18/12/2020

NEBOSH / HSE
Certificate in Process
Safety Management

What is
NEBOSH PSM?
• Level 4 qualification in UK and IRE educational
system and Level 6 In Scotland ES
• Process safety management target industries like
chemical, O&G, plastic etc
• PSM qualification is designed to equip
Learners with a broad understanding of the
accepted principles and recognised industrial
practices for the management of process risk.

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Contents
Unit PSM1: Process Safety Management

1. PROCESS SAFETY LEADERSHIP

2. MANAGEMENT OF PROCESS RISK
3. PROCESS SAFETY HAZARD CONTROL
4. FIRE PROTECTION AND EMERGENCY
RESPONSE

EXAM : 90 MIN EXAM WITH 40 NUMBER MULTIPLE

CHOICES QUESTION (SCENARIO BASED)

Element 1
PROCESS SAFETY LEADERSHIP

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Learning outcomes
1.1 Outline the meaning of process safety and how it differs from personal
safety.
1.2 Explain the role of leadership in process safety management.
1.3 Explain the purpose of organisational learning, the sharing of lessons
learnt and sources of information.
1.4 Explain how ‘change’ should be managed to effectively reduce risks to
people and plant.
1.5 Outline the benefits, limitations and types of worker participation and
engagement.
1.6 Outline what is meant by competence and its importance to process safety.

Element 1: Process safety leadership

1.1 Process safety management meaning.

1.2 Process safety leadership.

1.3 Organisational learning.

1.4 Management of change.

1.5 Worker engagement.

1.6 Competence.

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Group discussion

Process Safety vs Personal Safety

1. What do you understand by the term “process safety”?

2. How do you think this differs from “personal safety”?

Personal safety vs process safety

• process safety tends to focus on mitigating risks through the
inherent design of a system, whereas

• personal safety focuses on enforcing behavioural changes

in individual workers and teams in order to prevent
incidents.

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Hierarchy of control :

1. Elimination
2. Substitution
3. Engineered controls
4. Signage/warning/or administrative controls
5. PPE

Personal safety vs process safety

Personal Safety
– prevention of incidents causing injuries to
individuals;
– applicable in all workplaces.

Process Safety
– blend of engineering and management
skills;
– prevention or mitigation of catastrophic
failures;
– high-hazard industries.

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Element 1: Process Safety Leadership

1.1 Process safety management meaning.

1.2 Process safety leadership.

1.3 Organisational learning.

1.4 Management of change.

1.5 Worker engagement.

1.6 Competence.

Types of safety leader ship

Transformational (selling) Disadvantage
• People will follow a person who • Pasion and enthusiasm may not align
inspires them with reality
• Get things done is by generating • may think they are right but this only
enthusiasm and energy their belief
• Engage workforce to the vision of • Good in seeing bigger picture(vision)
the leader
but not the detail where the
For leader problem arise
• Clear idea of the way forward
• Always need to visible Focus on
• Motivate the workforce Supervisor support, training,
continually
and communication
• continually sell the vision

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Transactional(telling)
• People are motivated by reward and punishment
• Social system work best with a clear chain of command
• Do what your manager tells you to do
• Subordinate manager have the authorities over the subordinate and leader allocate the
work
• Subordinate is fully responsible whether or not they have the resources or ability to carry
it out. If not than punished for failure
• Concept is success require praise and reward and substandard performance needs
corrective action
Limitations
• Assumption that individual are simply motivated by reward and exhibit predictable
behaviour but it does not address the deeper needs identified by MASLOW Hierarchy
FOCUS on
Compliance rules and inspection

Maslow Hierarchy of needs

• Self-Actualisation Real mission of life

• Esteem Self esteem achievement

• Social Family & friend
• Safety or protection
Security from unemp
• Biological food/shelter

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Servant
• Leaders have a responsibility towards society and those who are
disadvantage
• Help workforce to achieve and improve their goals
• Trusting relationship to encourage the collaboration
• Creation of healthy environment where people can trust and work
together
• Well being of the workers is essential than any goals
Limitations
• May be viewed as an appropriate model of the employer but in
business sector it examined as to caring by share/stack holders
Focus on
Co-operation, consultation, personal growth and well being.

Hazard and risk awareness of

leadership teams
In process safety, leaders need to be:
• Competent and actively engaged.
• In possession of facts and data as decision makers.
• Aware of the hazards and risk potential of their plant and sites
through their life cycle:
− design;
− commissioning;
− operations;
− decommissioning.

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Group discussion

Board level commitment to process safety is often

achieved by being visible.

- What practical measures can board members take to reinforce

the importance of process safety?

Board level visibility

The Principles of Process Safety Leadership place emphasis on board
level visibility to promote process safety.

Practical measures can include:

• leading by example, eg, wearing PPE;

• following site rules;
• providing resource for site and projects;
• supporting the risk assessment process;
• carrying out site visits;
• asking questions!

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Process safety responsibilities

• Everyone has a role to play in process safety.
• Roles need to be clearly defined.
• Competency and accountability is a must:

− managers: allocate resources;

− engineers: design and maintain;
− safety professionals: advise and guide;
− workers: follow safety procedures.

Reasons for holding to account all

individuals with PSM responsibility
• High potential consequences, if fail to carry out
responsibilities adequately.
• Encourages engagement.
• Look for root causes.
NB need to avoid a blame culture.

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Responsibilities at senior leadership level

CEOs and leaders assure their organisation’s competence to
manage the hazards of its operations. They must:
• ask critical questions; • provide training and scenario
• ensure competence at all planning;
levels; • listen to process experts;
• ensure that there is continual • ensure the organisation
development of expertise, manages/reviews contractors
especially with new law and and third parties competency;
technology; • communicate effectively.
• provide adequate resources
and time for risk analysis;

The provision of adequate resources

“Appropriate resources should be made available to ensure a
high standard of process safety management throughout the
organisation and staff with process safety.”
Appropriate resources can be:
• human;
• financial; and
• physical.
Under-resourcing process safety is a risky business!

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Process safety objectives and targets

1. Establish overall
objectives

2. Set targets
4. Review regularly
(stepping stones)

3. Monitor progress
of indicators
Leading → Success
Lagging → Failure

Leading indicator
• Precursors that may lead to an accident, injury or disease
• Focus on improving health and safety performance &
• Reducing the probability of serious accidents.
Measures activates
• Proportion of employees who have access to OHS services
• Percentage of test of safety critical equipment completed
with a required time frame
• Percentage of required training completed
• Number of field visits and communication carried out.

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Lagging indicator
• Measures lost event that already occurred.
• Measures the past safety performance of the organization
regarding accident, incident, disease or failure of the system.
Measures
• Injury frequency and severity
• Reportable incident
• Lost workdays
• Worker compensation costs

Group discussion

Why might process safety be considered a continuous

improvement process?

- Suggest practical ways in which organisations can seek to

improve.

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Continuous improvement
Organisations change
• New processes and products.
• New operational conditions.
Technology changes
• New equipment available.
Standards change
• Benchmarking to other organisations.
• Legislation and guidance changes.

Element 1: Process safety leadership

1.1 Process safety management meaning.

1.2 Process safety leadership.

1.3 Organisational learning.

1.4 Management of change.

1.5 Worker engagement.

1.6 Competence.

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Group discussion

In groups, think about incidents you have been

involved in:
− What was the most significant in terms of actual
injury/harm?
− What had the greatest potential for injury?
− Do you think you learnt all you could from the potentially
serious event?

Learning lessons
• Investigate based on the potential AND the actual
consequences.
• Do not downplay the incident as a “near miss”.
• Incidents not investigated, could happen again with more
serious consequences eg:
‒ chemical reaction causes pipes to heat up.
If ignored as a near miss and not investigated
‒ later resulted in a chemical release and
serious injuries.

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Immediate and root causes

Immediate cause Root cause

Unsafe act or condition Underlying
that lead to the circumstances that
consequences (harm, allowed immediate cause
damage etc). to happen.

eg spillage, failure of a eg management or

vessel, removed guard. systems failures.

Group discussion

A flammable liquid has overflowed from a vessel

during the filling operation.

The liquid is transferred via a pump to a vessel where it is

metered in based on the transfer time and pump speed.

- Suggest reasons (root causes) for the incident.

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Root causes
✓ Pump changed for a higher rate.
✓ No/poor management of change process.
✓ No/failure of high level alarm.
✓ No automatic cut off.
✓ Operator error.
✓ Poor initial risk assessment.
✓ Process changes, eg bigger batches than
design intent.

Reasons for investigating accidents

and incidents
• To identify root causes of the incident.
• To prevent the incident happening again.
• To update risk assessments.
• To document/record the details for future use.
• To meet any legal requirements to report and investigate.
• To enable patterns and trends to be discovered.
• Demonstrates a desire to improve and learn lessons.
• To determine if any disciplinary actions are needed.

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Benefits of investigating accidents and

incidents
• Causes can be addressed through revised risk assessments.
• Fewer serious events should occur.
• Achievement of legal compliance.
• To assist with any civil claims.
• Workers will feel valued.
• Any disciplinary action will be fair.

Retention of corporate knowledge

Avoidance of “corporate amnesia”:

– retain information formally rather than relying on individuals;
– lessons learnt;
– decisions;
– designs, etc.

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Lessons learnt and benchmarking

Findings of accident and incident investigations.

Lessons learnt
Striving for continual improvement.

Comparing an organisation against:

• another organisation;
Benchmarking • a national standard, eg HSE accident
statistics publication; and/or
• an operational standard.

Group Discussion

− How do you share the lessons learnt from

incidents within your organisation?

− Is it a two-way process (ie do you also hear about

incidents)?

− Who do you benchmark against?

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Sources of Process Safety

Management Information
Process safety management information is necessary for the
safe operation and maintenance of process plant and should
be:
• documented;
• reliable;
• current; and
• easily available to the people who need to use it.

Sources of process safety

management information
Information internal to the organisation:

• safety data sheets (SDS); • piping and instrument

diagrams (P&IDs);
• process design criteria;
• process control systems;
• process flow diagrams (PFD);
• relief system design;
• safe operating procedures (SOPs);
• fire detection and protection
• inspection, audit and investigation
plans.
reports;
• maintenance records;

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Sources of process safety

management information
Information external to the organisation:
• EU Directives;
• the UK Health and Safety Executive (HSE);
• the US Occupational Safety and Health Administration (OSHA);
• harmonised European standards;
• British standards;
• International Labour Organisation (ILO);
• trade associations/professional bodies eg Institute of Chemical
Engineers (IChemE).

Group discussion

− Think about the sources of information available

in your organisation to assist in process safety
management.
− Are they documented, reliable, current and easily
available to the people who need to use them?

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Element 1: Process safety leadership

1.1 Process safety management meaning.

1.2 Process safety leadership.

1.3 Organisational learning.

1.4 Management of change.

1.5 Worker engagement.

1.6 Competence.

What is management of change (MOC)?

• Formally documented process.

• Authorises changes before they are

implemented.

• Ensures relevant safety (and process)

considerations have been made:

‒ hazard and risk analysis.

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The MOC process

Produce document detailing changes

Carry out risk assessment

Get authorisation for changes

Document and record changes

Consult and inform those affected

Element 1: Process safety leadership

1.1 Process safety management meaning.

1.2 Process safety leadership.

1.3 Organisational learning.

1.4 Management of change.

1.5 Worker engagement.

1.6 Competence.

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Group discussion

− What do we mean by ‘consultation’ and how is

it different to ‘informing’?
− How do you consult with workers?

Key term

Consultation

The two-way exchange of

information between parties, in
this case between employer and
worker. This is far more effective
than the one-way exchange that
we see when people are simply
informed.

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Consultation
ILO Encyclopaedia article consultation and information health and safety (part III, chapter 21)

ILO Occupation health and safety convention 1981 (C155)

Article 20, State the basic approach

“ Co-operation between management and workers and or their

representatives with in the undertaking shall be essential
element of organization and other measure taken in pursuance
of article 16 to 19 of this convention”

ILO occupational recommendation (94(

Benefits and limitations of consulting

Benefits Limitations
• Improves relationships. • Not all matters can be consulted
on.
• Demonstrates commitment.
• Takes time (which might not be
• Improves safety culture. available).
• Gains co-operation from workers. • Poor consultation processes are
• Harnesses workers’ practical worse than no consultation!
knowledge.

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When consultation is needed

✓ Introducing changes that affect health and
safety (new plant/processes/work
methods, etc)
✓ When implementing new technology.
✓ When appointing safety advisers.
✓ Development of training plans.
✓ Reviewing health and safety performance.
✓ Learning lessons from incidents and near
misses.

Types of cousultaion
Formal consultation
• Workers
• Workers representative
• Workers representative organization
• Union committee
• Labour committee

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Types of consultation(informal)
Safety Discussion Safety circles
committees groups Ideas-sharing
Worker and Volunteers group.
management interested in a
representatives. topic.

Departmental Email and web

meetings forums
Health and safety Helps engagement.
discussions allow
workers to voice
concerns.

Optional activity

Watch the following video of a health and safety

committee:
www.youtube.com/watch?v=uZcFj2ou2ys
Now discuss:
− Why is the committee proving to be ineffective?
− What would you change?

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Why include workers?

Its necessary
‒ Better understanding and involvement results in better
solutions.
Engagement should be a priority
‒ Do not allow it to fall by the
wayside.
‒ Schedule meetings and
activities.
‒ Hold people accountable.

Element 1: Process safety leadership

1.1 Process safety management meaning.

1.2 Process safety leadership.

1.3 Organisational learning.

1.4 Management of change.

1.5 Worker engagement.

1.6 Competence.

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Competence
• The ability to undertake responsibilities and to perform
activities to a recognised standard on a regular basis.

• A combination of practical
and thinking skills,
experience and knowledge.

The role of competence in safe working

and behaviours
Training in how to do the job safely
‒ Operational procedures.
‒ Emergency procedures.
Benefits of training
‒ Understand the job so work safely.
‒ Train to standards.
‒ Right first time.

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Competency management
Example of a training matrix:

Competency management
Assess
Build emergency
competency as
Establish policy management
an ongoing
skills
process

Determine
Gain ownership
minimum Maintain and
and
competency develop skills
commitment
standards

Analyse skill Continually

Recruit workers
gaps development

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Process safety training

At all levels:
‒ process safety leaders;
‒ managers/supervisors/designers/safety advisers/newly
qualified managers
‒ operators and technicians.

Training to include:
‒ standard operations;
‒ non-standard operations
(shut-down, etc);
‒ emergency training.

Element 1: Summary
1.1 Process safety management meaning.
1.2 Process safety leadership.
1.3 Organisational learning.
1.4 Management of change.
1.5 Worker engagement.
1.6 Competence.

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NEBOSH / HSE
Certificate in Process Safety
Management

Element 2
MANAGEMENT OF
PROCESS RISK

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Learning outcomes
2.1 Outline the purpose and importance of establishing a process
safety management system and its key elements.
2.2 Outline common risk management techniques used in process
industries.
2.3 Outline asset management and maintenance strategies for
process plant.
2.4 Explain the role, purpose and features of a permit-to-work.
2.5 Explain the key principles of safe shift handover.
2.6 Explain the principles of selecting, assessing and managing
contractors.

Element 2: Management of process risk

2.1 Establishing a process safety management system.

2.2 Risk management techniques used within the process
industries.
2.3 Asset management and maintenance strategies.

2.4 Role, purpose and features of a permit-to-work system.

2.5 Safe shift handover.

2.6 Contractor management.

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Reasons for developing a PSMS

OHS C155 Ar 16 1981
Moral reasons
– Avoidance of incidents and disasters.
Legal/compliance reasons
– Often a clear legal requirement.
– May be internal company standards.
Financial reasons
– Avoids losses associated with disasters.

Key elements of PSMS

Strong leadership Hazard analysis MOC

Detailed Understand
Sets direction and
understanding of consequences
determines
process hazards before changes
culture.
and risks. are made.

Operation within Competence

design intent management

Under all
conditions
Ongoing training.
including start-up
and maintenance. (Continued)

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Key elements of PSMS

Control of Emergency
Asset integrity
contractors response

Control of Maintenance Foreseeable

selection and (planned and incidents, eg loss
activities. breakdown). of containment.

Performance
Incident recording
monitoring and
and investigation management review

Leading and
Investigation to
lagging indicators
learn lessons.
reviewed.

Key elements of PSMS - PDCA

PLAN
• Policy.
• Planning.
DO
• Implementation and operation.
CHECK
• Checking and corrective action.
ACT
• Management review.
• Continual improvement.

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Licence to operate
• Application made to regulators to run process.
• Supply a ‘safety case’ during application:
− high hazards identified.
− major accident risks identified
and controlled.
− risks controlled to ALARP.

Major accident prevention policy (MAPP)

Contains:
• roles and responsibilities;
• Identification of major accident
hazards;
• operational control measures;
• emergency plans (on and off site);
• monitoring process;
• auditing process.

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Key terms

Leading indicators Lagging indicators

Proactive measurements of Reactive measures that look at

conditions that monitor process failures, such as the number of
safety before something goes injuries, near misses and spills
wrong and to see if things are which are reported, or excursions
operating as intended. where plant is operated outside
of the intended operational
envelope.

Leading indicator
• Involved precursor that will lead toward an accident, incident or
injury
• They focus on the improving the health and safety performance
and reducing the probability of serious accidents.
Measures activities
• Proportion of employees who have access to OHS services
• Percentage of required risk assessment carried out
• Percentage of required training completed
• Percentage of incident investigation with corrective actions
• Percentage of test of safety critical equipment completed within a
required time frame

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Lagging indicator
• Measures loss events that had already occurred
• Measures safety performance in terms of past incidents
For example
• Injury frequency record
• Reportable incidents
• Lost workdays
• Workers compensation costs

Development and implementation of PSIs

• Determine what can go wrong in the process and identify

risk controls to prevent such incidents.
• Establish lagging indicators to measure failure of these risk
controls.
• Establish critical actions for each risk control system and
develop leading indicators to monitor whether these are
working.
• Monitor and review indicators.

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Leading and lagging process safety

performance indicators (PSIs)
Checks and balances to determine how well the site is managing
process safety. Effective indicators of process safety:
Leading indicators Lagging indicators
– Proactive measures of – Measures of
conditions. failure.
– Identify problems – Example:
before harm occurs. accident, incident,
– Example: testing of near-miss data.
emergency systems vs
plan.

Key term

Auditing

A systematic, objective, critical

evaluation of how well an
organisation’s management
system is performing by
examining evidence.

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Auditing compliance

Audits:
• are proactive;
• check health and safety is managed;
• check controls are in place and working;
• identify areas for improvement which
can then feed new health and safety
plans – continual improvement.

Element 2: Management of process risk

2.1 Establishing a process safety management system.

2.2 Risk management techniques used within the process
industries.
2.3 Asset management and maintenance strategies.

2.4 Role, purpose and features of a permit-to-work system.

2.5 Safe shift handover.

2.6 Contractor management.

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Group discussion

What do you understand by the term “hazard”?

How do we determine the level of risk?

Key terms

Hazard Risk

Something that has the potential The likelihood that a hazard will
to cause harm. cause harm, in a combination
with the severity of injury,
damage or loss that might
foreseeably occur.

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Purpose and use of risk assessment

• Essential in the management of safety in workplaces.

• Identifies hazards and evaluates risks by considering the

likelihood and severity of harm occurring.

• Risk controls are identified, which reduce the risk to an

acceptable level.

General risk assessments

Basic risk assessment

process follows the HSE’s
five-step approach:

Adapted from INDG163: Five

steps to risk assessment

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Advanced risk assessments

Adapted from: Offshore Information Sheet 3/2006

- Guidance on Risk Assessment for Offshore
Installations

Qualitative, semi-quantitative and

quantitative risk assessments
Qualitative (Q)
– Determined as low, medium
or high.
Semi-Quantitative (SQ)
– Determined within ranges.
Quantitative (QRA)
– Fully calculated based on data.

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Barrier models
• There are barriers between hazard and loss.
• An incident only occurs when there is failure in each barrier.
• Sometimes known as the ‘Swiss cheese model’.
• When the holes line up there is an accident (ie the ‘hazard
is realised’).

The application of risk management

tools
• Most effective tools are initially considered at concept and
design stage.

• Before start-up, a more complete risk assessment should

be carried out.

• Additional controls may be needed during unusual process

activities, eg start-up and shut-down.

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Hazard realisation
• Hazard realisation requires the assessor to look at worst-
case scenarios.
• Once these are understood, controls can be implemented in
the form of ‘barriers’.
• These barriers can then be placed between the initiator
(triggering event) and the potential consequences to either
prevent or reduce the outcome.
• When drawn together, this is known as a ‘bow-tie’ diagram.

Bow Tie Model

Image from
‘Offshore
information
sheet No.
3/2006 guidance
on risk
assessment for
offshore
installations,
HSE, 2006

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Hazard and operability study (HAZOP)

• Multidisciplinary team approach.
• Breaks process into nodes (small chunks).
• Agree parameters to be studied:
− eg flow, pressure, temperature, etc.
• Agree guidewords to be used:
− eg more, less, no, reverse.
• Combine guidewords with parameters to
create ‘deviations’:
− more flow, less flow, no flow, etc.
• Identify potential causes and controls.

Tabular format
• The HAZOP findings are recorded in a tabular format and
retained as evidence of the study.
• Example extract from a HAZOP of a domestic shower:

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Hazard identification (HAZID)

• Multidisciplinary team
approach.
• Brainstorming process.
• May involve a walkthrough.
• Identifies hazards to feed the
risk assessment process.
• Top-down study
• Structured by keywords

Failure Mode Effect Analysis (FMEA)

Requires a multidisciplinary team to identify:
• failure modes (ways it can fail);
• effects (of the failure);
• severity (impact to the ‘customer’);
• cause (of the failure mode);
• occurrence (chance of it happening)
• detection (what is in place to spot it)
− determine risk priority (Risk Priority Number: severity × occurrence
× detection);
• recommended actions to be taken, by whom and by when.

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Event Tree Analysis (ETA)

What-if analysis
• Assessor uses risk realisation to identify the true potential
of the incident.

For example, loss of containment

of a flammable liquid could
potentially result in fire, explosion,
damage, injury and fatality,
even if it does not in a
particular incident.

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Concept of ALARP
(as low as is reasonably practicable)
• Cannot reduce all risk to zero.
• Introduce controls to reduce risk to lowest level
achievable without incurring disproportionate costs:
‒ some flexibility in how to achieve;
‒ balance risk vs cost/time/effort.
• Guidance provides information on what is considered
ALARP.

Hierarchy of Risk Controls

Inherent safety
Build safety in at design stage.
Elimination
Remove a hazard, minimise inventories.
Substitution
Lower hazard alternative.
Engineering controls
Segregation/spacing of process plant.
Administrative controls
Procedural/behavioural.

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Element 2: Management of process risk

2.1 Establishing a process safety management system.

2.2 Risk management techniques used within the process
industries.
2.3 Asset management and maintenance strategies.

2.4 Role, purpose and features of a permit-to-work system.

2.5 Safe shift handover.

2.6 Contractor management.

Integrity standards
• Consideration of relevant standards at design stage.
• Standards ensure safety and integrity.
• For example:
‒ EN ISO standards;
‒ welding standards;
‒ pressure ratings.

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Group discussion

An organisation doesn’t currently have a process to

manage and maintain the integrity of plant and process
equipment.

− What arguments could you use to convince the management

that such a system is needed?

Key terms

Asset Asset integrity

An item of equipment or an area The ability of an asset to operate

of production plant as intended effectively and
efficiently over its entire lifespan
whilst ensuring the health and
safety of those exposed to it,
including the environment.

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Consequences of failing to manage the

integrity of assets
• Damaged, wearing or defective
equipment can fail and cause leaks.
• Equipment failure can impact plant
safety and productivity.
• Safety systems may fail to operate.
• Breakdown maintenance is expensive
and less effective than preventative
maintenance.

Types of maintenance and strategies

• Planned preventive maintenance
• Preventive maintenance
• Condition based maintenance
• Breakdown maintenance

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Key term
ATEX

‘ATEX’ is commonly used to refer to the two EU

directives that control explosive atmospheres. It is
from the French title of the 94/9/EC directive:
Appareils destinés à être utilises en ATmosphères
Explosibles.

ATEX-approved equipment that is suitable for use in

an explosive atmosphere is given a symbol which is
shown on the next slide.

Selection of equipment for the operating

environment
Considerations include:
For example, in potentially
• flammable atmospheres. flammable atmospheres where
• wet conditions; vapour or dust can result in fire
• harsh environments (eg or explosion, ATEX approved
salty atmospheres); equipment must be used:
• corrosive chemicals.

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Asset integrity through the lifecycle

Phases
1. Design 4. Operations
Designed to be safe. Operate within design intent;
maintenance and inspection.
2. Procurement, construction
installation and testing 5. Modifications

Build completed correctly. Planned and assessed first.

3. Commissioning 6. Decommissioning

Standards checked and signed off. Safe removal from operations.

Plant maintenance documentation

• Maintenance records retained.

• Some are legally required, eg the statutory records of
pressure systems.
• Can be paper or electronic, must be traceable.

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Risk-based maintenance and inspection

strategies
Three types
• Breakdown maintenance.
• Condition monitoring.
• Planned preventive maintenance.

MUST retain records for all!

Group discussion

Which maintenance activities are carried out in your

organisation?

Fit them into the three maintenance types.

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Risk-based calibration of instrumentation

• An essential activity in the process industries
• The consequences of neglecting to maintain calibration can
cause:
– failure to meet the quality system;
– safety risks for employees and customers;
– poor product quality and loss of reputation;
– failure to comply with legislation, causing the loss of the license to
operate;
– unexpected downtime;
– economic losses.

Risk-based calibration of instrumentation

• The accuracy of measurement instruments drift over time.
• Users must check instruments periodically to see if they have
drifted and make adjustments as necessary.
• Process owners should take a risk based approach (SFARP) to
establishing calibration and inspection criteria.

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Group discussion

Give some examples of essential instrumentation in

your workplace.

Would workers die or be injured if the instrument did not

read correctly? (Confined Space Entry)

Element 2: Management of Process Risk

2.1 Establishing a process safety management system.

2.2 Risk management techniques used within the process
industries.
2.3 Asset management and maintenance strategies.

2.4 Role, purpose and features of a permit-to-work system.

2.5 Safe shift handover.

2.6 Contractor management.

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Key term

Permit-to-work
system
A formal, documented procedure that
forms part of a safe system of work. It is
commonly used for high-risk work and it
documents measures to reduce risks, such
as isolations. It is used to ensure that the
correct precautions are in place and that
all those who need to know about the
work are informed.

Why need PTW

• To ensure proper authorisation of the work
• To make clear exact identity nature and extent of the work
• To specify the time during which the work may be carried out
• To specify the precaution to be taken
• To specify the isolation
• To specify the gas testing procedure
• To ensure that a person is the overall charge is aware of every work is being
carried out
• To provide the system of continuous control and a record to show that the
nature of the work and any precaution have checked by an approved person
• To provide suitable display of permit
• To provide procedure when work suspended

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Element of PTW
• Hazard identification
• Risk assessment
• Control measures
• good clear communication

How to achieve the objectives

• Appropriate training
• Regular monitoring
Jobs required ptw
• Hot work
• Any work that may cause an uncontrolled hydrocarbons release
• Electrical work
• Entry in confined space
• Excavation
• Pressure testing operation
• Maintenance of critical safety system
• Work involving hazardous dangerous substance

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Types of permit
• Hot work permit
• Cold work permit
• Isloation permit
• Entry permit
• Radio active permit
• Explosive permit
• Man over water permit
• Third party equipment installation permit

PTW has four main sections

• Issue: the control that must be implemented for the work to
take place are defined.
• Receipt: the work sign onto the permit to signal that they
accept the condition of the permit and understand the
hazard and control measures detailed in it.
• Clearence: once the work is complete the workers sign to
say they have finished and are leaving the jobsite to allow
normal work
• Cancellation: control of the workplace is accepted back to
the issuer and the permit is cancelled

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Purpose and effective use of a permit-to-

work (PTW)
• Used in high-risk activities.
• Part of a safe system of work.
• Communicates hazards and controls to user.
• Links to:
‒ risk assessment and task/job safety analysis (used to
identify hazards and plan precautions);
‒ method statement (describes how (step-by-step) the
work will be done safely).

Element 2: Management of process risk

2.1 Establishing a process safety management system.

2.2 Risk management techniques used within the process
industries.
2.3 Asset management and maintenance strategies.

2.4 Role, purpose and features of a permit-to-work system.

2.5 Safe shift handover.

2.6 Contractor management.

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Importance of shift handover

Importance of safe shift handover
• Transfer of critical information to the incoming shift.
• Failure to do so can have devastating consequences as in Piper
Alpha.
Two-way communication and joint responsibility
• Joint responsibility of both outgoing and incoming shift leaders.
• Needs time to be done properly.
Competence
• Workers carrying out shift handovers must:
- have the right level of technical knowledge, expertise;
- be able to communicate effectively.

Shift handover requirements

Shift handover must be:
• given the highest priority;
• conducted face to face;
• done using accurate verbal and written communication
(handover logs are useful);
• based on information needs of incoming staff;
• given as much time as necessary.

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Typical information shared at shift

handover
The main issues communicated include:
• operational status of the plant;
• emergency situations or incidents;
• any safety issues;
• maintenance activities underway/planned;
• permit-to-work details, especially those still open;
• operational issues for the incoming shift (eg production plans);
• planned receipt of hazardous material deliveries;
• any drills or exercises planned;
• physical demonstration of plant state.

Element 2: Management of Process Risk

2.1 Establishing a process safety management system.

2.2 Risk management techniques used within the process
industries.
2.3 Asset management and maintenance strategies.

2.4 Role, purpose and features of a permit-to-work system.

2.5 Safe shift handover.

2.6 Contractor management.

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Scale of contractor use within the process

industries
A ‘contractor’ is an individual or organisation paid to deliver
a service without being directly employed.
Widely used in the process industries for:
• additional manpower and labour;
• specialist skills, eg designers, welders, etc.

Give examples of contractors you encounter in your workplace.

Group discussion

Identify factors that could be considered when selecting

a contractor and assessing their suitability for use on site.

(These might usefully be in a contractor approval checklist).

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Contractor selection
Assessed for suitability using criteria including:

• experience in the type of work;

• trained in specific safety requirements of the environment;

• suitability of the organisation’s health and safety policy;

• quality of their risk assessments;

• suitability of method statements;

• accident history, including near-miss reporting; (Continued)

Contractor selection
• Enforcement history and prosecutions;
• Health and safety performance monitoring;
• Qualifications of all workers (including managers);
• Membership of a professional body or trade association;
• Selection and management of subcontractors;
• Insurance cover;
• Liaison with clients;
• References from previous clients.

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Periodic review of contractor safety

performance
• Essential to ensure:
‒ working to agreed standards.
‒ compliance with documentation.
• The review may include:
‒ site inspections;
‒ safety tours;
‒ meetings to review performance.

Contractor Induction
Client to advise workers on site-specific hazards and procedures,
including:

• sign in/out procedures; • PPE requirements;

• emergency procedures; • permit-to-work requirements;
• site rules; • accident reporting
procedures;
• specific site hazards;
• near miss and hazard
reporting.

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Contractor supervision
Ownership of contractor activities:
• Include contractors in process risk assessments and safe
systems of work.
• Clearly identified person
responsible for approval and
day-to-day contractor management.
• Contractors should know who their
client contact is.

Auditing contractor performance

• Before work starts:
‒ initial assessment of paperwork.

• During the work:

‒ monitoring working practices.

• After completion:
‒ review performance, including accident history (to be
carried out between client and contractor).

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Handover to client
• Hand back of plant and equipment.
• Handover of building or installations arising from project.
• Information handed over includes:
‒ operation and maintenance manuals;
‒ pipework and instrumentation diagrams;
‒ updated layout plans, including location of services;
‒ design specifications;
‒ as-built drawings.

Siting of contractor accommodation

Process operators evaluate all newly sited structures under MOC
and include in the overall PHA.
Temporary accommodation
should be based on exclusion
zones for areas where explosions
are possible.
All occupied trailers should be
located outside of vulnerable
areas, (even if they are moved
beyond the facility’s boundary).

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Housing of contractors
Consideration given to the safe location of contractors on site:
• Facilities and amenities required.

• Located away from high-hazard

areas.

Element 2: Summary
2.1 Establishing a process safety management system.
2.2 Risk management techniques used within the process
industries.
2.3 Asset management and maintenance strategies.
2.4 Role, purpose and features of a permit-to-work system.
2.5 Safe shift handover.
2.6 Contractor management.

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 18/12/2020

NEBOSH / HSE
Certificate in Process
Safety Management

Element 3
PROCESS SAFETY
HAZARD CONTROL

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Element 3: Process safety hazard control

3.1 Operating procedures.
3.2 Safe start-up and shut-down.
3.3 Safety critical performance standards.
3.4 Utilities.
3.5 Electricity/static electricity.
3.6 Dangerous Substances.
3.7 Reaction hazards
3.8 Bulk storage operations

Safe operating envelope (SOE)

• Defines boundaries of a controlled reaction.

• The optimised conditions which keep the process under control.

• Operating outside this ‘envelope’ is unsafe.

• Typical parameters used to define boundary:

‒ pressure;
‒ temperature;
‒ flow rate.

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 18/12/2020

What parameters might define the SOE?

Monomer Cooling Coils

Feed

Cooling Water to Sewer

Example 1
Cooling
Water In

TC
Thermocouple

What parameters might define the SOE?

Unloading

Unloading
stations

stations
~

Ammonia Phosphoric
Solution Acid storage
L1 Storage tank Tank L1
F1 F1
Example 2
Outdoors
Enclosed
Work area
Diammonium phosphate (DAP)

~~~~~~~~~~~~~~~ Loading
~ Dap storage tank stations

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Purpose of standard operating procedures

(SOPs)
• Inform operator about the process safety hazards.

• Describe the control system.

• Describe standard operating
conditions (including allowable
range/excursions).

Key terms

Safety Proportional-integral
instrumentation derivative (PID)
system (SIS) Three separate elements
(proportional, integral and
The system for connections and derivative) which comprise the
equipment that operates control loop that regulates the
automatically the process process variables, eg, pressure.
controls, for example valves that This avoids the need to have
maintain the process in the SOE. manually operated process
control.

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Types of SOPs

• Start-up/shut-down.
• Plant and equipment maintenance and modifications /
changes.
• Responding to alarms tripping and emergencies.
• Filling/emptying/charging of vessels, pipelines and reactors.
• Responding to unplanned deviations and ‘abnormal
operations’.

Who is involved in developing SOPs?

• Operators.
• Maintenance team contractors.
• Design/engineering team.

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Group discussion

What are the reasons for involving operators in the

writing of procedures?

Group discussion
Reasons for involving operators in the writing of SOPs
• To ensure the procedure matches what is done.
• Involving operators increases acceptance and following of
procedures.
• It creates a sense of ownership.
• It reduces the likelihood for errors occurring.
NB - Not every relevant operator will be able to participate in the
drafting as there is a limitation of the effectiveness of individual
Performance.

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What should be included within SOPs?

• Purpose of the operation/process.
• Plant/equipment/materials being used.
• Process steps – who, what, where, how, why.
• Hazards and risks:
- controls required and order in which applied.
• Pictures, photos, drawings, flowcharts, checklists.
• Authorisation of workers to undertake procedure.
• PPE requirements.
• Availability/accessibility of spare parts, together with the
necessary standard.

Requirements for procedures to be clearly

understood

• Draft, trial and revise the procedure until it’s clear and easily
followed.

• Include operators in the drafting.

• Involve someone not familiar with the procedure to

demonstrate it can be followed.

• Explain not only ‘what’ and ‘how’, but also ‘why’.

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Video

When procedures aren’t fully understood, disasters

can happen.
Incident at the West Fertiliser Company in Texas.

Ensuring SOPs remain current and accurate

• Report and analyse all deviations from the expected process

parameters.
• Undertake programmed reviews and oversight of actual practice
(observation or retrospective analysis, eg quality of end product).
• Careful checking and monitoring of the SIS (linked to risk-based
inspection).
• Review of MOC reports, inspection records and reports.
• Review frequency of maintenance on safety-critical plant and
equipment

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Ensuring SOPs remain current and accurate

Variations are indicative of potential loss of the safety envelope.
They can be detected by:
• assessment of defect complaints;
• product out of specification;
• reports on deviations in the process;
• variations in yield;
• feedstock raw material records;
• adverse event reports.

Limitations of SOPs
Factors that affect operators to follow SOP
• Time pressure.
• Workload.
• Staffing levels.
• Training.
• Supervision.
• Human fallibility.
• Technical issues.

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Consequences of deviating from operating

procedures

• Organisational ‘drift’.

• Major disaster for both

operators, plant and
the organisation’s reputation.

Importance of responding to alarms

• Example of Three Mile Island
• Operators took 2.5 hrs to understand the problem
• Texas City – tired and poorly trained operators
• Essential that operators are trained, confident and well-
rehearsed in the required actions to take in the event of an
alarm activating
• Should reduce unplanned downtime, increase levels of
process safety, improve operator effectiveness and produce
better process performance

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Element 3: Process safety hazard control

3.1 Operating procedures.
3.2 Safe start-up and shut-down.
3.3 Safety critical performance standards.
3.4 Utilities.
3.5 Electricity/static electricity.
3.6 Dangerous Substances.
3.7 Reaction hazards
3.8 Bulk storage operations

Types of start-up and shut-down

• Follows pre-determined, controlled sequence
Planned • Includes a risk assessment

• Partial or complete
Unplanned • Can be dangerous in any event

• Type of unplanned shut-down

Emergency • Whenever a hazardous situation develops

• Usually a type of planned start-up/shut-down

Staged that requires staged processes

• When an issue has been raised, but an

Delayed assessment is made to control the situation
until shut-down is allowed to proceed

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Planned
• Start-up and shut-down (‘turnaround’) follow a pre-determined
sequence.
• Planned shut-down: when plant is closed for periodical
maintenance/replacements.
• Planning done well in advance
(months).
• Risk assessment.
• Linked to product supply and
assessment of plant requirements.

Unplanned
• Shut-down is unexpected, eg equipment malfunction, power
failure, operator error.
• May be partial or complete.
• The absence of a plan makes it more
dangerous.
• The nature for the require shut-down
will have a direct impact on the issues
to be addressed.
• Often involves only part of a plant.

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Emergency
• No pre-shut-down review.

• When a hazardous situation develops, usually as a result of a

breach in the safe operating envelope (out of normal scope).

• Human factor plays a paramount role.

• No stages, difficult to use checklists.

• Very high risk.

Staged
• Done in stages, eg some parts of a large plant may take
several days to shut down.

• Start-ups: progressive process

implementation.

• All planned shut-downs are

generally staged to prevent impact
on operations.

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Group discussion

Why do you think both start-up and shut-down are

potentially dangerous processes?

Group discussion
Some reasons start-up and shut-down are potentially dangerous
processes:
• Plant and process controls may be turned off or adjusted for
the shut-down.
• Never really know the full status of the process/plant.
• May not be able to plan for every contingency.
• Plant and process needs to be restored to its steady state and
this will require variations from normal operating status.

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 18/12/2020

Pre-start-up safety review

Factors to consider
• MOC.
• Pressure testing and gauge control setting.
• Safety systems all operational.
• Mechanical preparation.
• Chemical cleaning instructions.
• Physical cleaning instructions.
• Mechanical restoration.
• Machinery run-in.
• Tightness testing.

Pre-start-up safety review

• Electrical testing/functional tests/energising.
• Operation and calibration of alarms and RVs.
• Instruments calibration and functional test.
• Loading of chemicals.
• Loading of catalyst.
• Heaters drying.
• Chemicals boil out of steam generation facilities.

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Alarms
• Assist the operator to identify abnormal, hazardous and
unsafe plant and process conditions.
• Operators must be able to identify, understand and respond
to alarms appropriately.
• Consider:
‒ Do they require an operator response?
‒ How are they presented to the operator?

Plant shut-down
• Communications.
• Testing/checking of safety
and operational controls
(emergency blowdown,
ESDVs, PRVs, trips, alarms).
• Checking of plugs and blinds.
• Checking structural and
physical connections.

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Element 3: Process safety hazard control

3.1 Operating procedures.
3.2 Safe start-up and shut-down.
3.3 Safety critical performance standards.
3.4 Utilities.
3.5 Electricity/static electricity.
3.6 Dangerous Substances.
3.7 Reaction hazards.
3.8 Bulk storage operations.

Group discussion

1. What is a ‘performance standard’ for a safety

critical system or item of equipment?

2. Why are performance standards needed?

3. What are the sources of performance standards?

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 18/12/2020

Key term

Safety-critical element (SCE)

A good definition of this terms is included in UK regulations designed
for the offshore oil and gas industry.
“Such parts of an installation and such of its plant (including computer
programmes), or any part thereof:
1. The failure of which could cause or contribute substantially to; or
2. A purpose of which is to prevent, or limit the effect of a major
accident.”
Source: The Offshore Installations (Safety Case) Regulations 2005

Reasons for performance standards

for safety critical systems/equipment

• Necessary to ensure the safety of an asset.

• To ensure that Safety Critical Elements will perform according

to the design criteria and expectations.

• Each SCE is assessed and interdependencies/interactions

examined.

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Key terms
Performance Management of
standard (PS) change (MOC)
In high-hazard industries, it is
This is the general terms used to recognised that even seemingly small
mean an agreed standard that is set changes (eg to equipment) can have
and against which actual large potential consequences if they
performance is measured and are not thought through properly
judged. Various models and beforehand. MOC is a management
methods are used for setting control approach to make sure that
performance standards in process proposed changes are properly
safety eg, the ‘FARSI’ model. addressed and authorised.

FARSI

• F = functionality
• A = availability,
• R = reliability,
• S = survivability
• I = interdependency

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Key terms
Process hazard
analysis (PHA)
A systematic analysis of the
hazards (and their potential
causes and consequences)
relevant to a particular process.
This may use one or more
specific techniques such as
HAZOP, What-if of FMEA.

Reasons for performance standards

• Used as the basis for managing

the hazard through the life cycle
of the plant/installation.

• Provide assurance that critical

risk control systems will remain
suitable and continue to function
for their intended purpose.

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The FARSI model for defining performance

standards
• Functionality
• Availability
• Reliability
• Survivability
• Interdependence

Functionality
• The task the particular element is
required to perform.

• The standard it needs to perform to.

• How the performance can be

measured, eg fire drenching system
(reference to required water flow
rate, etc).

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Availability
• Proportion of time it needs to be available (and
capable) to perform.
• Will it perform under the
conditions which are
expected?

Key terms
Probability of failure Mean time between
on demand (PFD) Failure (MTBF)
This is the probability that a
component will fail to perform its This is the calculated average
safety function at the time it is time that elapses between
needed. Note that a component failures of a system, equipment
may have more than one safety or a component. This is used in
function/mode of operation and relation to predicted failures of
the PFD may be different for repairable systems.
each of these functions.

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Key terms
Safety integrity Safety instrument
level (SIL) system (SIS)
This is related to the concept of An instrumented system used to
safety integrity which is the average implement either a safety control
probability of a SIS performing its and/or protection function. An SIS is
function (under the stated conditions made up of three connected parts
for a required period to time). The (sensor/s, logic solver/s, final
SIL is then used to specify the safety elements). The logic solver decides
integrity requirements that the SIS what action to take depending on
needs to have. There are four levels the sensor input. The final element
in the SIL system, 1 being the lowest carries out the physical action, eg,
and 4 the highest. valve. The three parts of the SIS may
be based on programmable
electronics/software.

Reliability
• How likely is it to operate (or fail to operate) on demand

• Often expressed using PFD or MTBF values.

• Active systems can be assigned target values, eg no more

than 1% downtime for individual detectors in any 12 month
period.

• SIL value used to specify safety integrity needs for safety

instrumented systems (SISs).

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Survivability
• Operate under specified conditions, particularly post-
event.

• For example, fire and gas system shall survive fire or

explosion for as long as the temporary refuge is
protected for.

Interdependencies
• Do other systems require to be functional for it to
operate?
• Fire/smoke detection system have a dependency on
‘emergency power’ and an interaction with ‘HVAC
dampers’.
• ESD requires power to operate.

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Group discussion

What are the interactions/dependencies in each of

the following cases:
• Blowdown?
• Deluge?
• Emergency shut-down?

Element 3: Process safety hazard control

3.1 Operating procedures.
3.2 Safe start-up and shut-down.
3.3 Safety critical performance standards.
3.4 Utilities.
3.5 Electricity/static electricity.
3.6 Dangerous Substances
3.7 Reaction hazards.
3.8 Bulk storage operations.

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 18/12/2020

Group discussion

Outline five main uses of steam in your organisation.

Uses of steam within the processing

industries
As a source of heating (direct or indirect) for spaces and processes:

• steam for heating at positive pressure used in food processing

factories, refineries and chemical plants;

• saturated steam: heating source for process fluid heat

exchangers, reboilers, reactors, combustion air pre-heaters and
other types of heat transfer equipment;

• steam humidification is also used in space heating systems.

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Uses of steam within the processing

industries
• Motive power to drive equipment, eg
turbines.
• Move liquid and gas streams in piping.
• Separation of vapour streams, eg
‘steam stripping’ in distillation towers.
• Cleaning.

(Continued)

Uses of steam within the processing

industries
• Wetting - in processes requiring humidification or
moistening of materials, eg paper mills and production
areas using pellets.
• Atomising - injecting steam into fluids atomises the fluid
and increases surface area, eg flare stacks and other
burners.
• Sterilisation - in processes for microbiological control, eg
food, pharmaceuticals.

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Properties of saturated steam

• Produced at the boiling point of water (which

depends on pressure).
• Visible, eg vapour coming from a boiling kettle.
• Releases its heat immediately (more efficient than hot
water).

Properties of saturated steam

• Condensate formation:
‒ Steam still wet (3-5% of water may be entrained in the
steam).
‒ Reduces heat efficiency.
‒ Problems for pipe work and reactor vessel.
‒ Condensate has to be removed as near to the point of use
as possible by steam traps.
‒ Sometimes known as ‘wet steam’.

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Properties of superheated steam

• Made from saturated steam subjected to further pressure
and heat.
• An invisible gas.
• Temperature of > 200°C.
• Rapidly releases heat.
• Does not produce condensate when it meets air or surfaces.

Steam hazards
• Thermal expansion (of pipes, vessels, etc):
‒ Use flexible/expansion joints.

• Vacuum formation:
‒ Cooling creates condensate (volume reduction).
‒ Leads to vacuum formation.
‒ Use of ‘vacuum breakers’ in steam lines to equalise
pressure.
‒ Ensure sufficient pressure to discharge condensation.

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Steam hazards
• Water in steam lines (water hammer):

‒ Water in a pipeline striking a fixed object under high

pressure, eg a bend or tee in pipeline.

‒ Striking the bend/tee sets up vibrations caused by the

pressure shock that is imparted.

‒ Mild cases – knocking noise (hammer) + pipe movement.

‒ Severe cases – pipe fracture and loss of contents.

Steam hazards
• Water hammer (continued) – two basic mechanisms in
steam systems:

‒ water entrained in steam being rapidly moved through

pipe (as condensate);

‒ steam rapidly condenses (due to being surrounded by

lower temperature condensate). Large pressure drop
causes cooler condensate to rush in to fill the void
created.

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Steam hazards
• Water hammer control:
‒ good design of pipework and process controls;

‒ removal of condensate;

‒ maintaining steam traps and drainage;

‒ improving the quality of the steam (minimise water),

steam velocity and flow.

Steam hazards
• Water hammer control:
‒ maintain pipework insulation;

‒ control/avoid pressure drops;

‒ avoiding the risk of explosion by not mixing hot and cold

(high pressure steam with ‘cooled’ condensate);

‒ ensuring steam pressure and temperature are reached

before allowing steam flow.

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Water hazards
• Vacuum formation during draining operations:
‒ draining without proper venting can create (partial)
vacuum;
‒ vessel collapse/deformation;
‒ Ensure ‘vacuum breaker’ valves.

Water hazards
• Hydrostatic testing:
‒ used for final proof testing to identify leaks;
‒ vessel supports designed for gas vessel may not be designed to
withstand weight of water;
‒ vessel pressurised with water;
‒ check for leaks;
‒ water removed and vessel dried;
‒ possible vacuum formation on draining water;
‒ possible corrosion (contaminants in water);
‒ ensure SOP for venting, draining and removal of hazardous
conditions.

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Water Hazards
• The ‘weight’ method (alternative to hydrostatic testing):

‒ vessel pressurised with water;

‒ measure weight of water retained and expelled when the

pressure is released - to calculate the degree by which the
vessel itself expanded.

Water hazards
• Cooling towers – Legionella and water-fog:
‒ Legionella bacteria exists in water;
‒ grows between 20°C and 55°C (37°C is ideal);
‒ feeds on nutrients in water;
‒ risk of disease if water droplets
containing viable bacteria are inhaled;
‒ cooling towers - hot water/high air flow
generates aerosols (‘water-fog’).

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Water hazards
• Cooling towers – controls:
‒ treat water with a biocide;
‒ remove nutrients from water;
‒ controlling temperature in make-up water and in ponds;
‒ prevent the spread of escaping water droplets by fitting
drift eliminators.

Inert gases
• Noble gases (He, Ne, Ar) + Other gases (N2, CO2).

• Colourless and odourless.

• Generally unreactive (except in rare occasions).

• Used to exclude oxygen.

• Very good fire and explosion suppressants.

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Typical uses of inert gas

• Inerting equipment to prevent flammable atmospheres.
• Preparing equipment for maintenance by purging out
hydrocarbons.
• Removing air/oxygen in equipment before start-up.
• Blanketing tanks to prevent the ingress
of air.
• Certain welding operations.
• Decommissioning equipment to prevent
the ‘rusting’ process.
• Instrument air back-up.

Inerting/purging
• Inert gas is applied to reduce/remove oxygen (in air) – the air
is forced out.
• Important to ensure that:
‒ all the air is removed;
‒ overspill of the inerting gas is controlled;
‒ assessment made of the likelihood of any electrostatic
effects that might compromise the area as fluids are
removed or gases discharged.

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Inerting/purging
Uses:
• to prevent any fire or explosive atmosphere from forming by
removing air (oxygen) in the system;
• reaction processes: to displace oxygen and create a non-
explosive atmosphere;
• during maintenance: to remove flammable material and
ensure oxygen/flammable mixtures do not arise.

Inerting/purging hazards and risks

• Creates non-breathable atmosphere (displaces oxygen).
• Nitrogen differentially replaces carbon dioxide which
prevents the breathing reflex.
• Low temperatures - potential for serious cold burns:
‒ gaseous N2 and CO2 are liquid when compressed (CO2 - 20°C, N2 -
210°C);
‒ need to insulate storage vessels and pipe work to protect from the
danger of direct contact with people as well as to maintain
temperature.

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Blanketing of storage tanks

Addition of an inert gas into the head space of a tank

• Removes risk of flammable or explosive atmosphere as the

tank is being filled (or emptied, air entering via vents)

• Because an oxygen rich head space is left above the liquid in

the tank.

Fire-fighting agent
• Inert gases extinguish fire by replacing the oxygen.

• Risk of exposure to asphyxiating atmospheres.

• Typically:
‒ CO2 used in office areas and on some plant.
‒ 52% N2 , 40% Ar, 8% CO2 mixture for industrial and
process plant.

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Pipeline freezing operations

• N2 often used as a coolant because of its very low
temperature.
• Injecting liquid N2 in a blanket around a pipe freezes the
contents allowing:
‒ maintenance;
‒ alterations; and
‒ repair work.
• Cost effective and relatively easy.

Video

Hazards of asphyxiation and burns.

Pipe freezing.

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Nitrogen use as back up instrument air

• Valve and process operated pneumatically may in some

circumstances also be operated by N2.
• Dry and readily available.
• Will not support fire/explosion.
• Ensure safety of workers and pipe work is protected.
• O2 level detectors may be required in work areas to alert workers
in the event of a N2 leak (which will reduce O2 levels).

Element 3: Process safety hazard control

3.1 Operating procedures.
3.2 Safe Start-Up and Shut-down.
3.3 Safety Critical Performance Standards.
3.4 Utilities.
3.5 Electricity/Static Electricity.
3.6 Dangerous Substances.
3.7 Reaction Hazards
3.8 Bulk Storage Operations

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Basic circuitry for current to flow

Conventional current flow

switch
battery

Light bulb electron flow

Characterised by: Potential difference (voltage), Current, Resistance

Voltage × Current × Resistance

Potential difference (Voltage), Current and Resistance related by
the OHM’s law equation:

V=I×R

Quantity Unit name Unit symbol

Voltage Volt V
Electric current Ampere (amp) A
Resistance Ohm Ω

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Types of current
Direct current (DC):
‒ current flows in one direction with a constant voltage
polarity (same difference between each end of the wire);
‒ used in short distance applications, eg batteries.

Alternating current (AC):

‒ current that changes direction periodically (in phases
moving in both directions along the wire) along with its
voltage polarity;
‒ for applications requiring greater power (operates
effectively over much longer distances).

Hazards of Electricity
Depends on:
• Amount of current flowing through the body (Ohm’s law
- depends on V and R).
• Frequency.
• Path electricity takes through the body.
• Duration.

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Impact on the Body

0.5 – 2mA Threshold of perception
2-10mA Painful sensation
10 – 25mA Inability to let go. Danger of asphyxiation
25 – 80mA Loss of consciousness from heart
or respiratory failure
80 – 2000mA Ventricular fibrillation , (erratic heart functioning)
burns at point of contact

2000mA and above Cardiac arrest, burning of internal organs and

tissues leading to death

Impact on the Body

Frequency of the current may cause muscle spasm and result
in the muscles ‘freezing’:
– will cause the hand to hold on and the person will be
unable to let go;
– heart and lungs may also be affected and stop altogether.

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Electric arcs and sparks

• Occurs when two conductors are separated when carrying a
charge:
‒ break in the circuit can result in the current jumping from one
conductor to the other, eg a switch mechanism or a short
circuiting of a power supply line.

• Can be extremely violent -

extreme heat + bright light.

Electric arcs and sparks

• Risk to workers in the vicinity.

• Risk of ignition of any volatiles, dusts, clothing.

• Risk of explosion (ignition of

flammable atmosphere).

• Possible serious damage to

equipment and the power
distribution system.

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Video

Watch the following videos on arcing.

• Arc flash demonstration.

• Arc flash accident.

How arcs/sparks occur during normal

operations
• High-voltage switch rooms and panels.
• Defective or poorly wired cabling and connections.
• Operation of relays.
• Incorrect use of tools.
• Adopting incorrect procedures resulting in shorting or bypassing
of safety controls (live working especially).
• Low-voltage systems may be at greater risk as the automatic
circuit breaker may not be designed to act as fast as that on high
and very high voltage installations.

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How arcs/sparks occur during normal

operations
• Failures in switches.
• Accumulation of dust and debris, especially in
medium- and high-voltage systems in contact areas
may result in arcing.
• Condensation and corrosion.
• Poor or faulty design and installation.

Electrostatic charges
• Charge builds up on the surface of a non-conducting material which
is then dissipated by discharging it to a conducting material.

• May be created by pressing two materials together (if materials are

of the right type):
‒ electrons pulled from the surface of one of them onto the other;
‒ a static charge is then created (one surface becomes + and one – ).

• More efficient to rub two surfaces together ‘tribocharging’.

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Electrostatic charges
• Non-conductors give up or attract electrons relatively easily so that
when exposed to heat, pressure or friction electrons will be
released or absorbed.
• Material then becomes either negatively or positively charged
depending on whether it has absorbed or given up electrons.
• In this condition the material now represents a potential difference
to the surroundings which then creates a potential for sparking to
occur as the charge is dissipated.
• In an explosive or flammable atmosphere the discharging spark
may have sufficient energy to ignite it.

Electrostatic – other methods of

creation
• Pyroelectric effect: Applying heat to a material at one point
causes the electrons to move and one surface becomes
positively charged and the other negatively.
• Piezoelectric effect: Stress applied to certain crystals
creates a charge.
• Inducing a charge: Placing charged material near to a
conductor (or non-conductor) which allows its electrons to
move freely. The charged material induces a charge in the
originally uncharged material.

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Group discussion

Static in Process Settings

How can static charge occur in process settings?

Give some examples of how it can happen.

Types of static - spark discharges

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Types of static - corona discharge

Types of static - brush discharge

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Types of static - propagating brush

discharge

Types of static - conical pile discharge

(Maurer discharge)

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Types of static - streaming current charge

• Develops in flowing liquids in pipes (friction).

• Contact enables electron exchange to take place.

• Liquid picks up a charge which is then moved through the

pipe as the liquid flows, accumulating charge on the way.

• Insulating liquids unable to dissipate charge back through

the liquid and will discharge when coming into contact with
air or another conductor.

Typical situations that generate

electrostatic charge
• Movement on conveyer belts.
• Transporting materials.
• Pouring solids and liquids into containers.
• Sieving and grinding operations.
• Agitation and stirring.
• Creation of charge on workers walking in insulated shoes or
on an insulated surface.

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Control of electrostatic charges through

bonding and grounding
• Fixed objects - provide a permanent connection from the plant,
structure, etc to earth.

• Moveable objects (such a filling bins) - ‘flying’ lead attached to the bin
which is then clipped onto an earthing connection at the point of use.

• Both require a good connection – eg not covered in dust and debris.

• Where direct earthing not possible, eg liquids in glass-lined pipe or

containers, use a tantalum plug in the line or by dipping an earth lead
extended to the bottom of the container.

Group discussion

Planning for power outages

What consequences might a sudden power outage have

on an installation such as a refinery or large chemical
plant?

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Power outages
TWO approaches to consider

• Uninterruptible Power Supply (UPS) – for short time outages, up to

an hour.

• Generator – for longer outages (often in tandem with the UPS).

UPS
• Takes power (AC), stores it in a battery (DC) via a rectifier and
then passes it back through an inverter (which restores the
DC to AC) and then back into the distribution system.

• Three approaches:
‒ offline;
‒ online;
‒ line interactive.

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Video

Uninterruptible power supply (UPS).

Generators
Portable generators:

– can be used before the UPS ceases to function;

– matched to the power requirement of the equipment to

which they are to be connected;

– kept on site or hired in;

– safety procedures to ensure the safe connection and

disconnection in energised systems.

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Generators
Fixed generators:

– can be installed to match the expected total load or partial

required load of the plant;

– dead time between start of the outage and start up of the

generators;

– power surges.

Generators
TWO critical aspects with generators

• Maintenance and testing to ensure they are fit for purpose

when required in an emergency.

• Ensure adequate fuel supplies are available.

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Element 3: Process safety hazard control

3.1 Operating procedures.
3.2 Safe start-up and shut-down.
3.3 Safety critical performance standards.
3.4 Utilities.
3.5 Electricity/static electricity.
3.6 Dangerous Substances
3.7 Reaction hazards.
3.8 Bulk storage operations.

Group discussion
Physical forms of dangerous substances
There are three basic physical states in which
substances can exist:
1. gas;
2. liquid;
3. solid.
In groups – agree descriptions of the characteristics of each of
these states.

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Physical forms of dangerous

substances
Substances can
• Change state.
• Co-exist in more than one state.
• Have different forms (eg dust vs lump).
For example, water can be a:
• gas (superheated steam);
• liquid (at STP);
• solid (ice).

How form affects risk potential

Gases
• Fire and/or explosions:
‒ flammable gases/vapours form explosive mixtures with
air even at low concentrations.

• Harm to human health and/or damage

to materials;
‒ asphyxiants (eg N2, CO2);
‒ corrosive (eg NH3, Cl2 ).

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How form affects risk potential

Liquids
Much easier to contain a release (eg by bunding) than it is for
gases.
• Fire and/or explosion:
‒ fire spread through liquid flow (fuels and solvents).
• Harm to humans, plant and the environment:
‒ acids, alkalis, etc.

How form affects risk potential

Solids
• Risk depends on shape, form and size:
‒ large size harder to ignite/explode/react;
‒ smaller size (eg dusts, powders) much easier to ignite/react.
• Finely divided metals are highly dangerous, eg exposure of
aluminium powder to water.
• Dusts mixed with air present a very large surface area creating a
flammable atmosphere, eg sieving operations.

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Explosive substances
• Risk of exploding in the right mixture with oxygen (air) if
sufficient energy is available.

• Explosive substances have very low minimum ignition

energies.

• The energy may be created by heat, shock or electric charge

(such as electrostatic friction).

Oxidising substances
• Add oxygen to other substances.

• They easily ‘oxidise’ susceptible substances (eg metals, metal

hydrides and organics) and create conditions for a fire to
occur or make a fire worse.

• Examples of common oxidising agents: nitric acid,

hypochlorites (halogen) and hydrogen peroxide.

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Key term
Flash point

The lowest temperature at

which sufficient vapour is
given off to ‘flash’, ie ignite
momentarily (not continue to
burn), when a source of
ignition is applied to that
vapour.

Flammable Liquids
Flammable
liquid Condition
category
1 Flashpoint < 23°C AND Initial boiling point ≤35°C

2 Flashpoint < 23°C AND Initial boiling point >35°C

Flashpoint ≥23°C AND Initial boiling point ≤60°C

3
(i.e. flashpoint between 23°C and 60°C inclusive)

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Flammable Gases

Element 3: Process safety hazard control

3.1 Operating procedures.
3.2 Safe start-up and shut-down.
3.3 Safety critical performance standards.
3.4 Utilities.
3.5 Electricity/static electricity.
3.6 Dangerous Substances.
3.7 Reaction hazards
3.8 Bulk storage operations

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Group discussion

What is a chemical reaction?

What affects how quickly a reaction takes place (or

whether it happens at all)?

Effect of temperature

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pressure

Catalysts

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Exothermic and endothermic reactions

Exothermic (very common)

• Produces heat, eg combustion reaction.

Endothermic (less common)

• Takes in heat from the surroundings, eg reaction
between ‘vinegar’ and ‘washing soda’.

Thermal runaway reaction

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Thermal runaway reaction - causes

• Incorrect vessel charging:
‒ incorrect reactants;
‒ incorrect volumes of reactants;
‒ wrong specification of raw materials (impurities).
• Incorrect use of catalysts.
• Poor/failed temperature control.
• Poor/failed mixing.
• Loss of power (which affects critical controls).
• Maintenance failures.
(Continued)

Thermal runaway reaction - causes

• Instrumentation failures.
• Variations in operation:
‒ result of the failure to apply MOC procedures; or
‒ a basic lack of understanding of the reaction chemistry.
• Design failure resulting in insufficient controls, eg heat cooling.
• Insufficient operator training or familiarisation.
• Inadvertent addition of compressed air, nitrogen, steam, etc.
(increases pressure).
• Exposure of the vessel to fire.

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Thermal runaway reaction -

consequences
• Venting or dumping of product and materials.

• Loss of production and probably damage to equipment.

• Unintended chemical reactions, such as decomposition or

other runaway reactions.
• Vessel over-pressure:
‒ catastrophic rupture – missiles, etc;
‒ loss of containment – toxics, flammables (fire/explosion).

Video

Thermal Runaway Reaction - Consequences

The Seveso incident in Italy – 10 July 1976

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Thermal runaway reaction - protective

measures
• Containment within the reactor.

• Crash cooling.

• Drowning and quenching of reactor.

• Emergency venting/dumping of
reactants.

Element 3: Process safety hazard control

3.1 Operating procedures.
3.2 Safe start-up and shut-down.
3.3 Safety critical performance standards.
3.4 Utilities.
3.5 Electricity/static electricity.
3.6 Dangerous Substances.
3.7 Reaction hazards.
3.8 Bulk storage operations.

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Tanks
Eight types of tanks used to store liquids
• Fixed-roof tanks (atmospheric tanks).
• External floating roof tanks.
• Internal floating roof tanks.
• Domed external floating roof tanks.
• Horizontal tanks.
• Pressure tanks.
• Variable vapour space tanks.
• Liquefied Natural Gas (LNG) tanks.

Hazards and Risks

• Overfilling.
• Effects of vacuum.
• Overloading of foundations.
• Failure modes for tank shells and associated pipe work.

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Overfilling
Overfilling leads to:
• fluid overflows and escapes (to potential ignition sources –
fire and explosion risk);
• liquid released through the vents intended for vapour;
• over pressurisation of tank which then ruptures.

Typically due to:

• operators unaware of the level in the tank;
• instrumentation failure in automatic filling systems.

Effects of vacuum
• Created during tank emptying or draining.

• Tank will deform and/or collapse.

• Use of vacuum breaker valves - loss of pressure in the

head space above the liquid is compensated when the
tank is emptied.

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Overloading of foundations
Typically a combination of
• Loading exerted when (relatively light) tank is filled with
liquid:
‒ density of liquids varies/weight may be significantly
different from product to product;
‒ tank base may deform when filled/emptied.

• Ground instability (soft/liable to movement):

‒ loss of contents.

Overloading of foundations
• Ensure solid concrete foundation/circular ring beam
foundation.
• Design: tank design, construction and foundation
suitable for intended contents.
• Use of anchor bolts (eg where expect high winds).

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Failure Modes for Tank Shells and

Associated Pipe Work
Metals used for tanks and pipelines may fail, for
example:
• creep;
• stress;
• thermal shock;
• brittle fracture.

Failure modes for tank shells and

associated pipework

Creep
failure

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Failure modes for tank shells and

associated pipework
Stress:
Stress (loading on a material)
causes strain (deformation of
material).

Materials fall into two

categories:
• ductile - moves under strain;
• brittle - breaks under strain.

Failure modes for tank shells and

associated pipework
Stress/loading exerted by:
• the contents;
• temperature changes;
• variations in loading.

Stress failure also due to:

• stress corrosion - failure which occurs when a metal
corrodes;
• hydrogen embrittlement - incursion of hydrogen atoms.

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Failure modes for tank shells and

associated pipework
Thermal shock
• Rapid and extreme temperature changes.

• Different parts of the material expand and heat by different

amounts.

• Causes cracking to develop - failure.

Failure modes for tank shells and

associated pipework
Brittle fracture
• Occurs suddenly under excessive stress.
• No or limited elasticity.
• Known as ‘snatch’ loading.
• Low temperatures can increase risk of
fracture, eg materials used for storing and
conveying LPG.

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Failure modes for tank shells and

associated pipework
Fatigue failure

• The formation of cracks as a result of repeated application

of loads which individually do not cause failure.
• May appear as thermal fatigue, contact fatigue, surface or
pitting fatigue, subsurface cracking or subcase fatigue, and
corrosion fatigue.

Failure modes for tank shells and

associated pipework
Fatigue failure
Fatigue fracture is caused by the combination of:
• cyclic stress;
• tensile stress;
• plastic strain.

Storage tanks fatigue may also be induced by:

• wind load/vibration;
• pump-induced vibration;
• pedestrians walking on/over components.

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Group discussion

What sorts of things would you need to consider in siting

of bulk storage tanks for dangerous substances?

Considerations

• - Size and type of tank.

• - Contents (flammable, toxic, polluting).
• - Topography (level ground, sloping ground, high level, low level).
• - Purpose of tank in relation to process (feed stock or product,
proximity to point of use).
• - Land use planning requirements (legal requirements for siting
structures).
• - Total inventory (how much material is being stored).
• - Whether the tank is underground, above ground or mounded, etc.
• - Distance from sensitive areas (populations, environments, etc.)

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Siting of tanks - distance

(from people, property and other tanks)

Siting of tanks - ventilation

• To allow variation in internal and external pressure during
filling and emptying.
• Venting to atmosphere - dispersion of volatiles.

Avoid:
• Flammable/explosive mixtures.
• Release of toxic vapours.

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Filling of tanks
• System for filling a tank should be foolproof (required SIL).

• Speed - tank should be able to

equalise pressures by means of
the designed venting arrangements.

• Procedures and equipment.

• Competent operators.

Filling of tanks
Overfilling
• Continuous monitoring to prevent overfilling.
• Volume of vessel and content should be known before filling.
Alarms
• Two alarm trip systems:
‒ high level alarm (LAH) - normal operational level exceeded (not a
reference point for filling operation);
‒ high high level (LAHH) - maximum design capacity of the tank.
• If LAHH is exceeded the tank will overpressurise and overflow.

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Road tankers
• The mobile nature means there has to be a temporary
(flexible hose) connection made between the road tanker
and the storage vessel.

• Liquids are pumped between

the two (either using the site
pump or a local one on the
vehicle).

• This brings additional risks.

Road tankers
Risks
• Drivers drive off leaving the hose still coupled to the tanker:
‒ overcome by using breakaway couplings.
• Static - earth bonding:
‒ dipping rods should be earthed.
• Siphoning - end of the tank filling line below the lowest
normal operating level of the liquid.
• Splash filling - generation of static electricity.

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Floating roof tanks

• Roof floats on the top of the liquid inside the tank.
• Two types: internal and external.
• Advantage: no head space above the liquid:
‒ formation of vapour is virtually eliminated.
• Emissions to air controlled.
• Used for the more flammable liquids which have a high
vapour pressure, low flash point.

External floating roof tank (EFRT)

Key:
A: Flexible connectors and
valves from foam supply devices
B: Limit chain
C: Float check valve
D: Horizontal supply piping to
continuous linear spreader
nozzles

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Landing the roof

• Typically every 5-10 years (for maintenance).

• Roof of a FRT will be landed – rests on its legs (so 1.5-2m

high).

Hazard

• As tank is emptied/filled, space fills with vapour/air mixture

(venting is via in-breather/out-breather vents).

Sinking the roof

• Heavy rainfall can result in water loading on the roof.

• Sinking may result in loss of buoyancy in the roof due to an

imbalance in the supporting structure.

• Incorrect design - if weight of the roof is not supported by

the liquid on which it is floating due to insufficient buoyancy.

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Rim seal fires/failures

• Susceptible part of FRT is the seal between the roof and the
sides of the tank - rim seal.
• Double seal - designed to keep water out and vapour in.
Fails due to:
• wear and tear;
• tank movements;
• wind pressure, ground movement and internal pressure
changes (filling /emptying).

Rim seal fires/failures

Rim fails
• Rain water will enter and mix with the contents of tank.
• Surface exposed to air possibility of flammable or explosive
mixtures.
• Risk of fire.
• Fire protection system installed in the roof, eg foam discharge.
Ignition comes from either:
• lightning strike;
• localised induced static charge.

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Fixed roof tanks and

pressure and vacuum hazards

Bunding – design/construction
• At least 110% of the total volume of the tank(s).
• Effective to contain any boil over or top loss, and bottom loss
and catastrophic failure.
• Allow for access (for inspection, maintenance).
• Allow for rainwater (e.g. drain-off point).
• Maintained (age, deterioration, vegetation, etc.).
• Sealing where pipe work and valves break through wall.

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Bunding – design/construction
• Shut off valves both inside and outside the bund, inner shut
off close to the tank.

• Non-return valves on filling lines.

• Isolating valves and ROSOVs should be fully functional and

fail to safe.

• Lines for draining tanks and the valves blanked off.

Protection from extremes of weather

• Hot and cold climates: temperature variation will affect
tanks. Hence use of:
‒ insulation;
‒ trace heating.

• High wind loadings:

‒ distortion can be limited by girding the tank with metal
bands.

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Lightning strikes
• Can ignite volatiles and cause catastrophic failure.

• Can create a current which will induce sparking some

distance from the strike point.

• Puncture of the tank skin or formation of local hot spots will

ignite flammable vapours.

• Floating roof tanks susceptible to lightning strike.

Lightning strikes
Control measures:

• Lightening conductors at the appropriate attachment points:

‒ tank rim;
‒ roof when it is in a high position (EFRT).

• Inerting to keep the level of flammable vapours down.

• Ventilation to reduce the hydrocarbons in the air.

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Group discussion

Chemical warehousing
Storage of hazardous substances in warehouses presents a
number of risks, eg Allied Colloids fire.

What factors need to be considered when assessing the

potential chemical hazards present AND their storage
requirements?

.
• - The hazardous nature of the stored substances.
- The consequences arising from:
• - Inadvertent mixing of incompatible chemicals.
• - Leaking and spillage from containers.
• - Possible reactions from exposure to elevated temperatures.
• - Significant release of dust and powders and solvents.

• Look at factors needed to assess storage requirements – in small

groups. The next few slides take you through some of these issues
in more detail.

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Warehousing assessment
Understanding the hazardous nature of the substance(s) to be
stored:
• form (liquid, solid, powder, dust, etc);
• physical properties (flammability, pH, etc);
• relevant reaction chemistry information (eg reacts with
water);
• safety data sheets (SDS) (formerly MSDS);
• for substances created and stored on site similar set of
information required.

Warehousing assessment
• Transportation: in what and by what.
• Inventories.
• Sources of ignition - including electrostatic - or creation of
flammable /explosive atmospheres.
• Topography.
‒ Presence of drainage, water courses, etc.
‒ Vulnerability of buildings.
• Temperature effects.

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Warehousing siting, location and security

• Local topography.
• Proximity of community buildings, housing, schools, hospitals, etc.
• Legal requirements for separation distances of specified materials, e.g.
LPG cylinders.
• Routes for receiving and dispensing.
• Vehicle movements.
• Access for emergency vehicles.
• Fire-fighting facilities, eg open water.

Warehousing siting, location and security

• Trespassers.
• Arson.
• Stock control.
• Authorised people only.
• Windows and other openings.
• Security should not compromise fire safety.
• Physical controls, eg lockable doors.
• Inadvertent incorrect storage of incompatible materials.

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Warehousing inventory
Consequences of an untoward event:
‒ release;
‒ spillage;
‒ fire, etc.
Inventory management:
‒ reduce the total volume of material that is exposed at any one
time.
‒ separating storage so that the possibility of mass release is
avoided.
‒ Just-in-time resupply.
‒ direct delivery to point of use.

Warehousing inventory
separation and segregation of dangerous goods

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Warehousing - control of ignition sources

• Where flammables, identify and control:

‒ smoking;
‒ use of mobile phones;
‒ fork lift trucks/vehicles;
‒ hot work;
‒ maintenance activities.

Element 3: Summary
3.1 Operating procedures
3.2 Safe start-up and shut-down
3.3 Safety critical performance standards
3.4 Utilities
3.5 Electricity/static electricity
3.6 Dangerous substances
3.7 Reaction hazards
3.8 Bulk storage operations

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NEBOSH / HSE
Certificate in Process
Safety Management

Element 4
FIRE AND EXPLOSION
PROTECTION

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Learning Outcomes
4.1 Explain fire and explosion hazards relating to process
industries.
4.2 Outline appropriate control measures to minimise the
effects of fire and explosion in the process industries.
4.3 Outline how dusts have the potential to explode and
commonly used control measures adopted to prevent
and minimise explosion.
4.4 Outline the purpose and features of an emergency plan
and the requirements for the implementation.

Element 4: Fire and explosion protection

4.1 Fire hazards.

4.2 Fire and explosion control.
4.3 Dust explosions.
4.4 Emergency preparedness.

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Group discussion

What heat sources and fuels do you have in your

organisations?

The fire triangle

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Modes of heat transfer

Conduction Convection Radiation

Hot fluids rise

and cold fluids
sink, and as this Transfer of
Transfer through
happens, heat is radiant energy
solid materials
spread upwards from hot objects
from the seat of
the fire

Typical ignition sources in the process

industry
Many examples including:
• smoking;
• sparks;
• naked flames, eg as oxy-acetylene welding;
• processes involving electrical discharges, eg arc welding;
• hot surfaces;
• mechanical friction;
• lightning.

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Flammable/explosive ranges

Jet Fires

Mechanism
• Continuous, directed, spray of
fuel ignited immediately.
• Gas, liquid or vapour.

Consequences
• ‘Blowtorch’ jet of flame.
• Radiated heat.
• Can explode.

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Pool fires

Mechanism
• Spillage of liquid fuel.
• Can be on water.
• Vapour ignites above pool.

Consequences
• May flow if not contained.
• Unburnt fuel my form a vapour cloud which can explode.

Boiling liquid expanding vapour cloud

explosion (BLEVE)
Typical mechanism
• External jet fire attack - tank walls heat up.
• Liquid boils - PRV operates.
• Vessel weakens - crack develops.
• Catastrophic vessel rupture.
• Rapid depressurisation of superheated contents - cloud of fine
droplets formed.
Consequences
• Missiles, fireball, secondary explosion.

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Confined vapour cloud explosion (CVCE)

Mechanism
• Flammable vapour builds up within building, vessel, etc.
• Ignition occurs.
Consequences
• Shockwave.
• Overpressure.
• Heat.
• Missiles.

Unconfined vapour cloud explosion

(UVCE)
Mechanism
• Flammable vapour.
• Ignited before it disperses.

Consequences
• Shock waves.
• Overpressure.
• Heat.

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Element 4: Fire and explosion protection

4.1 Fire hazards.

4.2 Fire and explosion control.
4.3 Dust explosions.
4.4 Emergency preparedness.

Leak detectors

Operation (for gas/vapour leaks)

• Chemical sensor with alarm.

• Initiate investigation or shut-down.

• Manual or automatic.

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Spot and line detectors

Spot detectors:
• Localised detectors installed at a specific point.
• Only isolated areas may be covered.

Line detectors:
• A long cable is installed which can detect heat along its
length.
• Larger area can be covered.

Smoke detectors

Operation:
• Smoke enters chamber.
• Light or radiation beam disrupted.
• Alarm sounds.

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Flame detectors

Operation:
• Flickering or radiation emitted by fire.
• Detected by sensor:
‒ visible, UV or IR detectors.
• Alarm sounds.

Active and passive systems

Active fire protection:
“Equipment, systems and methods, which, following initiation, may
be used to control, mitigate and extinguish fires.”

Passive fire protection:

“coating or cladding arrangement..., which, in the event of fire, will
provide thermal protection to restrict the rate at which heat is
transmitted to the object or area being protected”.

BS EN ISO 13702:1999

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Passive fire protection

Preformed boards, cladding, wall linings, etc.

• Fire resistant materials bound into cement, etc.
Prefabricated walls, partitions, fire doors:
• Structures made in a factory to be assembled on site.
Spray coatings:
• Intumescent coatings sprayed onto structural steelwork,
etc.
Seals and sealants:
• Intumescent seals prevent the spread of smoke and fire.

Active fire protection

Sprinklers
• Water or foam.
• Heat triggers release.
• Cools or smothers fire.
Gas extinguishing
• Inert gas.
• Smothers fire.

• Need regular testing and maintenance.

• Can be manual or automatic.

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Hazardous area classification

and zoning
Flammable Vapours
• Zone 0 – present continuously.
• Zone 1 – present occasionally in normal operations.
• Zone 2 – present for short durations and not in normal operations.
Flammable Dusts
• Zone 20 – present continuously.
• Zone 21 – present occasionally in normal operations.
• Zone 22 – present for short durations and not in normal operations.

Example

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Equipment for use in flammable

atmospheres
Electrical and mechanical
• ATEX approved.

Electrical equipment categories

• Category 1
‒ Used in all zones.
• Category 2
‒ Used in Zone 1/21 and Zone 2/22.
• Category 3
‒ Used in Zone 2/22 ONLY.

Explosion protection systems

Atmosphere control
• Maintaining an atmosphere not in flammable range.

Pressure relief and explosion venting

• Designing ‘weak point’ in system.

Automatic suppression
• Detects pressure rise and injects inert media.

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Explosion protection systems

Automatic isolation
• Detects pressure rise.
• Cuts off supply.

Flame arrestors
• Fine mesh.
• Cools a flame as it passes through.

Chemical, foam and inert gas systems

Chemical systems, eg dry powder

• Inert powder smothers fire.
• Effective on jet and running pool fires.
• Can reignite.
• Messy/causes damage.

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Chemical, foam and inert gas systems

Foam
• Water based foam smothers fire.
• Good for pool fires, not on jet fires.
• Can reignite if foam layer is broken.

Inert Gas
• Removes oxygen and smothers.
• An asphyxiant so needs stringent controls.

Fire protection for tank farms

Water Monitors
• High volume water cannon.
• Fixed or portable.
Sprinklers
• Water or foam.
Deluge Systems
• High volume sprinklers.
• Cool and shield vessels.

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Mitigation of lightning strikes

Lightning Rod
• Attached to highest point.
• Connected to earth rod by
cables.
• Directs the electrical
discharge to earth.

Element 4: Fire and explosion protection

4.1 Fire hazards.

4.2 Fire and explosion control.
4.3 Dust explosions.
4.4 Emergency preparedness.

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Why dust explosions occur

The dust pentagon

Primary and secondary explosions

Primary Explosion
• Initial explosion within the process.
• May disturb lying dust in the room.

Secondary Explosion
• Often much larger.
• Involves dust stirred up by primary explosion.

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Prevention of dust explosions

Risk assessment:
‒ identify hazards, risks and controls.
Eliminate dusts at source:
‒ Example, pastes rather than powders.
Inerting:
‒ nitrogen blankets.
Dust extraction:
‒ minimise fugitive releases.
Control of ignition sources:
‒ zoned areas.

Mitigation of dust explosions

Explosion relief venting:
‒ directs pressure to a safe location;
‒ minimised damage.
Explosion suppression and containment:
‒ contain pressure in vessel;
‒ suppress explosion using inter media.
Plant siting and construction:
‒ locate in open air or away from occupied areas;
‒ build of weak vent panels rather than heavy construction.

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Element 4: Fire and explosion protection

4.1 Fire hazards.

4.2 Fire and explosion control.
4.3 Dust explosions.
4.4 Emergency preparedness.

Purpose of an emergency plan

To control and manage response to foreseeable

emergencies.

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Development of an emergency plan

• Sometimes a legal requirement (eg MAPP).

• Identify possible foreseeable scenarios and response required.
• Select people (on-site and off-site) to develop the plan.
• Determine resources needed.
• Evaluate external emergency response.
• Consider on-site and off-site medical response.
• Identify if an off-site plan is needed.

Group discussion

What foreseeable scenarios might your organisation need

to cover?

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Foreseeable emergencies

Depending on the organisation

• First aid/medical.
• Fire/explosion.
• Loss of containment/toxic release.
• Bomb threat/terrorist incident.
• Outbreak of disease.
• Flooding or adverse weather.

Specialists to develop the plan

On-site
• Engineers.
• Workers (process experts).
• Specialists (health and safety, etc.).

Off-site
• Regulators.
• Local authorities and councils.
• Water companies and authorities.
• Utility companies.
• Emergency services including the police and fire service.

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Group discussion

You are establishing the on-site emergency plan for a

chemical site. What resources do you think you might
need to enable an effective emergency response?

Resources
Examples
• Emergency control room.
• First aid equipment.
• AED and evacuation chair.
• Spill response kits.
• Telephone and radios.
• Site maps and drain plans.
• Safety data sheets.
• Computer and printer.

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Availability of external emergency

response (including medical)
• On-site emergency first aid usually adequate.
• May need additional response if:
‒ specialist hazards, eg chemicals
‒ isolated location;
‒ long response times.

On-site and off-site plans

• On-site and off-site plans may be required in law:

‒ on-site developed and managed by the
organisation;
‒ off-site developed and managed (and
implemented) by the authorities.

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Content of an emergency plan

Depending on legal requirements but to include:

• systems for alerting and warning workers on site, neighbouring
facilities and emergency services;
• responsibilities in the event of an emergency;
• expertise of teams involved in response (internal and external);
• evacuation/shelter arrangements;
• emergency shutdown of plant and services;
• consideration of vulnerable people;
• systems for accounting for workers.

Information management and media

liaison
Information and communications
• Real time information about the incident:
‒ chronological log.
• Hazard information.
• Casualty information.
• External reports to regulators.
• Media liaison:
‒ need media training;
‒ usually a prepared statement.

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Theoretical training

Tabletop exercises
• Trainer-led exercise.
• Carried out in accelerated time.
• Discuss possible actions.
• Respond ‘in theory’.
• Identify deficiencies.

Competency of response team and

commanders
• Incident commanders need:
• leadership experience;
• knowledge of plant;
• good communications skills.
• Team members:
• part of the site experience.
• practical skills:
‒ first aid, fire-fighting, rescue, etc.

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Practical testing of response

• Fire/emergency evacuation drill:
‒ trigger alarm;
‒ test workers and response team, eg roll-call and fire
wardens.
• Response team drill:
‒ practical mock-up scenarios;
‒ led by trainer;
‒ test actual response;
• Full-site response drill:
‒ full-site evacuation and test.

Provision of information to the public

During normal operations

• Potential incidents.
• Possible alarms.
• Action to be taken.
During an incident
• Information on the event.
• Action to be taken.
• May be assisted by authorities.

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Element 4: Summary

4.1 Fire hazards.

4.2 Fire and explosion control.
4.3 Dust explosions.
4.4 Emergency preparedness.

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