A Risk Based Inspection is used
to determine the interval of inspection, the decision of type of next
inspection (whether it will be external, internal or on-stream) and the extent
of next inspection. Normally a Risk Based
Inspection Assessment based on the probability and the consequences of a pressurized
equipment failure, is conducted to determine the risk. In this situation the
pressurized equipment is kept under control or within the limits to reduce the
severity of that risk. It shall include the evaluation of both the probability
and the consequence of an equipment failure.
1. Accessing the Probability of Failure
The assessment on the probability
of failure shall consider the all types of mechanical damage; cracking, metal
loss (either it is general or localized), creep, fatigue, embrittlement etc.
The assessment shall include the determination and evaluation of equipment
present condition and the effectiveness of corrosion monitoring program.
2. Accessing the consequence of
failure
It includes the release of fluid
which ensued from the equipment failure. The assessment shall consider all
those consequences that may take place as a result of fluid release. So the
consequences that could be expected are;
- Fire
- Explosion
- Release of poisonous substances
- Health impacts
- Environmental impacts and pollution
After All the factors are
determined in an RBI assessment, the upshot is used to define the interval of
inspection and the following precautionary measures to minimize the probability
and consequence of failure.
- In-service Repair
- Use of Inhibitors to prevent metal loss
- Process Changes to reduce the severity of equipment failure
What can be defined using an
Equipment Risk-Based Inspection?
Usefulness of RBI Inspection
The combination of both the
assessments in an equipment risk-based inspection helps to define the
following;
- The type of future inspection (external/internal/on-stream) to be included in the inspection plan.
- The appropriateness of non-destructive examination on the equipment.
- The parts of equipment that ought to be examined in the future inspection.
- The use of pressure testing if require
- The use of repair techniques (whether it will be permanent or temporary)
Role of a Certified Inspector
A certified inspector is
accountable to the equipment user to ensure the maintenance and QA/QC
inspection programs in accordance with appropriate design codes and standards.
He is to perform the visual inspections in order to determine all the factors
which are required in both probability and consequence assessments.
Comments
Once an RBI assessment is
conducted on a vessel, it should be revised after every vessel inspection,
process change and repair work and whenever an unpredictable breakdown takes
place.
References
American Petroleum Institute API
510; 3.1.65, 5.2
American Petroleum Institute API
580 Section 1.1.1
American Petroleum Institute API
581