Introduction_to_functional_safety-isa.ppt

Safety Solutions on Tour Introduction to Functional Safety

Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Functional Safety Agenda

1. What is Functional Safety 2. Why Modern Safety Systems 3. Key Technologies 4. Summary

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Safety in the Workplace Functional Safety Falling Electric Shock

Radiation

Temperature Noise

Crushing

Chemicals

Safety Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Functional Safety Definition

• Random hardware faults, systematic design errors or human mistakes shall not result in a malfunction of a safety related system with the potential consequence of: – Injury or death of humans or – Hazards to the environment or – Loss of equipment or production

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Main Goal: Keep People Safe

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What are Hazards on a Machine or Process? • Physical – Falling / Moving Objects – Collisions – Collapsing Structures

• Chemical – – – – –

Explosion Fire Toxic Material Release Wrong mix of chemicals Radiation

• Electrical – Flashover and Burns – Electrocution – Wrong Connection / Loose Connection

• Mechanical / Process – – – –

Pinch Points or Entanglement Abrasion, Grinding, Cutting Thermal Pressure Releasing Effects (Bursting Vessels, Jets of Gas or Liquids) – Welding Torches, Gases etc.

Hazards are physical objects or chemical substances that have the potential for causing harm to people, property or the environment Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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If there are hazards ... there must be Risk Reduction • Functional safety is based on the concept of Risk Reduction • A Risk Assessment is performed to quantify the hazards on a machine • For each hazard, risk is reduced by adding layers of protection

Unprotected Risk

Risk Reduction #1 Design Hazard Out of Machine

Lower Risk

Risk Reduction #2 Implement Safety Guarding

Risk Reduction #3

Lower Risk

Training on Safe Operating Procedures

Tolerable Risk

Layers of Protection Figure: Example of layered risk reduction Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Define and Quantify Risk

Risk

Consequences

Chances

Frequency

How Bad?

How Likely?

How Often?

TEXT

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Risk – Same Hazard / Different Locations Identical process incidents pose more risk in a populated area than in an unpopulated area

+

=

+

=

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Tolerable Risk •

Practically impossible to drive risk to zero

•

At some point we are willing to accept the amount of risk posed

•

This point is referred to as tolerable risk

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Risk Estimation • A common way to quantify the amount of risk to be reduced is to use a Risk Graph Consequence of Unwanted event

Frequency of Possibility to avoid Unwanted event unwanted event

Probability of Unwanted event Very Small

Minor injury

Small

Relatively High

Possible under right circumstances Exposure to hazard is rare Almost Impossible Serious injury or single death

Start

Possible under right circumstances Exposure to hazard is frequent

Almost Impossible Exposure to hazard is rare Death of several persons Exposure to hazard is frequent Death of many people

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Risk Reduction

Most Preferred

Design it out Fixed enclosing guard Monitoring Training & supervision Personal protective equipment

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Least Preferred

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What is the function of a Safety System? • The Function of a safety system is to monitor and control conditions on a machine or process that are hazardous in themselves or, if no action were taken, may give rise to hazardous situations

• The Safety System runs in parallel with the Production System – Focus of Production System is throughput – Focus of Safety System is protection

Control System Operating Equipment

Safety System Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Safety is a System View ... Sensors

Main Goals

(e.g. Door Interlock)

Actuator(s)

Sensors

Logic Solver

(e.g. E-Stop)

(e.g. Safety Relay or PLC)

(e.g. Motor)

Actuator(s) (e.g. clamp)

Sensors

• • • • •

Improve Safety Simplify LOTO Improve MTTR Increase Machine Availability Improve Cost of Doing Business

(e.g. Speed Reference)

• Each hazard on a machine will consist of one or more “safety loops” that monitor and control its supply of energy – As determined by the risk assessment

• Each safety product must be applied as part of a whole to effectively reduce risk – Safety is the sum of its parts and safety is only as good as its weakest link

• The complexity of the inputs (sensors) and outputs (actuators) and the flexibility of the control will determine the type of logic solver – Stand-alone relay, modular relay or safety PLC Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Key Takeaways • A safety system is only as effective as it’s weakest link. – You need to consider all aspects of the system (input, control, output) and how they work together to meet current safety standards.

• Safety is about assessing the danger presented by machine hazards and designing solutions to reduce the possibility of a dangerous failure – Risk reduction with a goal of eliminating the risk or reducing it within reason (tolerable risk)

• You should follow a process for developing, deploying and maintaining safety solutions – Consider using the Safety Lifecycle as a model

• Your primary goal for safety is to protect employee health and safety while maintaining or increasing productivity. • The Government (OSHA, NFPA,Other) is not responsible for safety systems ... You are! The government will only enforce regulations.

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Questions so far...

 1. What is Safety  2. Modern Safety Systems 3. Key Technologies 4. Summary

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Why Safety? • • • • • •

Is Safety New? - NO Is Safety Important? - YES Who is Responsible? - EVERYONE Are Safety and Productivity initiatives ever at odds? Are Safety Systems or Procedures Ever Bypassed? Are people ever injured in manufacturing machinery accidents? • Goals: Integrated Controls Solutions that are safer AND more productive BY DESIGN.

Safety Thinking is Evolving

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Safety - Continuous Changes

• • • •

New Manufacturing Processes New Design Processes New Operating Procedures New Standards and Specifications • New Safety Technologies

• New System Design Philosophies Safety Specifications and Technologies Evolving Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Challenging Conventions • Consumer Safety Culture – Expectations of populace – just look at cars! • Manufacturing Safety Culture – – – – –

Safety makes things STOP, not GO Safety costs $$$!! Safety by luck - “We are safe” (repeat 1000 times) Changes introduce risks  NOTHING HAPPENS Typical approach is REACTIVE • An injury results in the application of a few “widgets” • Incomplete, high variation, inconsistent – not good! • Manufacturers exposed to increased liability

Safety is not an Accident Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Safety Drivers • Global Standardization and Specification • Costs of non-compliance – Insurance, OSHA violations, employee turnover, workers comp., litigation, etc.

• “Soft” measure for Wall St. – Turnover, “Best Place to Work,” Insurance costs, Injury Rates

• Rallying point for labor organization

Safety has a Broad Reach

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Where is Your Company?

• Reactive or Proactive? • Safety philosophy driven from top down – Safety credo, specifications, etc.

• Safety driven from the bottom up – Safety addressed on a case-by-case basis (injury by injury!)

• Are formal Risk Assessments being performed? • Is safety Designed In or Added On? What is Your Company Culture? Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Modern Safety Thinking • It’s a Culture; It’s a Process; It’s a design Philosophy • It is a combination of people systems (procedures) and technologies (components, circuits) • It is a systematic approach – Not a component approach!!! – Machine Safety is like an anchor chain – only as strong as the weakest link.

• It is a lifecycle – from system concept, through Risk Assessment, Design, Build, Start-Up, Validation, Operations and Decommissioning

Safety Specifications drive the Safety Lifecycle Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Safety – the Bigger Picture

• Safety Impacts: – Floor space/Footprint via performance (Safe Distance) • Big money!! – Direct Labor Content and Operator Efficiencies • HUGE money!! – Ergonomics – Productivity (System Design considerations) – Insurance Costs, Cost of Doing Business – Employee Morale, Company Goodwill, Labor Relations

Safety is Good Business! Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Safety – Do we have a Problem? • Are Safety Procedures Ever Bypassed? – Do People take the “Short Cut” to expedite maintenance procedures? – Is LOTO (Lock Out Tag Out) always followed?

• Are Safety Systems or Technologies ever Bypassed? – Are people using a “Cheater Key”? – Note: Some systems are so poorly designed and integrated that maintenance people are forced to bypass the safety system just to get their jobs done!

?

?

Safety must be Easy and Intuitive Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Safety System Design Concepts • Passive System Design – Ensures the easy way is the safe way

• Configurable System Design – Ensures the necessary functionality to accommodate maintenance procedures without bypassing the safety system. – This approach will help to limit exposure to hazards while expediting maintenance procedures and reducing MTTR.

• Lockable Safety Systems

Easy, Intuitive and Secure Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Safety Application - Perimeter Guarding Example • Application of safety technology based upon the Risk Assessment. – Cross functional team including Operators, Skilled Trades, Engineers, etc.

• System is configured to control and manage exposure to the hazards within the work cell. – Gate Box approach – Trapped key approach

• Passive System Function • Lockable • May provide “Point of Operation” control via “Enable” pendant. Passive, Configurable, Lockable Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Improved Productivity via Safety System Design

Typical Downtime Event OK

OK Down

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Production Resumes

Machine back in Auto

Repair Tested

Machine Unlocked

Repair Performed

LOTO

Fault Identified

Maintenance Arrives

Machine Stops

MTTR = 12 minutes

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Improved Productivity via Safety System Design • If the safety system design meets target safety level, the safety system may be used in lieu of LOTO, reducing MTTR by ~3 minutes. • Manufacturer’s value of 1 minute of production = $12K • Average downtime events per plant per year = 3000 • Value of safety solution due to improved productivity (via reduced MTTR) = $12K X 3 X 3000 = $108M/yr

Safety = Productivity = Profitability

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Summary • Safety is a shared responsibility – we are all stakeholders! • Every manufacturer must provide for a safe work environment. • Well designed systems improve both Safety and Productivity. • Safety is a System Solution – not just components. – Integrated into the control, information and people systems

• Safety is Specification Based. • Leverage Internal and External application knowledge and expertise – Maintenance, Engineering, Operations, Suppliers

• Single source full service safety supplier can help with comprehensive safety solutions. Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Questions so far...

 1. What is Safety  2. Modern Safety Systems 3. Key Technologies  4. Summary

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What Makes a Product Safe? • Important Concept “What makes a product safe is that it is designed using safety principles and complies with recognized safety standards” • What are the principles common in products designed for safety? – The Three D’s of Safety – Duality, Diversity, Diagnostics – All safety products are designed using a combination of the Three D’s – The Three D’s are used so the system will react properly when a fault occurs (e.g. turn off outputs)

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The “Three D’s” of Safety • Duality (Also known as Redundancy) – If one thing fails, there is another thing that can bring the system to a safe state – In parallel for Inputs or in series for Outputs

• Diversity – Protects against two things failing in exactly the same way at the same time – Example: Using one NO and one NC set of contacts – Example: Using both a high and a low input channel to a safety device

• Diagnostics – Safety products spend much of their time performing self-diagnostics – If a problem is detected, the system will go to its “safe state” and will not allow the system to be restarted until the problem is fixed – Example: A safety PLC has a significantly higher degree of self-diagnostic versus a standard PLC (> 90% vs. ≈ 50%)

Two of the three methods mentioned above must be implemented to achieve Category 4 / SIL 3 Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

D D D 34

Processor Structure of Standard PLC

Standard PLC

Input Module

Output Module

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CPU Structure of Safety PLC / 1oo2D

Safety PLC Duality

Input Module

Diagnostics

Output Module Diversity

Can you find the Three D’s??? Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Structure of a Safety Relay System Diagnostics Diversity Duality

Can you find the Three D’s??? Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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What Makes Safety Components Safe? • Direct Driven Contacts – Actuating force drives contacts open (breaks welds). – These are the type of contacts that are in Safety Interlock Switches. – Does not rely on a spring to open contacts such as a Limit switch.

• Mechanically Linked

Welded contact isforced open when actuator is removed

Symbol Found on Switch

– Linked means that if one contact welds, all contacts stay closed – for monitoring! – These types of contacts are found in Safety Contactors and relays to detect faults.

• Redundant Contacts – Redundant contacts act as a back-up to each other in case a contact were to fail. This provides a higher degree of reliability – Example: Two normally closed, (1) N.O. and (1) N.C., or (2) PNP outputs

Symbol Found on Front of Contactor

• Tamper Resistance – Features designed into safety components inherently make the device more safe. – EXAMPLE: Coded magnetic safety switches

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How do I Know a Product is Safe? • All safety rated products are developed to meet specific standards for safety – EN 954-1 (Safety Categories) – IEC 61508 (Safety Integrity Levels for Programmable Safety Systems) – EN 1088 (Safety Interlocks)

• Most safety rated products are certified by professional 3rd party organizations to demonstrate compliance to specific safety standards – Examples of third party certification organizations include TUV Rheinland, TUV Nord and BG

www.tuv.com Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Questions so far...

 1. What is Safety  2. Modern Safety Systems  3. Key Technologies  4. Summary

Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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Let’s take a quiz 1) Implementing a safety system will cause reduced production? 2) Safety systems are complex and require a specially certified Engineer 3) The first step in the safety lifecycle is to identify risks 4) The main goal of implementing a safety solution is to increase productivity

False False True False

5) When identifying risks, you must consider the consequences, chances and frequency 6) The best engineering method for risk reduction is to deploy a safety control system 7) Who is responsible for safety?

True

8) One way a safety system can improve productivity is by reducing the duration of a down time event. 9) The 3 D’s of a safety product are: Duality, Diversity and Diagnostics

True

10) Rockwell Automation has the broadest offering of safety solutions Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

False All True True 42

Questions ??

   

1. What is Safety 2. Modern Safety Systems

3. Key Technologies 4. Summary

Copyright © 2006 Rockwell Automation, Inc. All rights reserved.

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