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Metegrity
has leading expertise and software that combined, create
world-class inspection and maintenance programs with unparalleled
long-term
cost savings.
According to
the American Petroleum Institute (API), RBI is a method
for using risk as the basis for prioritizing and managing
the efforts of an |
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inspection
program. In an operating plant, a relatively large percentage
of the risk is associated with a small percentage of the
equipment items. RBI permits the shift of inspection and
maintenance resources to provide a higher level of coverage
on the high risk items and an appropriate effort on lower
risk equipment. RBI provides a methodology for determining
the optimum combination of equipment inspection methods,
scopes and frequencies.
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| Simply put, RBI
is a system used to determine the likelihood
of failure, and the consequences
of failure. The likelihood and consequences are combined
to produce an estimate of risk for each equipment item and
piping system. This estimate can be used as a basis for
allocating inspection and maintenance resources so potentially
high risk areas can receive sophisticated and frequent attention,
while low risk areas are inspected in a manner commensurate
with the lower risk. |
| The end result
of the RBI Program is a systematic, logical, documented,
repeatable method of determining the scope and frequency
of equipment inspection. The RBI methodology helps allocate
inspection resources more efficiently while improving safety,
reliability and compliance with applicable Codes, Standards
and Regulations. Proper execution of these principles leads
to optimized inspection and maintenance strategies, extended
intervals between planned outages, increased plant availability
and extended plant and equipment life. |
| The RBI process
consists of performing a risk assessment of the equipment,
then determining inspection frequencies and scopes. |
A risk assessment
involves first establishing the current and anticipated
condition of the equipment, by asking the following questions:
- What material degradations
have been experienced?
- How likely are these
degradations to occur?
- What are the consequences
of these degradations?
The next step is to determine
the risk of operating equipment as the combination of
two separate terms: the likelihood
of failure and the consequence
of failure.
The likelihood
analysis assesses the probability and effects of specific
failure mechanisms based on:
- The history of the equipment
- The history of similar
or identical equipment in identical service conditions
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The consequence
analysis of a release (instantaneous or continuous) is
calculated by:
- Estimating the release
rate and release amount based on:
- Pressure differentials
- Size of opening
- Leak detection methods
- Isolation capabilities
- Predict the outcome of
the release based on:
- Amounts released
- Composition of released
material
- Impact area of released
material
- Environmental impact
- Business interruption
effects
The data from likelihood
and consequences analysis can then be combined to produce
an estimate of risk for each equipment item and piping
system. The risk factor can then be ranked and used to
determine inspection schedules.
The RBI program
is totally dynamic: risks are updated after inspections
or even the inspection of similar equipment, changes to
process conditions or even if new information becomes
available. Any of the above may result in a change in
inspection frequencies or changes to the inspection scopes.
The methods used to determine
the inspection intervals and inspection scopes are documented
and repeatable. This is important with National Board
Owner/User Inspection Programs, which are subject to audits
by the Regulatory Authorities. This is also documented
‘due diligence’ which may be required in the
future.
For a more detailed explanation
of Risk-Based Inspection and implementation information,
please click
here. |
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