First 90 Days in Ammonia Refrigeration Systems: A Technical Guidebook

By Kushal Aurangabadkar

Introduction

Ammonia refrigeration systems play a critical role in industries such as food processing, cold storage, and HVAC. For new operators and technicians, the first 90 days are crucial for understanding the fundamentals, ensuring safety, and building proficiency. This technical guide provides a structured pathway to help one succeed in the new role with the deeper understanding of the ammonia refrigeration system.

Understanding Ammonia Refrigeration Basics

Ammonia refrigeration uses ammonia (NH₃) as a refrigerant due to its high efficiency and low environmental impact. It is commonly used in industrial systems like food storage, breweries, and chemical plants.

Ammonia Refrigeration Basics

• Ammonia Compressor compresses low-pressure, low-temperature ammonia vapor into high-pressure, high-temperature vapor. There are reciprocating, screw, or centrifugal compressors. It is the heart of the refrigeration cycle, driving the system by raising the pressure and temperature of the refrigerant.
• Condenser converts high-pressure, high-temperature ammonia vapor into a high-pressure liquid by removing heat. There are three types of condensers as mentioned: air-cooled condensers, water-cooled condensers, and evaporative condensers (common in ammonia systems). The function is to reject heat from the refrigerant to the atmosphere or a cooling medium.
• Expansion Valve reduces the pressure of the liquid ammonia to prepare it for evaporation. It creates a pressure drop that facilitates the cooling process as ammonia enters the evaporator.
• Evaporator absorbs heat from the surroundings (or a process) into the refrigerant, causing the liquid ammonia to evaporate into vapor. There are different types of heat exchangers, such as shell-and-tube heat exchangers and plate heat exchangers. Their role is to provide the desired cooling effect.
• Receiver stores liquid ammonia after it condenses and before it enters the expansion valve. It acts as a buffer tank to regulate the supply of ammonia to the system.
• Oil Separator removes oil from the ammonia vapor coming out of the compressor. It ensures efficient operation by preventing oil contamination in the refrigeration cycle.
• Accumulators prevent liquid ammonia from reaching the compressor, which can cause damage. They separate liquid and vapor refrigerant in the suction line.
• Ammonia Pumps circulate ammonia in systems with flooded evaporators. They ensure consistent flow of refrigerant to maintain cooling performance.
• Piping and Valves transport ammonia throughout the system. Especially ammonia pipes must be corrosion-resistant and designed for high pressures.
• Safety Components are classified as pressure relief valves, ammonia detectors, shutoff valves, and so on. Pressure Relief Valves protect the system from overpressure. Ammonia Detectors monitor for leaks to ensure safety. Shutoff Valves isolate parts of the system for maintenance or emergencies.

Ammonia (NH₃) is a highly effective refrigerant but poses significant risks that require thorough understanding and vigilance.

Types of Ammonia Hazards

• Toxicity: Ammonia is a strong respiratory irritant. Exposure to concentrations above 25 ppm (OSHA's permissible exposure limit) can cause discomfort, while higher levels (>300 ppm) may result in severe respiratory damage or even fatality.
  Symptoms of exposure include coughing, throat irritation, difficulty breathing, and lung damage at high concentrations. Ammonia is corrosive and can cause chemical burns. Direct contact with liquid ammonia can result in frostbite due to its extremely low temperature. Symptoms include redness, swelling, burns, and in severe cases, permanent tissue damage.
• Flammability and Explosion Risk: Ammonia is combustible in air at concentrations between 15% and 28% by volume. While it's not highly flammable, the possibility of ignition exists under certain conditions, such as the presence of an open flame or spark in a confined space. Combustion of ammonia can lead to the formation of toxic byproducts, such as nitrogen oxides (NOx). In confined spaces, ammonia can contribute to explosive mixtures, especially if leaks are not controlled.
• Environmental Impact: Ammonia is harmful to aquatic life. Even small leaks can cause significant damage to nearby water bodies.

Common Sources of Hazards in Refrigeration Systems

The common sources of hazards in refrigeration systems are through leaks or system failures. Improper maintenance, corrosion of pipes, valve failures, or accidental damage are typical causes. Use ammonia sensors, handheld detectors, or chemical test paper to identify leaks early. Overpressure in the system can cause line ruptures or equipment damage. Equipment like compressors, condensers, and evaporators must be regularly inspected to ensure proper function.

Mitigation and Prevention

The hazards can be mitigated by engineering controls, proper use of PPE, and emergency planning. Ensure proper airflow in all areas housing ammonia systems. Install exhaust fans and emergency ventilation systems. Use properly rated pressure relief valves to prevent overpressure incidents.
PPE includes gloves resistant to chemical burns, splash-proof goggles, face shields for eye protection, proper clothing, and full-face respirators with ammonia-rated cartridges or self-contained breathing apparatus (SCBA).
Train personnel to handle ammonia leaks, spills, and exposures as part of an emergency response team. Establish clear evacuation routes and assembly points and provide eyewash stations and safety showers.

Ammonia Spill/Leak Response Protocol

• Alert Personnel: Notify the team and activate the alarm.
• Evacuate Area: Use pre-designated evacuation routes.
• Identify the Source: Trained personnel should locate the leak and isolate it if safe to do so.
• Ventilate the Area: Increase airflow to disperse ammonia vapors.
• Decontamination: Assist exposed individuals to safety showers or eyewash stations immediately.

Key Tips for New Operators and Technicians

• Treat even minor leaks seriously; they can escalate quickly.
• Understand alarm systems and respond promptly to warnings.
• Participate actively in all safety drills and inspections.
  By maintaining vigilance and adhering to safety protocols, you can effectively minimize risks associated with ammonia refrigeration systems.

Day 1 to Day 30 – Building the Foundation

• Training and Orientation
  Attend company-specific orientation programs to learn about system design and protocols. Shadow experienced technicians to observe daily operations. Study Standard Operating Procedures (SOPs) for operating and troubleshooting equipment. Learn about common system configurations, such as direct expansion and flooded systems.
• Check system pressures and temperatures.
• Inspect for visible leaks or abnormal noises.
• Ensure proper operation of compressors, condensers, and evaporators.
• Learn about ammonia sensors functionality and leak detectors.

Day 31 to Day 60 – Developing Competence

• Hands-On Maintenance and Monitoring Performance
  Practice basic maintenance tasks like oil changes and filter replacements. Learn to conduct leak detection using instruments such as ammonia sensors.
• Understand how to read system gauges and analyze performance trends.
• Record data regularly to identify potential inefficiencies.
• Identify common issues, such as pressure imbalances or compressor overheating. Follow diagnostic steps to isolate and resolve problems.

Day 61 to Day 90 – Building Independence

• Advanced Operations and Emergency Response Skills
  Understand how to adjust system settings for seasonal variations. Gain experience with defrost cycles and their impact on system performance. Participate in annual safety drills. Learn to manage ammonia releases safely and efficiently.

Maintenance Tips for Ammonia Refrigeration Systems

Proper maintenance of ammonia refrigeration systems ensures safety, operational efficiency, and equipment longevity. Below is a comprehensive guide for maintaining your system effectively:

Impact of Heat Transfer Efficiency in Refrigeration Systems Over Time

Interpreting the graph below, we can correlate that the heat transfer efficiency drops over time. The biggest and most common drivers are clogging of heat exchanger surfaces, oil contamination in the system, corrosion of the heat exchanger causing the system to operate at reduced capacity, poor maintenance of the heat exchanger, reduced airflow, and aging equipment.

Conclusion

The first 90 days as an ammonia refrigeration operator or technician are critical for mastering the basics, ensuring safety, and building a core foundation for long-term success. By following this structured guide, you'll be well-prepared to contribute effectively to your team and advance in your career.

Author

Kushal Aurangabadkar
Cargill Inc
Engineering Manager