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DNV-OSS-121 Classification Based on Performance Criteria Determined from Risk Assessment Methodology
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SECTION 1
IntroductionSec.1
A. General
Sec.1
A 100 Introduction
Sec.1 A
101 This document presents the DNV service specification for classification
of offshore installations based on risk assessment techniques. This
means that the acceptability of design and the extent of verification
are based on risk assessment rather than reliance upon prescriptive
rules.
Sec.1 A
102 The objective of this approach is to provide an alternative
route for classification of individual and novel designs whilst
maintaining an acceptable level of safety and integrity equivalent
to that achieved under more traditional classification rules. Although
not mentioned specifically through this service specification, avoidance
of adverse environmental consequences shall also be taken into account
as far as covered by traditional classification rules.Sec.1
A 200 Application
Sec.1 A
201 The requirements are applicable for fixed offshore installations,
including floating installations designed for use at a fixed location.
Sec.1 A
202 The service is alternative or complementary to classification
based on other DNV service specifications (DNV-OSS series) for such
installations. Where classification based on risk assessment is
applied only to a part of an installation, the remainder of the
installation shall meet the requirements of other applicable DNV
rules.
In such cases, it is important to ensure a safe interface
between the two classification methods i.e. that design based on
risk assessment does not have a negative effect upon safety or integrity
under classification rules and vice versa.
Sec.1
A 300 Scope
Sec.1 A
301 Under this service specification, risk assessment means the
systematic identification and evaluation of hazards to personnel
and plant (see 102).Risk assessment is the overall process of risk (hazard) identification,
risk analysis and risk evaluation. The results of the assessment
identify areas of most significant risk and enable risk reduction
measures to be targeted where most effective.
The use of risk assessment for classification shall include:
- Hazard
identification and evaluation of hazards and the risks
they pose to safety and integrity on the installation.
- Demonstrating that the risks
are acceptable, i.e. meet agreed risk acceptance criteria
and or target risk reduction.
- Identifying the safety-critical
elements and their required performance standards that
are required in order to meet the acceptance criteria.
Sec.1 A
302 In order to assign classification, DNV will review and approve
the selection of safety-critical elements and performance standards,
and verify their design, construction, installation and commissioning.DNV will establish an installation-specific verification scheme for
initial class entry as well as maintenance of class. The DNV scope
for approval and verification is detailed further in Sec.2 to Sec.4.
Sec.1 A
303 Maintenance of class shall be through ongoing verification
that the safety-critical elements remain in adequate condition and
repair to foreseeably meet their performance standards.
Whilst classification is maintained, DNV will retain the verification
scheme under review based on findings of verification activities.
DNV will issue an annual verification status report, which may be
used as documentation with other regulatory review requirements.
Sec.1 A
304 Classification in accordance with this specification indicates
that the installation has been verified as attaining, and should
foreseeably continue to attain, an acceptable level of safety and
integrity as specified by agreed risk criteria. The owner or operator
is responsible for ensuring compliance with requirements of maritime
administrations or conventions, and for seeking concessions where
any such requirements are not fulfilled.
Sec.1
A 400 Class notation
Sec.1 A
401 Offshore installations classed in accordance with the provisions
of this service specification (DNV-OSS-121) will be assigned the
class notation RA.Sec.1
A 500 Terms and conditions
Sec.1 A
501 The general terms and conditions for classification shall be
as stated in the relevant OSS for the unit type, for example DNV-OSS-102
for floating production units.
Sec.1 A
502 DNV will manage and document approval and verification activities
for class entry and maintenance of class. DNV will also interface
with and direct the risk assessment activities as necessary to ensure
acceptability for classification. The owner or operator is expected
to co-operate with DNV as necessary to establish and undertake the
approval and verification process.Sec.1
B. Definitions
Sec.1
B 100 Terms
Sec.1 B
101 Consequences are the
expected effects of an event occurring.
Sec.1 B
102 Frequency is the number
of occurrences of an event per unit time. In risk assessment, it
is usually expressed as the frequency per year.
Sec.1 B
103 Hazard is a source
of potential harm or a situation with a potential to cause loss
(any negative consequence).
Sec.1 B
104 An inspection and maintenance plan or schedule is a programme of scheduled
inspection and maintenance activities that ensure the safety-critical
elements continue to meet the identified performance standards to
maintain the safety and integrity of the installation.
Sec.1 B
105 Major hazards are hazards
with a potential for causing major accidents, i.e. involving fatality
due to fire or explosion, multiple fatalities, or severe damage
to the installation. Major pollution should be covered as indicated
in A102.
Sec.1 B
106 A performance standard is
a statement, which can be expressed, in qualitative or quantitative
terms as appropriate, of the performance required of a safety-critical
element in order to ensure the safety and integrity of the installation.
Sec.1 B
107 Risk is the combination
of likelihood and consequence of hazards being realised, i.e. the
chance of a specific event occurring within a specific period of
time.
Sec.1 B
108 Risk analysis is the
quantification of risks without making judgements about their significance.
It involves identifying hazards and estimating their frequencies
and consequences, so that the results can be presented as risks.
Risk analysis is sometimes known as risk estimation or risk quantification.
Sec.1 B
109 Risk assessment is
a systematic analysis of the risks from hazardous activities and
making a rational evaluation of their significance by comparison
against predetermined standards, target risk levels or other risk
acceptance criteria. Risk assessment is used to determine risk management
priorities.
Sec.1 B
110 Risk acceptance criteria are
standards by which the results of the risk assessment can be measured.
The acceptance criteria represent the acceptable level of safety
and integrity of the installation. They relate quantitative risk
estimates to qualitative value judgements about the significance
of the risks.
Sec.1 B
111 Safety-critical elements are
parts of the installation, or plant, which are essential to maintain
the safety and integrity of the installation. This includes any
items which:| — | if they failed, could cause
or contribute substantially to a major hazard affecting safety or
integrity of the installation; or |
| — | are intended to prevent or limit the effect of a major
hazard. |
Safety-critical elements include measures for prevention,
detection, control, mitigation (including personnel protection)
of hazards.
Sec.1 B
112 Verification is examination,
testing, audit or review to confirm that an activity, a product,
or a service, is in accordance with specified requirements.
For DNV classification, this normally includes verification
of the design, manufacturing, construction, installation, commissioning
and in-service condition of safety-critical elements such that they
fulfil the requirements of the performance standards.
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