Ammonia compression in an ammonia boil-off gas system involves several hazards that require careful risk assessment and control measures. Here's a breakdown of potential hazards and safety recommendations:

Hazards:

• Ammonia Exposure: Anhydrous ammonia is corrosive and toxic. Leaks can cause severe respiratory irritation, skin burns, and eye damage [1]. In concentrated atmospheres, a self-contained breathing apparatus is required [1].
• Pressure Build-up: Compressors increase the pressure of the ammonia gas, which can lead to over-pressurization of containers and equipment if not properly controlled [2].
• Equipment Malfunction: Compressors, relief valves, and automatic controls can fail, leading to uncontrolled releases or system failures [2].
• Fire and Explosion: While ammonia itself is not highly flammable, it can create flammable mixtures with air under certain conditions. Electrical equipment and static discharge can be ignition sources [3].
• Cold Temperatures: Refrigerated ammonia systems operate at low temperatures, which can cause frostbite and material embrittlement [4].

Risk Assessment and Control Measures:

1. Engineering Controls:

   • Install a suitable entrainment separator in the compressor suction line to minimize liquid entry [2].
   • Equip compressors with manual shutoff valves on suction and discharge connections, and install pressure gauges before these valves [5].
   • Implement an emergency alarm system that activates if the pressure in the container rises to the maximum allowable operating pressure [2].
   • Install an emergency alarm and shutoff in the condenser system to respond to excess discharge pressure caused by cooling medium failure [2].
   • Ensure safety-relief valves are arranged to minimize tampering and are plainly marked with relevant information [1].
   • Install hydrostatic relief valves in liquid ammonia piping where liquid may be trapped [1].
   • Design or locate safety relief devices or vent piping to prevent moisture collection and freezing [4].
   • Use properly sized safety relief devices, ensuring they discharge unobstructed to the outdoors, away from personnel and structures [4].

2. Administrative Controls:

   • Develop and enforce strict operating procedures for the ammonia boil-off gas system.
   • Ensure that unloading operations are performed by reliable, properly instructed personnel with the authority to monitor compliance [6].

3. Personal Protective Equipment (PPE):

   • Provide at least two suitable gas masks in readily accessible locations, with full-face masks and approved ammonia canisters [1].
   • For concentrated ammonia atmospheres, provide self-contained breathing apparatus [1].
   • Ensure easy access to a shower or a 50-gallon drum of water for emergency washing [1].

4. Monitoring and Review:

   • Regularly inspect and maintain all components of the ammonia compression system, including compressors, valves, and safety devices.
   • Conduct periodic leak tests and address any leaks promptly.
   • Review and update safety procedures and training programs regularly.

Specific Recommendations:

• Material Compatibility: Ensure all materials used in the system are compatible with anhydrous ammonia, especially at low temperatures [4].
• Electrical Safety: Use general-purpose or weather-resistant electrical equipment and wiring appropriate for ammonia installations [3].
• Ventilation: Ensure adequate ventilation in areas where ammonia leaks could occur [7].
• Emergency Shutdown: Implement a clear and accessible emergency shutdown procedure for the ammonia compression system.
• Training: Provide comprehensive training to all personnel involved in the operation and maintenance of the system, covering ammonia hazards, safe operating procedures, and emergency response [6].