Case Study: Hazardous Chemical PHA Case Study
Industry: Starch Manufacturing
Purpose of the Case Study
This case study describes a PHA that ADF performed for a starch manufacturer that uses POCl3 (phosphorus oxychloride) in the modification of starch. POCl3 reacts violently with water to produce strong acid. Even small amounts of moisture can create hazardous acid mist and contact with personnel can be deadly.
Although the client only utilizes small quantities of this material, the handling of the incoming material and scrubbing of the vent is a very serious matter.
During the PHA, ADF carefully dis-assembled the steps of this process and analyzed the hazards to identify the necessary measures to ensure safe operation, even during non-routine tasks, such as equipment maintenance.
Brief Overview of Process Safety Management and PHA
Process Safety Management (PSM) is a systematic, performance‑based management framework designed to prevent catastrophic releases of hazardous chemicals (toxic, flammable, reactive, or explosive). In the U.S., it is defined by OSHA 29 CFR 1910.119 and applies to processes exceeding specific chemical thresholds.
PSM focuses on how hazardous processes are designed, operated, maintained, and changed over time, using administrative, technical, and cultural controls. Core elements include maintaining accurate process safety information, formal operating procedures, training, mechanical integrity, management of change, incident investigation, emergency planning, and regular audits.
Process Hazard Analysis (PHA) is a key element within PSM and refers to a structured, systematic evaluation of process hazards to identify potential accident scenarios, assess risk, and verify that safeguards are adequate.
PHAs are typically conducted using recognized methodologies such as HAZOP, What‑If, Checklist, FMEA, or LOPA, and they examine process nodes, deviations, causes, consequences, and existing protections. The output of a PHA is a set of documented findings and recommendations that drive risk reduction through engineering controls, procedural changes, or additional safeguards.
PHAs must be periodically revalidated to ensure continued effectiveness.
Project Background and Context
Starches are often modified with hazardous chemicals to produce the desired product qualities. In this case, the manufacturer uses small quantities of POCl3, which produces acid violently when in contact with water, to modify the starch.
The hazards are focused on the transfer of chemical drums into a use tank and venting to a scrubber, which forcibly converts the chemical vapors into acid in a controlled environment. The tank only vents to the scrubber while the tank is being filled from drums.
In the past, a seal pot was used upstream of the scrubber. However, this led to an incident of personnel exposure and the seal pot was removed from the process.
The PHA was conducted to review the revised process following this event.
Industry Overview
Starch is typically modified with ethylene oxide or propylene oxide, which are highly explosive, as well as toxic. These processes must be designed carefully to avoid even accidental releases of these dangerous chemicals.
Facility Description
Facility Overview
The client’s facility is a large starch plant in the US Midwest.
The Company’s Process and Operations
The company produces food ingredients produced mainly from corn, including a variety of starches.
ADF’s Process Hazard Analysis Methodology
Assessment Techniques
The first step in the process is to determine the hazardous characteristics of the chemicals handled on the site, based on one or more of the following:
- Toxicity
- Flammability
- Reactivity
The next step is to set up the PHA by determining the appropriate areas of risk in the process from current Process Flow Diagrams or P&ID’s, which must accurately show all steps in the process, including start-ups, shutdowns, emergency releases, or maintenance procedures.
The actual PHA review meeting may then be held at the site and must include the following participants, at minimum:
A. Qualified PHA Facilitator
B. Site Engineer
C. Experienced Operator and/or Maintenance Personnel
D. Facility or Operations Manager
E. Site Safety Manager
The duration of the on-site PHA review depends upon the overall complexity and size of the facility, the materials handled and the accuracy and completeness of the process documentation. Information to be identified and evaluated at the PHA includes:
A. Review of hazardous chemicals handled
B. Identification of all potential areas of risk and likelihood in each process node
C. Safe operating ranges
D. Explosion, fire, or release prevention and protection methods
F. Propagation paths and potential for exposure
G. Recommendations for additional protection measures
Finally, the PHA Facilitator will summarize the identified hazards, and agreed upon implementation plan and schedule to address all risks to an acceptable level.
Furthermore, all future changes to the processes or chemicals handled must be documented through a Management of Change procedure to determine necessary safety system changes and kept with the official PSM documentation by the facility safety coordinator.
Data Collection
Generally, the Safety Data Sheets provide comprehensive information on hazardous chemicals. If this data is unavailable, a qualified lab will need to be contacted.
Risk Identification
ADF utilizes PHA-Pro software for Process Hazard Analyses and has experience with PHA-Works software if desired.
Project Findings and Analysis
Hazard Identification
The sole hazardous chemical used in this process was POCl3.
Risk Assessment
ADF utilized PHA-Pro software for this Process Hazard Analysis.
Safety Systems Evaluation
The existing process nodes and procedures were identified in advance of the on-site PHA.
ADF’s Post Analysis Recommendations
Preventive Measures
The PHA found that the risks associated with the scrubber were easily manageable since venting only occurs during tank filling. Check valves and other safeguards were added for the drum tipping operation to prevent hazards related to this part of the process.
Employee Training and Awareness
Site employees and contractors are trained in the hazards of this specific chemical. The best way to train employees in the conduct of Process Hazard Analyses is through direct involvement. It is recommended to include a variety of employees at all levels when conducting site PHAs.
PHA Implementation—Our Project Management Approach
ADF’s Project Planning and Execution
ADF managed the process upgrades following the PHA.
Timeline and milestones
A temporary scrubber was found to operate efficiently and safely, so it was made into a permanent solution. Upstream recommendations for drum tipping were implemented immediately after the PHA.
Innovative Solutions and Technologies
ADF was able to confirm the safety of the temporary scrubber operation to avoid the cost of implementing a more costly system, while recommending minor upgrades to the drum tipping procedure.
Continuous Improvement
The PHA must be re-validated every five years or whenever a process change is made.
Project Conclusion
Summary of Key Findings
High-cost combustible powders can be recovered to the process if the collectors can be installed above the existing equipment.
The improved hood designs significantly reduced the accumulation of combustible dusts in the process area, avoiding an expensive electrical area classification change.
Summary of PHA Implementation
ADF supported the start-up of this process and worked closely with the site to develop appropriate safety measures.
Contact and Engagement Information
Contact Details:
Matt Williamson, P.E.
Director of Engineering
(937) 510-7375
mwilliamson@adfengineering.com
