Process Safety Management

PROCESS SAFETY MANAGEMENT

Bayu Nurwinanto

Process Safety Information

Hazards of the chemicals Used in the process

Complete and accurate written information concerning process chemicals, process technology, and process equipment is essential to an effective process safety management program and to a process hazard analysis. The compiled information will be a necessary resource to a variety of users including the team performing the process hazard analysis as required by PSM (Process Safety Management) those developing the training program and the operating procedure; contractors whose employees will be working with the process; those conducting the planners and insurance and enforcement officials.

The information to be compiled about the chemicals, including process intermediate, needs to be comprehensive enough for an accurate assessment of the fire and explosion characteristics, reactivity hazards, the safety and health hazards to workers and the corrosion and erosion effect on the process equipment and monitoring tools. Current material safety data safety data sheet (MSDS) information can be used to help meet this requirement but must be supplemented with process chemistry information, including runaway reaction and over-pressure hazards, if applicable.

Technology of the process

Process technology information will be a part of the process safety information package and should include employer established criteria for maximum inventory levels for process chemicals; limits beyond which would be consequences or results of deviation that could occur if operating beyond the established process limit. Employers are encouraged to use diagrams that will help users understand the process.

A block flow diagram is used to show the major process equipment and interconnecting process flow lines and flow rates, steam composition, temperature and pressures when necessary for clarity. The block flow diagram is a simplified diagram.

Process flow diagram are more complex and show all main flow steams including valves to enhance the understanding of the process as well as pressure and temperatures on all feed and product lines within all major vessels and in and out of headers and heat exchangers and points of pressure and temperature control (see figure for sample process flow diagram). Also information on construction materials, pump capacities and pressure heads, compressor horsepower and vessel design pressure and temperature are shown when necessary for clarity. In addition, process flow diagrams usually show major components of control loops along with key utilities.

Equipment in the process

Piping and instrument diagrams (P&ID) may be the more appropriate type diagram to show some of the above details as well as display the information for the piping designer and engineering staff. The P&ID are to be used to describe the relationships between equipment and instrumentation as well as other relevant information that will enhance clarity. Computer software programs that do P&ID or other diagram useful to the information package may be used to help meet this requirement.

The information pertaining to process equipment design must be documented. In other words, what codes and standard were relied on to establish good engineering practice? These codes and standard are published by such organization as the ASME, API, ANSI, National Fire Protection Association, American Society for Testing and Materials, The National Board of Boiler and Pressure Vessel Inspectors, National Association of Corrosion Engineers, American Society of Exchange Manufacturers Association ad Model building Code groups.

For existing equipment designed and constructed many years ago in accordance with the codes and standards available at that time and no longer in general use today, the employer must document which code and standards were used and that the design and construction along with the testing, inspection and operation are still suitable for the intended use. Where the process technology requires a design that departs from the applicable codes and standards, the employer must document that the design and construction are suitable for the intended purpose.

Process Hazards Analysis

A process hazards analysis (PHA), or evaluation is one of the most important elements of the process safety management program. A PHA is an organized and systematic effort to identify and analyze the significance of potential hazards associated with the processing or handling of highly hazardous chemical. A PHA provides information that will assist employers and employee in making decisions for improving safety and reducing the consequences of unwanted or unplanned releases of hazardous chemicals.

A PHA analyzes potential causes and consequences of fires, explosions, releases of toxic or flammable chemicals and major spills of hazardous chemicals. The PHA focuses on equipment, instrumentation, utilities, human action (routine and non-routine) and external factors that might affect the process.

The selection of a PHA methodology or technique will be influenced by many factors including how much is known about the process. Is it a process that has been operated for a long period of time with little or no innovation and extensive experience has been generated with its use? Or, is it new process or one that has been changed frequently by the inclusion of innovation features? Also, the size and complexity of the process will influence the decision as to the appropriate PHA methodology to use. All PHA methodologies are subject to certain limitations. For example, the Checklist methodology works well when the process is very stable and no changes are made, but it is not as effective when the process has undergone extensive change. The checklist may miss the most recent changes and consequently they would not be evaluated. Another limitation to be considered concerns the assumptions made by the team or analyst. The PHA is dependent on good judgments and the assumptions made during the study need to be documented and understood by the team and reviewer and kept for a future PHA.

The ideal team will have an intimate knowledge of the standards codes, specifications and regulations applicable to the process being studied. The selected team members need to be compatible and the team leader needs to be able to manage the team and the PHA Study. The team needs to be able to work together while benefiting from the expertise of others on the team or outside the team to resolve issues and to forge a consensus on the findings of the study and recommendations.

The application of a PHA to a process may involve the use of different methodologies for various parts of the process. For example, a process involving a series of unit operation of varying sizes, complexities and ages may use different methodologies and team members for each operation. Then the conclusions can be integrated into one final study and evaluation.

Finally, when an employer has a large continuous process with several control rooms for different portions of the process, such as for a distillation tower and a blending operation, the employer may wish to do each segment separately and then integrate the final results.

Small business covered by the rule often will have processes that have less storage volume and less capacity and may be less complicated than processes at a large facility. Therefore, OSHA would anticipate that the less complex methodologies would be used to meet the process hazard analysis criteria in the standard. These process hazard analyses can be done in less time and with fewer people being involved. A less complex process generally means that less data, P&ID, and process information are needed to perform a process hazard analysis.

Operating Procedures

Operating procedures describe tasks to be performed, data to be recorded, operating condition to be maintained, sample to be collected and safety and health precautions to be taken. The procedures need to technically accurate, understandable to employees and revised periodically to ensure that reflect current operations. The process safety information package helps to ensure that the operating procedures and practices are consistent with the known hazards of the chemicals in the process and that the operating parameters are correct. Operating procedures should be reviewed by engineering staff and operating personnel to ensure their accuracy and that they provide practical instructions on how to actually carry out job duties safety. Also the employer must certify annually that the operating procedures are current and accurate.

Operating procedures provide specific instruction or details on what steps are to taken or followed in carrying out the stated procedures. The specific instructions should include the applicable safety precautions and appropriate information on safety implications. For example, the operating procedures addressing operating parameters will contain operating instruction about pressure limits, temperature ranges, flow rates, what to do when an upset condition occurs, and other subjects. Another example of using operating instructions to properly implement operating procedures is in stating up or shutting down the process. In these cases, different parameters will be required from those of normal operation. These operating instruction need to clearly indicate the appropriate allowances for heating up a unit to reach the normal operating parameters. Also the operating instructions need to describe the proper method for increasing the temperature of the unit until the normal operating temperatures are reached.

Computerized process control systems add complexity to operating instructions. These operating instructions need to describe the logic of the software as well as the relationship between the equipment and the control system; otherwise, it may not be apparent to the operator. Operating procedures and instructions are important for training operating personnel. The operating procedures are often viewed as the standard operating practices (SOP) for operations.

Contractor

Employers who use contractors to perform work in and around processes that involve highly hazardous chemicals have to establish a screening process so that they hire and use only contractors who accomplish the desired job tasks without compromising the safety and health of any employees at a facility. For contractors whose safety performance on the job is not known to the hiring employer, the employer must obtain information on injury and illness rates and experience and should obtain contractor references. In addition, the employer must ensure that the contractor has the appropriate job skill, knowledge and certifications (e.g., for pressure vessel welders). Contractor work methods and experience should be evaluated. For example, does the contractor conducting demolition work swing loads over operating processes or does the contractor avoid such hazards?

Maintaining a site injury and illness log for contractors is another method employers must use to track and maintain current knowledge of activities involving contract employees working on or adjacent to processes covered by PSM (Process Safety Management). Injury and illness logs of both the employer’s employees and contract employees allow the employer to have full knowledge of process injury and illness experience. This log contains information useful to those auditing process safety management compliance and those involved in incident investigations.

Pre-Startup Safety Review

For new processes, the employer will find a PHA helpful in improving the design and construction of the process from a reliability and quality point of view. The safe operation of the new process is enhanced by making use of the PHA recommendations before final installations are completed. P&ID should be completed, the operating procedures put in place, and the operating staff trained to run the process, before startup. The initial startup procedures and normal operating procedures must be fully evaluated as part of the pre-startup review to ensure a safe transfer into the normal operating mode.

For existing processes that have been shutdown for turnaround or modification, the employer must ensure that any changes other than “replacement in kind” made to the process during shutdown go through the management of change procedures. P&ID will need to be update, as necessary, as well as operating procedures and instructions. If the changes made to the process during shutdown are significant and affect the training program. The operating personnel as well as employees engaged in routine and non-routine work in the process area may need some refresher or additional training. Any incident investigation recommendations, compliance audits, or PHA recommendation need to be reviewed to see what affect they may have on the process before beginning the startup.

Mechanical Integrity of Equipment

Employers must review their maintenance programs and schedules to see if there are areas where “breakdown” maintenance is used rather than the more preferable on-going mechanical integrity program. Equipment used to process, store, or handle highly hazardous chemicals has to be designed, constructed, installed and maintained to minimize the risk of releases of such chemicals. This requires that a mechanical integrity program be in place to ensure the continued integrity of process equipment.

Elements of a mechanical integrity program include identifying and categorizing equipment and instrumentation, inspections and tests and their frequency: maintenance procedures; training of maintenance personnel; criteria for acceptable test results: and documentation of manufacturer recommendations for equipment and instrumentation.

Inspection and Testing

The mean time to failure of various instrumentation and equipment parts would be know from the manufacturer’s data or the employer’s experience with the parts, which the influence inspection and testing frequency and associated procedures. Also, applicable codes and standards such as the National Board Inspection Code, or those from the American Petroleum Institute, National Fire Protection Association, American National Standards Institute, American Society of Mechanical Engineers and other group provide information to help establish an effective testing and inspection frequency, as well as appropriate methodologies.

The applicable codes and standards provide criteria for external inspections for such items as foundation and supports, anchor bolts, concrete or steel support, guy wires, nozzles and sprinklers, pipe hangers, grounding connections, protective coatings and insulation, and external metal surface of piping and vessels. These codes and standards also provide information on methodologies for internal inspection and a frequency formula based on the corrosion rate of the materials of construction. Also, internal and external erosion must be considered along with corrosion effects for piping and valve. Where the corrosion rate is not known, a maximum inspection frequency is recommended (method of developing the corrosion rate are available in the codes). Internal inspections need to cover items such as the vessel shell, bottom and head; metallic linings; inspection for erosion, corrosion, cracking and bulges: internal equipment like trays, baffles, sensors and screens for erosion, corrosion of cracking and other deficiencies. Some of these Inspections may be performed by state or local government inspector under state and local statutes. However each employer must develop procedures to ensure that tests and inspection are conducted properly and that consistency is maintained even where different employees may be involved. Appropriate training must be provided to maintenance program procedures, safe practices and the proper use and application of special equipment or unique tools that may be required. This training is part of the overall training program called for in the standard.