Process safety management ( PSM) is process hazard analysis (PHA)-a careful review of what could go wrong and what safeguards must be implemented to reduce the frequency and severity of incidents resulting from releases of chemicals and other energy sources.
Process means a series of actions to achieve an objective. Its operations in industries may entail combinations of materials, as initial or intermediate inputs, or additives; actions like carrying, placing, mixing, involving in reaction, changes in compositions; formations in particular shape/size,…. and so on.
Several calamities have occurred, taking heavy toll of life, health and assets. Single case of Bhopal tragedy in India in 1984, killed 2000 people in single night, crippling 2 lakh population, because of release of large quantity of deadly MIC gas from an abandoned plant of insecticide product. Such situations require for preventing or minimizing the consequences of catastrophic releases of toxic, reactive, flammable, or explosive chemicals, which result in toxic, fire or explosion hazards.
Process unit startups and shutdowns are significantly more hazardous than normal oil refinery or chemical facility operations. A startup is a planned series of steps to take a process from an idle, at rest, state to normal operation. A shutdown is the reverse sequence.
Many studies identify and addresses process safety needs within the chemical, pharmaceutical, and petroleum industries, determined that a majority of process safety incidents occur during a plant startup, even though it represents only a small portion of the operating life of a plant. Process safety incidents occur five times more often during startup than during normal operations. 50% of process safety events occur during startups, shutdowns, and other cases that infrequently occur. This is because startup and shutdown periods involve many non-routine procedures, and these periods can result in unexpected and unusual situations.
To prevent these types of incidents from occurring, facilities should employ effective communication, provide workers with appropriate training, and have in place strong and up-to-date policies and procedures for hazardous operations such as startups and shutdowns.
Lessons learned from the events include effective process safety management, which could have prevented these incidents.
1. Implementing written safe operating procedures for startup following an emergency shutdown such as:
- Conducting and completing a thorough pre-startup safety review
- Following proper safe work practices for opening lines and equipment following a shutdown
- Conducting a management of change (MoC) analysis for equipment, processes and procedures that are not replacements in kind.
2. Written operating procedures need to have sufficient detail to avoid the likelihood of valve misalignments during startups and shutdowns. Written checklists and diagrams to verify proper valve positioning should be provided, if needed.
3. Operational variances were often made prior to these incidents during startup or shutdown where the impact of the change was not known. A review of the MoC policy should occur to ensure it adequately addresses changes due to operational variance. To maximize the effectiveness of MoC, the following activities should be included:
- Define safe limits for process conditions, variables, and activities—and train personnel to recognize significant changes. Combined with knowledge of established operating procedures, this additional training will enable personnel to activate the MoC system when appropriate.
- Apply multidisciplinary and specialized expertise when analyzing deviations.
- Use appropriate hazard analysis techniques
- Authorize changes at a level commensurate with risks and hazards
- Communicate the essential elements of new operating procedures in writing
- Communicate potential hazards and safe operating limits in writing
- Provide training in new procedures commensurate with their complexity
- Conduct periodic audits to determine if the program is effective.
4. Ensure the facility’s lockout/tagout (LOTO) program requires equipment is rendered safe prior to opening for inspection or maintenance. Equipment opening procedures should contain a stop work provision that requires higher levels of management review and approval when safe opening conditions, such as equipment depressurization, cannot be verified.
5. Ensure proper procedures are used to isolate equipment after a shutdown. Do not rely on a single block valve closure, which may leak. Instead, use a double block and bleed; insert a blind flange, or physically disconnect the piece of equipment to ensure it is properly isolated. For equipment placed in “standby mode” continue to monitor critical parameters, such as pressure and temperature, while the equipment is “offline” and ensure operating procedures address the conditions under which “standby” equipment should be deinventoried( draining and emptying) and shut down.
6. Computerized control systems should include a process overview and, as appropriate, material balance summaries to ensure full process oversight by operators.
7. In complex and critical process systems, multi-channel communication with feedback provides the best opportunity for operators to establish and maintain a mutual understanding of the process unit and its expected future state. During times of abnormal operating conditions, such as unit startup, the risk of operators having dissimilar or incompatible understandings of the state of the processing unit is even greater, making effective communication vital and feedback essential.
8. Ensure operators are supervised and supported by experienced, technically trained personnel during unit startups and shutdowns and they are sufficiently trained on the control systems they will be operating. Consideration should be given to the use of simulators for training operators in abnormal situations during startups and shutdowns.
9. For high-hazard processes, establish a shift work policy to minimize the effects of fatigue. Individuals are poor self-assessors and are less likely to admit they are too fatigued to work safely. The shift work policy should aim to manage both normal shift patterns/rotations and temporary situations, such as turnarounds, by limiting the number of working hours per 24-hour period and the number of consecutive days at work.
10. Newly installed computer controls need to be calibrated and tested for functionality before being used in a unit startup.
11. Critical safety devices must not be bypassed during troubleshooting operations during unit startups and shutdowns.
The following elements of Process Safety Management are important which should be implemented to achieve process control through hazard identification, risk analysis and assessment, risk mitigation, hazard management control and emergency action plan.
Article by Dr.Yashoda Tammineni,
MSc, Ph.D.
HSE,HOD at NIFS
No comments:
Post a Comment