Incorporating Safety during Process Design

Process facilities are generally designed in accordance with good engineering practice. Safety features like inherently safer design, Basic Process Control Systems (BPCS), Alarms, Relief valves, Shutdown, etc. are incorporated to take care of upsets during Normal/ Emergency operation, as well as Startup.

Equipment and Piping are designed to withstand the maximum expected pressures, which can be foreseen during the design and engineering phases of a Project. This however should not lull the operators into a sense of complacency and lead them to believe that the facility will be operated with unlimited flexibility. Problems can arise if due attention is not given to the criteria adopted for the design of various systems. This could happen if critical parameters are not monitored, good operating practices are not followed and abrupt changes are made in feed composition or operating conditions. Inherent safer practice has also been challenged with the introduction of electric submersible pumps (ESPs) in new and existing wells as the maximum discharge pressure under block-in conditions exceeds the maximum allowable working pressure (MAWP) of existing piping. A safe alternative to replacing the piping is the use of a high integrity pressure protection system (HIPPS). Though HIPPS protects the downstream piping, but can result in significant ESP damage and production losses due to blocked ESP discharge.

 It is understandably difficult to incorporate multiple features to guard against mal operation or human failure, but is desirable to try and anticipate problems and take pre-emptive action at the design stage rather than carry out corrective actions following a failure. Some of these aspects are illustrated with a description of the fall out on account of not taking into consideration the limitations in the design of the existing facilities.