Assess the circuit and operating modes
Ammonia at work presents inhalation and contact hazards, as well as a fire hazard under certain conditions. Its usefulness as a refrigerant does not reduce the need to prevent releases. Assess normal operation, start-up, shutdown and maintenance as different operating situations.
Activities such as hot-gas defrosting or oil removal need specific assessment. Trapped liquid can develop excessive pressure as it warms, and some flow changes create dynamic loads. Safety therefore involves much more than checking the main compressor while the system is running.
Maintain mechanical integrity
The programme should address pipes, vessels, valves, supports, insulation and protective devices. Corrosion, unusual ice, vibration or damaged vapour barriers are reasons to investigate. Recording a defect without correcting it does not control its continued deterioration or the potential for a release.
Operating records help identify trends in pressure, temperature, lubrication and intervention results. Interpret these against the particular system. Clear equipment and valve identification helps maintenance personnel work on the correct component and understand which other parts of the circuit connect to it.
Machinery rooms and modifications
Ventilation, detection and alarms must be designed and checked for the installation. Emergency controls need to be accessible without requiring entry into a hazardous area. Alarm settings and sensor positions are matters for the design and applicable requirements, not generic values.
Changing automation, setpoints or pipe arrangements can affect the intended protection. Modifications require technical review and updated documentation and instructions. Only authorised personnel should be able to alter settings that influence process safety or the response of protective systems.
Prepare for a release
The Emergency plan must distinguish people who evacuate from those trained and equipped to respond. Noticing an odour or receiving an alarm does not authorise someone to search for and close a valve inside a release. Activate the planned communications and access restrictions.
Coordination with external responders includes system information, access and hazards. Emergency showers and eyewash facilities should be available where required, without replacing prevention and suitable protection. Restarting requires identifying the cause, making repairs and verifying conditions before the system returns to service.
