Article citation information:
Orymowska, J., Sobkowicz, P. Hazard
identification methods. Scientific
Journal of Silesian University of Technology. Series Transport. 2017, 95, 145-158. ISSN: 0209-3324.
DOI: https://doi.org/10.20858/sjsutst.2017.95.14.
Joanna ORYMOWSKA[1],
Paulina SOBKOWICZ[2]
HAZARD IDENTIFICATION METHODS
Summary. This article presents the main
hazards that occur in the context of inland navigation and their impact on the
vessel. First, characteristics are extracted from the following methods with
regard to identifying threats: involving steering gear damage to an inland
vessel moving on a straight waterway. Next, a hazard identification model is
presented, which is appropriate to a situation involving steering gear damage
to an inland vessel moving on a straight fairway.
Keywords:
hazards identification; inland shipping; HAZOP; FTA; ETA; FMEA; SWIFT; risk
analysis.
1. INTRODUCTION
Inland waterway
transport is considered as one of the safest and most cost-effective modes of
transport. Still, the operation of inland units is associated with a risk of,
e.g., damage to the cargo and the ship, a threat of human life and environment
pollution. Hazard identification is the first step in any formal safety
assessment, whose purpose is to identify all the factors that may affect the
operational safety of the vessel. Understanding the actual threats allows for
the development of appropriate procedures, aimed at the elimination of the
threats’ source.
2. INLAND WATERWAYS HAZARDS
Risks occurring in inland transport can be
classified according to the factors that cause them. These are:
- Hazards resulting from the transport of cargo
- Hazards resulting from human error
- Hazards resulting from the failure of navigation
devices, steering or other equipment
- Area-specific hazards
2.1. Hazards resulting from the
transport of cargo
Inland shipping is a
type of transportation, which deals with the carriage of all kinds of cargo,
including oversized cargo and containers. In the case of river units,
especially sea-to-river vessels, it is important to load the vessel correctly,
as the uneven distribution of a load in the cargo spaces or on deck can affect
the heel or trim of the vessel. Too much trimming, especially at higher speeds,
results in an increase in the subsidence of the vessel. This phenomenon is
particularly dangerous on shallow waters, such that the under-keel clearance is
limited. The lack of monitoring and control of the value of the current draught
and its relation to the depth can lead to grounding. Regarding the carriage of
containers, as their subsequent layers increase the supply surface, it can be
difficult to manoeuvre a vessel on open waters and with a strong wind. A
special type of cargo is dangerous goods, the carriage of which is associated
with risks, such as explosions. It is necessary for such cargo to be properly
distributed and kept under appropriate conditions during transportation [6].
2.2. Hazards resulting from human
error
A major factor behind
accidents caused in inland areas is human error. In shipping, the 80:20 rule is
typically asserted: this states that 80% of accidents are human-caused, while
20% are due to other reasons. Regardless of whether human error is intentional
or unintentional, it can lead to an accident. Fig. 1 presents the
classification of human errors [7].
Fig. 1. Classification of human errors
[7]
If the descent of the unit from the
axis of the fairway is observed early enough, and the person on the bridge
behaves in accordance with the given procedures (putting the unit back on the
right course), the event will not generate any losses. Meanwhile, the lack of
an adequate response to the descent of the unit from the axis of the fairway
may result in:
- collision with another vessel, especially while
overtaking or passing
- collision with another moored vessel
- collision with the jetty
- collision with a fixed object
- grounding
The consequence of each event is
different and depends on many factors, including the speed of the ship, the
kinetic energy of a collision or impact, and the place of contact with the
ship’s bottom. In the case of a collision, crash or grounding, demurrage,
towing or necessary repairs could be among the consequences.
2.3. Hazards resulting from the failure of
navigation devices, steering or other equipment
Each item of
navigation or steering equipment is characterized by the intensity of damage.
This means that, within a specified time period (hours or years), the vessel
may crash. To determine the reliability of the technical support unit, it is
necessary to qualify the reliability of each of its components. In the case of
a ship, this represents a complex challenge, given that its construction
comprises various pieces of equipment, such as radar, a main engine, aggregates
and generators. To determine the intensity of damage to individual devices, the
number of failures within a fixed period of time must be specified [6], while
the intensity is dependent on the use of data elements, e.g., in the case of
the rudder, its moves are important, while hydrometeorological conditions can
affect the engine.
2.4. Area-specific hazards
By appreciating the characteristics
of the analysed area, it is possible to identify risks such as: grounding,
restrictions in the vertical plane, insufficient clearances under bridges and
the conformation of a navigation route. Knowledge about navigation hazards
helps to avoid risks. From a safety point of view, it is critical to have
access to data on visibility, currents and wind. Other factors to be taken into
consideration include the presence of RIS and the movement of other vessels [6].
3. METHODS USED TO
IDENTIFY HAZARDS
The main ideology
behind hazard identification is to identify all the possible strings of events
leading up to an event threatening the safety of the unit. According to the
literature, early detection and determination methods are available for the
effective prevention of threats. These methods are as follows: HAZOP, FTA, ETA,
FMEA and SWIFT.
3.1. HAZOP technique
This is one of the most commonly
used analytical methods, otherwise known as the guide words technique, which is
conducted in order to indicate deviation from acceptable levels on the basis of
being too high, too low, too little, too much etc. HAZOP is mainly employed in
order to determine a ship’s systems, while analysis using this method is
carried out by experts (engineers, technologists, designers, control and test
facility experts) under the direction of a leader [3, 4, 5]. Table 1 presents
an example set of words used in hazard identification based on the HAZOP
technique.
Table 1. An example sets of words
used in hazard identification,
based on the HAZOP technique [9]
|
NO or NOT |
|
MORE |
|
LESS |
|
PART OF |
|
OTHER THAN |
|
EARLY |
|
LATE |
|
BEFORE |
|
AFTER |
The HAZOP technique, which can be
applied to each stage in the construction or operation of the relevant
technology [9], mainly generates qualitative results. HAZOP technology is based
on a systematic review of the design intent and the technological process
concerning deviations from the accepted parameters. Typically, it is employed
in order to determine any possible incident that may endanger health and human
life or the environment, as well as cause damage to equipment and create
technological problems. Fig. 2 shows the main steps in the proceedings when
applying the HAZOP technique.
The form used when applying the HAZOP technique
consists of the following elements [2,5]:
- Guide words for identifying potential deviations from
the design intent
- Variations, i.e., changes in the actual operating
system
- Real causes behind these deviations during a
“brainstorm”, i.e., what are the consequences of the incorrect functioning of
the system?
- Security measures to prevent deviation
- Recommendations to improve security
Sample form for hazard identification by HAZOP
method presents table 2.
Fig. 2. The main stages in the HAZOP
procedure [4]
Table 2. Sample worksheet for HAZOP analysis [4]
|
HAZOP |
Project: Object: Page: Date: |
|||||||
|
No. |
Guide word |
Deviations |
No. |
Causes |
No. |
Effects |
Safety measures |
Recommenda-tions |
|
|
|
|
|
|
|
|
|
|
3.2. FTA technique: the construction
of an incapacity/fault tree
The model built using FTA techniques aims to
identify the relationship between damaged equipment on ships and errors
resulting from human or external factors. The construction of a fault tree
starts with the identification of the effects of an event, as well as considers
the course of previous events. In the process, a range of possible combinations
of events is specified. The event tree is used for qualitative and quantitative
analysis [2], while FTA employs Boolean logic. The main steps in FTA are:
- Determination of the initial events
- Determination of the events/indirect damage
- Construction of the tree damage, using event-binding
logical gates
- Identification of the fundamental event leading up to
the main event
- Specification of the probability of occurrence of the
initial event
- Calculation of the probability of occurrence of the
final event
- Analysis of the results, along with the fixing of the
dominant events
- Sensitivity analysis to check how changes in the probability
of the damage to one item from a set of influences affect the likelihood of the
occurrence of peak events
The purpose of this method is to
identify the cause of failure instance, determine the frequency of the
occurrence of dangerous states, and identify critical components of the system.
The basic elements of the event (or fault) trees are gates and events [3, 4, 5].
Table 3 shows the gateway used for FTA.
Table 3. Gate symbols used in FTA [4]
|
Gate symbol |
Gate name |
Symbol meaning |
|
|
AND |
The output event occurs if all
input events occur simultaneously |
|
|
OR |
The output event occurs even if
there is only event input |
|
|
Inhibit gate |
The input-output product is
followed by a conditional event |
|
|
Priority AND gate |
Precedence over the conjunction of
events from left to right |
|
|
Exclusive OR gate |
The output event occurs if
followed by one (but not more than one) input event |
|
|
m out of n gate |
The output event occurs if and m
exit/n enter event occurs |
Hazard identification involving FTA
is used in risk analysis and the determination of reliability to specify the
relationship between the peak events and the underlying events. Fault tree
construction uses a gateway connecting the event via a logical relationship.
With reference to the fault tree, it can be determined exactly which errors
were committed, which actions have not been observed and which actions have
been performed to prevent accidents.
3.3. ETA technique:
building an event tree
ETA technology is based on a graphical
model depicting the relationship between cause and effect in an event. Hazard
identification begins by determining the initialization event and considering
all possible strings of events, which are consequences of the initialization
event. The probability of the effect is determined by multiplying the
probability of all the events. The ETA technique analyses the situation from
beginning to end, taking into account partial events that may have decisively
impacted on the status of the analysis process. In many cases, a single event
can result in different consequences, depending on the performance or failure
of equipment, systems or operator activities. ETA is a method used to build an
object model of probability for risk analysis. There are two approaches to this
technique: before an accident and after an accident. The technique used before
an accident is applicable when there is a need to determine possible events and
the likelihood of their occurrence. The technique used after an accident seeks
to analyse and identify the functional safety system failures.
The ETA procedure consists of six
major stages:
- Identifying the initiating event that can lead to a
specific failure
- Identifying the safety features that are applied to
mitigate the effects of the initiating events
- Constructing an event tree
- Describing the findings in light of the construction
of the tree sequence
- Specifying the minimum cross sections of the tree
- Developing the documentation
Fig. 3 presents the method for conducting an
analysis of the data using the event tree.
Each event has two branches that
determine the success (positive) or the lack of success (negative), while the
probability of events contains between ‘0’ and ‘1’. The sum of the
probabilities of the event and its lack thereof is equal to ‘1’. Hence, if the
entire event is described, a collection of this success can be described as P
(A), while the failure is an event to the contrary:
1- P (
Fig. 3. ETA stages [4]
3.4. FMEA technique
This technique is used to determine
the damage, which significantly impacts the operation of the entire system
(mainly its efficiency), and evaluate the reliability of individual components
of the system. In FMEA, the types and effects of damage are considered in relation
to elements of the systems and other equipment, as well as the possible damage
and effects on other components, systems or the state. The purpose of the FMEA
is to identify specific shortcomings in the process and how to exclude or
minimize their effects. This is achieved by determining the cause and effect
relationships, depending on the potential creation process, with the defects,
while taking into account the risk factors. Thanks to this process, continuous
improvements are possible by carrying out in-depth analyses and introducing
amendments, which are aimed at eliminating the sources of defects and enhancing
the performance capabilities of the product. The FMEA method, which is
described in standard PN-IEC 812 [7], is divided into two types:
- Product FMEA – This is a technology-oriented approach,
which optimizes the reliability of the product. On the basis of the assessment,
the product can be made stronger by addressing its weak points.
- Process FMEA – This consists of determining the
disorganizing factors in the production process.
FMEA consists of five main steps:
- Identification of the characteristics of the system
and its basic functions, as well as the minimum requirements that determine its
operation
- Identification of possible malfunctions and system
failure
- Identification of the consequences of each system
failure
- Determination and evaluation of methods to detect
system failure
- Description of the reduction and elimination of
adverse effects
The
quantitative analysis of defects is used to describe the cause-defect-effect
relation, while the assessment of this relationship is determined on a scale
from one to 10, divided into three categories:
- Risk of defects/causes - R
- Ability to detect the emergence of causes before any
defects occur - W
- Importance of disadvantages to the user - Z.
Based on the determination of these
values, the level of priority, which takes a numerical value between one and
1,000, can be established. As the value increases, so does the risk of defects.
The formula for calculating priorities as a numerical value is as follows:
FMEA
documentation should take the form of an at-a-glance a report describing the
effects of any damage to the equipment/system, as well as other
devices/components of the system. Table 4 sets out the FMEA documentation.
Table 4.
FMEA documentation [6]
|
System: |
Drafted by: |
||||||||||||
|
Table no.: |
Date: |
Page: |
|||||||||||
|
System description |
Damage description |
Damage effect |
Failure rate |
Ranking of seriousness |
Risk reduction measure |
Comments |
|||||||
|
No. |
Function |
Operating mode |
Damage mode |
Damage cause or
mechanism |
Detection of damage |
Subsystem |
System function |
Resulting state |
|||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
3.5. SWIFT method
This
technique involves team “brainstorming”, in which experts ask each other
questions and identify potential risks. The SWIFT method aims to:
- identify risks
- determine the effects of the occurrence of each event
- designate possible measures/methods of reducing risks
The SWIFT is divided into three
stages:
- Stage 1. Preparation – This involves the analysis of
the current situation, as well as examining with the applicable rules and
procedures. During this stage, specific questions will be put to a team of
experts.
- Stage 2. Review – This involves the presentation of
the problem and asking the right questions in order to identify risks and
develop remedial procedures.
- Stage 3. Documentation – This involves the compilation
of a report based on the outcomes from using the SWIFT, including the
identified hazards and their effects.
To document
the outcomes from using the SWIFT technique, a worksheet similar to that
presented in Table 5 can be used.
Table 5. Example of a
SWIFT worksheet [5]
|
NAME…………………………………………………….. DATE………………… |
|||
|
DOCUMENTATION
NO……………………………………... |
|||
|
MEMBERS
OF THE TEAM………………………………... |
|||
|
WHAT-IF |
CONSEQUENCES/HAZARD |
REMEDIES |
RECOMMENDATIONS |
|
|
|
|
|
4. HAZARD IDENTIFICATION MODEL USING THE
EXAMPLE OF STEERING GEAR DAMAGE
The analysed event involves an
inland vessel passing through a straight fairway. During the passage, the
vessel’s steering gear is damaged (initialization event).
This type of event, which is
independent of any human factor, can lead to the corruption of the navigation
device and steering gear on the ship. The immediate threat concerns whether
control can be maintained over the movement of the vessel, while longer-term
consequences include the costs of repairing and servicing equipment. Rudder
damage can also lead to the loss of a ship’s control.
The initiating event concerns damage
to the steering gear. Table 5 shows the hazard identification model developed
on the worksheet used in the HAZOP analysis.
Deviation (the state that deviates
from the proper operation of the unit) is represented by the loss of control
over the ship. This may be caused by damage to the rudder, which can affect the
units of the axes along the navigation route or cause a blackout. In the event
of damage to the rudder, security measures in the form of frequent checks are
required in order to detect any irregularities in the functioning of the
steering gear. It is also recommended to check the rudder before the output
units, as damage to the rudder during transition along the shipping route can
endanger the safety of the units and other users of the fairway. As a result of
a blackout, the vessel may stop responding to movement, which could lead to the
ship colliding with another unit, object or jetty. To prevent such a situation,
installing sensors and alarms to monitor the energy facilities is advisable.
Security measures should again involve frequent checks and a review of the
devices. Table 7 presents the hazard identification model developed with the
aid of the FMEA worksheet.
Fig. 4.
Hazard identification model constructed using ETA techniques
Table 6. Example of a HAZOP worksheet [4]
|
HAZOP |
Project: Object: Page: Date: |
|||||||
|
No. |
Guide word |
Deviations |
No. |
Causes |
No. |
Consequences |
Safety measures |
Recommenda-tions |
|
1. |
Lack |
Loss of
manoeuvrability |
1. |
Rudder damage |
1. |
Descent from the
axis of the fairway |
Frequent checks |
Rudder control
before leaving the port |
|
2. |
Blackout |
2. |
Vessel not under
command |
Frequent mainte-nance
of whole energetic system |
Sensors, alarms |
|||
Table 7. Example
of an FMEA worksheet [8]
|
System: |
Drafted by: |
||||||||||
|
Table no: |
Date: |
Page: |
|||||||||
|
System
description |
Damage
description |
Damage effect |
Fail-ure rate |
Seriousn-ess ran-king |
Risk reduction
measures |
Amendments |
|||||
|
Fun-ction |
Work mode |
Dama-ge mode |
Dama-ge cause or mechanism |
Damage dete-ction |
Sub-system |
Function of the
system |
Resul-ting state |
||||
|
Stee-ring gear
damage |
Nor-mal |
Sudden |
Rudder break-down |
Alarm sound |
Stee-ring pump |
No effect |
Descent from the
axis of the fairway |
Rare |
Serious |
Tur-ning off |
Re-pair |
The analysis carried out by FMEA is
a method that allows for a precise description of the both the test system,
which is experiencing failure, and the effects of the damage. The considered
damage is divided into components, which are analysed separately in order to
determine the full impact of the damage on the function of the system.
Table 8 presents the hazard
identification model, as developed on the worksheet used in SWIFT analysis.
Table 8. Example of a SWIFT worksheet
|
NAME…………………………………………………….. DATE………………… |
|||
|
DOCUMENTATION NO……………………………………... |
|||
|
TEAM MEMBERS………………………………... |
|||
|
WHAT-IF |
CONSEQUENCES/HAZARDS |
REMEDIES |
RECOMMENDATIONS |
|
Steering gear damage during passage on a straight
fairway |
Descent from the axis of the fairway/collision
with the jetty/another vessel/object |
Steering gear controls/checklists |
Tests of the steering gear before
departure/sensors/alarms |
The SWIFT method is one of the most
straightforward ways to identify risks, as it is based on posing simple
questions. Typically, a SWIFT worksheet consists of four questions:
- If a threat occurs, what kind of threat is it?
- What can be the effect?
- What measures should be taken?
- What recommendations should be made?
In this case, the threat involves damage to the
steering gear. The effect is considered to be on the unit’s descent along the
axis of the fairway, which generates another threat in the form of the
possibility of collision with another unit, a jetty or an object. In order to
ensure safety, the introduction of checks of the controls of the steering gear
and the rudder before departure is recommended. Additional threat indicators
are sensors and alarms, as their use allows for the earlier detection of a
problem and its quick elimination
5.
Conclusions
Hazard identification is an
important element in the risk estimation procedure. Its main advantage is the
ability to determine possible problems and events, which can impact the vessel
and other users on the fairway. A commonly used method in the analysis of risks
is HAZOP, which is characterized by a thorough review of the assumptions of the
entire technological process, as well as designed to specify all possible
deviations from the accepted standards. A HAZOP worksheet takes into account
deviations, and their causes and effects, safety measures, and recommendations
for use. Meanwhile, the SWIFT method is based on questions that can help to
define potential problems and find appropriate solutions. This is one of the
more creative methods because it is based on the so-called “brainstorming”
approach. As with HAZOP and FMEA methods, the outcomes when employing the SWIFT
method should be documented on worksheets, which define the risks in words.
Methods such as ETA or FTA identify hazards by visualizing the problem using
gates depicted as a set of appropriate symbols. The estimation of the impact of
damage on the process allows for remedies and recommendations to be specified,
which in turn can ensure safety and minimize the risk of hazards.
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Received 18.03.2017; accepted in revised form 10.05.2017
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