Kushal Aurangabadkar is engineering manager at Cargill. Views are the author’s own.
Industrial ammonia refrigeration keeps food safe and is an efficient user of energy but when something goes wrong, the consequences can escalate fast. To help staff deal with risk, facilities typically maintain piping and instrumentation diagrams, operating procedures, maintenance programs, emergency plans and alarms. The problem is that these resources tend to be stored in different systems and aren’t connected in a way that enables teams to use them day to day. This gap is where incidents hide.
LOOP-BAR is a framework intended to fix this problem by making process safety visible. It overlays protection layers directly onto a simplified ammonia refrigeration system diagram so it shows not just what equipment is being used but what protects the system, who owns each safeguard and how teams know it works. Although the framework was developed from the perspective of industrial ammonia refrigeration systems, it could technically be adapted to other chemical processing industries or such where there is heavy reliance on preventive maintenance, safeguards and functionality testing.
Diagrams over documents
Operators and technicians tend to learn refrigeration systems visually, through diagrams of compressors, condensers, receivers, valves and evaporators, while they tend to learn process safety management, or PSM, as a checklist of requirements. When safety isn’t part of the same diagram as operations, several things tend to happen: controls get mistaken for protection, safeguards are assumed to exist but aren’t verified, multiple “layers” quietly depend on the same sensor or power source and accountability for barriers becomes unclear.
What our team calls LOOP-BAR puts safety architecture on the same page as refrigeration flow, creating a shared language across operations, maintenance, engineering and leadership.
What counts as a real protection layer?
Borrowing from layers of protection analysis, or LOPA, LOOP-BAR applies a simple test: a protection layer must do something specific, at a defined trigger point, and be verifiable. Not every safeguard qualifies.
A basic control loop keeps the plant running. A protection layer keeps people and the community safe during abnormal conditions.
Each layer in LOOP-BAR is defined by a clear trigger and action, independence from other layers, a performance standard (setpoint, response time, test method), an accountable owner and objective proof that it works.
If a safeguard can’t meet those criteria, it’s treated as supporting and isn’t counted as independent protection.
Turning diagrams into a barrier assurance register
The heart of LOOP-BAR is the barrier assurance register, or BAR. For every protection layer shown on the diagram, the BAR captures what the barrier does, where it acts in the system, who owns it, how often it’s tested and where the evidence lives, whether in CMMS, calibration records, drills or inspections.
Instead of safety information scattered across binders and databases, teams get a single, traceable view of barrier health.
Receiver overpressure
Consider a common scenario: liquid ammonia blocked in a high-pressure receiver. The consequence could be relief valve lift, toxic release and emergency response activation. With LOOP-BAR, teams can immediately see whether the scenario is protected by a balanced set of layers:
- A properly sized and maintained relief valve.
- A high-pressure alarm with trained operator response.
- A high-pressure shutdown or interlock.
- Verified pump-down and valve lineup procedures.
- Ammonia detection and ventilation response.
Just as importantly, the framework reveals whether those layers are truly independent or whether several rely on the same transmitter, programmable logic comptroller, or PLC, or human action window.
How facilities actually use it
LOOP-BAR isn’t a one-time study. Facilities use the overlay and BAR during shift handover discussions, maintenance planning and line-break reviews, process hazard analysis and LOPA revalidations, management of change and pre-start-up safety review, audit preparation or incident investigations.
When a barrier test is overdue or a detector is bypassed, it shows up immediately as a leading indicator, not months later in an audit finding.
Why this matters
Strong process safety management isn’t just about compliance but whether protection layers are real, owned, tested and understood by the people closest to the system. By making safety visible on the same diagrams that teams already trust, LOOP-BAR helps organizations spot weak or dependent safeguards early, before a near-miss becomes an incident.
In ammonia refrigeration, where the margin for error is thin, clarity itself becomes a safety system.
