fluid Power (Pneumatics and Hydraulics) Design Requirements
6.4.1 Protective Stops in Fluid Power Systems
6.4.2 Reset Function of Safety Valves
6.4.3 Reapplication of Pressure
6.4.4 Fluid Power Valve Crossover
7 Fault Consideration
7.1 Fault Exclusion
7.2 Electrical Failure Modes
7.2.1 General Failure Modes
7.3 Fluid Power Failure Modes
7.3.1 General Failure Modes
7.3.2 Pneumatic Failure Modes
7.3.3 Hydraulic Failure Modes
8 Monitoring / Diagnostic Coverage
8.1 Electrical Monitoring / Diagnostic Coverage Methods
8.1.1 Input Masking on Series Connected Devices
8.2 Fluid Power Monitoring / Diagnostic Coverage Methods
9 Design Requirements - Input Devices (Engineering Control - Devices)
9.1 Emergency Stop Devices
9.1.1 Design Requirements
9.1.2 Design Considerations
9.1.2.1 Tampering/ Defeat
9.1.2.2 Failure Modes
9.1.3 Application Examples
9.1.3.1 Single Channel E-stop Using a Control Relay (Category 1)
9.1.3.2 Low/ Intermediate Risk Reduction (Category 2)
9.1.3.3 Intermediate / High Risk Reduction (Category 3)
9.1.3.4 Highest risk reduction (Category 4)
9.2 Mechanical (Contacting) Guard Interlocking Devices
9.2.1 Design Requirements
9.2.2 Design Considerations
9.2.2.1 General Information
9.2.3 Application Examples
9.2.3.1 Basic Circuit (Category B)
9.2.3.2 Lowest Risk Reduction (Category 1)
9.2.3.3 Low/ Intermediate Risk Reduction (Category 2)
9.2.3.4 Intermediate / High Risk Reduction (Category 3)
9.2.3.5 Highest Risk Reduction (Category 4)
9.3 Non-Contact Guard Interlocking Devices
9.3.1 Design Requirements
9.3.2 Design Considerations
9.3.3 Application Examples
9.3.3.1 General information
9.3.3.2 Basic Risk Reduction (Category B)
9.3.3.3 Low/ Intermediate Risk Reduction (Category 2)
9.3.3.4 Intermediate/ High Risk Reduction (Category 3)
9.3.3.5 Highest Risk Reduction (Category 4)
9.4 Guard Locking Interlocks
9.4.1 Design Requirements
9.4.2 Design Considerations
9.4.3 Application Examples
9.4.3.1 General Information
9.4.3.2 Low/ Intermediate Risk Reduction (Category 2)
9.4.3.3 Intermediate/ High Risk Reduction (Category 3)
9.4.3.4 Highest Risk Reduction (Category 4)
9.5 Optical Presence Sensing Devices
9.5.1 Design Requirements
9.5.2 Design Considerations
9.5.2.1 General Information
9.5.2.2 Safety Light Curtains
9.5.2.3 Single/Multiple Safety Beam Devices (Point or Grid Devices)
9.5.2.4 Scanners
9.5.3 Application Examples
9.5.3.1 Lowest Risk Reduction (Category 1)
9.5.3.2 Low/ Intermediate Risk Reduction (Category 2)
9.5.3.3 Intermediate/ High Risk Reduction (Category 3)
9.5.3.4 Highest Risk Reduction (Category 4)
9.6 Safety Mats / Edges
9.6.1 Design Requirements
9.6.2 Design Considerations
9.6.3 Application Examples
9.6.3.1 Low/ Intermediate Risk Reduction (Category 2)
9.6.3.2 Intermediate / High Risk Reduction (Category 3)
9.7 Two-Hand Control
9.7.1 Design Requirements
9.7.2 Design Considerations
9.7.2.1 General Information
9.7.2.2 Tampering/ Defeat
9.7.2.3 Failure Modes
9.7.3 Application Examples
9.7.3.1 Lowest Risk Reduction Two Hand Control (Type Illa Category 1)
9.7.3.2 Intermediate/ High Risk Reduction Two-Hand Control (Type lllb Category 3)
9.7.3.3 Intermediate/ High Risk Reduction Two-Hand Control {Type lllb Category 3)
9.7.3.4 Highest Risk Reduction Two-Hand Control (Type Ille Category 4).
9.8 Speed Detection
9.8.1 Design Requirements
9.8.2 General Information and Design Considerations
Common means of determining speed are given below
9.8.2.1 Back EMF Sensing
9.8.2.2 Encoder Sensing
9.8.2.3 Proximity Switch Sensing
9.8.2.4 Tampering/ Defeat
9.8.2.5 Failure Modes
9.8.3 Application Examples
9.8.3.1 Lowest Risk Reduction (Category 1)
9.8.3.2 Intermediate/ High Risk Reduction (Category 3)
9.9 Enabling Devices
9.9.1 Design Requirements
9.9.2 Design Considerations
9.9.2.1 Tampering/ Defeat
9.9.2.2 Failure Modes
9.9.3 Application Examples
9.9.3.1 Low/ Intermediate Risk Reduction (Category 2)
9.9.3.2 Intermediate/ High Risk Reduction (Category 3)
9.9.3.3 Enabling Device with Manual/Auto Switch (Category 3)
9.9.3.4 Highest Risk Reduction (Category 4)
10 Design Requirements - Logic Devices
10.1 General
10.1.1 Design Requirements
10.1.2 Design Considerations
10.1.2.1 Safety Interface Module General Information
10.1.2.2 Tampering / Defeat
10.1.2.3 Failure Modes
10.1.2.4 Reset Function of the Safety Circuit
10.1.3 Application Examples
11 Design Requirements - Output Devices (MPCE)
11.1 Relays and Contactors
11.1.1 Design Requirements
11.1.2 Design Considerations
11.1.2.1 Tampering/Defeat
11.1.2.2 Failure Modes
11.1.3 Application Examples
11.1.3.1 Lowest Risk Reduction (Category 1)
11.1.3.2 Low/ Intermediate Risk Reduction (Category 2)
11.1.3.3 Intermediate/ High Risk Reduction (Category 3)
11.1.3.4 Highest Risk Reduction (Category 4)
11.2 Power Drive Systems for Safe Torque Off
11.2.1 Design Requirements
11.2.2 Design Considerations
11.2.2.1 General Information
11.2.3 Application Examples
1.1.2.3.1   Lowest Risk Reduction (Category 1)
11.2.3.2 Intermediate/ High Risk Reduction (Category 3)
11.2.3.3 Highest Risk Reduction (Category 4)
11.3 Pneumatic Systems
11.3.1 Design Requirements
11.3.2 Design Considerations
11.3.3 Application Examples
11.3.3.1 Supply Circuit
11.3.3.2 Exhaust (Blocking, Dump) Valve
11.3.3.3 Directional Valve Selection
11.3.3.4 Spring Return Blocking and Pilot Operated Check Valves
11.3.3.5 Flow Controls
11.3.3.6 Rod Locks and Brakes
11.3.3.7 Velocity Fuse
11.4 Hydraulic Systems
11.4.1 Design Requirements
11.4.2 Design Considerations
11.4.3 Application Examples
11.4.3.1 Dump and Blocking fluid to the hazardous motion
11.4.3.2 Directional Valve Selection
11.4.3.3 Spring Return Blocking and Pilot Operated Check Valves
11.4.3.4 Counter Balance Valves
11.4.3.5 Flow Controls
11.4.3.6 Rod Locks and Rod Brakes
11.5 Velocity Fuse
12 Validation
Annex A - Symbols
Annex B - Performance Levels and Safety-Related Block Diagrams
Annex C - Categories and How to Make a Selection
Annex D - Section 1: Mean Time to Failure, Dangerous (MTTFo)
Annex D - Section 2: Diagnostic Coverage
Annex D - Section 3:  Estimating the Common Cause Failure (CCF)
Annex E – Calculation Aids for Determination of SRP/CS PFHo & PL
Annex F - Analysis of Circuit Considerations
Annex G - Failures, Systemic
Annex H - General Overview of Valves
Annex I -   Performance of the Safety-Related Function(s) (Overview)
Annex J - Safety-Related Performance
Annex K - External Device Monitoring by the Safety-Related Function
Annex L - Validation Tools for Mechanical Systems
Annex M -Validation Tools for Pneumatic Systems
Annex N - Validation Tools for Hydraulic Systems
Annex O -Validation Tools for Electrical Systems

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