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mikemccue.gif (8327 bytes) Mike McCue: The Process Safety Advisor
Tools to help prevent a catastrophic incident
Mike McCue is a consultant specializing in chemical process safety, plant security and environmental compliance management.  He is experienced in a variety of industries including pharmaceutical, chemical and oil refining, specialty chemicals, ammonia refrigeration, and chlorine water/wastewater treatment.  His clients have included Johnson & Johnson, Merck, Amerada Hess, Sunoco and FMC Corporation.  He has experience in governmental and regulatory affairs at both the state and federal level.  He holds a B.S. and M.S. in Chemical Engineering, a M.B.A. and a law degree.  You can reach Mike at, Phone: (609) 758-6535, Fax: (609) 758-3180.

The more you know: Process Safety Information (PSI)

The Process Safety Information (PSI) requirement of PSM/RMP ensures that the management of highly hazardous materials is based on accurate, up-to-date information.  PSI is the backbone of a process safety program.  PSI is used as a basis for other PSM/RMP elements including: Process Hazard Analysis, Operating Procedures, Operator Training, Mechanical Integrity and Management of Change and Emergency Response.  PSI is important for a number of reasons:


  • Records of design criteria ensure that on-going operations and maintenance are consistent with the original intent
  • It serves as a basis for future additions or expansions, thereby managing change
  • Demonstrates use of good engineering practice in designing, operating and maintaining the facility



PSI requirements


PSI includes information pertaining to:

  1. the hazards of the regulated substances used or produced by the process;
  2. the technology of the process; and
  3. the equipment in the process.



Information pertaining to the hazards of the regulated substances in the process.


This information shall consist of at least the following:

(1) Toxicity information;

(2) Permissible exposure limits;

(3) Physical data;

(4) Corrosivity data;

(6) Thermal and chemical stability data applicable to the process in which an EHS is being used, handled, stored or generated: stability (unstable or stable), conditions to avoid for instability, incompatibility (materials to avoid), hazardous decomposition (products or byproducts), hazardous polymerization (may occur or will not occur), and conditions to avoid for polymerization; and

(7) Hazardous effects of inadvertent mixing of different materials that could foreseeably occur. Much of this information can be found in a Material Safety Data Sheet for the specific regulated substance.



Information pertaining to the technology of the process.


Information concerning the technology of the process shall include at least the following:

(1) A block flow diagram or simplified process flow diagram;

(2) Process chemistry;

(3) Maximum intended inventory;

(4) Safe upper and lower limits for such items as temperatures, pressures, flows or compositions; and

(5) An evaluation of the consequences of deviations. Where the original technical information no longer exists, such information may be developed in conjunction with the process hazard analysis in sufficient detail to support the analysis.



Information pertaining to the equipment in the process.


Information pertaining to the equipment in the process shall include:

(1) Equipment specifications including materials of construction;

(2) Piping and instrument diagrams (P&ID's);

(3) Electrical classification;

(4) Relief system design and design basis;

(5) Ventilation system design;

(6) Design codes and standards employed;

(7) Material and energy balances for processes built after June 21, 1992; and

(8) Safety systems (e.g. interlocks, detection or suppression systems).


The owner or operator shall document that equipment complies with recognized and generally accepted good engineering and operating practices.  For existing equipment designed and constructed in accordance with codes, standards, or practices that are no longer in general use, the owner or operator shall determine and document that the equipment is designed, maintained, inspected, tested, and operating in a safe manner.


One of the most important sets of information is the piping and instrumentation diagram (P&ID) which often lacks key elements.


What must be included (as an absolute minimum) on a P&ID?

  1. All regulated substance-containing equipment, including pressure vessels, tanks,  heat transfer equipment, pumps, transfer/unloading stations, etc.
  2. Essential valves, such as isolation valves and control stations, as well as all safety relief elements (valves, disks, etc.).
  3. Controls (regulators, float switches, etc.) and solenoid valves.
  4. Control schemes including interlocks, permissives, etc.
  5. Permanent instruments and sensors (pressure/temperature/flow transducers, meters, etc.).
  6. Flow direction: at a minimum, always show the permitted-flow direction on a check valve.
  7. Line sizes/reducers; expansion tie-ins and block valves, etc.
  8. Design working pressure and other pressure-vessel/equipment label information.
  9. Support equipment and non-chemical lines such as condenser water pumps, secondary heat transfer fluid (glycol/brine) loops.
  10. Equipment/valve numbering: Proper labeling, both on the P&ID and in the field, will reduce the risk of operator error and simplify the writing of operating procedures.
  11. Legend defining symbols and abbreviations.


What should be included?

  1. Purge/gauge valves.
  2. Line designations/purposes: some processes, such as refrigeration, have recognized systems for line designation. For others, use a system that explains the line's function and optionally includes other information such as temperature and pressure levels, etc.
  3. Safety relief valve specifications: information on the relief valve “design and design basis is required before starting the PHA study.

Any item omitted on the list above should be available in another form (such as a list of safety relief valve specifications).

After P&IDs are prepared, they should be verified against field conditions. We recommend that each and every line, valve, sensor, or other P&ID item be checked visually against the as-built system, even for supposedly
"as-built" drawings.



Current PSI


One of the most important aspects of PSI is keeping the information current and up-to-date.  Usually the element where this is most difficult to maintain is P&IDs.  Once drawings have been brought up-to-date, a technique that is useful for changes is known as "red-lining".  For those of you who are not familiar with this technique, master sets of drawings are marked up using a red pencil.  This denotes a change that has not yet been incorporated into the electronic originals.  These "red-lined" drawings can be used by operating and maintenance personnel with a degree of confidence that the information is up-to-date.  Master drawings should be up dated with the "red line" changes at least once per year, more frequently as appropriate.





In the distant past, key information was passed on by word of mouth between the more experienced and the novice.  This still continues today, where the concept of on-the-job training is an important and widely used tool.  However, there is a considerable need to have accurate, up-to-date information that can be readily accessible.  A robust management program that maintains Process Safety Information is critical to a Process Safety Management/Risk Management Program.


By: Mike McCue, Process Safety Columnist for

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