3.2 Process Safety Information

Process safety information (PSI) is 1910.119(d). OSHA wants a compiled, written body of facts before you rely on procedures and PHAs. If the P&ID is wrong, the HAZOP of “what happens if this valve is closed” is theater. If nobody recorded maximum intended inventory, you cannot even prove whether the process is over the 10,000 lb anhydrous threshold. Treat PSI as the source documents a CIRO uses when training a new operator, briefing a contractor, or arguing that a vessel is still inside its design.

OSHA groups PSI into three required sets. Memorize the three headings; then memorize the bullet lists under each. On the exam, distractors mix a chemical fact into the equipment list or bury consequences of deviation in the contractor element. Keep the buckets clean.

Bucket 1 — Hazards of the highly hazardous chemicals

For each highly hazardous chemical in the process, PSI must include:

An SDS is a start, not a complete PSI chemical file by itself. SDS pages often omit plant-specific mixing (for example, overfeeding oil into a recirculator, or pulling a dirty water-wash into an evaporator drain). OSHA’s list is process-specific. If a foreseeable mix can happen in your engine room, the hazardous effect belongs in PSI.

IDLH 300 ppm and the OSHA-cited 20 ppm odor threshold belong in the toxicity/physical picture operators carry. Odor at 20 ppm is below the 50 ppm PEL and far below 300 ppm IDLH — which is why “I would smell it” is not an engineering control. Detectors, ventilation, and PPE are designed against numbers in this file, not against someone’s nose.

Bucket 2 — Technology of the process

Technology information answers: what is this plant doing with ammonia, how much is in it, and what happens when it leaves the safe envelope? Required items:

• A block flow diagram or simplified process flow diagram. This is not the full P&ID. It is the one-page story: compressors, condensers, high-pressure receiver, recirculators or DX coils, suction accumulators, intercoolers on two-stage plants, and the major liquid and vapor paths. CIRO exam screens make more sense when you can sketch this from memory.
• Process chemistry. For a single-refrigerant ammonia plant this is the refrigeration cycle — evaporation, compression, condensation, expansion — not an organic-synthesis recipe. For NH3/CO2 cascade or glycol secondary loops, chemistry includes why those fluids are there and how they interface with ammonia.
• Maximum intended inventory. The largest ammonia mass the process is intended to hold, including vessels, packages, and piping that are part of the process. This number is compared to the 10,000 lb TQ. It is also the number emergency planners use when they describe a worst-case or alternative release in RMP (later chapter). Do not substitute “what we think is in it today after a leak last winter.”
• Safe upper and lower limits for temperatures, pressures, flows, or compositions. Examples: high-side pressure relative to relief settings and condenser capability; vessel level bands on a surge drum; oil-temperature limits on a screw package; minimum suction pressure that still keeps motor amps and discharge temperature inside design. Limits must be written, not tribal knowledge.
• An evaluation of the consequences of deviations, including those affecting employee safety and health. If level goes high in a recirculator, liquid carries over and wrecks a compressor — and can throw liquid into relief paths. If discharge pressure exceeds design, relief valves lift and a release can fill the machinery room. If someone bypasses a high-level cutout, the PHA will later ask why the administrative control was the only layer. Consequences of deviation are how PSI talks to the PHA.

Bucket 3 — Equipment in the process

Equipment information is the iron and the safeties:

Material and energy balances for processes built after May 26, 1992 is a favorite exam detail because the date is the original PSM effective-design line. Older plants still need the rest of the equipment list. They do not get a free pass on P&IDs or relief design basis just because the engine room predates 1992.

Safety systems in PSI are the list and function of interlocks and detection — “what is installed and what it is supposed to do.” Operating procedures later tell the operator how to run when those systems trip. Mechanical integrity later proves they still work. Do not dump the full IIAR 2 detector-setpoint lesson into PSI; do record that detectors and emergency ventilation exist and what design they follow.

RAGAGEP

The employer must document that equipment complies with recognized and generally accepted good engineering practices (RAGAGEP). For industrial ammonia, RAGAGEP typically includes ANSI/IIAR 2 (ammonia machinery-room and system design), ASHRAE 15 (general refrigeration safety), ASME boiler and pressure-vessel rules for vessels, ASME B31.5 for refrigeration piping, and ANSI/IIAR 6 for inspection, testing, and maintenance of existing equipment. You already have an IIAR/ASHRAE chapter; here the point is the PSM hook: those standards are how you demonstrate RAGAGEP, not optional reading.

For existing equipment designed to codes, standards, or practices no longer in general use, OSHA does not require a time machine. The employer must determine and document that the equipment is designed, maintained, inspected, tested, and operating in a safe manner. That sentence is why a 1980s vessel without a modern IIAR 2 nameplate is not automatically illegal — and why “grandfathered, so we never inspect it” is not RAGAGEP. Mechanical integrity (later) is how you keep that documentation alive.

PSI must stay true

PSI is not a binder that is right on commissioning day and decorative thereafter. When piping, setpoints, inventory, or safety systems change enough to alter the facts in the three buckets, management of change (later chapter) and PSSR (this chapter’s last section) exist to force an update before ammonia is introduced or reintroduced. A CIRO who finds a field-installed bypass that is not on the P&ID has found a PSI failure, not a clever workaround.

Walk a real package with the three-bucket test: Can you point to toxicity and PEL? Can you point to a flow diagram, max inventory, and safe limits with written consequences? Can you point to materials, P&IDs, electrical class, relief basis, ventilation, codes, balances if post-1992, and the safety-system list? If any answer is “in someone’s head,” PSI is incomplete, and every element downstream is standing on sand.