Bow-tie Lessons Learned Slide 1

Risktec Solutions

Lessons Learned from Real World Application of

Bow-tie Method

2010 International Symposium

BEYOND REGULATORY COMPLIANCE, MAKING SAFETY SECOND NATURE

risk management and assessment for business

www.risktec.com

Bow-tie Lessons Learned Slide 2

Purpose of presentation

Bow-tie method

Example case study

Practical uses and benefits

Tips for successful use

Bow-tie Lessons Learned Slide 3

The “bow-tie” diagramC

on

seq

uen

ces

Process upset

Cau

ses

Preventive

controlsRecovery

preparedness

Bow-tie Lessons Learned Slide 4

In more detail

Hazard Conseq-uence

Threat

Top EventThreat

Threat

Conseq-uence

Conseq-uence

Prevention Mitigation

Barriers

Bow-tie Lessons Learned Slide 5

Example case study

Loss of containment

LPG storage bullets

Torch, pool or flash fire

Third-party interference

Internal corrosion

Overfill bullets

Overpressure bullets

other threats

Unignited VC - buildings

Unignited VC - neighbors

BLEVE

Bow-tie Lessons Learned Slide 6

Overpressure bullets

Loss of containment

What are the preventive controls?

Bullets rated 250/operate

179 psi

Operator monitors

level, P, T & quality.

PAH, LAH, TAH

HH –P trip (179 psi) S/D feed

Two PRVs (250 & 262 psi), sized

for fire case

Bow-tie Lessons Learned Slide 7

What are the mitigative measures?

Torch, pool or flash fire

Gas detection 10% LEL >> alarm, 40% >> plant ESD feed trip & isolation

Detect leak & alarm via

operator rounds or

CCTV. Plant S/D at local ESD buttons

or C/R

Muster & acct for

personnel

Fireproof supports

…8 mitigation measures in total

Multiple muster

areas on site, plus

offsite point

Muster areas impaired

Bow-tie Lessons Learned Slide 8

It’s more than a picture: who’s responsible and what must they do?

Torch, pool or flash fire

Gas detection 10% LEL >> alarm, 40% >> plant ESD feed trip & isolation

Multiple muster

areas on site, plus

offsite point

Muster areas impaired

Instr. Tech

Detect leak & alarm via

operator rounds or

CCTV. Plant S/D at local ESD buttons

or C/R

Operator

Muster & acct for

personnel

Training

Fireproof supports

Mech. Eng.

Safety Eng.Test and calibrate critical instrumentation, ESDs, P

& flow sensors & alarms, F&G detection

Bow-tie Lessons Learned Slide 9

What is the critical documentation?

Operator schedule &training matrix

Torch, pool or flash fire

Gas detection 10% LEL >> alarm, 40% >> plant ESD feed trip & isolation

Detect leak & alarm via

operator rounds or

CCTV. Plant S/D at local ESD buttons

or C/R

Muster & acct for

personnel

Fireproof supports

Multiple muster

areas on site, plus

offsite point

Muster areas impaired

Instr. Tech Operator

TrainingMech. Eng.

Safety Eng.Protective sys. spec. &

performance stds.

Emergency response plan

Review ER provision

PFP spec. & perf. stnds.

Bow-tie Lessons Learned Slide 10

Catalogue of process safety-critical activities

Safety-critical role Instrument Technician

Maintain protective instrumentation

Test (incl. integrity w hazardous area classification) & calibrate critical instrumentation in field locations:

- ESD systems

- P & flow sensors/alarms

- F&G detectors, systems & alarms

- Corrosion injection system alarms

Safety-critical activity Procedure Verification

SAP work order

Completed SAP work

order

Bow-tie Lessons Learned Slide 11

How good are the controls? Example barrier effectiveness rating scheme

Every barrier must be suitable: (1) independent and (2) competent responsible person undertakes critical activity to provide barrier

Barrier Rating Used? Does it work/is it effective?

Very Good Always Always (>99%)

Good Frequently Generally (75% - 99%)

Unknown Unknown/not guaranteed

Unknown/cannot be guaranteed (50% - 75%)

Poor Occasionally Possibly (25% - 50%)

Very Poor Rarely Currently ineffective (<25%)

Un-assessed - Insufficient information

Bow-tie Lessons Learned Slide 12

How good is each control?

Torch, pool or flash fire

Gas detection 10% LEL >> alarm, 40% >> plant ESD feed trip & isolation

Detect leak & alarm via

operator rounds or

CCTV. Plant S/D at local ESD buttons

or C/R

Muster & acct for

personnel

Fireproof supports

Multiple muster

areas on site, plus

offsite point

Muster areas impaired

Instr. Tech Operator

TrainingMech. Eng.

Safety Eng.

Bow-tie Lessons Learned Slide 13

What about overall control?

Every threat and consequence for every hazard must have sufficientbarriers of adequate rating

Requires scheme for assessing overall control– Avoid counting barriers (scheme

should be relative, not absolute)

Bow-tie Lessons Learned Slide 14

Overall control?

Provides a guide for focusing effort on risk reduction, rather than measuring acceptability:– What else can we do?– Can we improve control effectiveness?– Can we add more controls?– Is it practical to do so?

Bow-tie Lessons Learned Slide 15

Can we improve control effectiveness?

Operator

Torch, pool or flash fire

Gas detection 10% LEL >> alarm, 40% >> plant ESD feed trip & isolation

Detect leak & alarm via

operator rounds or

CCTV. Plant S/D at local ESD buttons

or C/R

Muster & acct for

personnel

Fireproof supports

Multiple muster

areas on site, plus

offsite point

Muster areas impaired

Instr. Tech.

TrainingMech. Eng.

Safety Eng.

Recommendation

Confirm muster pt. locations & arrangements appropriate for all credible

major accident scenarios (e.g. outside LFL)

Bow-tie Lessons Learned Slide 16

The complete picture

Display altogether, or one branch at a time

Strengths and weaknesses in process safety clearly visible

– Coloring of barriers

– Coloring of threats & consequences

Bow-tie Lessons Learned Slide 18

How can we use it in practice?

Logical structured approach

Do we have any gaps in risk control?

Communication How do we engage non-risk specialists?

Formal demonstration Can we really demonstrate control?

Specific risks Will we be in control?

Critical roles Do our people know what is expected of them?

Competencies Are competence and control requirements aligned?

Critical procedures Are they complete and effective?

Auditing How can we focus audits on what really matters?

Critical systems and performance standards

What are they?

Bow-tie Lessons Learned Slide 19

What do bow-ties do for you?

1. Improved understanding– Powerful communication tool– Readily understood– Clear identification of links– Keeps sight of big picture– Captures previous incidents

Bow-tie Lessons Learned Slide 20

What do bow-ties do for you?

2. Greater ownership– Encourages wide participation– Promotes positive ownership– Clear identification of roles and

responsibilities

Bow-tie Lessons Learned Slide 21

What do bow-ties do for you?

3. Efficiency gains– Less labor intensive – Helps focus resources– “A picture paints a thousand

words”– Targets critical maintenance,

inspection & testing activities – Avoids reinventing the wheel

Bow-tie Lessons Learned Slide 22

Tips for success

1. Pitch at the right level

2. Involve the right people

3. Use method to full potential

4. Avoid barrier counting but do verify quality of controls

5. Focus on risk reduction

Bow-tie Lessons Learned Slide 23

Summary

Improves understanding and encourages ownership of process safety

Provides missing link between plant, procedures & people (not just a pretty picture)

Provides structured framework for determining whether current control of process safety is good enough

Helps to ensure that risks are managed rather than just analyzed