Risk Assessment for Increase in Plant Capacity
CCPS Middle East Conference on Process Safety
2017
2017 Middle East Process Safety Conference
General Submissions
Poster Session
Tuesday, October 10, 2017 - 1:15pm to 2:00pm
Different Risk Assessment approaches can be used in such scenario like HAZOP, What IF Analysis etc., but typical HAZOP guide words / deviations cannot provide the complete coverage of risk related issues as this is a very special case where all aspects of risk associated right from human factor to catalyst performance needs to take into account. For such cases, one of the approaches adopted is taking into account the layers of protection approach. This structured manner for each selected node with its different layers of protection, will help to check and assess any gaps to bring the overall process at acceptable risk level, while being operated at higher capacity load.
Following layers of protections are taken into account for Risk Assessment study:
BPCS (Basic Process Control System)
- Review of existing Alarm levels
- Control valves (output and response)
- Load margins with pumps/motors/prime movers
- Change in set points for controllers, alarm switch etc.
- Chemical Kinetics at elevated load (runaway reactions)
Equipment (pressure vessels, columns, HEX, pipelines etc.)
- Review of design data sheet.
- Past records of reliability and Turnaround history for equipment
- Erosion issues due to high throughput
- Review of Pressure drop across HEX, columns etc.
ESD / SIS
- Review of existing ESD/SIS data and requirement to change set points due to elevated plant load conditions.
Mechanical Protection system
- PSVs / RD capacity as per the design data sheet and elevated load conditions
Human Factors
- Operators response time in emergency
- Change in operating procedures and trainings
- Upgrade of Emergency Response plan
For a selected node or for any critical piece of equipment like Reactor, all above mentioned factors to be assessed and compared with the design parameters / simulation study and conclude that if the Risk is under acceptable level or not. All relevant process streams to be checked and assessed as per the above mentioned criteria to ensure all hazards and associated risks are taken into account while the plant operated at elevated load capacity.
This approach has been very useful ensuring that hazards and risks associated are taken care with increase in plant load, especially beyond design capacity. This approach can be used with any risk assessment model like What IF analysis or HAZOP while checking each and every parameters (as mentioned above) with available safeguards or recommendations.