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Catch the Big Hazards with Comprehensive PHA Questions

Don't Let Critical Hazards Slip Through: The Power of a Comprehensive PHA Question Set!

Process Hazard Analysis (PHA) is crucial for identifying potential hazards and preventing incidents in process industries. Using comprehensive question sets is a proven method within PHA to ensure thorough hazard identification.

This article provides a sample of key questions from a more extensive Process Hazard Review Question library. The full library, included in our What-If PHA Automated Excel Spreadsheet product, contains over 700 "what-if" questions designed to prompt critical thinking and in-depth analysis of your processes.

Please note: The questions below are just a sample. The complete question set in our PHA product offers far more comprehensive coverage.

These questions are designed to stimulate detailed evaluations and discussions within your PHA team, and should not be answered with a simple "Yes" or "No". Consider these questions across all operating modes – from steady state and startup to shutdown, maintenance, and upset conditions. Applying a thorough question set like the complete library can significantly enhance your hazard identification process and contribute to a safer operating environment.

I. Process

A. Materials and Flowsheet

  • What materials are hazardous (e.g., raw materials, intermediates, products, by-products, wastes)? Are any prone to form vapor clouds? Which ones are acutely or chronically toxic, flammable, combustible, or unstable?
  • What are the key properties of the process materials, including physical, toxicological, reactive, combustion, and environmental properties?
  • What unwanted hazardous reactions or decompositions could develop due to improper storage, abnormal process conditions, or mechanical failures?
  • What data is available or should be obtained on the amount and rate of heat and gas evolution during reactions?

B. Unit Siting and Layout

  • Can the unit location minimize the transportation of hazardous materials?
  • What hazards does this unit pose to the public, workers in control rooms or adjacent areas from toxic releases, thermal radiation, overpressure, noise or contamination?
  • Conversely, what hazards do adjacent facilities pose to personnel or equipment within the unit itself?
  • What external forces (weather, natural disasters, adjacent plant releases) could impact the site and create hazards?

II. Equipment

A. Pressure and Vacuum Relief

  • Is equipment designed to withstand maximum credible overpressure?
  • Are emergency relief devices (relief valves, rupture disks) appropriately located and sized based on potential scenarios like utility failures or runaway reactions?
  • Is the relief system designed for two-phase flow if necessary?
  • Are rupture disks in series with relief valves properly monitored and maintained?

B. Piping and Valves

  • Is the piping specification suitable for process conditions, considering compatibility, pressure, temperature, and cyclical conditions?
  • Are there special considerations that could promote piping failure, such as flashing liquids, freezing, cryogenic conditions, or corrosion mechanisms?
  • Can piping sizes or lengths be reduced to minimize hazardous material inventory?
  • Are piping systems provided with adequate freeze protection and drainage capabilities?

C. Pumps

  • Can pump discharge pressure exceed the design pressure of the casing or downstream equipment?
  • Are pumps protected with relief valves or minimum flow bypasses?
  • Can pump suction be isolated in an emergency, and are isolation valves safely accessible?
  • Is leakage of process fluid into the pump motor a potential hazard?

D. Compressors

  • Similar to pumps, can compressor discharge pressure exceed design limits?
  • Are compressors protected by relief or recycle valves?
  • Are air compressor intakes protected from contaminants, and are gas detection and ventilation safeguards in place if compressors are in enclosed buildings?

E. Reactors

  • What could cause an exothermic reaction in the reactor, such as quench failure, reactant excess, contaminants, or agitation loss?
  • What are the potential hazards associated with the reactor catalyst, including pyrophoric nature or toxicity?
  • What hazards are associated with catalyst regeneration processes?

F. Vessels (Tanks, Drums, Towers, etc.)

  • Are vessels regularly inspected for localized damage and pressure tested?
  • Is pressure relief adequate for various scenarios like cooling water failure or external fire?
  • Are vessel levels monitored if they are critical for process operation?
  • Are contents of all storage vessels properly identified?

G. Heat Exchangers

  • What are the consequences of a tube failure, including potential reactions, flashing, or corrosion?
  • Is pressure relief adequate for both sides of the heat exchanger?
  • What if the exchanger is exposed to external fire or blocked in conditions?
  • Is the cooling water supply reliable with backup systems and spare capacity?

H. Furnaces and Boilers

  • Is the firebox protected against explosions, and does the burner control system meet safety standards?
  • Are proper purging procedures in place before start-up?
  • Are critical safety shutoff valves and alarms configured and tested?
  • Is the furnace adequately protected against tube failures with flow controls and isolation valves?

I. Instrumentation

  • Have instruments critical to safety been identified with their safety functions and alarm setpoints documented?
  • Has the safety function of instrumentation been integrated with process control design?
  • Are instruments designed to minimize response time lag and backed up by independent systems where necessary?
  • What is the effect of faulty sensors or recorders, and how are failures detected?

J. Electrical Power

  • What is the area electrical classification, and are equipment and protective techniques consistent with it?
  • Are electrical interlocks and shutdowns fail-safe and periodically tested?
  • Are trucks and railcars properly grounded during loading/unloading?
  • Are conduits sealed against flammable vapors in hazardous areas?

K. Miscellaneous

  • Are special seals necessary for severe service conditions?
  • Do rotating equipment have adequate integrity shutdowns (e.g., lube oil shutdown)?
  • Is vibration signature routinely monitored to detect incipient failures?
  • What could cause catastrophic failure of piping or equipment?

III. Operations

  • What human errors could lead to catastrophic consequences, and what measures are in place to mitigate them?
  • Are complete and current procedures available for all operations (normal, startups, shutdowns, emergencies)?
  • Are procedures regularly reviewed and updated, involving operator feedback?
  • Are procedures written clearly for all workers to understand, considering language and background?

IV. Maintenance

  • Are written procedures in place and followed for hot work, confined space entry, lockout/tagout, and other critical maintenance tasks?
  • Are crane and heavy equipment operations properly governed, including operator certification and equipment inspections?
  • Is complete process shutdown necessary for certain maintenance tasks, and are proper isolation and blanking procedures in place?
  • Are the right tools available and used, including special tools for specific tasks?

V. Personnel Safety

  • Are building structures (stairways, platforms) designed and maintained to safety standards and well-lit?
  • Does the control room provide a safe haven during emergencies with adequate protection and evacuation plans?
  • What fire and explosion hazards are present in operating areas, and how are they mitigated (e.g., flammable materials, ignition sources)?
  • What chemical hazards are present and how are they mitigated (asphyxiants, carcinogens, irritants, etc.)?

VI. Fire Protection

  • What combustible mixtures can occur in equipment under normal and abnormal conditions?
  • What is the inventory of flammable liquids, and is it minimized?
  • Are major storage tanks located to minimize hazard to process equipment?
  • Are firewalls and partitions in place to separate critical areas?
  • Are critical isolation valves fire-safe and will actuators withstand fire exposure?

VII. Environmental Protection

  • Are there chemicals particularly sensitive from an environmental standpoint (carcinogens, volatile toxics)?
  • Have all effluent streams been defined and are they properly treated and monitored?
  • Are there procedures and equipment for spill response, and is the spill response team adequately trained and equipped?
  • Are there any suppression, absorption, or cleaning media that are prohibited due to incompatibility or environmental concerns?

VIII. Management and Policy Issues

  • Is upper management's commitment to employee health and safety clearly communicated and believed by employees?
  • Does safety have equal status with other business objectives, and how is a "safety first" approach promoted?
  • Is there a policy that clearly establishes the authority to stop work if safety requirements are not met?
  • Is there an audit program that regularly reviews safety compliance, involving workers in the process?
  • Are there programs for identifying and helping workers with substance abuse or mental health problems?

Note: Above is a sample of process hazard review questions. A comprehensive PHA would involve a much larger and more detailed set of questions, tailored to the specific process and facility.

Implement Industry Best Practices for Process Hazard Analysis Worldwide. The What-If PHA Automated Excel Spreadsheet provides a comprehensive 700+ question Process Hazard Review library to support rigorous What-If analyses and significantly reduce process safety risks across international operations. Explore the What-If PHA Automated Excel Spreadsheet and Improve Your PHA.