Introduction to Machine Risk Assessment and Functional Specification Development
Upcoming SlideShare
Loading in...5
×
 

Introduction to Machine Risk Assessment and Functional Specification Development

on

  • 119 views

Machine risk assessment provides the framework for existing machinery and new machine designs. By properly identifying hazards and risk associated with machine interaction, you can apply more ...

Machine risk assessment provides the framework for existing machinery and new machine designs. By properly identifying hazards and risk associated with machine interaction, you can apply more effective and suitable methods of safeguarding measures that are conformant with today’s global machine safety standards and regulations. This session will showcase the process of performing a machine risk assessment process, including its place in the safety life cycle and use of available tools to expedite and document the process. We recommend attending SF01-Safety System Development Process and Configuration Tools Overview prior to this session.

Statistics

Views

Total Views
119
Views on SlideShare
119
Embed Views
0

Actions

Likes
0
Downloads
14
Comments
0

0 Embeds 0

No embeds

Accessibility

Categories

Upload Details

Uploaded via as Adobe PDF

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

Introduction to Machine Risk Assessment and Functional Specification Development Introduction to Machine Risk Assessment and Functional Specification Development Presentation Transcript

  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. PUBLIC INFORMATION SF02 - Introduction to Machine Risk Assessment and Functional Specification Development
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 2 The Machine Safety Lifecycle STEP 5 MAINTAIN & IMPROVE SAFETY SYSTEM STEP 1 RISK OR HAZARD ASSESSMENT STEP 4 SAFETY SYSTEM INSTALLATION & VALIDATION STEP 3 SAFETY SYSTEM DESIGN & VERIFICATION STEP 2 SAFETY SYSTEM FUNCTIONAL REQUIREMENTS Safety Life Cycle
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. The Purpose of Risk Assessment  Properly identifies and assesses the real hazards involved in operating a particular machine.  Determines equivalent levels of protection for safeguards when stating OSHA’s minor service exception.  Takes away guesswork when estimating risk and prescribing safety system performance.  Serves as documented proof of your ―due diligence‖.  Establishes the foundation for the design and implementation of an effective machine safety program. 3 The risk assessment process:
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 6 As Referenced in U.S. Standards Risk assessment is often referenced throughout mainstream U.S. machinery safety standards: ANSI ASSE Z244.1
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 7 As Referenced in U.S. Standards Risk assessment is often referenced throughout mainstream U.S. machinery safety standards: ANSI B11.19
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 8 As Referenced in U.S. Standards Risk assessment is often referenced throughout mainstream U.S. machinery safety standards: ANSI / RIA R15.06
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 9 As Referenced in U.S. Standards Risk assessment is often referenced throughout mainstream U.S. machinery safety standards: NFPA 79
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 10 In Europe Risk assessment is a requirement for machinery directive compliance (2006/42/EC). Applies to those delivering CE compliant machinery to Europe.
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 11 Getting Started It is quite common for any group, whether it be a new equipment OEM or a facility End-user, to have a multitude of questions and concerns when starting at the beginning of the machine safety system lifecycle.  What does the word safety really mean, and how is it achieved?  What is risk? How is it measured?  Do I need a PHD in mathematics to analyze probability and risk?  How safe do I need to make this machine?  How do I go about identifying hazards? The risk assessment process answers most of these questions for us!
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Before we can understand what exactly we achieve through risk assessment, it will be important to provide an answer for the first few questions.  What does the word safety really mean, and how is it achieved?  Safety, with respect to machinery operation is defined in IEC 62061:2005 as:  This immediately gives us a definition for safety in terms of risk, so it now starts to become more clear how risk assessment plays a part in achieving safety! …Safety is freedom from unacceptable risk 12 What is “safety” exactly?
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 13 What is risk? Now we must define risk? Under the same standard, risk can be defined as: Risk is the combination of the Severity of harm, and the probability of occurrence of that harm (Frequency of exposure + Avoidability). What severity of harm would come to the skydiver if his parachute did not open? + What is the probability that the parachute(s) will not open and the skydiver will experience this harm? Probability factors might be: How frequent does the person skydive? + If the parachute(s) do not open, is the skydiver able to avoid or limit the harm from the fall?
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 14 Defined Risk Scale  If we can then define risk in terms of parameters that can be easily selected and summed together, then we will have a simple method for estimating risk relative to machine hazards.  Risk assessment methodologies provided in machine standards provide this method through risk graphs and matrices, as we will see later. Risk = Severity of Harm + Probability of Occurrence of Harm Negligible Low Medium High
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Acceptable Risk 15 Acceptable risk may differ from organization to organization, and therefore this value is not purely defined in any standard or methodology. The important thing is that your organization (and the risk assessment team) determine this threshold prior to starting the risk assessment. Since safety is freedom from unacceptable risk, we will need to establish a value on our range that determines a threshold between acceptable, and unacceptable. Various standards will provide guidance on how to determine when acceptable risk has been achieved. Negligible Low Medium High Acceptable Risk
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 16 How Standards Help With Risk Assessment What is the risk associated with this task? RISK RATING CRITERIA
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 17 How Standards Help With Risk Assessment What should I do to reduce risk? SAFE GUARD SELECTION
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 18 How Standards Help With Risk Assessment What level of performance is required? CIRCUIT PERFORMANCE CRITERIA
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. What is the risk associated with this task? 19 How Standards Help With Risk Assessment What level of performance is required? CIRCUIT PERFORMANCE CRITERIA RISK RATING CRITERIA What should I do to reduce risk? SAFE GUARD SELECTION Different terms, same methodology and purpose
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. What is a Risk Assessment? 20 ANSI B11.0
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Fundamental Process Risk Evaluation Risk Reduction Risk Reduction Complete for particular hazard OK Unacceptable Risk Estimation Next hazard Hazard Identification Define all known machine characteristics and limits
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Assessment Tool / Worksheet A typical risk assessment worksheet will allow each item of data that will be collected and/or determined to be recorded:
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Fundamental Process Risk Evaluation Risk Reduction Risk Reduction Complete for particular hazard OK Unacceptable Risk Estimation Next hazard Hazard Identification Define all known machine characteristics and limits
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Hazard Identification  The first pass of hazard identification is performed on the machine while ignoring all current safeguards that may be in place  All risks must be identified and estimated  It needs to be determined whether or not the existing safeguard and it’s performance are applicable and appropriate for the level of risk  All tasks are broken down into individual steps  Allows each step to be assessed more thoroughly for exposure to hazards  Provides a flow and outline for the risk assessment process
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. With a task and hazard identified, we enter this data into our worksheet Assessment Tool / Worksheet Hazard Type Hazard Description: May include Event or Failure mode, hazardous energy source Reference to supporting photo / drawing
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Pallet Nailing Example 30
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Pallet Nailing Example Tasks – What did you see?  What was the operator doing?  What were the steps the operator had to go through to accomplish the task?  Unseen tasks… What if everything didn’t go perfectly? Break tasks into manageable chunks  Did you observe normal operation? Maintenance tasks? Other?  Let’s look at normal operation, loading raw materials
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Assume No Guards Present! 32
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Pallet Nailing - Hazard Identification What hazard(s) does the operator encounter while loading raw materials?  What is the potential hazard?  Event or failure that leads to exposure?  Hazardous energy sources? What if…  The robot traveled outside of the area intended?  The operator dropped a piece of wood?  The fixture started rotating while the operator was still working?
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 34 Pallet Nailing - Hazard Identification
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Pallet Nailing - Hazard Identification Unexpected start of fixture start while loading raw materials.  What is the potential hazard?  Event or failure that leads to exposure?  Hazardous energy sources?  Impact by rotating pallet fixture  Operator doesn’t finish task on time  Error - start command issued by control system  Electric motor  More detail is good! ―Fixture Turret Motor‖, ―Motor 117‖  Drive? Contactor? HP?
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Pallet Nailing - Hazard Identification Task: Normal Operation Step: Load raw materials into fixture Affected personnel: Operators Hazard: Impact by rotating table due to unexpected start Hazardous energy source: ―Fixture Motor‖, 2HP, 480VAC
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Fundamental Process Risk Evaluation Risk Reduction Risk Reduction Complete for particular hazard OK Unacceptable Risk Estimation Next hazard Hazard Identification Define all known machine characteristics and limits
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Risk Graphs/Matrix/Chart Depending on our objectives, we can use various other methods. We should consider that one objective is to define our safety performance, and that our process must provide a method for doing so…..
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Risk Estimation - HRN Two fundamental questions:  If something happens, how bad will it be? (Severity)  What are the chances it will happen? (Probability)  What is the Degree of Possible Harm (DPH)?  What is the Frequency of Exposure (FE)?  What is the Likelihood of Occurrence (LO)?  What is the Number of Persons at Risk (NP)? HRN = DPH x FE x LO x NP
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Pallet Nailing – Risk Estimation Task: Normal Operation Step: Load raw materials into fixture Affected personnel: Operators Hazard: Impact by rotating table due to unexpected start Degree of Possible Harm (DPH) Value Fatality 15 Amputation of two limbs,eyes or total loss of hearing or sight 10 Amputation of a limb, one eye or partial hearing loss 6 Fracture: major bone or major illness (temporary) 4 Fracture: minor bone or minor illness (temporary) 2 Burn, cut, short illness 0.5 Scratch / Bruise 0.1
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Frequency of Exposure (FE) Value Constantly 5 Hourly 4 Daily 2.5 Weekly 1.5 Monthly 1 Annually 0.5 Pallet Nailing – Risk Estimation Task: Normal Operation Step: Load raw materials into fixture Affected personnel: Operators Hazard: Impact by rotating table due to unexpected start
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Likelihood of Occurrence (LO) Value Certain – No doubt 15 Probable – Can be expected 10 Probable – Not surprising 8 Although improbable, it may happen 5 Possible, but unusual 2 Improbable, but still possible 1.5 Highly improbable, but still possible 1 Little/low possibility, extreme circumstances 0.033 Pallet Nailing – Risk Estimation Task: Normal Operation Step: Load raw materials into fixture Affected personnel: Operators Hazard: Impact by rotating table due to unexpected start
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Number of Persons at Risk (NP) Value More than 50 persons 12 16 - 50 persons 8 8 - 15 persons 4 3 - 7 persons 2 1- 2 persons 1 Pallet Nailing – Risk Estimation Task: Normal Operation Step: Load raw materials into fixture Affected personnel: Operators Hazard: Impact by rotating table due to unexpected start
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Pallet Nailing – Risk Estimation Task: Normal Operation Step: Load raw materials into fixture Affected personnel: Operators Hazard: Impact by rotating table due to unexpected start Degree of Possible Harm (DPH) Fracture: major bone or major illness (temporary) 4 Frequency of Exposure (FE) Constantly 5 Likelihood of Occurrence (LO) Probable – Not surprising 8 Number of Persons at Risk (NP) 1- 2 persons 1 HRN = DPH x FE x LO x NP 160
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. We now enter the risk estimation parameter selections into our worksheet Pallet Nailing – Risk Estimation Risk Parameters: NP, FE, LO, DPH
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Fundamental Process Risk Evaluation Risk Reduction Risk Reduction Complete for particular hazard OK Unacceptable Risk Estimation Next hazard Hazard Identification Define all known machine characteristics and limits
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Pallet Nailing – Risk Evaluation We have measured the initial risk, is it acceptable?
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Pallet Nailing – Risk Evaluation Task: Normal Operation Step: Load raw materials into fixture Affected personnel: Operators Hazard: Impact by rotating table due to unexpected start: HRN = 160 HRN Risk Comment 0-5 Negligible Risk Presents very little risk to health and safety. The residual risks are to be controlled by awareness training and in some cases by warning signs. 5 – 50 Low but significant risk These are risks that need to be reduced by applying suitable control measures but are not considered urgent 50 - 500 High risk Having potentially dangerous hazards, which require control measures to be implemented urgently Above 500 Unacceptable Risk These hazards are extreme and the equipment should not be operated until the level has been reduced.
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Fundamental Process Risk Evaluation Risk Reduction Risk Reduction Complete for particular hazard OK Unacceptable Risk Estimation Next hazard Hazard Identification Define all known machine characteristics and limits
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. HRN Risk Safeguard Performance Above 500 Unacceptable Risk Hazard elimination 0-5 Negligible Risk Awareness means(8) a 5 – 50 Low but significant risk Non-interlocked barriers, clearance, Performance Level ISO 13849-1 2006 e / d d d / c c b b 50 - 500 High risk Engineering controls Pallet Nailing – Risk Reduction Task: Normal Operation Step: Load raw materials into fixture Affected personnel: Operators Hazard: Impact by rotating table due to unexpected start: HRN = 160 Adapted from ANSI B11.0 Table D-4
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. HRN Risk Safeguard Performance Above 500 Unacceptable Risk Hazard elimination 0-5 Negligible Risk Awareness means(8) a 5 – 50 Low but significant risk Non-interlocked barriers, clearance, Performance Level ISO 13849-1 2006 e / d d d / c c b b 50 - 500 High risk Engineering controls Pallet Nailing – Risk Reduction Our risk measurement correlates with a Performance Level d circuit, so our next step is to implement a PLd circuit, right? Adapted from ANSI B11.0 Table D-4 WRONG!(but this is a good thing!)
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. What will we do? Design it out Fixed enclosing guard Monitoring Access / Interlocked Gates Awareness Means, Training and Procedures (Administrative) Personal protective equipment Most Effective Least Effective Hierarchy of Protective Measures
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. What will we do? Design it out Materials Fixture Completed Pallets Rack Robot Operator Automate? What Else?
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. What will we do? Fixed enclosing guard Monitoring Access / Interlocked Gates Materials Fixture Completed Pallets Rack Robot Fixed Guard? Interlocking Guard?
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. What will we do? Fixed enclosing guard Monitoring Access / Interlocked Gates Materials Fixture Completed Pallets Rack Robot Light Curtain? Scanner / Mat?
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. What will we do? Awareness Means, Training and Procedures (Administrative) Personal protective equipment Materials Fixture Completed Pallets Rack Robot
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Safeguarding Concept 62 Application requirements:  Single zone with simple control scheme  Allow free operator access  Category 3 / PLd required  Leave existing motor / drive combo in place Our conceptual design is a safety scanner that shuts down the fixture motor
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Risk Reduction 63
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Fundamental Process Risk Evaluation Risk Reduction Risk Reduction Complete for particular hazard OK Unacceptable Risk Estimation The process of risk reduction may have to be implemented several times before the risk is mitigated to an acceptable value
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Pallet Nailing – Risk Estimation Task: Normal Operation Step: Load raw materials into fixture Affected personnel: Operators Hazard: Impact by rotating table due to unexpected start Safeguard: Approaching fixture causes fixture to stop Degree of Possible Harm (DPH) Value Fatality 15 Amputation of two limbs,eyes or total loss of hearing or sight 10 Amputation of a limb, one eye or partial hearing loss 6 Fracture: major bone or major illness (temporary) 4 Fracture: minor bone or minor illness (temporary) 2 Burn, cut, short illness 0.5 Scratch / Bruise 0.1
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Frequency of Exposure (FE) Value Constantly 5 Hourly 4 Daily 2.5 Weekly 1.5 Monthly 1 Annually 0.5 Pallet Nailing – Risk Estimation Task: Normal Operation Step: Load raw materials into fixture Affected personnel: Operators Hazard: Impact by rotating table due to unexpected start Safeguard: Approaching fixture causes fixture to stop
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Likelihood of Occurrence (LO) Value Certain – No doubt 15 Probable – Can be expected 10 Probable – Not surprising 8 Although improbable, it may happen 5 Possible, but unusual 2 Improbable, but still possible 1.5 Highly improbable, but still possible 1 Little/low possibility, extreme circumstances 0.033 Pallet Nailing – Risk Estimation Task: Normal Operation Step: Load raw materials into fixture Affected personnel: Operators Hazard: Impact by rotating table due to unexpected start Safeguard: Approaching fixture causes fixture to stop
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Number of Persons at Risk (NP) Value More than 50 persons 12 16 - 50 persons 8 8 - 15 persons 4 3 - 7 persons 2 1- 2 persons 1 Pallet Nailing – Risk Estimation Task: Normal Operation Step: Load raw materials into fixture Affected personnel: Operators Hazard: Impact by rotating table due to unexpected start Safeguard: Approaching fixture causes fixture to stop
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Pallet Nailing – With Safeguard In Place Task: Normal Operation Step: Load raw materials into fixture Affected personnel: Operators Hazard: Impact by rotating table due to unexpected start Degree of Possible Harm (DPH) Scratch / Bruise 0.1 Frequency of Exposure (FE) Constantly 5 Likelihood of Occurrence (LO) Little/low possibility, extreme circumstances 0.033 Number of Persons at Risk (NP) 1- 2 persons 1 HRN = DPH x FE x LO x NP 0.02
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Residual Risk Rating 70
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Risk Assessment Documentation Risk assessment documentation should contain the following information: Information relevant for the machinery being assessed (machine limits, specs) Any relevant operational or design assumptions (loads, strengths, safety factors) Identified hazard scenarios The information on which the risk assessment was based; • The data used and the sources (accident histories, experience through safeguarding similar machinery, etc.) • The uncertainty associated with the data used and its impact on the risk assessment. • Photos, video, and other supporting data. Risk reduction measures assessed and applied in the determination of risk reduction Residual risks associated with the machinery
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 72 Next – Functional Specification STEP 5 MAINTAIN & IMPROVE SAFETY SYSTEM STEP 1 RISK OR HAZARD ASSESSMENT STEP 4 SAFETY SYSTEM INSTALLATION & VALIDATION STEP 3 SAFETY SYSTEM DESIGN & VERIFICATION STEP 2 SAFETY SYSTEM FUNCTIONAL REQUIREMENTS Safety Life Cycle
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Where are we now?  Risk Assessment Complete  Output of the assessment is a CONCEPTUAL Design  Concept should include:  Detail on the task being performed  Risk measurement for the hazard  Potential safeguard (usually the INPUT)  Detail on the hazard (what am I shutting off?)  Requirement for circuit performance (PLr, SIL, Control Reliable)  Next – fashion these details into HOW the system will work
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. How we got to concept 74  Measured risk level for the task  Used the mitigation hierarchy to choose an engineering safeguard and specify a circuit performance requirement to match the risk level
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Safeguarding Concept Application requirements:  Single zone with simple control scheme  Allow free operator access  Category 3 / PLd required  Leave existing motor / drive combo in place Our conceptual design is a safety scanner that shuts down the fixture motor – a Safety Function 75
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Next Step – Safety Function 76  A safety function is a control function that affects safety  Behaves like any other control function, but with higher integrity  Like any control function, has Input, Logic, Output subsystems  ―High integrity‖ implies certain things aside from ―safety rated‖  Source of hazardous energy directly controlled (not removing an enable signal)  Circuit performance maintained through I, L, O subsystems I L O
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Next Step – Safety Function  Safety function protects persons from a specific hazard  In our example, violation of scanned area stops fixture movement  Safety functions can be described with multipart requirements. In our example:  The fixture cannot start turning until the operator is clear  Approaching the fixture will cause the fixture to stop  Backing away will not restart the fixture  The circuit that issues the stop command is required to meet the requirements of PLd / Cat 3 / Control Reliable 77
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 78 Specifying Safety Functions  Functional Safety Specifications outline how a safety system responds to system inputs to control system outputs. Functional safety specifications must at least consider the following: a) results of the risk assessment for each specific hazard or hazardous situation; b) machine operating characteristics, including • intended use of the machine (including reasonable foreseeable misuse), modes of operation (e.g. local mode, automatic mode, modes related to a zone or part of the machine), cycle time, and response time; c) emergency operation; d) description of the interaction of different working processes and manual activities (repairing, setting, cleaning, trouble shooting, etc.); e) the behavior of the machine that a safety function is intended to achieve or to prevent; f) condition(s) (e.g. operating mode) of the machine in which it is to be active or disabled; g) the frequency of operation; h) priority of those functions that can be simultaneously active and that can cause conflicting action.
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 79 Specifying Safety Functions  What is the triggering event?  What is the reaction?  What is the safe state?  What is the behaviour of the system in the presence of faults?  How does normal operation resume?  Standards to meet? Required circuit performance? Other considerations? Interruption of the sensing zone of the SafeZone scanner Contactors (name? size?) opened, energy to motor (name?) removed Electrical energy removed, motor at rest Faults (which ones?) detected before / on demand, energy removed On reset, contactors close / energy restored, motion does not resume Shall be designed and constructed to meet requirements of ISO 13849-1 PLd, Safe distance according to ISO 13855, etc…
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 80 Specifying Safety Functions In all modes of operation, interruption of the configured sensing zone of the Fixture Scanner (SCN_01) laser scanner is sensed by the Fixture Safety Relay (MSR_01) and stops and prevents hazardous motion by opening Fixture Motor Contactors 1 and 2 (K1, K2) removing power to the Fixture Motor. The motor coasts to a stop (Stop Category 0). When the scanner is reset, hazardous motion and power to the motor do not resume until a secondary action occurs—the Start button depressed. A fault at the laser scanner is detected before the next safety demand.. The safe distance from the location of the laser scanner to the hazard must be established, per EN ISO 13855, such that hazardous motion must be stopped before the user can reach the hazard. The safety function shall be designed and installed to meet the requirements of PLd, Cat. 3 per EN ISO 13849-1.
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. 81 Specifying Safety Functions
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Specifying Safety Function 82  Safety Functions can be generalized for reuse  Two different interlocking guards on two different machines operate in a similar fashion  Basis for many corporate standards  Some Common Safety Functions include:  E-stop  Light Curtains – muting  Light Curtains – non muting  Two hand control  Enabling Switch  Guard-locking  Tongue switch interlock  Safety Camera  Area Scanner (Single & Multi)  Pull-cord  Hinge switch interlock  Non contact interlock  Safe Speed Control  Safe Stop
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Rockwell Safety Functions Library 83
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Specifying Safety Function 84  Generalized Functional Specification
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Summary: Risk Assessment  A good Risk Assessment  Takes a comprehensive view of the machine, including  The machine operating parameters and limits  Task / Hazard identification  Risk Estimation  Risk evaluation / risk reduction measures  Establishes the required safety performance for machine safeguards  Generates OPTIONS for safeguarding  Provides documentation of your due diligence …Is the foundation for ALL Machine Safety Decisions
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Summary: Specifying Safety Functions  Safety Functions  Are similar to other control functions, performed with higher integrity  Are developed with the results of the assessment in mind  Human interaction with machine  Ensure person is able to do their job  Careful not to give incentive to defeat safeguards  Can be generalized and applied to many machines Safety Functions are ALWAYS specified, just not always in writing!
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. Example
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. We care what you think!  On the mobile app: 1. Locate session using Schedule or Agenda Builder 2. Click on the thumbs up icon on the lower right corner of the session detail 3. Complete survey 4. Click the Submit Form button 107 Please take a couple minutes to complete a quick session survey to tell us how we’re doing. 2 3 4 1 Thank you!!
  • Copyright © 2014 Rockwell Automation, Inc. All Rights Reserved. www.rsteched.com Follow RSTechED on Facebook & Twitter. Connect with us on LinkedIn. PUBLIC INFORMATION Thank you!