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.
