IEEE Electrification Magazine - September 2017 - 47

The system-based verification approach is a systematic and structured assessment of a ship's capabilities
regarding SRtP requirements. It is focused on the ship as
a whole complex system, considering all its internal systems' interrelations. The flowchart depicting all the steps
needed to perform the assessment process is shown in
Figure 8. It starts with a step dedicated to the collection of
specific information, documents, and drawings about the
ship design, as stated in the June 2010 IMO report MSC.1/
Circ.1369 (i.e., the "ship's definition"). The second step is
the overall assessment of essential systems, which is
committed to examining essential systems to identify the
possible presence of critical systems. These are systems
that are classified as essential that may fail to operate
adequately due to a casualty below the threshold. If no
systems are found to be critical, then no further analysis
is needed; thus, the design can be approved. Otherwise,
all the identified critical systems must be analyzed in
detail. If, and only if, the performance of all the critical
systems is considered acceptable, then the design is compliant with SRtP regulation and approved for building.
Conversely, a redesign activity must be performed to
solve the issues identified during the assessment.
Concerning the space-by-space approach, it involves
building a spatial model of the ship with the essential systems allocated to their specific spaces onboard (related
auxiliaries and supplies included). The resulting threedimensional model of the overall ship is then used to verify the compliancy of the ship with SRtP rules by iteratively
assuming the presence of the casualties in each onboard
space and evaluating their effects. The final objective is to
demonstrate that, for each possible casualty, the appropriate essential systems continue to operate despite the
casualty presence. If this is true, the system design is considered to be compliant with SRtP requirements. Otherwise, it is not and must be redesigned. In practice, the
space-by-space analysis process can be considered composed of two main steps: the first is dedicated to the verification of the compliancy of the single system's design
with the chosen criteria, while the second is dedicated to
the verification of the correct interrelations among all the
essential systems.
The first step depends on the criteria used to design the
specific system during the analysis. Concerning redundant
systems, the verification is done by hypothesizing the presence of a casualty in the ship spaces to evaluate the cases
in which the systems remain in operation and in which the
systems fail. The correct application of the redundancy
design criteria is verified if, and only if, for each possible
casualty, a failure in an essential component is balanced by
the operation of the redundant one. Conversely, for the systems designed using only the separation criteria, it must
assess the possibility to reach an operative configuration
after a casualty by separating parts of the system through
automatic and/or manual actions (specified in the dedicated manual). Not only must the effectiveness of the specific

Ship Definition
Include Documents
About Ship
System Capability

Redesign

Overall Assessment
of Essential Systems

Design None
Acceptable

Critical
Essential
Systems
Identified?
Yes
Acceptable in
General?

Yes

Detailed Assessment No
Redesign in
of Critical Systems
General?

Performance
of All Essential
Systems
Acceptable?

Yes
Final Design
(All Essential Systems,
Including Critical
Systems)
Documentation and
Approval
(All Essential Systems,
Including Critical
Systems)
Figure 8. The system-based approach to the verification of SRtP
compliancy for passenger ships.

set of operations be assessed, but the required execution
time must also be analyzed, given the mandatory time
limit set for performing the manual actions.
The second step implies the verification of the correctness of the relations between essential systems and
between them and other systems. Each onboard system
has a set of inputs (other systems that must be in operation
to allow the correct operation of the system in analysis) and
outputs (other systems that require the correct operation of
the analyzed system to correctly operate themselves).
These relationships must be mapped, and the impact of
the casualties on each input and output system must be
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Table of Contents for the Digital Edition of IEEE Electrification Magazine - September 2017