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HAZOP STUDY
HAZard and OPerability
An introduction
Oct. 3, 2013 Risk Management 2
Content
History
Purpose
Hazards
Deviations
Parameters
Guidewords
Consequences
Safeguards
Application
HAZOP in Dow
HAZOP Process
Nodes
Starting the Study
Oct. 3, 2013 Risk Management 3
Origins of HAZOP
Concept dreamed up by Bert Lawley at I.C.I.
in the late 1960’s
Result of a desire to have structured check
on P. & I.D.s
Spread through I.C.I. in early 1970’s
Endorsed by the “Health and Safety
Directorate” of the U.K. government
NL, Belgian and U.K. etc. governments have
adopted HAZOP
Oct. 3, 2013 Risk Management 4
HAZOP in the 1980’s
U.K. HSE and the Dutch Arbeidsinspectie
began to mandate HAZOP as part of Safety
Report for “Seveso Directive”
I.C.I. by this time were doing HAZOP on
“everything”
Dow incorporated in its Risk Management
process based on its own criteria (focusing
on highest risk)
Oct. 3, 2013 Risk Management 5
Purpose of HAZOP
To identify credible causes, consequences and safeguards before INCIDENTS occur
To define recommendations to minimize the HAZARD by eliminating or controlling the cause or providing “lines of defence”
Provide compatible information for subsequent Process Safety efforts (i.e. LOPA scenarios)
Comply with regulatory Process Safety requirements
Oct. 3, 2013 Risk Management 6
Scope of HAZOP
Review is limited to the piping, instrumentation and equipment shown on the P&ID’s (do not re-design)
Review is limited to deviations from normal operations
Impact of process unit on the utility systems or other process units will be noted as requiring further study
Primary intent is to identify hazards and define action items for additional safeguards if appropriate
Oct. 3, 2013 Risk Management 7
HAZARDS
Fire and Explosion
Reactive Chemicals Incidents
Toxic Exposure
Corrosion
Radiation
Vibration
Mechanical Hazards
Oct. 3, 2013 Risk Management 8
“Deviations”
Hazards are caused by DEVIATIONS
from the DESIGN INTENTION
HAZOP is a method for generating
these “DEVIATIONS” using “GUIDE
WORDS”
Oct. 3, 2013 Risk Management 9
Study is based on
“PARAMETERS”
Flow
Temperature
Pressure
Level
Composition
Agitation
Anything it is important to control
Oct. 3, 2013 Risk Management 10
In combination with “GUIDE
WORDS”
“No”
“Less”
“More”
“Reverse”
“Instead of ” or “Other than” (e.g.
something else or wrong composition)
Oct. 3, 2013 Risk Management 11
Combinations of parameters and
guide words are “DEVIATIONS”
No flow
Less flow
More flow
Reverse flow
Flow of something not planned
More temperature
Less temperature
And so on…...
Oct. 3, 2013 Risk Management 12
Deviations are logical
combinations like...
More temperature
Less pressure
Ignore illogical combinations like….
X Reverse temperature
Oct. 3, 2013 Risk Management 13
Determining the causes for a
deviation
Consider only the causes that originate within the node (consequences may be outside of the node)
Deviations could be caused by: Equipment or process control failure
Human error
Loss of utilities
External events such as fire
Long term processes, e.g. erosion, corrosion, coking
If process instrumentation crosses a node boundary, control malfunction is considered a cause in both nodes
Deviations that require the simultaneous occurrence of two or more unrelated causes are not considered
Oct. 3, 2013 Risk Management 14
Consequences
Describe all consequences, even those that propagate outside the node.
Consequences may include: Personnel injury
Environmental damage
Equipment damage
Property loss
Extended downtime
Operability/Quality problems
Consequences are described assuming there are no safeguards
Describe consequences as a chronological sequence of events
Oct. 3, 2013 Risk Management 15
Safeguards
Safeguards may include: Equipment design
Instrumentation (control, alarm and shutdown)
Pressure relief devices
Administrative procedures
Only list those instrument systems that have at least an alarm as a safeguard
Control instrumentation must automatically correct or mitigate a process deviation
Operator training and administrative procedures should be listed provided they are part of ODMS
Oct. 3, 2013 Risk Management 16
What can HAZOP be applied
to?
Continuous processes
Batch processes
Operating procedures
Maintenance procedures
Any operation where the Design Intention is
defined and deviations are possible
Oct. 3, 2013 Risk Management 17
Recommendations
Recommendations are made to: Eliminate a cause
Prevent or mitigate the consequence
Reduce the likelyhood that the hazard will occur
Examples of recommendations include: Equipment/instrumentation changes/additions
Further study needed
Inspection and maintenance
Training
Administrative systems to manage hazards
Verification of design assumptions
Oct. 3, 2013 Risk Management 18
HAZOP Process
Team maximum 6 persons from (example):
run plant engineer
programmer
process control
process chemist
shift operations team member
study leader/facilitator
Oct. 3, 2013 Risk Management 19
Nodes P&ID’s for the process are broken into manageable
sections called nodes
Nodes generally consists of unit operations and associated piping and connect to upstream and downstream units
Nodes are defined by the HAZOP team and can be redefined as needed
A “Global issues” node can be included to capture hazardous events that can impact the entire process unit. For example:
Loss of containment
Sampling
Utility failure
Oct. 3, 2013 Risk Management 20
Typical nodes
E 201
R 201
P 201
NODE 1
NODE 2
Oct. 3, 2013 Risk Management 21
Nodes
There is no “right” way to define nodes
Usually start with a small node
As experience builds, move to a larger node
Follow the leader’s intuition
If the team gets bored, the node is probably
too small
If the team gets confused, the node is
probably too big
Oct. 3, 2013 Risk Management 22
Starting the study:
The most knowledgeable person describes
the INTENTION of the node
Composition (which chemicals are in the
equipment)
Flow, temperature, pressure, phase,
quantity, agitation etc
…. Anything important to the process
Leader records for study team reference
Oct. 3, 2013 Risk Management 23
Start with Deviation “No Flow”
Team gives all the causes for no flow in the lines and equipment inside the node
Leader prompts their thinking
Team can add but not delete
These causes are recorded in software package
The library in the software can be consulted for possible additional causes
When the ideas “dry up” move on to CONSEQUENCES
Oct. 3, 2013 Risk Management 24
Team decision on “ACTION”
column Team may decide if any new action is
needed
Can record any protective devices or
alarms which become active e.g. PSV’s
Can refer decision outside the team
Can refer serious consequences for
“consequence analysis”
MUST NOT REDESIGN THE PLANT in
the Hazop study session!!
Oct. 3, 2013 Risk Management 25
After “no flow”
Repeat exercise for “less flow”
(usually similar to “no flow”
Repeat exercise for “more flow”
Repeat exercise for “reverse flow”
Repeat exercise for “composition”
(other than expected material
composition)
UNTIL “FLOW” is completely studied
Oct. 3, 2013 Risk Management 26
After “flow”
List causes for “more temperature”
proceed to consequences for “more
temperature”
repeat all steps as for flow
when temperature is studied, go to pressure
after pressure, consider other parameters,
e.g. agitation (use design intention as a
guide)
Oct. 3, 2013 Risk Management 27
When parameters are all done
for node 1
Repeat whole process for node 2
And all the other nodes defined in the
study scope
List actions and responsibility for follow
up