Periodic Hazard Review (PHA Revalidation)

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Process Safety Guide:
GBHE-PSG-HST-080
Periodic Hazard Review
(PHA Revalidation)
Process Information Disclaimer
Information contained in this publication or as otherwise supplied to Users is
believed to be accurate and correct at time of going to press, and is given in
good faith, but it is for the User to satisfy itself of the suitability of the information
for its own particular purpose. GBHE gives no warranty as to the fitness of this
information for any particular purpose and any implied warranty or condition
(statutory or otherwise) is excluded except to the extent that exclusion is
prevented by law. GBHE accepts no liability resulting from reliance on this
information. Freedom under Patent, Copyright and Designs cannot be assumed.

Process Safety Guide: Periodic Hazard Review (PHA Revalidation)
CONTENTS
1.0 PURPOSE
1.0.1 Team
1.0.2 Timing
1.0.3 Preparation
1.0.4 Documentation
PERIODIC HAZARD REVIEW (PHR): APPLICATION
1.1 HAZARD STUDY 1
1.2 HAZARD STUDY 2
1.3 ACTIONS ARISING FROM PHR
1.4 REVIEW OF PHR
APPENDIX A RISK MATRIX
A.1 RISK MATRIX
A.2 RISK MATRIX - GUIDANCE FOR CONSEQUENCE CATEGORIES –
SAFETY AND HEALTH INCIDENTS
A.3 RISK MATRIX GUIDANCE FOR CONSEQUENCE CATEGORIES –
ENVIRONMENTAL INCIDENTS

1.0 PURPOSE
The objective of a Periodic Hazard Review (PHR), or as described in the USA, a
Process Hazard Analysis Revalidation, is to produce an updated process hazard
analysis that adequately identifies, evaluates and proposes controls for the
hazards of the process as they are currently understood. The reasons why the
current understanding of the hazards associated with the process differ from that
at the time of the previous hazard analysis may include:
• Process changes have introduced new hazards or accentuated existing
ones;
• Changes in on-site or off-site occupancy patterns have changed the ’at
risk’ population;
• New knowledge is now available to better understand the hazard potential,
revealing potentially more serious consequences;
• Actual incidents have revealed scenarios not previously identified in the
process hazard analysis;
• Safeguards previously credited in the process hazard analysis have been
removed, inadequately maintained, compromised or discredited.
The above examples illustrate why the process may have become more
hazardous. However, the revalidation may reveal that the process has become
less hazardous:
• By the use of a less hazardous material (e.g. an aqueous system instead
of a flammable one);
• The better appreciation of safeguards for which proper credit was not
given in the earlier analysis, or
• The addition of new safeguards.

The periodic hazard review / studies should:
(1) Consider opportunities for hazard reduction or elimination and risk
reduction;
(2) Provide assurance that the process risk control measures are sufficient for
the continued operation of the plant, or
(3) Identify process risks for which the control measures are no longer
sufficient and require action.
The decision to carry out a PHR on an existing operation could be based on:
· Legal (e.g. OSHA/PSM or EPA/RMP), or
· Corporate (RCMS Guidelines) requirement, or
· After an acquisition, or
· A review after a series of incidents.
This document should be used in conjunction with the following books:
o CCPS book ‘Revalidating Process Hazard Analyses’. This is a
concise, highly focused document that should be read by anyone
carrying out a major revalidation. This guide incorporates much of
its methodology.
o IChemE book 'HAZOP: Guide to best practice'. Although the book
describes the HAZOP process in detail (equivalent to Hazard Study
3), general aspects of the methodology in chapters 5, 6, 7 and 8
can be applied to this study.
1.0.1 Team
The hazard study leader should be an accredited practitioner, of a level
appropriate for the complexity and hazard level of the facility and preferably
should not be part of the plant / process organization. If an independent leader is
not available it is essential that an experienced independent safety professional
should attend the meetings.
The ideal size of the 'core' team is about six people.

Other members of a typical team might include:
· The operating manager;
· The engineering manager;
· A process engineer;
· An operator;
· A maintainer (mechanic);
· A process control engineer or technician;
· Other expertise relevant to the hazards of the process studied, e.g. a
process chemist.
The above team composition meets the OSHA requirement that the team shall
include "at least one employee who has experience and knowledge specific to
the process being evaluated and one person knowledgeable in the specific
process hazard analysis methodology being used".
Ideally the core team should be a mix of those present at the previous study and
new members.
1.0.2 Timing
For plants with significant process hazards a PHR should be held every five
years starting from the date of the first meeting unless triggered by an incident or
required by law. (The legal requirements in the USA – OSHA’s PSM standard
and the EPA’s RMP standard require PHA revalidation every 5 years.) If an
investigation following an accident, or dangerous occurrence or learning event
recommends that the plant is restudied, the process will probably involve the
repeat of Hazard Studies 1, 2 and 3.
Longer periods between reviews may be appropriate for plants of lesser hazard
or risk and in some cases more frequent reviews may be necessary.

1.0.3 Preparation
The scope of the periodic hazard review will normally be that of the original and /
or the previous studies.
However the scope could expand as a result of a Process Safety Management
(PSM) or GBHE Engineering Procedure (GBHE_EP) (or in the USA 29 CFR
(OSHA) 1910.119) audit of the facility.
The following information should be made available for the study. Items marked
'essential' are essential for the revalidation of the hazard studies or process
hazard analyses themselves.
(a) A complete set of the hazard studies to be revalidated and any related
hazard studies including lists of actions and records of action reviews
providing confirmation of closure (essential);
(b) Plant process description (essential);
(c) Control philosophy (essential);
(d) list of incidents, accidents and near misses / dangerous occurrences (and,
preferably, the associated reports) which have occurred on the plant and
similar plants. Associated transportation incidents should be included
(essential);
(e) Material properties, (including HDS or MSDS) and the material
compatibility matrix. Preceding audits should have checked that these are
kept up-to-date (essential);
(f) Health reviews and studies (e.g. Occupational Health Statements, Control
of Substances Hazardous to Health assessment, Toxic Substances
Control Acts). The responsible occupational health professionals should
be able to provide any significant trends in the health of the operators and
maintenance workers on the plant (optional);
(g) Environmental reports or studies. A list of any excursions from the
permitted aqueous and atmospheric discharges should be available
together with any prosecutions / citations. Any conditions imposed should
be noted, and assurances should be obtained from operating staff that
they are being observed (essential);

(h) Siting reviews paying particular attention to personnel densities and
location of critical receptors (non essential);
(j) Any reports / documentation required to meet legal requirements, (e.g.
OSHA, Health & Safety Policy, COMAH report) (non essential);
(k) Organization chart (non essential);
(l) Emergency facilities and instructions (non essential);
(m) Process flowsheets and Piping and Instrument Diagrams (P&IDs) or
Engineering Line Diagrams (ELDs) (essential);
(n) Relief and blowdown schedule / reports (non essential);
(p) Trip and alarm system schedule and trip logic diagrams (essential where
complex systems exist);
(r) Original design manual and specification for the equipment (less
essential);
(s) Operating and maintenance instructions (essential);
(t) History of the operation and list of all modifications and (management of)
changes and associated documentation since the previous PHR
(essential);
(u) SSHE dossier information including any Fire Reviews, Toxic Emission
studies, etc. (non essential);
(w) Human factors study (essential);
(y) Other related studies and documentation (including relevant audit reports).
Visits to, and inspections of, the plant are recommended.

1.0.4 Documentation
The output of the PHR should be retained in the SSHE dossier. This may be in
the form of missing or updated sections of Hazard Study 1. For Hazard Study 2
and 3 the original documents should be copied and the copies that have been re-
titled should be updated to reflect the revalidation. Supporting documents such
as the PFDs or P&IDs / ELDs used in the PHR should be attached together with
action lists update plan and documentation produced arising out of or supporting
actions. It is however also essential to retain the original hazard study reports in
their unaltered form.
In the USA it is advisable to file a copy of the version of the methodology used for
the revalidation.

PERIODIC HAZARD REVIEW (PHR): APPLICATION
The following sections 1.1 to 1.4 describe how to conduct a PHR.

1.1 HAZARD STUDY 1
An existing operation should have a Hazard Study 1 report
and this should be reviewed to see that it is up-to-date.
Changes to the report should be issued as a supplement,
or a revision, to the original report. If a Hazard Study 1
report does not exist then consideration should be given to
the writing of such a report. This may not be necessary if
the information exists in a suitable alternative form, for
example in acquisitions or SSHE dossier.
Each of the sections of the Hazard Study 1 report should be checked to ensure
that it is up-to-date. The sections are listed below; see GBHE-PSG-HST-020 for
details on each section:
1.1 Project Definition. Establish the scope of the plant to be studied.
1.2 Process Description.
1.3 Materials Hazards
1.3.1 Material List
1.3.2 Hazard Data Sheets
1.3.3 Chemical Hazards
1.3.4 Loss of Containment
1.4 External Authorities
1.5 Organization and Human Factors
1.6 Additional Activities to be completed
1.6.1 Control Philosophy
1.6.2 Incident Review
1.6.3 Inherent SHE
1.6.4 Safety Risk Criteria
1.6.5 Health
1.6.6 Environment
1.6.7 Material Transport and Siting
1.6.8 Design Guidelines and Codes
1.6.9 Emergency Facilities
1.6.10 Further Studies

1.2 HAZARD STUDY 2
Hazard Study 2 is conventionally based on process
flowsheets, but periodic hazard studies apply to existing
operations. At this stage the following will exist:
(a) The actual plant.
(b) The operating team.
(c) The maintenance team.
(d) The operating records.
The plant is divided up into small sections (container, pipeline, machine or
activity), usually on the basis of unit operations. Then, working from the process
flowsheets, the team applies the Hazard Study 2 methodology to each section or
stage of the operation in sequence.
In carrying out the Hazard Study 2, emphasis should be paid to:
(1) The application of the current materials hazard data;
(2) Human factors;
(3) Facilities layout;
(4) Environmental impact.
Where a Hazard Study 2 has already been carried it may be sufficient to
revalidate that study.
The output from Hazard Study 2 should be ranked using the risk matrix from that
study guide (see GBHE-PSG-HST-030).
From the risk matrix the recommendations will be categorized into A, B and C.
o A - Start immediately, do within 12 months.
o B - Do within 24 months.
o C - Do within 5 years

1.3 ACTIONS ARISING FROM PHR
Actions will be identified, i.e. P&ID, relief stream calculations, or
Hazard Study 3.
Repeating part, or all, of Study 3 should be considered if any, or
all, of the following apply:
(a) Audits have revealed deficiencies in the hazard study
process;
(b) Significant design deficiencies have become apparent;
(c) The original hazard studies were poor or part, or all, of the documentation
has been lost;
(d) The plant has not run smoothly;
(e) There have been major incidents;
(f) There have been many modifications;
(g) Modifications, singularly or in combination have not been hazard studied;
(h) The plant does not have a good modification procedure;
(j) Key documents such as the process flowsheets have not been kept up-to-
date;
(k) New requirements, statutory or corporate such as new regulations
(particularly in the USA), clarifications, or technical approaches have
arisen since the original studies or since the last periodic study.
If it is decided to repeat Study 3 on all, or part, of the plant for any of the reasons
given above, it is essential to have the process flowsheets checked before
starting the study itself. Again, particular attention should be paid to see if
recommendations of ongoing follow-up actions such as checks, testing, etc. were
implemented and those procedural recommendations were incorporated into the
operating instructions.
Study 3 is necessarily more time consuming than other study techniques, but the
results provide a comprehensive insight into operating deviations, some of which
can cause safety-related problems.
The main advantage of Study 3 is that it highlights operating problems,
particularly related to start-up and shutdown sequences, as well as identifying
critical operator interaction with the process, and providing the basis for
reviewing operating instructions. Also, when carried out rigorously, it covers all
deviation possibilities, and this can sometimes stimulate lateral thinking into new
directions, which subsequently reveals unforeseen problems.

Study 3 has the disadvantage of also identifying minor hazards or operating
problems that may distract efforts from the major issues. Therefore, it is vital that
the means of handling these minor issues is agreed as part of the overall method
of the study. For example, it may be decided that issues that the team agree are
’minor hazards or operating problems’ will not be noted as part of the formal
documentation of the study, but that the relevant member of the team such as
the plant supervisor makes a note to follow them up separately. Alternatively, it
could be decided that potential operating problems in particular will not be noted,
as important ones will be known by experience and there will not be the resource
available to evaluate all of the potential problems.
For complex modifications to existing plants, a full Hazard Study 3 of the
changes should be carried out.
1.4 REVIEW OF PHR
In the normal hazard study process for a new plant, hazard
study actions will be reviewed at the next study with a
requirement that all actions for Hazard Studies 1 to 5 will be
completed before plant start-up. In the case of periodic studies
no such deadline exists and so an action plan together with
target dates for the completion of actions should be drawn up
and dates set for the review of progress. These should be
recorded on the Periodic Hazard Review (PHA Revalidation)
Actions worksheet (worksheet z). Proper action progressing
may be a legal requirement (e.g. USA).

Periodic Hazard Review (PHA Revalidation)

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